About this family
A polyester carries the ester group –C(=O)O– in the main chain rather than hanging off it, which is the distinction that separates this family from the acrylates. Put the linkage in the backbone and it stops being a side group that modifies the chain and becomes a structural member of it: every property below follows from what sits between successive esters, and from the fact that the linkage itself can be hydrolysed apart.
Most of these are made by step-growth – a diol and a diacid (or its ester) condensed with removal of water or a small alcohol. That mechanism has consequences the chain-growth families do not share. High molecular weight arrives only at very high conversion, so stoichiometry has to be near-exact and the condensate has to be stripped continuously; and because the reaction is an equilibrium, it also runs backwards. Wet poly(ethylene terephthalate) melt-processed without drying will hydrolyse in the extruder and come out with a lower molecular weight than it went in with, which is why drying is not an optional step.
What sets the properties
Backbone rigidity sets the thermal properties, and an aromatic ring is the stiffest thing you can put between two esters. Poly(ethylene terephthalate) has a Tg of 75 °C and melts at 260 °C; replace the benzene with the larger fused naphthalene unit and poly(ethylene naphthalate) rises to 120 °C and 265 °C. Take the ring out entirely and everything collapses: poly(ethylene adipate), an all-aliphatic polyester of the same ester density, has a Tg of −50 °C and melts at 50 °C. That is the whole aromatic–aliphatic divide in the family, and it is why the aromatic polyesters are engineering plastics and fibres while the aliphatic ones are soft segments, adhesives and degradable materials.
Lengthening the diol softens the chain without changing the chemistry, and does something more useful besides. Poly(butylene terephthalate) sits at 40 °C and 225 °C against PET's 75 and 260 – but the extra flexibility also lets it crystallise far faster, which is why PBT is the injection-moulding grade and PET, which can be quenched to a clear amorphous solid, is the bottle and fibre grade. The same two polymers, differing by two methylene groups, end up in entirely different processes for reasons of crystallisation kinetics rather than of equilibrium properties.
The ester link is hydrolysable, and that is a feature as often as a liability. It is why the aliphatic polyesters dominate degradable medicine – polylactide, polyglycolide, poly(caprolactone) and their copolymers, whose degradation rate is tuned by the ratio – and why polyester-based polyurethane soft segments fail in humid service where a polyether would survive. Those lactone-derived polyesters are made by ring-opening rather than condensation and so live on the ring-opening page, even though the linkage is identical.
All 170 in the library
Sorted by parent name, ignoring the leading "poly" and any locants – so poly(2-hydroxyethyl methacrylate) files under H. 167 of the 170 carry a note, and every one is searchable by drawn structure on the structure search page. 17 have a CAS registry number for the polymer; most specialty polymers have never been assigned one, and the number you find in a catalogue is usually the monomer's, which is why the field is blank rather than borrowed here.
A
Agarose
The gel every molecular biology lab runs DNA through. Its disaccharide repeat contains a bridged anhydro sugar that forces a helical twist, and on cooling the helices bundle into fibres that trap water into a gel with pores of a controllable few hundred nanometres - which is exactly the size range that sieves DNA by length. It melts near 85 C and sets near 35 C, a hysteresis wide enough to pour a gel that then stays solid. Not drawn: the repeat is a bridged bicyclic disaccharide whose geometry is the point.
Alginate
The seaweed polysaccharide that gels the instant it meets calcium, without heat, solvent or chemistry - which is why it is the default for encapsulating live cells. Calcium ions sit in pockets formed between paired guluronate blocks, the egg-box model, so gel strength depends on how the two uronic acids are arranged along the chain and not merely on how much there is. The drawn repeat is one uronic acid unit; a real chain is a block copolymer of the two epimers.
Alginate lyase-degraded oligoalginate
Alginate cut by a lyase into short unsaturated fragments, which no longer gel with calcium - the egg-box needs long guluronate blocks - but do something the polymer cannot: they diffuse into a biofilm and disrupt the alginate matrix a Pseudomonas colony builds around itself. That is the basis of using them as an adjunct to antibiotics in cystic fibrosis. Not drawn: a length distribution of a known backbone.
Poly(aluminium chloride)
Pre-hydrolysed aluminium salts that have already condensed into charged polynuclear clusters before they reach the water being treated, so they coagulate over a far wider pH range than alum and leave less residual aluminium behind. Nearly all municipal drinking water passes through this. Undrawn: an inorganic cluster of variable nuclearity.
Poly(beta-amino ester)
A gene delivery polymer whose appeal is how easily it is varied. A diacrylate and an amine simply add together at mild temperature with no catalyst and no by-product, so hundreds of structures can be made in parallel in a plate and screened - which is how the field found its best performers rather than by design. The tertiary amines in the backbone protonate to bind nucleic acids, and the ester linkages then hydrolyse to release them, so binding and release are separate handles. Not drawn: the point of the class is combinatorial variation, so no single repeat represents it.
Amylopectin
The branched majority of starch - about three quarters of it - with an alpha-1,6 branch roughly every twenty-five glucose units. That branching is functional: it packs the molecule into a compact form that can hold enormous mass, and it multiplies the chain ends an enzyme can start from, so a branched store is mobilised far faster than a linear one. It is why amylopectin-rich waxy starches thicken and stay clear while amylose-rich ones set to a gel. Not drawn: the branch points are the structure and a linear repeat cannot show them.
Amylose
The linear fraction of starch, and cellulose's mirror twin. Same glucose, same 1,4 linkage, but joined alpha rather than beta, so successive rings do not flip - the chain coils into a helix instead of lying flat, cannot pack into sheets, and is digestible and swellable where cellulose is neither. One stereocentre is the whole difference between food and firewood. Not drawn: without stereochemistry its connectivity is identical to cellulose's, so a flat structure would claim the two are the same molecule.
Poly(aryl ether nitrile)
An aromatic polyether whose distinguishing group is the nitrile, which is strongly polar and can crosslink on heating. The polarity raises the dielectric constant enough to matter for film capacitors, and the same nitriles can be cured into a network for a thermoset that starts as a processable thermoplastic.
Polyarylate
An aromatic polyester from bisphenol A, sitting between polycarbonate and the high-temperature aromatics: transparent like polycarbonate, with a glass transition some 40 C higher and far better ultraviolet stability, because it undergoes a photo-rearrangement that forms a self-protecting surface layer. The mixed iso/terephthalate ratio is what keeps it amorphous and processable. Not drawn: the isomer ratio is the specification.
Poly(arylene ether sulfone) with quaternary ammonium
The anion-conducting counterpart to a proton-exchange membrane, made by chloromethylating an aryl ether sulfone and quaternising it. Its defining problem is chemical rather than mechanical: hydroxide attacks the benzylic quaternary ammonium by Hofmann elimination and substitution, so the membrane loses conductivity over weeks. Most work in the area is about placing the cation where hydroxide cannot easily reach it. Not drawn: substitution is partial.
B
Bacterial cellulose
Chemically this is cellulose - the same beta-1,4-glucan repeat unit, drawn here identically - and the entry exists because the material is not. Grown by Komagataeibacter rather than extracted from a plant, it arrives free of lignin and hemicellulose and as a hydrated ribbon network of much higher crystallinity and purity, which is what the medical and acoustic uses are actually buying. Nothing about that difference lives in the repeat unit.
Bis-MPA polyester dendrimer
A dendritic polyester from a monomer with one acid and two alcohols, which is what makes branching automatic. Unlike the amine dendrimers it is neutral and hydrolysable, so it degrades rather than accumulating - the reason it is preferred where a dendrimer must eventually clear. Sold commercially in the hyperbranched form, made in one pot with a distribution of defects, which is far cheaper than the perfect dendrimer and adequate for most uses.
