10498
Macromolecules 2010, 43, 10498–10504 DOI: 10.1021/ma102206f
Influence of the Degree of Sulfonation on the Structure and Dynamics of Sulfonated Polystyrene Copolymers Alicia M. Castagna,† Wenqin Wang,‡ Karen I. Winey,*,‡ and James Runt*,† †
Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States, and ‡Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States Received September 23, 2010; Revised Manuscript Received November 17, 2010
ABSTRACT: The structure and dynamics of sulfonated polystyrene (SPS) acid copolymers were investigated using X-ray scattering and broadband dielectric relaxation spectroscopy (DRS). Evidence of acid group aggregation was found at 3.5, 6.7, and 9.5 mol % sulfonation. An increase in the segmental relaxation time and dielectric relaxation strength was observed with increasing acid content. The average state of dipolar interactions was quantified as a function of temperature using the Onsager equation and the Kirkwood-Fr€ ohlich correlation factor. Two high-temperature relaxation processes at frequencies 4-7 decades below the segmental relaxation were identified and are proposed to originate from Maxwell-Wagner-Sillars interfacial polarization and association dynamics of various assemblies of acid groups.
Introduction Ion-containing polymers are of interest in a variety of applications, ranging from high-performance coatings to ion transport for actuation and battery materials. Ionomers, copolymers with a small fraction (
