利用光学显微镜研究溶剂诱导的梯形苯基聚倍半硅氧烷结晶

通过溶剂诱导结晶的方法研究了梯形苯基聚倍半硅氧烷(PPSQ)的球晶结构. 采用光学显微镜研究了溶液的浓度、溶剂的挥发时间以及温度等影响因素对梯形苯基聚倍半硅氧烷的球晶结构形貌的影响. 实验结果表明:稀释溶液浓度与提高结晶温度在改变球晶的形态方面具有相同的效果. 球晶的尺寸会随着溶液浓度的降低或者结晶温度的升高而增加. 这都归因于梯形苯基聚倍半硅氧烷在二甲苯中的溶解度的增加. 在不改变其它结晶条件的情况下,延长溶剂的挥发时间也会形成更大的球晶. 当在光学显微镜下旋转样品时球晶的结构不会发生改变,这表明球晶具有均一的晶体学取向结构. 负性球晶的特征也表明梯形苯基聚倍半硅氧烷的分子链是沿着球晶的切线方向排列. 考虑到梯形苯基聚倍半硅氧烷具有刚性的分子链,还提出了梯形苯基聚倍半硅氧烷可能的球晶结构模型.

An Optical Microscopy Study on the Solvent-Induced Crystalline Morphology of Ladder Polyphenylsilsesquioxane

Spherulites of rigid chain ladder polyphenylsilsesquioxane(PPSQ) were produced through solvent-induced crystallization.The influences of solution concentration,solvent evaporation time,and temperature on the spherulitic morphology of PPSQ were studied by optical microscopy.Diluting the solution was found to have the same effect as elevating the crystallization temperature.The size of the spherulites increases with either decreasing concentration or increasing temperature.This is caused by the enhanced solubility of PPSQ in xylene under such conditions.Extending the solvent evaporation time while leaving the other conditions unchanged also leads to the formation of larger spherulites.The invariance of spherulitic structure upon sample rotation suggests that the spherulites possess a uniform crystallographic orientation.The negative optical characteristics of spherulites indicates that the PPSQ molecular chains are oriented in the tangential direction of the spherulite.Considering the high rigidity of the molecules,an organization model of PPSQ spherulite is proposed.