Poly(bisphenol A carbonate-co-siloxane)
Polycarbonate with siloxane blocks built in to fix its two weaknesses at once: notch sensitivity in the cold, and flammability. The rubbery siloxane phase separates into domains that blunt a crack tip, so impact strength survives well below where plain polycarbonate turns brittle, and the silicon chars rather than feeding a flame. Not drawn: it is a segmented block copolymer whose properties depend on block length, not on a repeat unit.
Poly(butylene adipate)
A wholly aliphatic polyester, readily attacked by soil enzymes, and the flexible half of the compostable copolyesters. On its own it melts near 60 C and is too weak to use, which is exactly why it is copolymerised with terephthalate; it also serves as the soft block of hydrolysable polyurethanes.
Poly(butylene adipate-co-terephthalate)
The flexible half of most compostable plastic film. Aliphatic adipate segments are attacked readily by soil enzymes; aromatic terephthalate segments supply the strength and melt behaviour that a purely aliphatic polyester lacks. The composition is chosen to sit just below the aromatic content at which biodegradation stalls, which is the whole design problem - too little aromatic and the film is too weak to use, too much and it stops composting. Usually blended with polylactide, which is stiff and brittle where this is neither. Not drawn: it is a random copolyester and one repeat unit cannot represent it.
Poly(butylene azelate)
Azelaic acid from oleic acid ozonolysis, giving an odd-carbon bio-based polyester that resists crystallising.
Poly(butylene carbonate)
An aliphatic polycarbonate, which despite the shared name has nothing structurally in common with the bisphenol A material that windows are made of - no aromatic ring, no rigidity, and it hydrolyses. Short chains of it are the soft segment in the polyurethanes chosen for implants, because a carbonate resists the enzymatic hydrolysis that eventually eats a polyester soft segment.
Poly(butylene furanoate)
A furanoate polyester: the furan ring replaces terephthalic acid, and it comes from sugar rather than from xylene. The ring is kinked where a benzene ring is straight, which is why these pack differently and give the barrier properties that make poly(ethylene furanoate) interesting for bottles.
Poly(butylene glutarate)
An amorphous aliphatic polyester used as a plasticising soft segment.
Poly(butylene isophthalate)
An amorphous aromatic polyester, used to suppress crystallinity when blended into PBT.
Poly(butylene naphthalate)
The naphthalate counterpart of PBT, standing to it as PEN stands to PET. The larger fused ring stiffens the chain and raises both transitions, while the butylene glycol keeps crystallisation fast enough for injection moulding - so it fills the gap between an easily moulded polyester and one that survives heat, mainly in automotive connectors.
Poly(butylene sebacate)
A long-chain aliphatic polyester whose diacid comes from castor oil, so it is bio-based at the acid end without any fermentation step. The ten-carbon spacing makes it softer and lower melting than poly(butylene succinate), and it is used to plasticise stiffer biodegradable polyesters without adding a migratory small molecule.
Poly(butylene succinate)
Poly(butylene succinate-co-adipate)
Poly(butylene succinate) with adipate units mixed in to spoil its crystallinity on purpose. The parent is too stiff and slow to degrade for a compostable film; the adipate disrupts the lattice, lowering the melting point and speeding up enzymatic attack, so the copolymer composts on a useful timescale while staying flexible. Not drawn: the ratio is the design variable.
Poly(butylene terephthalate)
C
Polycarbonate (bisphenol A)
Amorphous; the carbonate linkage makes it a polyester of carbonic acid.
Poly(carbonate urethane)
The material chosen when a polyurethane must last decades inside a body: the polycarbonate soft segment resists the oxidative attack that cracks polyether urethanes and the enzymatic hydrolysis that eats polyester ones. Pacemaker lead insulation is the demanding case, where a crack means a reoperation. Undrawn: a segmented block copolymer whose behaviour is set by segment lengths, not by one repeat unit.
Carboxymethylcellulose
The most widely used cellulose derivative, and the one that turns a neutral polysaccharide into a polyanion. Carboxymethyl groups both prevent crystallisation and add charge, so it dissolves in cold water and its viscosity responds to pH and salt. It thickens ice cream and toothpaste, stops drilling mud losing fluid to the formation, and is the binder holding graphite to a lithium cell's anode. Drawn fully substituted; the degree of substitution is the specification.
Carrageenan
Agarose's sulfated cousin from red seaweed, and sold in three forms distinguished only by how many sulfates sit on the disaccharide. One sulfate gives a firm brittle gel that needs potassium, two give a soft elastic one that needs calcium, three prevent gelation entirely and give a thickener - a clean illustration of charge density controlling assembly. It is what suspends the cocoa in chocolate milk. Not drawn: the sulfation pattern is what distinguishes the types.
Cellulose
The most abundant organic polymer on the planet, and the reason wood and cotton behave as they do. Glucose rings joined beta-1,4 alternate their orientation along the chain, which lets the chain lie flat and hydrogen-bond to its neighbours in sheets - so cellulose is crystalline, does not melt, and dissolves in almost nothing despite being covered in hydroxyls. Every industrial use is a way around that: derivatise it, dissolve it in something exotic, or regenerate it. The drawn repeat is the glucose unit; note that starch has the same 2D connectivity and differs only in the anomeric configuration.
Cellulose acetate
The oldest way round cellulose's intractability, and still the largest. Capping the hydroxyls as acetates breaks the hydrogen bonding that makes cellulose insoluble, so the material dissolves and can be spun, cast or moulded - as cigarette filters, photographic film base and reverse-osmosis membranes. The drawn unit is the fully substituted triacetate; commercial grades are partly hydrolysed back, because the degree of substitution is what sets solubility.
Cellulose nanocrystal
The repeat unit is cellulose because a nanocrystal is cellulose: sulfuric acid removes the disordered regions and leaves the crystalline domains behind as rods a few nanometres across. The difference is entirely one of dimension and surface - the hydrolysis leaves anionic sulfate half-esters that keep the rods dispersed - and none of that is visible in one glucose unit.
Cellulose sulfate
Cellulose turned into a strong polyanion, which lets it form a membrane on contact with a polycation - the basis of the capsules used to encapsulate live cells for transplantation, since the shell forms in seconds under physiological conditions with no solvent or heat. The high sulfate density also mimics heparin closely enough to show anticoagulant and antiviral activity. Drawn fully substituted.
Chitin
Cellulose with an acetamide where one hydroxyl should be, and the second most abundant natural polymer - the structural material of insect cuticle, crustacean shell and fungal cell wall. The extra amide adds a hydrogen bond donor and acceptor per ring, so it is even more tightly packed and less soluble than cellulose. Most of what is done with it starts by deacetylating it to chitosan, because chitin itself is so intractable.
Chitosan
Chitin with the acetyl groups removed, which changes everything: the free amine protonates below about pH 6.5, so unlike every other abundant polysaccharide chitosan is a polycation and dissolves in dilute acid. That single property carries most of its uses - it sticks to the negatively charged surfaces of cells and mucosa, complexes DNA, flocculates, and is antimicrobial. Sold by degree of deacetylation rather than as a pure compound, because the reaction never goes to completion.
Chitosan oligosaccharide
Chitosan cut short. The repeat unit is unchanged; what changes is chain length, and with it everything practical - the oligosaccharide is water-soluble at neutral pH where the polymer needs acid, and it is short enough to be absorbed rather than merely act as a bulk material.
Chondroitin sulfate
The glycosaminoglycan that hangs off aggrecan by the hundred to make cartilage's bottlebrush. Each disaccharide carries a carboxylate and at least one sulfate, so the charge density is far higher than hyaluronan's, and it is that charge - drawing water in and resisting its expulsion under load - that lets cartilage carry a joint's weight. Not drawn: the sulfation pattern varies along the chain and between tissues, and picking one would assert a regularity the molecule does not have.
