About this family
Almost all pairs of polymers are immiscible. Blend two of them and they separate into domains large enough to see, and the blend is weak at every interface. Join the same two chemistries end to end with a covalent bond and they still try to separate – but a junction point cannot travel, so the separation can only run as far as the length of a single chain. What would have been a macroscopic phase split becomes microphase separation, into domains of ten to a hundred nanometres.
That constraint is the whole subject. A block copolymer gives you both chemistries in one material, at a domain size set by molecular weight and a morphology set by composition, arranged periodically without anyone having to pattern it.
What sets the properties
Which morphology you get is governed by the volume fraction of the blocks: a small minority block forms spheres in a matrix of the major block, a larger one forms hexagonally packed cylinders, and a roughly equal split gives alternating lamellae, with the gyroid appearing in between. Whether the material orders at all is governed by the product of the interaction parameter and the degree of polymerisation – strongly incompatible blocks separate at low molecular weight, marginally incompatible ones need long chains or will simply mix.
The engineering payoff is clearest in the thermoplastic elastomers. In a glassy–rubbery–glassy triblock such as styrene–butadiene–styrene, the polystyrene end blocks collect into hard domains that anchor both ends of every rubbery midblock, so the material behaves as a crosslinked elastomer at room temperature. The difference from a vulcanised rubber is that these crosslinks are physical: heat the material above the polystyrene glass transition and the domains soften, the network dissolves, and it flows and can be moulded or recycled. Cool it and the network reassembles. The segmented polyurethanes reach the same end by a different architecture, with hard segments that hydrogen-bond rather than vitrify.
In solution the same immiscibility drives self-assembly. An amphiphilic block copolymer in water buries its insoluble block and forms micelles, worms or vesicles depending on the same volume-fraction argument, which is the basis of most polymeric drug carriers here. The Pluronic-type PEO–PPO–PEO triblocks add a temperature axis: the propylene oxide block becomes less soluble as it warms, so these solutions gel on heating and liquefy on cooling, the reverse of an ordinary gel.
All 29 in the library
Sorted by parent name, ignoring the leading "poly" and any locants – so poly(2-hydroxyethyl methacrylate) files under H. 29 of the 29 carry a note, and every one is searchable by drawn structure on the structure search page. 3 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.
B
Polybutadiene-b-poly(ethylene oxide)
The reference amphiphile for polymersomes, where the aggregate shape follows the hydrophilic weight fraction rather than the chemistry: near 0.35 it forms bilayer vesicles, 0.40-0.50 gives wormlike micelles and Y-junction networks, and above about 0.55 curvature forces spheres. The membranes are an order of magnitude tougher and far less permeable than a phospholipid bilayer, and the residual backbone double bonds are a convenient handle for crosslinking after assembly. Note the polymersome-grade material is 1,2-rich polybutadiene made anionically, not the stereoregular cis-1,4 linked here: the block Tg differs by roughly 70 C between the two microstructures, so do not carry the cis-1,4 value across.
Poly(butylene terephthalate)-b-poly(tetrahydrofuran)
The polyester counterpart of polyether block amide, and the other half of the segmented-TPE pair: crystalline PBT hard segments form lamellae that act as both physical crosslinks and reinforcing filler on a rubbery poly(tetramethylene oxide) matrix, adding the tear strength, creep resistance and hot-oil resistance the styrenic triblocks lack. Modulus and service temperature scale almost linearly with hard-segment weight fraction, which is what separates the grades. Like PEBA it is a segmented (AB)n multiblock from melt transesterification, with statistical segment lengths rather than a discrete ABA architecture.
C
Poly(caprolactone)-b-poly(lactide)
A fully resorbable diblock pairing a soft, slowly hydrolysing PCL block with a stiff, faster-degrading polylactide block; the ABA triblock form is the one that behaves as a resorbable thermoplastic elastomer, since a diblock forms no physical network. A useful diagnostic: sequential ring-opening polymerisation is prone to transesterification, and a single intermediate Tg in place of the two block transitions means the product has been scrambled into an effectively random copolymer.
