Amphiphilic diblock copolymer nano-objects can be readily prepared using reversible addition-fragmentation chain transfer (RAFT) polymerization. In particular, poly(glycerol monomethacrylate) (PGMA) chain-transfer agents can be chain-extended using 2-hydroxypropyl methacrylate (HPMA) via aqueous dispersion polymerization to form well-defined spheres, worms or vesicles at high solids (= 25%).The worm morphology is of particular interest since inter-worm contacts lead to the formation of soft free-standing thermo-responsive gels. However, the critical gelation temperature (CGT) for such gels is rather low (< 20�C) for biomedical applications. Thus a series of diblock copolymers were prepared in which the core-forming block consisted of a statistical mixture of HPMA and di(ethylene glycol) methyl ether methacrylate (DEGMA), which is a more hydrophilic monomer than HPMA. Statistical copolymerizations proceeded to high conversion and low polydispersities were achieved in all cases (Mw/Mn < 1.20). The resulting PGMA-P(HPMA-stat-DEGMA) diblock copolymers undergo polymerization-induced self-assembly at 10% w/v to form free-standing worm gels. SAXS studies indicate that reversible (de)gelation occurs below the CGT due to a worm-to-sphere transition, with further cooling causing molecular dissolution. The CGT can be tuned by varying the mean degree of polymerization and DEGMA content of the core-forming statistical block. For example, a CGT of 31�C was obtained for PGMA59-P(HPMA91-stat-DEGMA39). This is sufficiently close to physiological temperature to suggest that these new copolymer gels may have biomedical applications as readily-sterilizable scaffolds that allow facile cell harvesting after a thermal cycle.

Thermo-responsive diblock copolymer worm gels with tunable critical gelation temperature

248th National Meeting (2014)

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