Condensed tannin
Flavonoid units linked carbon to carbon, from bark and grape seed and the reason strong tea is astringent - the polymer binds and precipitates salivary proteins. That same protein affinity is what tans hide into leather, and it is now used as a formaldehyde-free wood adhesive. Undrawn: the linkage position varies between units within a single chain.
Curdlan
A bacterial glucan linked beta-1,3 instead of beta-1,4, which coils it into a triple helix rather than laying it flat. Heating a suspension gives two different gels depending on temperature - a reversible one below 60 C, an irreversible one above it - so the same material sets soft or firm according to how it was cooked. The drawn ring is the glucose unit; the 1,3 linkage geometry is not captured by a flat structure.
Curdlan sulfate
A sulfated beta-1,3-glucan, and one of the earlier polysaccharide antivirals - the sulfates mimic the cell-surface heparan sulfate that HIV's envelope protein binds to, so the polymer competes for that interaction before the virus reaches a cell. The same logic recurs for every enveloped virus that uses a sulfated glycan as its foothold. Not drawn: sulfation is partial and its position varies.
Cutin
The polyester skin on every leaf and fruit, and the largest reservoir of polymerised lipid on land. Hydroxy and epoxy-hydroxy fatty acids esterify into a network that limits water loss and blocks pathogens; tomato peel is nearly pure cutin and is now studied as a feedstock for bio-based polyesters. Undrawn: an irregular crosslinked network.
Poly(cyclohexylenedimethylene terephthalate)
PET with a cycloaliphatic diol instead of ethylene glycol, which pushes the melting point to about 290 C - high enough for a polyester to survive lead-free solder reflow, which PET and PBT do not.
D
Poly(decamethylene adipate)
Ten methylenes between esters, so the chain is mostly polyethylene by mass and behaves accordingly - it crystallises into the same orthorhombic cell that polyethylene does, with the ester groups accommodated as defects. It is the point at which an aliphatic polyester stops being a polyester with hydrocarbon spacers and becomes a polyethylene with ester defects.
Poly(decamethylene sebacate)
Both halves ten carbons long, giving the lowest ester density and slowest hydrolysis of the common aliphatic polyesters.
Poly(decamethylene terephthalate)
A term in the series that runs from PET upward through PBT and PTT: as the diol lengthens, the melting point falls and the polymer becomes progressively more polyethylene-like. By ten carbons the aromatic rings are dilute enough that the crystal is dominated by the methylene runs, which is why the series is used to study how aromatic content controls a polyester's transitions.
Deoxyribonucleic acid
Carried without a drawn repeat unit, and not as a gap to be filled later: DNA has FOUR repeat units, not one. The backbone is a regular phosphodiester-linked deoxyribose, but each sugar bears one of four bases, so no single graph describes the chain the way one does for a synthetic homopolymer. The structure search matches repeat-unit graphs and would have nothing correct to match against. As a polymer it is a semiflexible polyanion with a persistence length near 50 nm, about a hundred times a synthetic coil, which is why it behaves like no other water-soluble polymer at the same molar mass.
Dermatan sulfate
Chondroitin sulfate in which the glucuronic acid has been epimerised at one carbon to iduronic acid - a single stereocentre flipped, and the consequence is conformational freedom the rigid glucuronate does not have. That flexibility is what lets the chain wrap around a protein, which is how it accelerates thrombin inhibition and why it accumulates in skin and blood vessel wall rather than cartilage. Not drawn: epimerisation is partial and irregular along the chain.
Dextran
Glucose joined 1,6 instead of 1,4, which puts a free-rotating CH2 in every linkage and makes the chain unusually flexible and very soluble. Made by bacteria rather than extracted, in tightly controlled molar masses, so it has long served as the calibration standard for aqueous size-exclusion chromatography and as a plasma volume expander. Its clean hydroxyl chemistry makes it a common carrier for drugs and contrast agents.
Poly(diol citrate)
Made by melting citric acid with a diol and letting it condense - no catalyst, no solvent, no initiator, which is about as simple as a synthesis gets. Citric acid's third carboxyl becomes the crosslink, so the network density is set purely by cure time, and the residual carboxyls and hydroxyls make the surface unusually friendly to cells. Undrawn as a network.
Poly(2,6-diphenyl-1,4-phenylene oxide)
The phenyl version of the polymer in Noryl, and the standard adsorbent for trapping volatile organics from air: it is stable to 350 C, so a trapped sample can be driven off thermally straight into a chromatograph without any solvent. Its low affinity for water is what makes it work on humid samples where charcoal fails.
Poly(disulfide)
A backbone whose every linkage exchanges with its neighbours under mild reduction or light, so the polymer reshuffles rather than breaking - the archetype of a dynamic covalent backbone. That gives self-healing, reprocessable networks, and in a biological setting a chain that falls apart in the reducing interior of a cell while surviving the oxidising exterior.
E
Epoxy (DGEBA-amine)
The adhesive and composite matrix that works because nothing leaves. An amine opens the epoxide ring and adds across it, generating the hydroxyl that helps it stick to metal and glass, with no water or other by-product to escape - so it cures in a thick section without voids and barely shrinks, which is why it bonds and why it holds carbon fibre. Cure chemistry sets everything: an aliphatic amine cures at room temperature and softens near 60 C, an aromatic one needs an oven and reaches 200 C. Not drawn: a network with no repeat unit.
Poly(ester carbonate)
Polycarbonate with aromatic ester units built into the chain, which raises the heat distortion temperature by thirty to fifty degrees while keeping the transparency and much of the toughness. It occupies the gap between polycarbonate and polyarylate, and is used where a transparent part must survive an autoclave or a headlamp. Not drawn: the ester fraction is the specification.
Poly(ester urethane)
The polyurethane whose soft block is a polyester, which buys higher strength, better oil resistance and superior abrasion resistance than the polyether version - and pays for it with hydrolysis. Ester soft blocks degrade in warm damp service in a way ethers do not, which is the single most common failure of a polyurethane part and the reason the choice between the two is the first decision a formulator makes. Not drawn: a segmented block copolymer.
Poly(ether ether ketone ketone)
One more ketone per repeat than PEEK, which stiffens the chain and lifts the melting point above 360 C. The whole polyaryletherketone family is a single design variable played out: ethers are the flexible joints and ketones the rigid ones, and the ratio between them sets the melt and glass transitions almost linearly. More ketone also means a narrower processing window.
Poly(ether ketone ketone)
Two ketones per ether instead of PEEK's one, which raises the glass transition and lets the crystallisation rate be tuned by the ratio of para to meta linkages in the acid - unusual control for a semicrystalline engineering polymer, and the reason PEKK is favoured for laser sintering and for composite tape laying where the melt has to stay workable for a while.
Poly(ether sulfone ketone)
Sulfone and ketone in the same chain, which puts the glass transition above polysulfone's while retaining some crystallinity from the ketone - the two families' properties are usually mutually exclusive. It is one of the clearest illustrations that the aryl ether backbone is a construction kit rather than a fixed material.
Poly(ether urethane)
The hydrolytically stable half of the polyurethane choice, its soft block a polyether - usually poly(tetrahydrofuran) - so there are no ester bonds to hydrolyse. That stability is why every long-term implanted polyurethane is ether-based, though the ether then has its own failure mode: oxidative degradation by enzymes and metal ions, which is what cracks pacemaker leads over years. Not drawn: a segmented block copolymer.