D
Poly(dimethylsiloxane)-b-poly(ethylene oxide)
The siloxane block sits near 20 mN/m, so the surface-energy gap across the junction drives the molecule to any interface and pulls surface tension below what a hydrocarbon surfactant can reach. Silicone polyethers are the cell stabilisers of polyurethane foam: they emulsify the reacting mix, nucleate bubbles, and hold the draining cell walls open by the Gibbs-Marangoni effect until gelation. Worth knowing which architecture you have - most commercial foam stabiliser tonnage is a graft or rake copolymer with polyether combs hung off a siloxane backbone, and the genuinely linear AB and ABA grades described here are a smaller, separately patented class.
Poly(dimethylsiloxane)-b-poly(methyl methacrylate)
The same silicon-versus-organic etch contrast as PS-b-PDMS with a polar organic block, which changes the surface-energy balance and the selective solvents available. The two blocks are about as far apart in glass transition as any pair here - PDMS near -125 C against PMMA near 105 C - so the material is a rubbery phase and a glassy phase side by side at room temperature.
E
Polyether block amide
A thermoplastic elastomer in which crystalline polyamide-12 hard segments provide the physical crosslinks and poly(tetramethylene oxide) soft segments provide the elasticity, with stiffness dialled across a wide range purely by the hard:soft ratio. Unlike the styrenic triblocks this is a segmented multiblock made by melt polycondensation of dicarboxyl-terminated PA12 with polyether diol, so segment lengths are statistical and the chain is -(hard-soft)n- rather than a discrete ABA. Used for ski boots, running-shoe plates and catheter tubing.
Poly(2-ethyl-2-oxazoline)-b-poly(caprolactone)
A PEG alternative: poly(2-ethyl-2-oxazoline) is a water-soluble, low-fouling pseudo-polypeptide made by living cationic ring-opening polymerisation, and it is cleared renally rather than degraded, so only the PCL block of this micelle is resorbable. Reported paclitaxel loadings are modest (roughly 0.5-8 wt%); the much higher loadings quoted for polyoxazoline micelles belong to the hydrophobic-core PMeOx-b-PBuOx-b-PMeOx triblocks, not to this one.
Poly(ethylene oxide)-b-poly(acrylic acid)
Double-hydrophilic rather than amphiphilic: both blocks dissolve, so nothing assembles until assembly is triggered by pH, by multivalent cations, or by an oppositely charged polyion, whereupon the neutralised polyacid collapses into a core under a stabilising PEO corona. Those polyion complex micelles are the standard vehicle for carrying polycations, proteins and nucleic acids behind a stealth shell. The same free polyanion block chelates calcium and adsorbs onto growing mineral faces while the tethered PEO gives steric stabilisation, which is why it works as a scale and crystal-growth inhibitor at single-digit ppm and as a pigment dispersant.
Poly(ethylene oxide)-b-poly(caprolactone)
The rubbery, semicrystalline PCL core takes higher drug loadings than a glassy polyester core such as PDLLA, and degrades over months to years without the acid-autocatalysed burst that PLGA depots show. Both blocks crystallise and both have a glass transition near -60 C, so the amorphous fraction is small and the Tg step is often not detectable at all in bulk DSC - the melting endotherms, not the glass transitions, are what the trace shows.
Poly(ethylene oxide)-b-poly(lactide)
A hydrophobic polylactide core solubilises a water-insoluble drug while the PEG corona provides steric stealth and colloidal stability, and the ester backbone hydrolyses to lactic acid. Genexol-PM is the clinical proof: mPEG 2000-b-poly(D,L-lactide) 1750 micelles about 24 nm across carrying paclitaxel with no Cremophor EL, which raised the maximum tolerated dose to 390 from 175 mg/m2 for Taxol.
Poly(ethylene oxide)-b-poly(lactide-co-glycolide)
Adds a tunable degradation clock to the PEG-b-PLA idea: the glycolide fraction sets the hydrolysis rate of the hydrophobic block, fastest near a 50:50 lactide:glycolide ratio and slower in either direction as the block becomes more crystalline. Note the hydrophobic block is itself a random lactide/glycolide copolymer, so this is a two-block architecture whose second block is statistical - the components list names its monomers, not three discrete blocks.
