Low concentration thermoresponsive hydrogels from readily accessible triblock copolymers

Dilute (<1 wt%) aqueous solutions of ultrahigh molecular weight triblock copolymers (with M-n up to 500 000 g mol(-1)) comprising a long central hydrophilic block of polydimethylacrylamide and shorter terminal blocks of poly(N-isopropylacrylamide) form gels on heating. The incorporation of a charged monomer, 2-acryl-amido-2-methylpropanesulfonic acid, into the central block leads to significant improvements in mechanical properties and formation of a crosslinked network at concentrations as low as 0.05 wt%. All monomers and transfer agents used in the study are available on an industrial scale.