Macromolecules, 2016, vol 49, 11, pp. 4236-4244
A novel thermogelling polyhedral oligomeric silsesquioxane–poly(2-(dimethylamino)ethyl methacrylate-b-N-isopropylacrylamide), POSS–(PDMAEMA-b-PNIPAm)8, star-shaped block copolymer was synthesized by using RAFT polymerization. In aqueous solution this copolymer (≥10 wt %) underwent sol-to-gel transition as the temperature increased. The network structure and rheology properties of POSS–(PDMAEMA-b-PNIPAm)8 block copolymers could be facilely tuned by blending the poly(vinyl alcohol) into the in situ forming gel system. The presence of PVA could enhance not only the rheological properties but also the thermal sensitivity of the hydrogels. It was observed that the highest storage modulus G′, which is 25 times larger than that of pure star-shaped block copolymer gel, was achieved with 3 wt % content of PVA in the mixture. Moreover, it was found that the addition of PVA could markedly counteract the effect of intramolecular interaction of “arms”. Network structures formed by physically close-packed star-shaped polymer aggregates and PVA interpenetrating within 3D star-shaped polymer network were proposed to be responsible for the dramatic change of rheological behaviors observed in this study, which is also correlated to their corresponding morphologies investigated by using ATR-FTIR, SAXS, and DLS.