Effects of the Neutralization Degree on Morphologies in "Drying-Mediated" Samples of Sodium Neutralized Poly(styrene-ran-methacrylic acid) Copolymers in THF

Abstract

To understand the effect of neutralization degree on surface morphologies of drying-mediated samples, un-neutralized, partially and fully Na-neutralized poly(styrene-ran-methacrylic acid) (PSMAA) prepared from THF solutions were investigated using a scanning electron microscope (SEM). We varied the content of acid groups as well as the degree of neutralization of the PSMAA copolymers. The neutralization degree changed the surface morphologies of the polymers significantly. When the acid group content was low (<9.4 mol%), the morphologies of PSMAA were found to be very similar to that of homo-PS, forming a continuous matrix with a number of circular pores. Upon neutralization, the shape of the pores changed to non-circular form and the porous matrix was mingled with the congregated aggregates. With increasing neutralization degrees, the boundary between porous films and deformed sphere-shaped aggregates became unclear. For fully neutralized forms, only highly porous layered films were formed, indicating micro phase separation between solvent and aggregated copolymer networks.