Poly(ethylene oxide-b-propylene oxide)
A PEO-PPO-PEO triblock surfactant. The hydrophilic PEO and hydrophobic PPO blocks drive micellization and gelation, used in drug delivery and as a nonionic surfactant.
I
Poly(N-isopropylacrylamide)-b-poly(ethylene oxide)
Double-hydrophilic below about 32 C, where both blocks are hydrated, and amphiphilic above it, where the PNIPAM block dehydrates and collapses into a core while the PEO block keeps the particle colloidally stable - the reason this micellises reversibly on warming where PNIPAM homopolymer simply precipitates. The 32 C transition is a solution cloud point (LCST), not a glass transition, and will not appear on a dry DSC scan.
L
Poly(lactide)-b-poly(ethylene oxide)-b-poly(lactide)
An injectable depot that needs no crosslinker: cold, it is a free-flowing sol, and on warming toward body temperature the polylactide end-blocks dehydrate and aggregate, each chain bridging between micellar junctions into a percolated gel. Release is then governed jointly by diffusion and by hydrolysis of the polylactide junctions. The sol-gel window is very sensitive to the PEG block length and the lactide:ethylene oxide ratio, so small compositional changes move it out of the useful range. Distinct from the PLGA-PEG-PLGA thermogel sold as ReGel, and from the inverted PEG-PLLA-PEG triblock of the original 1997 report.
Poly(lactide-co-glycolide)-b-poly(ethylene oxide)-b-poly(lactide-co-glycolide)
A reverse-thermal-gelling ABA triblock: soluble in cold water at roughly 15-23 wt% and gelling as it warms to body temperature, so a drug is mixed into the cold sol and the depot forms in situ after injection. Marketed as ReGel, and as OncoGel with paclitaxel at 6 mg/mL. Both end blocks are random lactide/glycolide copolymers, and the components list cannot express the ABA ordering that makes the gel work.
M
Poly(methyl methacrylate)-b-poly(butyl acrylate)
The diblock half of the MAM system and a standard demonstration polymer for controlled radical polymerisation, since both monomers are radically polymerisable and the second block can be grown straight from a macroinitiator. Widely used as a compatibiliser and as a model for acrylic microphase separation; as a diblock it is not itself an elastomer.
Poly(methyl methacrylate)-b-poly(butyl acrylate)-b-poly(methyl methacrylate)
The all-acrylic answer to SBS: glassy PMMA end-blocks pin both ends of a rubbery poly(n-butyl acrylate) mid-block into a physical network, but with no backbone unsaturation, so it keeps the weatherability and clarity that the styrenic dienes lack. Made industrially by nitroxide-mediated controlled radical polymerisation rather than anionically, and sold as Arkema Nanostrength for toughening epoxies and acrylics, where it self-assembles into nanodomains inside the cured matrix.
S
Polystyrene-b-poly(2-vinylpyridine)
High chi relative to PS-b-PMMA, so it reaches smaller domains, and the pyridine nitrogen binds metal salts - the basis of block-copolymer micelle nanolithography, where reverse micelles loaded with a gold precursor are deposited as a monolayer and plasma-treated to leave a hexagonal array of gold nanodots with controllable spacing (Spatz and Moeller). The two block Tg values are close, so microphase separation is established by scattering and microscopy rather than by DSC.
Polystyrene-b-poly(4-vinylpyridine)
The 4-substituted pyridine is the less hindered, stronger hydrogen-bond acceptor, which makes this the classic supramolecular comb-shaped scaffold: small amphiphiles such as 3-n-pentadecylphenol hydrogen-bond to the P4VP block and generate a second, finer length scale inside the block-copolymer morphology - structure within structure (Ikkala and ten Brinke). Also widely used as a nanoporous membrane template, since the P4VP domains swell and open in acid.
Polystyrene-b-poly(acrylic acid)
The crew-cut micelle system: with a long insoluble PS block and a short PAA corona, shrinking the corona walks the aggregate through spheres, rods, bicontinuous structures, lamellae, vesicles and large compound micelles, so morphology becomes a formulation variable rather than a fixed property (Zhang and Eisenberg). Usually made by hydrolysing poly(styrene-b-tert-butyl acrylate) rather than by direct copolymerisation, so any styrene/acrylic-acid registry number describes a different material.