Ethylcellulose
The cellulose ether that is not water-soluble. Two carbons per ether instead of one is enough to tip the balance, so it dissolves in organic solvents and forms tough, flexible films - which is precisely what a moisture barrier or a sustained-release tablet coating needs. It is also the binder in many inks and, being non-nutritive and tasteless, a permitted food coating.
Poly(ethylene adipate)
Low-melting aliphatic polyester used as a polyol soft segment in polyurethanes.
Poly(ethylene azelate)
Azelaic acid has nine carbons - an odd number, from ozonolysis of oleic acid - and odd-numbered diacids pack badly, so this polyester melts some 20 degrees below its even-numbered neighbours. The odd-even alternation in aliphatic polyester melting points is one of the cleanest structure-property relationships in the field.
Poly(ethylene dodecanedioate)
A long-diacid polyester approaching polyethylene in its aliphatic run length, with esters only every fourteen atoms.
Poly(ethylene furanoate)
The bio-based answer to PET, with a furan ring from sugar in place of the terephthalate from oil. It is not merely a substitute: the furan ring is bent rather than linear and rotates far more sluggishly, so chain motion is slower and the barrier to oxygen and carbon dioxide improves by roughly an order of magnitude over PET - which matters commercially for bottled drinks. The same sluggishness makes it crystallise slowly, which complicates processing.
Poly(ethylene glutarate)
The odd five-carbon diacid disrupts crystallisation, so this stays amorphous where the adipate and succinate crystallise.
Poly(ethylene isophthalate)
PET's meta isomer, and it does not crystallise - the 120 degree kink at every ring stops the chains registering with one another. That makes it useless alone and valuable as a comonomer: a few percent of isophthalate in PET slows crystallisation enough to blow a clear bottle instead of a hazy one. The same atoms as PET, arranged so they cannot pack.
Poly(ethylene naphthalate)
Stiffer, higher-barrier cousin of PET; the naphthalene ring raises Tg and modulus.
Poly(ethylene oxalate)
The shortest possible aliphatic polyester diacid, two carbonyls bonded directly to each other. That adjacency makes the ester unusually electrophilic and the polymer hydrolyses far faster than any other polyester of its kind - fast enough to be a nuisance rather than a feature, which is why it appears mainly as a sacrificial or rapidly resorbing component.
Poly(ethylene sebacate)
A long-chain aliphatic polyester whose diacid comes from castor oil. Lengthening the diacid from adipic to sebacic pushes the structure toward polyethylene, so the melting point and crystallinity rise while the ester density - and with it the rate of hydrolysis - falls. The aliphatic polyesters are essentially one series with that trade running through it.
Poly(ethylene succinate)
Poly(ethylene terephthalate)
Both transitions move with crystallinity, which is why sources spread: Odian's Table 1-3 gives 61 °C and 270 °C against the 75 °C and 260 °C here. Quenched amorphous PET reads at the low end of Tg, drawn and crystallised PET at the high end.
Poly(ethylene terephthalate-co-cyclohexylenedimethylene terephthalate)
PET made deliberately unable to crystallise. Around a third of the ethylene glycol is replaced with the bulkier cyclohexanedimethanol, which disrupts the chain regularity enough that the polymer stays amorphous and clear however slowly it is cooled - so it thermoforms into thick transparent sections and prints well, where PET would go hazy. Not drawn: the diol ratio is the specification.
F
Fucoidan
A sulfated fucose polymer from brown seaweed, structurally irregular in a way that has frustrated its development: linkage pattern, sulfation and branching all vary with species, season and extraction, so results from one preparation rarely transfer to another. It is studied for anticoagulant and antitumour activity broadly attributed to its charge density mimicking heparin's. Not drawn: irregularity is the defining property.
Poly(furfuryl alcohol)
Made from corn cobs and sugarcane bagasse by way of furfural, and one of the oldest bio-based thermosets. Acid condensation links the furan rings through methylene bridges; the linear chain shown is what forms first, before further condensation and ring opening turn it black and infusible. Its char yield on pyrolysis is high enough that it is used as a carbon precursor for glassy carbon.
G
Galactomannan
The family that guar, locust bean and fenugreek gums belong to, all a beta-1,4 mannan differing only in how often a galactose hangs off it. That ratio alone determines whether the gum thickens cold water, gels with borate, or synergises with xanthan - a single structural variable spanning the whole commercial range. Undrawn: the substitution is statistical.
Gellan gum
A bacterial polysaccharide sold in two forms that behave oppositely: with its acyl groups intact it gives a soft elastic gel, deacylated it gives a hard brittle one, from the same backbone. The deacylated form sets a clear gel at under a percent, which is why it has largely replaced agar in plant tissue culture and appears in fluid-gel beverages that suspend particles without feeling thick. Not drawn: the repeat is a tetrasaccharide whose acylation is the variable.
Beta-glucan
Glucose joined by a mixture of beta-1,3 and beta-1,4 links in an irregular sequence, which is precisely why it dissolves where pure beta-1,4 cellulose does not - the occasional 1,3 kink breaks up the flat ribbon before it can crystallise. The viscous solution it forms in the gut is what lowers cholesterol, and it is one of very few food claims with a solid mechanism. Undrawn: the linkage sequence is irregular.
Poly(glycerol adipate)
Glycerol has three hydroxyls but an enzyme will only use the two primary ones, so a lipase-catalysed polymerisation gives a linear polyester with a free secondary alcohol on every repeat unit. Chemical catalysis would give a crosslinked mess. That pendant hydroxyl is then the attachment point for drugs, and the selectivity is entirely the enzyme's doing.
Poly(glycerol sebacate)
A soft degradable elastomer from two metabolites - glycerol and a fatty diacid - crosslinked through glycerol's third hydroxyl. It recovers elastically at strains where the stiff degradable polyesters have long since yielded, which suits tissues that move: heart, blood vessel, nerve. Because the crosslinks are esters it erodes from the surface rather than crumbling. Not drawn: it is a thermoset network whose crosslink density depends on cure, so there is no repeat unit.
Glycogen
Amylopectin's animal counterpart, branched about twice as often - every ten or so residues - which is the whole design. Denser branching means more non-reducing ends per molecule, and since phosphorylase works only from those ends, the store can be mobilised as fast as a sprint demands. It also folds into a compact sphere around a protein core, so a liver cell can hold a great deal of glucose without the osmotic cost of free sugar. Not drawn: a hyperbranched molecule with no repeat unit.
Poly(glycolide-co-trimethylene carbonate)
The chemistry behind a monofilament absorbable suture. Polyglycolide alone is strong but so stiff that a monofilament of it will not tie; blending in carbonate units softens the chain enough to handle like nylon while keeping the strength and the resorption schedule. The carbonate also degrades to a neutral diol, which moderates the acidity that pure polyglycolide generates. Not drawn: the ratio is the design.
Guar gum
A mannan backbone with a galactose on roughly every second unit, which is precisely what keeps it soluble - the bare mannan would hydrogen-bond to itself and precipitate. It hydrates in cold water to give very high viscosity at low concentration, and its hydroxyls crosslink with borate into the reversible gels used to carry proppant in hydraulic fracturing. Not drawn: the galactose substitution is statistical, not periodic.
Gum arabic
Tapped from acacia trees in the Sahel and still without a synthetic substitute. It is a highly branched arabinogalactan carrying a small protein core, and that protein is the point: it anchors at an oil-water interface while the sugar arms stay in the water, so the molecule emulsifies where a plain polysaccharide only thickens. It keeps soft-drink flavour oils dispersed. Undrawn: branched and heterogeneous.
H
Heparan sulfate
Heparin's less-sulfated relative, and unlike heparin it is on the surface of nearly every animal cell. Its sulfation is not uniform but arranged in highly modified domains separated by plain stretches, and those domains are read as a code by growth factors and by viruses looking for a foothold - the SARS-CoV-2 spike among them. Sequence, not overall charge, is the function. Not drawn: the sulfation pattern is the molecule.
