作者：G Wu, SC Chen, Q Zhan, YZ Wang
关键字：Amphiphilic，Biodegradable，Comb-Like Graft Copolymers，Thermoresponsivity
论文来源：期刊
具体来源：Macromolecules
发表时间：2011年

As an extremely promising characteristic, the transformation between a lower critical solution temperature (LCST) and an upper critical solution temperature (UCST) has rarely been reported until now. In the present paper, a three-step strategy, based on "grafting onto" concept, was implemented to synthesize a novel thermoresponsive amphiphilic biodegradable and biocompatible poly(p-dioxanone)-grafted poly(vinyl alcohol) (PVA-g-PPDO) copolymer with well-define structure. A transformable thermoresponsivity from a LCST to an UCST can be achieved facilely via changing the graft chain length of the resulting PVA-g-PPDO copolymers. The results of transmittance indicate that a wide range of LCST and UCST between 30 and 80 degrees C can be achieved easily, which is attributed to the controllable structures and hydrophobic/hydrophilic ratio of copolymers by adjusting degree of polymerization (Dp) of PPDO prepolymers and molar feed ratios in the last esterification coupling step. This is the first example having the feature of architecture-determined different-type thermoresponsivities by a facile change of side chain length from an identical comb-like graft copolymer family, and displaying a wide range of controllable LCST and UCST. The influence of solution concentrations on thermoresponsivities has been investigated by UV-vis spectrometer, and the solution properties of copolymers have also been evaluated by dynamic light scattering (DLS). The results show that the self-assembly of copolymers displaying different thermoresponsivities can be observed and regulated by changing the structure and temperature.