Polystyrene-b-poly(dimethylsiloxane)
A high-chi block copolymer, so it microphase-separates to much smaller domains than PS-b-PMMA and reaches sub-10 nm features. The silicon content is the other half of its appeal: an oxygen plasma converts the PDMS domains to a silica-like oxide while burning the organic block away, giving an etch contrast far larger than any all-organic pair. The cost is a large surface-energy mismatch, so the film needs a top coat or a neutral layer to orient the domains.
Polystyrene-b-poly(ethylene oxide)
A classic amphiphilic block copolymer: a hydrophobic polystyrene block and a hydrophilic PEO block. It self-assembles into micelles and ordered nanostructures, and is a model system for block-copolymer phase behavior.
Polystyrene-b-poly(methyl methacrylate)
The workhorse of directed self-assembly lithography. PS and PMMA have nearly identical surface energies at annealing temperature, so neither block preferentially wets the free surface and the lamellae stand perpendicular to the substrate without a top coat - the geometry a patterning process needs. PMMA is then selectively removed by UV or acetic acid, leaving PS as an etch mask. The same low chi that matches the surface energies also caps resolution, plateauing near 11-12 nm half-pitch.
Polystyrene-b-poly(tert-butyl acrylate)
Chiefly a protected precursor: the tert-butyl ester is polymerised cleanly by anionic or controlled-radical methods where acrylic acid itself is not, then removed thermally or with acid to give poly(styrene-b-acrylic acid) with the block lengths set before deprotection. Useful in its own right as a well-defined amorphous diblock, both blocks glassy at room temperature.
Polystyrene-b-polybutadiene
The diblock counterpart of SBS and one of the model systems for block-copolymer phase behaviour, where the volume fraction of one block selects spheres, cylinders, gyroid or lamellae. Unlike SBS it is not an elastomer: with only one junction the rubbery chain has a free end and no load-bearing network forms, which is precisely why the commercial thermoplastic elastomer is the ABA triblock.
Polystyrene-b-polybutadiene-b-polystyrene
Glassy polystyrene end-blocks phase-separate into domains that act as physical, thermally reversible crosslinks, tying both ends of the rubbery polybutadiene mid-block into a network: rubber elasticity without vulcanisation, and melt processability above the PS Tg. Reinforcement fades from about 60-70 C, well below the PS domain Tg, which sets the service ceiling near 80 C. Commercial grades run 25-40 wt% styrene; the base polymer for hot-melt adhesives, bitumen modification and footwear.
Polystyrene-b-polyisobutylene-b-polystyrene
The saturated answer to SBS: glassy polystyrene end-blocks pin a rubbery polyisobutylene mid-block into a physically crosslinked network, but with no backbone unsaturation to oxidise or crosslink, so it survives as a permanent implant coating where SBS or SIS would degrade. It is the drug-carrier matrix of the TAXUS paclitaxel-eluting coronary stent, releasing by diffusion from a non-degradable film rather than by erosion, and the dense PIB packing also makes it an excellent gas barrier. Textbook product of living cationic polymerisation by sequential monomer addition, a chemistry few block copolymers come from.
Polystyrene-b-polyisoprene
The system the classical diblock phase diagram was mapped on (Khandpur et al., Macromolecules 1995, 28, 8796): composition, not chemistry, selects the morphology, and the same sequence of spheres, cylinders, gyroid and lamellae recurs in every strongly segregated diblock. Like PS-b-PB it is not an elastomer - a diblock leaves one rubber chain end free and forms no network.
Polystyrene-b-polyisoprene-b-polystyrene
The same physical-crosslink mechanism as SBS, but the isoprene mid-block gives a softer, tackier rubber phase that accepts tackifying resin readily, which is why SIS rather than SBS dominates pressure-sensitive adhesives. Styrene contents are lower than in SBS (typically 14-22 wt%), keeping the PS domains discrete spheres. Isoprene differs from butadiene by a methyl substituent, not an extra double bond; both dienes carry one C=C per 1,4 repeat unit.