Morphology and surface properties of polystyrene-block-poly(N-isopropylacrylamide) films

Abstract

The self-assembly of diblock copolymers in thin films offers a promising method for developing innovative products in biomedical and engineering applications. In this study, we utilized amphiphilic polystyrene-block-poly(N-isopropylacrylamide) (PS-b-PNIPAM) diblock copolymers to explore and analyze the distinctive properties exhibited by their thin films when formed on the substrate. PS-b-PNIPAM copolymers, with different molecular weights (MWs) and narrow MW distributions, were synthesized via atom transfer radical polymerization. The subsequent fabrication of thin films, achieved through the spin coating method, revealed microphase separation phenomena. The interplay of MW and composition exerted a notable influence on the ordered structures, giving rise to a diverse array of morphologies within the thin films. This intricate relationship between molecular characteristics and the resulting material structures highlights the importance of tailoring both MW and composition for the precise control and manipulation of thin film properties in the context of PS-b-PNIPAM copolymers. We also examined the impact of conducting the direct immersion annealing (DIA) on surfaces created with the amphiphilic PS-b-PNIPAM copolymer. The thermo-responsivity of amphiphilic PS-b-PNIPAM copolymer and the effect of DIA on the surface properties were examined. Our results showed that the surface morphology could be controlled by the DIA process. Furthermore, it was observed that the MW of the diblock copolymers played a significant role in influencing the orientation of the separated microdomains, further emphasizing the multifaceted interplay of parameters in tailoring the properties of surfaces created with PS-b-PNIPAM copolymers.

Graphical Abstract