Poly(styrene-b-isobutylene-b-styrene) block copolymers and ionomers therefrom: morphology as determined by small-angle X-ray scattering and transmission electron microscopy

Solvent-cast films of poly(styrene-b-isobutylene-b-styrene) (PS-PIB-PS) blo ck copolymers and block ionomers were analyzed using small-angle X-ray scat tering (SAXS) and transmission electron microscopy (TEM). Four block copoly mer samples with center block molecular weights of 52,000 g mol(-1) and PS volume fractions (phi(PS)) ranging from 0.17 to 0.31 were studied. Block io nomers were produced by lightly sulfonating the PS outer blocks of the PS-P IB-PS block copolymers. Sulfonation levels were 1.5 and 3.4 mol%, and sodiu m and potassium counterions were studied. All samples exhibited hexagonally packed cylinders of PS within the PIE matrix. Cylinder spacing was in the range 32-36 nm for most samples, while cylinder diameters varied from 14 to 21 nm. Pored analysis of the scattering data indicated the presence of iso lated phase mixing and sharp phase boundaries. (C) 2000 Elsevier Science Lt d. All rights reserved.