Smart pH/temperature Sensitive Hydrogels with Tailored Transition Temperature

Dual pH- and temperature-sensitive hydrogels have been prepared based on N-isopropylacrylamide (NIPAAm) and either potassium 5-methacryloyloxy-pentanoate (M4K) or potassium11-methacryloyloxy-undecanoate (M10K) as comonomers. The gels containing M10K (longer methylene chain) showed a slightly lower swelling capacity than the gels containing M4K. Hydrogels were produced with specific phase transition temperature (Tcr) in the range from 12 to 76 oC for NIPAAm-C4 hydrogels (containing M4K) and from 16 to 36 oC for NIPAAm-C10 hydrogels (containing M10K) by controlling: the type and comonomer content, and the pH of water. The type of transition changes from discontinuous (below the critical pH of the acid comonomer) to continuous (above de critical pH of the acid comonomer). The title hydrogel materials are promising candidates for biomedical applications.