Two-Level Optical Birefringence Created by Evaporation-Induced Polymer Crystallization in Sessile Droplets
作者:
Song, TT (Song, Tiantian) [1] , [2] ;
Wu, XX (Wu, Xiaoxue) [1] , [2] ;
Xu, J (Xu, Jun) [4] ;
Ye, HM (Ye, Haimu) [5] ;
Shi, WC (Shi, Weichao) [1] , [2] , [3]
MACROMOLECULES
DOI
10.1021/acs.macromol.2c02247
在线发表
JAN 2023
已索引
2023-01-25
文献类型
Article;
Early Access
摘要
Controlling deposited crystal structures in sessile droplets is the basis for applying recent droplet-making techniques in processing semicrystalline polymer solutions. But it remains a fundamental challenge to clarify the relationship between solvent evaporation and polymer crystallization. Here, we study the solvent evaporation-induced crystallization in poly(ethylene oxide) sessile droplet and reveal a two-level optical birefringence in the dried film. We find that the evaporation-induced shear flow promotes crystal growth in the radial direction, which generates anisotropic spherulites with a noncentrosymmetric orientation sensitive birefringence, while the whole film in a droplet exhibits a centrosymmetric negative birefringence. The two-level optical birefringence is dependent on the molecular weight and polymer concentration in the morphology diagram and is proven a general phenomenon in more kinds of semicrystalline polymers. Careful analysis on evaporation dynamics indicates that the anisotropic crystal growth is a competitive result of evaporation, polymer relaxation, and crystallization. The findings in this study shed insight into the evaporation-induced crystallization in polymer droplets and offer a generic method to create anisotropic crystal patterns using droplet-processing techniques.