Syndiotactic polystyrene/ethylbenzene complex: Chain conformations and phase behaviour

Syndiotactic polystyrene (sPS) has been studied, primarily in the delta (solvent-stabilised) and gamma phases. Crystallisation from dilute ethylbenzene solution at 40 degrees C leads to a lamellar morphology, with a similar unit cell for the polymer/solvent complex as that proposed by Chatani et al for the sPS/toluene complex [1]. As the temperature is raised, the X-ray long period increases in the temperature range of decomplexation, becoming constant in the gamma phase before increasing again on annealing in the alpha phase. Neutron scattering measurements show negligible isotopic fractionation and only a small increase in the radius of gyration in the plane of the sedimented delta phase mats (R-xy) with increasing molecular weight. Together with model simulations which reproduce satisfactorily both the form of Kratky plots and the values for R-xy, this evidence points strongly towards a sheetlike structure (as is obtained for other non-complexing solution-grown polymer crystals). Increases in R-xy and changes in the scattering curves from those characteristic of sheetlike structures in the gamma phase are interpreted as indicating movement of crystal stems out of the sheers.