Synthesis and Characterization of Biocompatible Thermo-Responsive Gelators Based on ABA Triblock Copolymers

Li, Chengming; Tang, Yiqing; Armes, Steven P.; Morris, Christopher J.; Rose, S. F.; Lloyd, Andrew W.; Lewis, Andrew L.

doi:10.1021/bm049331k

Cited by 161 publications

(162 citation statements)

References 25 publications

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“…Recently, stimulus-responsive polymer gels have become an important area of research, with thermo-, [1][2][3][4] pH-, 4,5 redox- 6 and light-responsive 7 examples being reported in the literature. There are two main classes of polymer gels.…”

Section: Introductionmentioning

confidence: 99%

Tuning the critical gelation temperature of thermo-responsive diblock copolymer worm gels

et al. 2014

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Abstract. Amphiphilic diblock copolymer nano-objects can be readily prepared using reversible addition-fragmentation chain transfer (RAFT) polymerization. For example, poly(glycerol monomethacrylate) (PGMA) chain transfer agents (CTA) can be chain-extended using 2-hydroxypropyl methacrylate (HPMA) via RAFT aqueous dispersion polymerization to form welldefined spheres, worms or vesicles at up to 25% solids. The worm morphology is of particular interest, since multiple inter-worm contacts lead to the formation of soft free-standing gels, which undergo reversible degelation on cooling to sub-ambient temperatures. However, the critical gelation temperature (CGT) for such thermo-responsive gels is < 20C, which is relatively low for certain biomedical applications. In this work, a series of new amphiphilic diblock copolymers are prepared in which the core-forming block comprises 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/w solids to form free-standing worm gels. SAXS studies indicate that reversible (de)gelation occurs below the CGT as a result of a worm-to-sphere transition, with further cooling to 5 °C affording weakly interacting copolymer chains with a mean aggregation number of approximately four. This corresponds to almost molecular dissolution of the copolymer spheres. The CGT can be readily tuned by varying the mean degree of polymerization and the 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 (37°C) to suggest that these new copolymer gels may offer biomedical applications as readily-sterilizable scaffolds for mammalian cells, since facile cell harvesting can be achieved after a single thermal cycle.

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Section: Introductionmentioning

confidence: 99%

Tuning the critical gelation temperature of thermo-responsive diblock copolymer worm gels

et al. 2014

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“…This BAB triblock copolymer forms a network of bridged flower-like micelles above 32 °C at a concentration as low as 5 wt%. 72 The same polymer was also synthesized with a biodegradable unit inside the A block. The resulting gel formed under physiological conditions at 37 °C and could be turned into a free-flowing liquid through the addition of glutathione, which cleaved the disulfide bond introduced into the central A block.…”

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confidence: 99%

Smart hydrogels based on responsive star-block copolymers

Schmalz

Müller

2012

Soft Matter

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“…[18,19] Quite importantly, although less extensively studied, higher levels of organization can be observed, that is, assembly into clusters, networks, and gels. Stimulus-triggered aggregation of micelles has been reported for ABA triblock copolymers in a solvent selective for the B block, [9,[20][21][22][23][24] with special attention paid to the well-known polyoxyalkylene-type ABA copolymers (mainly Pluronics). [9,20,21] Among other responsive systems, Armes and coworkers synthesized biocompatible ABA triblocks, where A is poly(N-isopropylacrylamide) and B is poly(2-methacryloyloxyethyl phosphorylcholine).…”

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Fast Multiresponsive Micellar Gels from a Smart ABC Triblock Copolymer

et al. 2007

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Self-assembly of block copolymers in a solvent selective for one block is at the origin of unique behaviors of micellar particles, such as stimuli responsiveness. [1][2][3][4] ABC triblock copolymers are very versatile precursors of micelles, whose internal structure is dictated by the constitutive blocks and their sequential arrangement. Accordingly, smart materials can be contemplated, including multiresponsive ones. Herein, we report on pH-and temperature-sensitive gels formed by an amphiphilic ABC triblock copolymer, polystyrene-bpoly(2-vinylpyridine)-b-poly(ethylene oxide). The selfassembly of this copolymer into core-shell-corona (CSC) micelles [5,6] is observed in N,N-dimethylformamide upon addition of water. The micellar solution forms a soft gel at a lower threshold copolymer concentration (8 wt %) than other systems. [7][8][9] This soft gel is reversibly converted into an optically clear hard gel by merely decreasing the pH value or increasing the temperature. The ordered packing of the CSC micelles and the fast response to pH value were investigated by small-angle neutron scattering (SANS) and rheological measurements.Block copolymers consist of two or more chemically different polymer chains covalently bonded at their chain ends to form one single linear macromolecule.[10] The freeenergy-driven micellization of these copolymers takes place in a selective solvent, that is, a nonsolvent for one block and a good solvent for another. This self-association phenomenon is based on the phase separation of the insoluble blocks, which is, however, restricted to the nanometric scale by a surrounding shell of soluble blocks. Depending on the nature, length, and number of constitutive blocks and their interaction with the solvent, a variety of nanoobjects can be formed in dilute solutions, ranging from typical core-shell nanospheres [11][12][13] to cylinders, [12,14] vesicles, [12,15,16] and tubules, [16] as well as multilayered (onion), [5,17] non-centrosymmetric ("Janus"), and segregated structures. [18,19] Quite importantly, although less extensively studied, higher levels of organization can be observed, that is, assembly into clusters, networks, and gels. Stimulus-triggered aggregation of micelles has been reported for ABA triblock copolymers in a solvent selective for the B block, [9,[20][21][22][23][24] with special attention paid to the well-known polyoxyalkylene-type ABA copolymers (mainly Pluronics). [9,20,21] Among other responsive systems, Armes and coworkers synthesized biocompatible ABA triblocks, where A is poly(N-isopropylacrylamide) and B is poly(2-methacryloyloxyethyl phosphorylcholine).[24] Because of the thermosensitivity of the outer A blocks, micellization and ultimately gelation occurred above a lower critical solution temperature (LCST) of 37 8C. In recent years, increasing attention was paid to sol-to-gel transitions exhibited by multitalented ABC terpolymers. In addition to the synthesis of several isomers of a triblock terpolymer (ABC, BAC, and ACB) by Patrickios and co-workers that were...

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Synthesis and Characterization of Biocompatible Thermo-Responsive Gelators Based on ABA Triblock Copolymers

Cited by 161 publications

References 25 publications

Tuning the critical gelation temperature of thermo-responsive diblock copolymer worm gels

Tuning the critical gelation temperature of thermo-responsive diblock copolymer worm gels

Smart hydrogels based on responsive star-block copolymers

Fast Multiresponsive Micellar Gels from a Smart ABC Triblock Copolymer

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