Heparin
The most negatively charged biological molecule known, up to three sulfates per disaccharide, and the anticoagulant given by the million of doses. Its action is not general charge but a specific pentasaccharide sequence that binds antithrombin and changes its shape; only about a third of the chains in a preparation carry it. Not drawn: the sulfation pattern is irregular and is the pharmacology.
Heparosan
The unsulfated backbone from which heparin is built, made by bacteria including E. coli K5. Because it is not sulfated it does not bind proteins and is not anticoagulant, yet the body recognises it as self - so it circulates for a long time without provoking a response, which is the argument for it as a PEG replacement. Undrawn: a disaccharide repeat whose linkage positions I will not draw without a source to check against.
Poly(hexamethylene adipate)
One of the standard polyester polyols used as the soft block of polyurethane. Polyester soft blocks give better oil resistance and higher strength than polyether ones, and worse hydrolytic stability - the ester bonds that make them tough are the ones that fail in warm damp service, which is the choice every polyurethane formulator makes.
Poly(hexamethylene butylene urethane)
An aliphatic polyurethane hard segment. Aliphatic isocyanates do not yellow in sunlight the way the aromatic ones do, which is the whole reason they cost more.
Poly(hexamethylene carbonate)
The polycarbonate diol behind the most durable polyurethane coatings and the longest-lived implantable elastomers. Six methylenes between carbonates is enough to crystallise slightly and enough to stay flexible, and the carbonate link resists both hydrolysis and oxidation better than the ester or ether soft segments it competes with - which is measured in years of implant life, not laboratory hours.
Poly(hexamethylene ethylene urethane)
The shortest common aliphatic urethane hard segment, with the highest urethane density and the strongest hydrogen bonding of the aliphatic family.
Poly(hexamethylene furanoate)
A furanoate polyester: the furan ring replaces terephthalic acid, and it comes from sugar rather than from xylene. The ring is kinked where a benzene ring is straight, which is why these pack differently and give the barrier properties that make poly(ethylene furanoate) interesting for bottles.
Poly(hexamethylene hexamethylene urethane)
Both halves six carbons: the most symmetric of the aliphatic urethanes, and the most crystalline hard segment the family offers.
Poly(hexamethylene sebacate)
A long-chain aliphatic polyester from two bio-derived monomers, sebacic acid coming from castor oil. Sixteen backbone atoms per repeat with only two esters puts it close to polyethylene in behaviour - waxy, crystalline, melting near 70 C - while remaining hydrolysable and enzymatically degradable. It serves as a soft segment where a polyester polyol needs to be less polar than adipate.
Poly(hexamethylene succinate)
A biodegradable polyester with a long diol and the shortest practical diacid.
Poly(hexamethylene terephthalate)
One step further along the terephthalate series than PBT, with a lower melting point and more flexible chain.
Humic acid
What is left when plant matter has decayed as far as biology can take it, and by mass one of the largest pools of organic carbon on Earth. Whether it is a polymer at all is disputed - the current view is a supramolecular association of smaller molecules rather than covalent chains. Undrawn, necessarily: it has no defined structure and possibly no defined molecule.
Hyaluronan
The only glycosaminoglycan that is not sulfated and not attached to a protein, and the backbone that aggrecan hangs from to build cartilage's bottlebrush-on-bottlebrush. A carboxylate on every disaccharide makes it a polyanion that holds enormous amounts of water - a few milligrams per millilitre gives a viscoelastic solution - which is why it fills the eye, lubricates joints and is injected as a dermal filler. Turnover in the body is fast, so the medical forms are crosslinked to slow it down.
Poly(4-hydroxybutyrate)
A polyhydroxyalkanoate with no side group at all, the hydroxyl sitting four carbons along instead of three. Without a branch to disrupt it the chain is flexible and the polymer is a strong elastomer rather than a brittle solid - unique in the family - and it degrades to a compound already present in the body. It is approved for surgical mesh and suture.
Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)
The copolymer that spans the widest property range in the polyhydroxyalkanoate family: at low 4HB content it is a stiff crystalline plastic, and by about half it is a soft elastomer, with everything in between available from one fermentation by changing the feed. That range, plus degradation to metabolites, is why it carries approvals for implantable devices. Not drawn: the ratio is the design.
Poly(hydroxybutyrate-co-hydroxyhexanoate)
The polyhydroxyalkanoate that finally solved PHB's brittleness: a few mole percent of the six-carbon comonomer disrupts the crystal enough to give real elongation, and unlike most bioplastics it degrades in seawater as well as in compost. It is the first bio-based plastic certified for marine biodegradation at scale. Undrawn: a random copolymer whose comonomer fraction is the design variable.
Poly(hydroxybutyrate-co-hydroxyvalerate)
Bacteria make this as a carbon store, and it is one of the few plastics that is both bio-based and marine-degradable. Pure poly(3-hydroxybutyrate) is unusable - so crystalline that it is brittle, and its melting point sits close to where it degrades. Feeding the bacteria a little propionate makes them copolymerise a valerate unit in, which disrupts the crystal, opens a processing window and buys toughness. Not drawn: the copolymer ratio is the whole design, and it is set by what the bacteria are fed.
Poly(3-hydroxydecanoate)
Two carbons longer again, and by this point the side chains are long enough to crystallise on their own, so the polymer shows a side-chain melting transition well below the backbone's. It is a soft tacky solid used as a bio-based pressure-sensitive adhesive, and it composts - which most adhesives conspicuously do not.
Hydroxyethylcellulose
Cellulose reacted with ethylene oxide, which puts a short hydroxyl-ended arm on the ring rather than a cap - so unlike methylcellulose it stays soluble however hot the water gets, and unlike carboxymethylcellulose it carries no charge, so salt and pH leave it alone. That indifference is why it thickens latex paint and shampoo, where an ionic thickener would be disturbed by everything else in the formulation.
Poly(3-hydroxyhexanoate)
A medium-chain-length polyhydroxyalkanoate, with a propyl side group where poly(3-hydroxybutyrate) has a methyl. That longer branch keeps the polymer from crystallising hard, so where the butyrate is brittle and awkward to melt-process this is soft and tough - the reason it is copolymerised into PHB to make it usable at all.
Poly(3-hydroxyoctanoate)
A medium-chain polyhydroxyalkanoate with a pentyl side chain, long enough that crystallisation is largely suppressed and the polymer is a soft, tacky elastomer with a glass transition well below zero. Pseudomonas makes it from fatty acids or even from waste oils, and the side-chain length simply follows what the organism is fed - a rare case of a polymer's mechanical properties being set by diet.
Hydroxypropyl methylcellulose
Both ethers on the same backbone, which lets the thermal gelation temperature be dialled in: methyl groups drive the gelation, hydroxypropyl groups raise the temperature at which it happens. It is the vegetarian capsule shell, the controlled-release matrix in a great many tablets, and the thickener in eye drops. Not drawn: two substituents at variable ratio on three hydroxyls is a distribution, not a structure.
Hydroxypropylcellulose
A cellulose ether soluble in both cold water and many organic solvents, which is unusual and useful. Its more striking property is optical: at high concentration the stiff chains order into a cholesteric liquid crystal whose pitch lands in the visible, so concentrated solutions and dried films are iridescent and change colour with concentration, temperature or pressure. That makes it a cheap responsive photonic material.
