About this family
The polymers here are built by joining aromatic rings to each other rather than by adding across a double bond, and the resulting backbone is a chain of rings instead of a chain of sp3 carbons. That makes them stiff, and stiffness is what they have in common. What separates them into two very different technologies is whether the connection between rings preserves conjugation.
Link the rings directly, carbon to carbon, and the p-orbitals overlap continuously along the chain. The result is a delocalised π system running the length of the backbone – a one-dimensional semiconductor, which on oxidation or reduction becomes a conductor. That discovery, on doped polyacetylene, took the 2000 Nobel Prize in Chemistry. Put an oxygen, a sulfur or a sulfone between the rings instead and the conjugation is broken at every linkage: the chain keeps the rigidity and the thermal stability but is an insulator. Those are the high-performance engineering thermoplastics, and they occupy the other half of this page.
What sets the properties
The conducting members share one practical problem: a rigid, planar, strongly interacting backbone is neither soluble nor fusible, and unsubstituted polythiophene or poly(p-phenylene) is an intractable powder. Nearly every processable conjugated polymer in this list is therefore a substituted one, where flexible side chains have been hung off the ring for no electronic reason at all – poly(3-hexylthiophene) is the canonical case, and the alkyl series from butyl to dodecyl here maps how much solubilising chain is needed against how much it dilutes the active material. Poly(3,4-ethylenedioxythiophene) solves the same problem differently, dispersed as a complex with a polyanion to give the transparent conductor used in displays and antistatic coatings. Polyaniline is the outlier: it is switched between insulating and conducting forms by protonation rather than by redox doping, so its conductivity depends on pH.
The non-conjugated half trades that electronic behaviour for temperature. Poly(ether ether ketone) melts at 343 °C with a Tg of 143 °C, and is semicrystalline, so it keeps useful stiffness well above the glass transition – the reason it is machined into aerospace and implant components. Poly(p-phenylene sulfide) melts at 285 °C and crystallises readily. The amorphous members go higher in Tg but have no crystal to fall back on: poly(ether sulfone) reaches 225 °C and poly(2,6-dimethyl-1,4-phenylene oxide) 210 °C, both transparent and both used up to but not beyond that transition. In each case the aryl rings supply the rigidity and the linking heteroatom supplies just enough rotational freedom to let the polymer be processed at all.
All 40 in the library
Sorted by parent name, ignoring the leading "poly" and any locants – so poly(2-hydroxyethyl methacrylate) files under H. 39 of the 40 carry a note, and every one is searchable by drawn structure on the structure search page. 6 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
Polyaniline
The conducting polymer with a switch built in. Unusually, it is doped by acid rather than by oxidation: the half-oxidised emeraldine base is an insulator, protonating the imine nitrogens turns it into the conducting emeraldine salt, and base switches it back, with a colour change each way. That makes it a sensor as much as a conductor. The drawn repeat is the reduced amine unit; a real chain is a mixture of amine and imine units whose ratio is the oxidation state, so treat the structure as one component of a variable material.
Poly(anthracene)
Three linearly fused rings in the backbone, and the classic photodimerising unit: two anthracenes facing each other join across the 9,10 positions under ultraviolet light and come apart again on heating or at shorter wavelength. That makes it a reversible crosslink driven purely by light, with no initiator and no byproduct.
B
Poly(benzodithiophene)
A benzene with a thiophene fused on each side, symmetric and rigidly planar, and the single most common electron-rich unit in high-performance organic solar cells - the donor half of PTB7, PM6 and most of what followed. Its virtue is dullness: it contributes a flat, well-behaved, deep-lying orbital and lets the acceptor unit do the tuning.
Poly(benzothiadiazole-alt-thiophene)
The archetype of the donor-acceptor design: an electron-rich thiophene alternating with electron-poor benzothiadiazole gives a band gap neither unit has alone, because the occupied level sits on one and the empty level on the other. Nearly every low-band-gap polymer since has been a variation on this pairing.
