Pseudo interpenetrating polymer networks (IPN’s) of linear syndiotactic polystyrene (syn-PS) and cross-linked atactic polystyrene (c-PS) were prepared and characterized. The crystalline behavior of syn-PS in polymer networks and the morphology of pseudo-IPN’s of syn-PS/c-PS have been studied by DSC and SEM. Pseudo-IPN’s of linear isotactic polystyrene and c-PS as well as linear syn-PS and cross-linked atactic poly(methyl methacrylate) were also prepared for comparison with the pseudo-IPN’s of syn-PS and c-PS.