Poly(hydroxyurethane)
A polyurethane made without isocyanate: a five-membered cyclic carbonate opens with an amine to give the urethane directly, and the reaction leaves a hydroxyl behind on the neighbouring carbon. Since the cyclic carbonate itself can be made from carbon dioxide and an epoxide, the route avoids phosgene entirely - which is the whole point, isocyanate manufacture being the most hazardous step in the polyurethane industry.
I
Inulin
A fructose polymer rather than a glucose one, which is why it passes through the small intestine undigested - humans have no enzyme for the beta-2,1 linkage - and is fermented in the colon instead. That makes it the archetypal prebiotic dietary fibre and a fat replacer, since concentrated dispersions form a creamy particulate gel. The internal repeat is drawn; real chains are short and terminate in a glucose, which is a chain end rather than part of the unit. Compare levan, the same sugar joined beta-2,6 instead.
Poly(isophoronylene butylene urethane)
A cycloaliphatic diisocyanate with two very different NCO groups - one on the ring, one on a methylene - which react at different rates and give the staged cure that coatings formulators exploit.
K
Keratan sulfate
The only glycosaminoglycan with no uronic acid - galactose takes its place, so the charge comes from sulfate alone. It is a major side chain on aggrecan alongside chondroitin sulfate, and it dominates the cornea, where the chains are short and regularly spaced enough to keep the collagen fibrils at a uniform separation. That spacing is what makes the cornea transparent. Not drawn: chain length and sulfation vary by tissue.
Poly(ketal)
A backbone that is stable at blood pH and hydrolyses quickly one pH unit lower, which is exactly the drop between the bloodstream and the inside of an endosome. Unlike a polyester it produces no acid as it degrades, so it cannot catalyse its own breakdown or acidify the tissue around it - the recurring complaint against poly(lactide) implants.
Konjac glucomannan
A beta-1,4 chain of mixed glucose and mannose with scattered acetyl groups, and the highest-viscosity natural polysaccharide known - a one percent solution is barely pourable. Removing the acetyls with alkali lets the chains associate into a thermally irreversible gel, which is what turns konjac flour into shirataki noodles. Its bulk and indigestibility make it a satiety agent, with the known hazard that a dry piece can swell in the throat. Not drawn: the sugar sequence and acetylation are irregular.
L
Poly(lactic-co-glycolic acid)
A resorbable polyester copolymer; the lactide:glycolide ratio tunes the degradation rate, which is why it dominates controlled-release implants and sutures.
Poly(lactide-co-caprolactone)
The copolymer that turns two brittle-or-slow homopolymers into an elastomer. Polylactide is stiff and degrades in months, polycaprolactone soft and degrades over years; mixing the units disrupts both crystal lattices, giving a rubbery material that recovers from large strains and resorbs on a tunable schedule - which is what a vascular or nerve scaffold needs. Not drawn: the ratio is the design.
Levan
The other bacterial fructan, differing from inulin only in running beta-2,6 instead of beta-2,1 - a single carbon's difference in where the ring is attached. That one change collapses the chain into a compact sphere rather than an extended coil, so levan solutions stay thin at concentrations where inulin would be a paste, and it is the reason levan behaves as a film-former where inulin behaves as a fibre.
Lignin
The second most abundant biopolymer, the stiffening in wood, and the one nobody has tamed. Three phenylpropanoid alcohols are polymerised by radical coupling that is not enzymatically directed, so the linkages form wherever radicals meet and the result is a randomly crosslinked aromatic network with no repeat unit and no two molecules alike. Vast quantities are produced as a pulping by-product and mostly burned. Not drawn: it has no repeat unit to draw, which is the central fact about it.
Lignosulfonate
The water-soluble lignin, and the reason sulfite pulping has an economic by-product where kraft pulping mostly burns one. Sulfonate groups introduced during the cook make the randomly crosslinked aromatic network disperse in water, giving a cheap polyelectrolyte used by the megatonne as a concrete plasticiser, a dust suppressant and a dye dispersant. Not drawn: lignin has no repeat unit and sulfonation adds another layer of irregularity.
Lipopolysaccharide
The outer leaflet of a Gram-negative bacterium, and the molecule the innate immune system reacts to most violently - nanogram quantities cause fever, which is why every injectable and every implant is tested for it. The repeating O-antigen is what serotyping distinguishes. Undrawn: three chemically distinct regions, only one of which repeats.
Liquid bisphenol A epoxy resin (EEW 185-192)
The undiluted difunctional liquid epoxy resin that most epoxy work starts from, and the other half of the stoichiometry the polyetheramines are sold against: at 188 g/eq against JEFFAMINE D-230's AHEW of 60, 32 parts of amine cure 100 parts of resin. Weight per epoxide is a specification, 185-192 g/eq, not a typical value - the batch-to-batch spread is why the ratio is calculated per lot rather than assumed. Not drawn: at n of about 0.14 the liquid resin is mostly the discrete difunctional molecule rather than a chain with a repeat unit, so there is nothing to bracket.
M
Poly(malic acid)
A water-soluble polyester with a free carboxyl on every repeat - unusual, since most degradable polyesters are hydrophobic and offer nothing to attach to. Those acids are the attachment points for drugs and targeting groups, and the backbone hydrolyses to malic acid, a Krebs cycle intermediate. Produced by moulds, which is how it is obtained in useful quantity.
Poly(malic acid-co-lactide)
Polylactide's problem as a carrier is that it offers nothing to attach a drug to; copolymerising malic acid units in supplies a free carboxyl at a chosen density without changing the degradation chemistry. The ratio therefore sets loading capacity and hydrophilicity independently of the backbone's identity. Not drawn: the composition is the design variable.
Methylcellulose
Cellulose whose hydroxyls are capped as methyl ethers, which breaks the hydrogen bonding that makes cellulose insoluble - so it dissolves in cold water. It then does something almost unique: it gels on HEATING and redissolves on cooling, because warming strips the water sheath from the methyl groups and lets them associate. That inverse behaviour is what stops a fried batter absorbing oil and what firms a plant-based burger as it cooks. Drawn fully methylated; commercial grades are partly substituted.
Poly(methylenedicyclohexylene butylene urethane)
The hydrogenated MDI: same geometry, no aromatic ring, so it keeps the stiffness while losing the ultraviolet yellowing - the basis of light-stable elastomers and coatings.
Poly(methylenediphenylene ethylene urethane)
A short, densely hydrogen-bonded aromatic hard segment; the ethylene glycol chain extender packs the urethane groups closer than butanediol does, raising the hard-segment melting point.
Poly(methylenediphenylene hexamethylene urethane)
A longer chain extender softens the MDI hard segment and drops its melting point, which is how a formulator tunes processing temperature without changing isocyanate.
O
Organosolv lignin
Lignin extracted with hot aqueous ethanol rather than with sulfite or sulfide, so it carries no sulfur and dissolves in ordinary organic solvents - which is what makes it usable as a polymer feedstock rather than as boiler fuel. It is the fraction of lignin closest to its native structure, and the closest thing to a route from wood to aromatic chemicals. Undrawn: a randomly branched network with at least three distinct monomer units.
Poly(ortho ester)
A degradable polymer designed so that its own degradation products do not accelerate the process. Polyesters hydrolyse to carboxylic acids, which catalyse further hydrolysis, so a thick implant degrades from the inside out and can dump its contents - the well-known autocatalysis problem. An ortho ester hydrolyses to neutral products instead, and the linkage is acid-sensitive rather than acid-generating, so erosion stays at the surface and can even be tuned by the pH of the tissue it sits in. Not drawn: the family covers several distinct linkage chemistries.
P
Pectin
The polymer that sets jam, and one that gels by two entirely different mechanisms depending on how much of its acid is esterified. Above about half esterified it needs acid and sugar to gel, by hydrogen bonding and hydrophobic contact; below that it gels with calcium in the egg-box way alginate does. Degree of esterification is therefore the specification, not a detail. Drawn as the fully methylated unit.
