正电子湮没技术研究双酚-A聚碳酸酯薄膜的结晶行为

Positron Annihilation of Crystallization of Bisphenol-A Polycarbonate Thin Films

双酚-A聚碳酸酯的半刚性结构使其热结晶速率慢且结晶度低.在有机溶剂丙酮的蒸汽氛围下,聚碳酸酯会以较快的速率完成结晶过程.本文采用X射线衍射(XRD)和正电子湮没寿命谱(PALS)研究了丙酮蒸汽诱导聚碳酸酯薄膜结晶行为和微结构转变.随着丙酮蒸汽作用时间增长,XRD图谱显示27.3°处的衍射峰有"出现-消失-出现"现象,而PALS结果则显示正-电子偶素(o-Ps)寿命是增大趋势,o-Ps强度是先增大后减少.研究结果分析认为,双酚-A聚碳酸酯薄膜经丙酮蒸汽作用发生"结晶-重结晶"现象;重结晶引起了平均自由体积孔洞尺寸继续增大,而自由体积浓度却进一步增大.

Bisphenol-A polycarbonate（BAPC）with semi-rigid segments exhibits low thermal crystallization rate and low crystallinity.The crystallization rate of BAPC was strongly enhanced by its exposure to the vapor of acetone.In this paper,crystallization behavior of BAPC thin films induced by acetone-vapor was studied by X-ray diffraction（XRD）and positron annihilation lifetime spectrosoopy（PLAS）.With the increase of exposure time,the diffraction peak at 27.3°shows a variation of＂appearance-disappearance-appearance＂in the XRD patterns.Results of PALS show that the lifetime of ortho-positronium（o-Ps）increases while the intensity of o-Ps first increases and then decreases.The results indicate that there is a＂crystallization-recrystallization＂process during the acetone-vapor treatment;However,the sizes of free volume holes increase and the concentration of free volume decreases due to crystallization,while the sizes of free volume holes further increase and the concentrations of free volume increase during recrystallization in the BAPC thin films.