电位滴定法测定聚酰胺酸固相热环化动力学

针对二步法合成聚酰亚胺的固相热环化过程,采用改进的自动电位滴定法和GPC测定了反应的剩余聚酰胺酸含量及相对分子质量随反应时间及反应温度的变化。结果表明:聚合物平均相对分子质量随热处理时间和温度的增加而逐步增大,相对分子质量分布指数则呈现先增后降的变化趋势。聚合物剩余聚酰胺酸的质量分数随热处理时间增加而逐渐降低,并出现初期的快速和后期的慢速2个阶段。提高热处理温度,则环化速率明显增大,环化程度亦增大。采用两步一级动力学模型关联并得到了2个阶段的热环化动力学参数,快速和慢速阶段的活化能较为接近,而指前因子和过渡熵相差较大。

Kinetics of thermal imidization for a poly(amic-acid) in solid state with potentiometric titration

The kinetics of thermal imidization of a poly(amic-acid) in solid state was investigated with an improved potentiometric titration device and GPC. The results showed that the molecular weight of the polymer is increased with increasing of the reaction time and reaction temperature, and the molecular weight distribution index of the polymer presents an initial increase and then a decrease during the imidization process. The higher the reaction temperature, the faster the reaction rate of the imidization is and the larger the imidization degree is. The imidization process follows two first-order step kinetics models. The relevant parameters are obtained for the initial-stage model and the later-stage model. The actvation energies of the two stages were close, but the frequency factor and the activation entropy of the two stages are didn't.