Phenol-formaldehyde resin
The first fully synthetic plastic, and the archetype of a thermoset: methylene bridges link phenol rings in every direction until the material is one covalently bonded network that cannot be melted or dissolved again. Two versions exist by design - a novolac made with excess phenol needs a separate hardener, a resole made with excess formaldehyde carries its own. Still the binder in brake pads, foundry sand and circuit-board laminate because it chars instead of dripping. Not drawn: a random network has no repeat unit.
Poly(phenylene butylene urethane)
A rigid, symmetric aromatic hard segment that crystallises far better than MDI, giving elastomers with unusually good high-temperature performance and rebound.
Poly(phenylene ether ketone)
The one-ether member of the ether-ketone family that PEEK belongs to. Raising the ratio of ketone to ether stiffens the chain and pushes both transitions up, so PEK melts higher than PEEK and is correspondingly harder to process - the family is a straight trade of processability against temperature, tuned by how many ethers sit between the ketones.
Poly(phenylene ether)-polystyrene blend
One of the very few genuinely miscible polymer pairs, and the commercial answer to a polymer nobody could process: poly(phenylene ether) has a glass transition near 210 C and degrades before it flows properly. Blending polystyrene in - which mixes at the molecular level, not as domains - drops the glass transition to wherever the ratio puts it, giving a family of engineering plastics from one pair. Not drawn: a miscible blend, not a copolymer.
Poly(phenylene sulfide ketone)
PPS with a ketone inserted between phenylenes, giving a melting point near 350 C against PPS's 285 C. It sits in the gap between commodity PPS and the far more expensive PEEK, and the sulfur retains PPS's near-total resistance to solvents - there is no known solvent for it below 200 C.
Poly(phenylene sulfide sulfone)
Poly(phenylene sulfide) with sulfone groups worked into the backbone, which raises the glass transition by over a hundred degrees and turns a semicrystalline polymer into an amorphous one. The trade is deliberate: PPS's crystallinity gives chemical resistance but limits its use temperature to its glass transition, and this recovers the temperature at the cost of the solvent resistance.
Polyphenylsulfone
Polysulfone with a rigid biphenyl in place of the bisphenol A unit, which removes the isopropylidene bridge that limits the parent's toughness and chemical resistance. The result survives repeated steam autoclaving and aggressive disinfectants without crazing, which is why surgical instrument trays and aircraft interior panels are made from it.
Polyphosphate
A chain of phosphates joined by anhydride bonds - chemically the same linkage ATP stores energy in, extended to hundreds of units. It is found in every cell from bacteria to human platelets, and industrially it sequesters calcium, which is why it is in detergents and processed cheese. Undrawn: a wholly inorganic backbone the structure editor here does not represent.
Poly(phthalazinone ether ketone)
The twisted, non-coplanar phthalazinone unit prevents the chain packing, so this polyaryletherketone is amorphous and soluble in ordinary solvents while still having a glass transition above 260 C - higher than PEEK's. Solubility at that temperature rating is rare enough to be the point. Undrawn pending a repeat unit I can check rather than infer.
Poly(phthalazinone ether sulfone)
A high-temperature poly(ether sulfone) built around a twisted, non-coplanar phthalazinone unit rather than a flat aromatic one. The twist is deliberate: it stops chains packing and crystallising, so the polymer stays amorphous and soluble in ordinary solvents while its glass transition sits above 260 C - unusually, both processable and heat-resistant, which the fully planar aromatics are not. Not drawn: the phthalazinone unit is reported with several attachment patterns and drawing one would assert a regiochemistry the class does not fix.
PIM-1
A polymer that is microporous without being a network: the spiro centre puts a rigid right-angle kink in the chain, so the chains cannot pack and the free volume between them stays open and connected. The result is a soluble, film-forming solid with the surface area of a zeolite, and it reset the upper bound on what a gas separation membrane could achieve. Not drawn: each pair of catechol oxygens closes a dioxin ring onto the nitrile ring, so the chain is a ladder with no two-ended repeat unit.
Poly(propylene adipate)
The odd-carbon diol suppresses crystallinity, giving a polyester diol that stays liquid at room temperature - convenient for handling, at the cost of the strength a crystalline soft segment would add.
Poly(propylene fumarate)
A degradable polyester with a carbon-carbon double bond in the backbone, which is the whole design: the polymer is injected as a viscous liquid and then crosslinked through those alkenes in place, so it sets inside a bone defect and takes its shape. Degradation gives fumaric acid, a normal metabolite.
Poly(propylene furanoate)
A furanoate polyester: the furan ring replaces terephthalic acid, and it comes from sugar rather than from xylene. The ring is kinked where a benzene ring is straight, which is why these pack differently and give the barrier properties that make poly(ethylene furanoate) interesting for bottles.
Poly(propylene sebacate)
The odd diol keeps this amorphous while the long diacid keeps it soft - a liquid polyester diol at room temperature.
Poly(propylene succinate)
A biodegradable polyester whose odd diol leaves it largely amorphous, degrading faster than poly(butylene succinate) for that reason.
Pullulan
A fungal glucan whose linkages alternate in a fixed pattern - two alpha-1,4 bonds then one alpha-1,6, repeating - which is unusual for a polysaccharide and is why it behaves as it does. The regular kink stops it crystallising, so films cast from it are transparent, oxygen-impermeable and dissolve instantly in the mouth: breath strips and capsule shells. Not drawn: the repeat is a trisaccharide with two linkage types, and drawing it flat would lose the alternation that matters.
R
Ribonucleic acid
DNA's less stable relative, and the difference is one hydroxyl: the 2'-OH that ribose carries and deoxyribose does not sits perfectly placed to attack its own phosphate backbone, so RNA hydrolyses in minutes at high pH where DNA lasts. That instability is why it works as a message rather than an archive, and why an mRNA vaccine must be kept cold and its uridines chemically modified. Not drawn: the four bases give four repeat units, and the sequence is the molecule.
Rosin ester
Pine rosin esterified with glycerol or pentaerythritol to raise its softening point and stop it crystallising. Strictly an oligomer rather than a polymer, but it belongs here because it is the tackifier in a large fraction of adhesive formulations and the density modifier in citrus soft drinks. Undrawn: rosin is a mixture of at least half a dozen isomeric diterpene acids.
S
Salicylate polyanhydride
The drug is the polymer. Salicylic acid is built into the backbone rather than dispersed in it, so hydrolysis of the anhydride releases aspirin's active metabolite at a rate set by the chain rather than by diffusion - weeks of steady delivery with no burst release and no inert carrier left behind.
Poly(sebacic anhydride)
The polymer behind implantable chemotherapy wafers, and the clearest case of surface erosion. The anhydride linkage hydrolyses far faster than water can diffuse into the solid, so degradation is confined to the outside and the implant thins from the surface inward rather than falling apart throughout - which means drug release tracks geometry and stays near zero order. A polyester in the same shape would take up water everywhere and dump its payload when the matrix finally collapsed.
Self-assembled DNA bottlebrush
A bottlebrush held together by charge rather than by covalent bonds, built to settle whether a dense corona makes a semiflexible chain behave more like a rod. An engineered protein with a twelve-lysine binding block and a four-hundred-residue random coil sticks along DNA electrostatically, giving a brush about 30 nm thick with roughly one side chain every 2.7 nm of duplex. The corona did stiffen the DNA, but it thickened it more, so the effective aspect ratio fell - confirming the theory that a brush coating only raises aspect ratio for very long side chains at very high density. Liquid crystallinity survived anyway, appearing at 8 mg/mL of DNA, about ten times more dilute than bare DNA, and going hexagonal by 12 mg/mL. The lesson is that lower aspect ratio and easier ordering are not contradictory, because the corona also adds excluded volume. Storm, Kornreich and co-workers (de Vries group, Wageningen), J. Phys. Chem. B 2015.
