Morphological Studies of Poly(styrene)-<i>b</i><i>lock</i>-poly(ethylene-<i>co</i>-butylene)-<i>b</i><i>lock</i>-poly(methyl methacrylate) in the Composition Region of the “Knitting Pattern” Morphology^§

Abstract

To investigate the stability of the knitting pattern (kp) morphology in poly(styrene)- block -poly(ethylene- co -butylene)- block -poly(methyl methacrylate) (SEBM) triblock copolymers, several SEBM with slightly different compositions have been synthesized. Sample preparation was done by solvent casting and melt processing techniques. Morphological investigations using transmission electron microscopy (TEM) on films cast from chloroform revealed that several polymers exhibited the kp morphology. Polymers with a higher poly(styrene) content and the same amount of poly(ethylene- co -butylene) as the kp polymers exhibited predominantly a lamellar morphology from chloroform cast films. Symmetric SEBM polymers with a decreased midblock content in films from chloroform resulted in a cylinder-between-lamellae (lc) morphology. Melt processed samples exhibited a predominantly co-continuous-like structure with a mixture of layerlike and cylindrical poly(ethylene- co -butylene) microphases between poly(styrene) and poly(methyl methacrylate). Samples that have been cast from chloroform prior to compression molding displayed predominantly the kp morphology. Additional morphological investigations on samples cast from toluene and roll-cast from chloroform were conducted, which lead to some features of the kp morphology.