拉曼光谱法研究聚乙二醇的非等温结晶及其相变行为

摘要

利用拉曼光谱研究不同分子量聚乙二醇(PEG)在温度变化过程中的结晶及其相变行为.结果表明,PEG的结晶形态与分子量大小无关,这是因为尽管PEG具有不同的分子量,但其分子结构完全一致,因此不同分子量的PEG具有相同的结晶相态.实验进一步表明,不同分子量的PEG在等温结晶过程中球晶形成的大小和结晶速度与分子量紧密相关,这与PEG在结晶过程的成核方式有关.当PEG的分子量比较小时,分子链较为伸展,倾向于均相成核,容易形成较大的球晶,晶体生长速度慢;高分子量PEG的熔体黏度大,链段彼此相互交叠重合在一起,容易形成微小晶区,体系倾向于发生异相成核,因此球晶体较小,晶体的生长速度快.本研究为聚乙二醇在共混体系中的应用提供理论支撑.%Raman spectroscopy was used to study the crystallization and phase transition behavior of polyethylene glycol (PEG) with different molecular weight during temperature change.The experimental results show that the crystal structure of PEG is independent of the molecular weight due to the same molecular structure in PEG.The spherules size and crystallization speed of PEG are closely related to the molecular weight during isothermal crystallization,which associates with the nucleation mode of PEG during the crystallization process.The homogeneous nucleation could be easily formed when the molecular weight of PEG is small.Oppositely,the heterogeneous nucleation could be easily forued when the molecular weight of PEG is large,and then the chain segments of PEG overlap with each other to form a small crystal zone to accelerate the crystal growing.This study provides theoretical support for the application of polyethylene glycol in the blending system.