Shellac
Secreted by the lac insect on trees in India and Thailand, and the only commercial resin of animal origin. It is a polyester of hydroxy fatty acids and sesquiterpene acids, cross-esterified into a network that dissolves in alcohol and sets by evaporation. It coated gramophone records before vinyl, and still coats pharmaceutical tablets and confectionery. Undrawn: the natural mixture has no single repeat unit.
Polysialic acid
A long chain of sialic acid found on the neural cell adhesion molecule during brain development, where its bulk and charge hold cells apart and keep them able to move. Some bacteria coat themselves in the identical polymer, which is why the immune system tolerates them - it cannot distinguish the capsule from self. That same invisibility is why it is used to extend the circulating life of drugs, as an alternative to PEG. Not drawn: the sialic acid unit is a nine-carbon sugar with a variable linkage.
Polysilicate
Silicate tetrahedra condensing into chains, sheets and eventually a three-dimensional gel - the same polymerisation that makes glass, run in water at room temperature. It was among the first inorganic materials understood in polymer terms, and the sol-gel process that follows from it is how most oxide coatings are made. Undrawn: an inorganic network.
Sporopollenin
The outer wall of a pollen grain and among the most chemically inert substances biology makes - it survives concentrated acid, alkali and hundreds of millions of years in sediment, which is why pollen is the palaeobotanist's fossil of choice. Its structure resisted determination until 2019, and is now understood as polyhydroxylated aliphatic units crosslinked by phenolics. Undrawn as a network.
Suberin
The waterproofing polyester of cork and of potato skin, laid down wherever a plant needs a barrier at a wound or a root boundary. Long-chain hydroxy acids esterified through glycerol give the aliphatic domain, and ferulic acid ties that to the lignin beneath. It is more than half of cork by mass and the reason a cork floats and a bottle stays sealed. Undrawn: a crosslinked network of variable chain lengths.
Polysulfide rubber
One of the first synthetic rubbers, and still the sealant in aircraft fuel tanks and insulating glass units. Disulfide links in the backbone give near-total resistance to fuel and solvent and very low gas permeability; they also exchange under stress, so the material creeps and self-heals rather than tearing. It cures by oxidation of thiol end groups, needing no heat. Its odour is famous and is the same chemistry.
Sulfonated poly(ether ether ketone)
PEEK sulfonated on the electron-rich ring between the two ethers, giving a proton-conducting membrane at a fraction of Nafion's cost. The trade is structural: sulfonate too little and it does not conduct, too much and it swells and eventually dissolves in the hot water a fuel cell produces. The usable window is narrow, which is why it has not displaced the perfluorinated membranes. Not drawn: degree of sulfonation is the specification.
Sulfonated polysulfone
The same idea applied to polysulfone, and the standard way of turning a hydrophobic engineering polymer into a charged ultrafiltration membrane. The sulfonates make the pore walls hydrophilic, which is what stops protein fouling - the failure mode that otherwise ends a membrane's life in days. Not drawn: sulfonation is partial and positional.
Polysulfone
A transparent, autoclavable engineering thermoplastic, and the membrane material behind most of the world's haemodialysis. The sulfone group is already fully oxidised, so it resists further oxidation and hydrolysis, and the aromatic backbone holds the glass transition near 185 C - high enough to steam-sterilise repeatedly. Differs from poly(ether sulfone) by the bisphenol A unit, which adds flexibility and lowers the glass transition in exchange for easier processing.
T
TDI-terminated polyether prepolymer (Adiprene L 100)
The other half of every polyurethane in this library: a polyether already capped with toluene diisocyanate, sold by its free isocyanate content rather than by molar mass, and cured to a rubbery solid with a diamine - classically MBCA - to 88-92 Shore A. Available NCO is the whole specification, because it is what the curative is weighed against and it drifts as the drum ages. A range of 3.95-4.30% is a spread of about 8% in equivalent weight, which is why the ratio is recalculated per lot rather than carried over from the last pour. Not drawn: a prepolymer is a polyether block with urethane links and isocyanate ends, not a chain built from one repeating unit, so there is nothing to bracket.
Teichoic acid
The wall polymer of Gram-positive bacteria, and structurally a polyester of phosphoric acid rather than a carbon-backbone polymer: glycerol linked 1,3 through phosphodiester bridges. Every repeat carries a phosphate, so the chain is strongly polyanionic at physiological pH, which is what binds the divalent cations the cell wall depends on and what makes these polymers the dominant surface antigen. The free 2-hydroxyl shown here is where D-alanine and sugar substituents hang in the real material.
Thermotropic liquid crystal polyester
Rigid aromatic esters that stay ordered in the melt, so the chains are already aligned before they enter a mould and need no drawing to develop strength. That gives near-zero shrinkage, the ability to fill wall sections a tenth of a millimetre thick, and a skin far stronger than the core. The same self-alignment makes properties strongly directional, which is a design constraint rather than a defect. Not drawn: a random copolyester whose two-monomer ratio suppresses crystallinity enough to melt at all.
Poly(thioether ketone)
The thioether analogue of a polyetherketone, and of interest because the C-S bond is weaker than C-O and can be broken deliberately: thioether-linked networks exchange bonds at temperature, so a thermoset built this way can be reshaped and reprocessed. That is the vitrimer idea applied to a high-temperature backbone.
Poly(thiourethane)
A urethane in which the alcohol is replaced by a thiol, and the reason high-index spectacle lenses exist. Sulfur is far more polarisable than oxygen, so the refractive index climbs above 1.6 and beyond - a lens can be made thinner for the same prescription. The thiol-isocyanate reaction is also fast and clean enough to cast lenses directly in a mould.
Poly(tolylene butylene urethane)
The flexible-foam workhorse. Toluene diisocyanate is cheaper than MDI and more volatile, which is why its handling is the more hazardous of the two.
Poly(tolylene ethylene urethane)
The shortest chain extender on the cheapest aromatic isocyanate, giving the highest urethane density and the hardest segment of the TDI family.
Poly(trimethylene terephthalate)
The 'odd' methylene count gives a kinked chain and good elastic recovery in fibers.
U
Polyurethane (MDI-butanediol)
The hard segment of a segmented polyurethane, which is the form nearly all polyurethane is used in. Diisocyanate and a short diol give a rigid, strongly hydrogen-bonded block; alternating it with a soft polyester or polyether block gives a material whose hard blocks aggregate into physical crosslinks and whose soft blocks supply the elasticity, so the same two-phase argument as a styrenic thermoplastic elastomer. Changing the soft block from polyether to polyester trades hydrolytic stability for oil resistance. Drawn here as the hard segment alone.
X
Xanthan gum
A cellulose backbone wearing a charged trisaccharide on every second glucose - a natural bottlebrush, and the reason it thickens so strongly. The side chains fold back against the backbone into a rigid helix, giving solutions that are enormously viscous at rest and thin dramatically under shear, then recover instantly. That is what makes salad dressing pourable and drilling mud able to carry rock cuttings. Not drawn: the repeat is a pentasaccharide with variable acetylation and pyruvylation.
Xylan
The main hemicellulose, and cellulose minus one carbon: xylose is glucose without the C6 hydroxymethyl, so the chain cannot form the sheet-stabilising hydrogen bond that cellulose relies on and stays amorphous and extractable. That is why hemicellulose comes out first in any biorefinery, and why xylan is the feedstock for xylitol. In the plant it coats the cellulose fibres and ties them to lignin.