Poly(3-butylthiophene)
The shortest 3-alkylthiophene that dissolves usefully. Being shorter than hexyl it packs the backbones closer together, which raises interchain transport, but it also crystallises so readily from solution that film morphology becomes hard to control - which is the practical reason hexyl rather than butyl became the standard.
C
Poly(2,7-carbazole)
Fluorene's nitrogen analogue, and the substitution that fixes fluorene's known defect. Where polyfluorene's bridging carbon oxidises to a fluorenone and turns the blue emission green over time, carbazole's bridging nitrogen simply carries the solubilising alkyl chain and cannot oxidise the same way, so the emission colour is stable.
Poly(cyclopentadithiophene)
Two thiophenes bridged by a single carbon that carries the solubilising chains, so the alkyl groups point away from the plane instead of forcing the rings apart. The backbone stays flat, the band gap narrows, and the polymer absorbs deep into the near infrared - which is what a solar cell needs and a plain polythiophene cannot do.
D
Poly(9,9-dihexylfluorene)
The shorter-chain member of the polyfluorene family, and more prone than the dioctyl version to forming the beta phase - a planarised chain conformation with a distinctly red-shifted, narrower emission. That phase can be induced deliberately by solvent vapour or thermal cycling, which makes it a way to tune emission colour without changing the molecule.
Poly(diketopyrrolopyrrole)
The pigment in Ferrari red, repurposed as a semiconductor. The fused bislactam core is a strong acceptor and its flanking thiophenes lock flat by hydrogen bonding to the carbonyls, giving the highest charge mobilities recorded in any polymer - above ten square centimetres per volt second, which is amorphous silicon's territory.
Poly(2,6-dimethyl-1,4-phenylene oxide)
Oxidative-coupling polymer; usually blended with polystyrene (Noryl).
Polydimethylsilane
A backbone of silicon atoms and nothing else - no oxygen, unlike a siloxane. Sigma bonds between silicon atoms delocalise along the chain, so a polysilane absorbs in the ultraviolet and conducts charge in a way no ordinary saturated polymer does, a phenomenon called sigma conjugation. Its main industrial use is as the precursor that is pyrolysed to silicon carbide fibre. Do not confuse with poly(dimethylsiloxane), which has oxygen in the backbone and is the ordinary silicone.
Poly(9,9-dioctylfluorene)
The blue emitter of the polymer LED family. Two benzene rings locked coplanar by a bridging carbon give a wide band gap and efficient blue fluorescence, and that bridging carbon is quaternary, so the two octyl chains hang off it without twisting the conjugated system - solubility bought at no optical cost, which is rare. Its known failure is a green emission band that grows with use, traced to oxidation at the bridge to a fluorenone.
Poly(dithienosilole)
The same bridged bithiophene with silicon at the bridge instead of carbon. Silicon's empty d-orbitals mix with the ring system and pull the lowest unoccupied level down, narrowing the gap further than a carbon bridge can, and the longer Si-C bonds relieve strain enough that the film crystallises better. A single atom substitution worth about 0.2 eV.
Poly(3-dodecylthiophene)
The long end of the 3-alkylthiophene series, where the side chains are long enough to crystallise among themselves and push the conjugated backbones far apart. Solubility is excellent and charge mobility poor, which completes the trend the family demonstrates: the alkyl chain that makes the polymer usable is also what dilutes the property it was made for.
E
Poly(ether ether ketone)
High-performance semicrystalline thermoplastic; three aryl rings per repeat.
Poly(ether sulfone)
Amorphous, transparent high-temperature thermoplastic; the sulfone group stiffens the chain.
Poly(ethylene disulfide)
A Thiokol-type polysulfide rubber; the S-S linkages give the solvent and weathering resistance used in sealants. The repeat unit is drawn disulfide-centered (-CH2-S-S-CH2-).
