Effects of molecular weight distribution on the self-assembly of end-functionalized polystyrenes

Abstract

The molecular weight distribution (MWD) of polymers shows effects on their phase separation, crystallization, self-assembly, and mechanical properties. It is well known that the architecture of polymers plays a crucial role in the self-assembly of patterned porous films via the breath figure method. However, the effect of MWD is still unknown. In this work, we synthesized a series of hydroxyl-end-functionalized polystyrenes with a narrow MWD by atom transfer radical polymerization (ATRP). MWD was further broadened by mixing the polystyrenes. Honeycomb-patterned porous films were prepared from the polystyrenes. For a unimodal distributed sample with a wide MWD, the optimal concentration for patterned film formation is expanded. However, an improvement cannot be observed in bimodal distributed polymers. The high heterogeneity of the bimodal system weakens the cooperation of components with different molecular weights in stabilizing water droplets. Furthermore, it is interesting to note that the stiffness of patterned porous films can be enhanced by tuning the MWD. The present study demonstrates the effects of the MWD of polymers on the self-assembly behaviors, providing new insights into the breath figure process and the design of robust patterned porous films.