N-烷基壳聚糖玻璃化转变温度的研究

Studies on Glass Transition Temperature of N-alkyl Chitosan

采用差示扫描量热(DSC)法和热释电流(TSC)法研究了N-烷基壳聚糖的玻璃化转变行为.DSC法中采用二次扫描以消除溶剂和热历史的影响,并利用物理老化方法来增强N-烷基壳聚糖在DSC曲线上的玻璃化转变区域的热焓吸热峰,以克服DSC法的不灵敏性.两种研究方法的结果一致表明,三种N-烷基壳聚糖的玻璃化转变均发生在110～150℃温区内;取代的柔性烷基越大,玻璃化转变温度(Tg)越低;但N-甲基壳聚糖例外,其Tg略高于壳聚糖,空间阻碍在这里起决定的作用.

The glass transition behaviors of N-alkyl chitosan were investigated by means of differential scanning calorimetry （DSC） and thermally stimulated current （TSC） spectroscopy. In DSC measurements, the second heating run was used to eliminate the effect of solvents and heat history on glass transition temperature （Tg）, and also physical aging was used to improve the sensitivity of Tg measurements by enhancing the enthalpy endothermal peaks. The results of two techniques showed that the glass transition temperatures of three N-alkyl chitosans were all within 110-150℃. When the length of flexible side-alkyl groups was larger, the transition points shifted to lower temperature. But N-methyl chitosan is an exception, its Tg is slightly higher than chitosan because of the steric hindrance of side group.