Poly(3,4-ethylenedioxypyrrole)
PEDOT's nitrogen analogue, with the same dioxyethylene bridge blocking the reactive positions. The pyrrole nitrogen is more electron-rich than thiophene's sulfur, so it oxidises at a lower potential and the neutral form is transparent rather than blue - which makes it the complementary colour to PEDOT in an electrochromic device that needs to switch between two states rather than to clear.
Poly(3,4-ethylenedioxythiophene)
The conducting polymer that actually ships, in touchscreens, antistatic films and organic solar cells. Bridging the 3 and 4 positions with a dioxyethylene ring does two things at once: it blocks those positions so the chain cannot branch there, and it pushes electron density into the ring so the doped state is stable in air. It is intractable by itself, so it is sold dispersed with poly(styrene sulfonate), which acts as the counter-ion and carries it into water - the familiar PEDOT:PSS is that pair, not one polymer.
F
Polyfuran
The oxygen member of the five-membered heterocycle set that includes polythiophene and polypyrrole, and the least useful of the three: oxygen is small and electronegative enough that the ring is easily over-oxidised during polymerisation, so the chains end up short and defective. Its interest is that furan comes from sugars rather than oil.
G
Polygermane
The germanium analogue of a polysilane, with the same sigma-conjugation along a chain of group 14 atoms but with electrons more loosely held - so the absorption sits further to the red and the photoconductivity is higher. Descending the group from silicon to germanium to tin shifts the optical gap systematically, which is what makes the series worth studying. Not drawn: germanium is outside the element set.
H
Poly(3-hexylselenophene)
The selenium analogue of P3HT. Swapping sulfur for selenium narrows the band gap by about 0.2 eV and extends absorption further into the red, because the larger, more polarisable chalcogen raises the energy of the highest occupied level. The trade is a lower ionisation potential and correspondingly poorer stability in air.
Poly(3-hexylthiophene)
The workhorse of organic electronics, and a lesson in why regiochemistry matters more than molar mass. A hexyl chain on every third position makes polythiophene soluble in chloroform without breaking the conjugation - but only if the rings are joined head-to-tail. Head-to-head junctions put two hexyls side by side, the rings twist out of plane to avoid each other, and the conjugation and the mobility collapse. Regioregular material stacks into ordered lamellae and carries charge along and between chains; the same polymer made carelessly is an insulator by comparison.
I
Poly(isoindigo)
Built on a dye related to indigo, and strongly electron-accepting because of the two lactam carbonyls pointing outward from the central double bond. Isoindigo copolymers give ambipolar transistors - electrons and holes move about equally well - which is rare and useful, and the starting material is cheap in a field where most acceptors are not.
M
Poly(3-methylthiophene)
The shortest substituent that still blocks the 3-position, and it shows what the alkyl chain is actually for. A methyl stops branching at that carbon, which raises conductivity well above unsubstituted polythiophene, but it is far too short to confer solubility - so the polymer is still intractable. Everything longer is a compromise between processability and how far apart the chains end up.
O
Poly(3-octylthiophene)
P3HT with two more carbons on the side chain, which is enough to change the solid state: longer chains push the polymer backbones further apart, lowering the interchain charge transport that P3HT depends on. The alkyl length is a design variable trading solubility against mobility, and hexyl is where the field settled.
P
Poly(phenylene ethynylene vinylene)
Alternating triple and double bonds between phenylenes, which fixes the two failings of its parents: the pure ethynylene polymer is too rigid to process and the pure vinylene too easily oxidised. The mixed backbone keeps the rod-like shape and the bright emission while remaining soluble.
Poly(phenylene ethynylene)
Rings joined by triple bonds, which cannot twist the way a single bond can, so the backbone is rigid and the conjugation is uninterrupted along its length. That rigidity makes the fluorescence exceptionally bright and, more usefully, exceptionally quenchable: one bound analyte molecule can quench an entire chain, giving the amplified response behind trace-vapour sensors.
