聚乙烯吡咯烷酮/壳聚糖共混水凝胶的制备与水的状态

Preparation and water adsorption of polyvinylpyrrolidone/ chitosan blend hydrogel

以戊二醛作为交联剂,制备了聚乙烯吡咯烷酮(PVP)/壳聚糖(CHI)共混水凝胶,共混物的玻璃化转变温度Tg随CHI含量的升高而升高,SEM图谱观察到PVP/CHI凝胶表面呈现随CHI∶PVP比而变化的微相分离·凝胶溶胀率随着PVP含量升高、PVP分子量降低、CHI脱乙酰度增大而升高·DSC分析表明,非冷冻状态下,CHI∶PVP为1∶2时,游离水、可冻结结合水、非冻结结合水含量分别为42·7%、43·3%、14·0%;CHI∶PVP为1∶8时,凝胶中含非冻结结合水少,DSC曲线上只有一个明显的失水吸热峰,由游离水与可冻结结合水叠加而成·-123℃冷冻条件下凝胶的DSC升温曲线在0、38、53℃观察到一组明显的焓化峰,这是由于低温时冻结为结晶相的游离水、可冻结结合水,随温度升高吸热又转化为游离水、可冻结结合水所致.

A polyvinylpyrrolidone （PVP）/chitosan （CHI） blend hydrogel was prepared with ammonium cerous sulfate as initiator and glutaraldehyde as crosslinking agent. It was found that the glass transition temperature （Tg） of the blend increased with increasing of PVP content. Microzone of CHI and PVP were observed over the surface of hydrogel from SEM micrographs. The swelling ratio of the hydrogels increased with increasing of PVP content, decreasing PVP molecular weight or increasing deacetylation degree of CHI. At normal temperature, there were three endothermic peaks observed from DSC thermograms of the hydrogel with a CHI ： PVP ratio of 1 ： 2 due to water loss, and the content of free water, freezing bond water and non-freezing bond water are 42.7%, 43.3% and 14.0% respectively. However, there was only one peak when the CHI ： PVP ratio was 1 ： 8. A group of peaks were observed at 0℃, 38℃ and 53℃ from DSC thermograms of the hydrogel is the freezing state of -123℃. It was resulted from the transition from crystalline water （formed from free water and freezing bond water at a low temperature） and back to free water and freezing bond water at a higher temperature.