Poly(p-phenylene sulfide)
Poly(p-phenylene)
Nothing but benzene rings joined para. Rigid, conjugated and extraordinarily stable thermally, and correspondingly impossible to dissolve or melt - the reason it is usually met as a building block inside a copolymer or with solubilising side chains rather than on its own. Its stiffness is the structural argument behind the aramids and the polyphenylenes generally.
Poly(3,4-propylenedioxythiophene)
PEDOT with a seven-membered bridging ring instead of six, which sounds trivial and changes the application. The larger ring holds the chains further apart, so ions move in and out of the film far faster - and that switching speed, plus a much larger change in transmittance between oxidation states, is what makes ProDOT rather than PEDOT the electrochromic polymer for smart windows and displays.
Polypyrrole
The conducting polymer that can be grown straight onto an electrode. Pyrrole oxidises at an accessible potential in water, so a film deposits electrochemically wherever the current flows, at whatever thickness the charge passed dictates - no solution processing, and patterning comes free from the electrode shape. It is stable in air and reasonably biocompatible, which is why it turns up on neural electrodes and biosensors more than in bulk electronics.
S
Polyselenophene
Polythiophene with selenium in place of sulfur. The larger, more polarisable atom narrows the band gap by roughly 0.3 eV and strengthens the interchain contacts, pushing absorption further into the red - which is why selenophenes appear in solar cell polymers designed to harvest the part of the spectrum thiophenes miss.
Poly(spirobifluorene)
Two fluorenes sharing one tetrahedral carbon, so the two halves sit at right angles. That single geometric fact solves polyfluorene's worst problem: the chains cannot stack into the aggregates that turn blue emission green over a device's lifetime. The glass transition also rises above 200 C, so the film does not reorganise in service.
Polystannane
A backbone of nothing but tin atoms. Sigma bonds between heavy main-group elements delocalise almost like a pi system, so this is a one-dimensional semiconductor built from single bonds - it absorbs in the visible and conducts when doped. It is also photosensitive to the point of being difficult to handle, which is where the interest in it as a resist comes from.
T
Poly(thiazole)
Thiophene with one carbon replaced by nitrogen, which lowers both frontier orbitals without disturbing the ring geometry - the cheapest way to turn a donor into an acceptor. The nitrogen also accepts a hydrogen bond, so thiazole polymers pack more tightly than their thiophene counterparts and are correspondingly harder to dissolve.
Polythiophene
The parent of the most useful family of conducting polymers. Sulfur in the ring stabilises the conjugated backbone against the oxidation that destroys polyacetylene, so the material survives in air, and the 2,5-linkage keeps the rings coplanar enough for the electrons to delocalise. Unsubstituted polythiophene is still intractable; the whole point of the alkyl-substituted versions is to keep this backbone and make it dissolve.
Poly(thiophene-3-acetic acid)
A conjugated backbone made water-soluble by hanging a carboxylic acid off each ring, so it can be processed from water and used in contact with biology. Binding anything to those acids twists the backbone and shifts its colour and emission, which turns the polymer itself into the transducer - the principle behind conjugated-polymer biosensors.
Poly(triarylamine)
The standard hole-transport polymer, amorphous by design. The nitrogen's lone pair makes each unit easy to oxidise, so positive charge hops readily between them, while the propeller-shaped triarylamine refuses to crystallise - which matters because grain boundaries in a crystalline transport layer trap charge. It is the hole layer in most perovskite solar cells.
Poly(triptycene)
Triptycene is three benzene rings locked at 120 degrees around a common axis, so it sweeps out a volume no neighbouring chain can enter. Built into a conjugated backbone it prevents the chain stacking that quenches fluorescence, which is why the amplifying fluorescent polymers used in trace vapour detection are built on it - one bound molecule quenches an entire chain's worth of excitation.