Structure-property relationships of ethylene-styrene interpolymers and their blends

Recent developments in catalyst technology make available copolymers of ethylene with large amounts of styrene, which have been termed ethylene-styrene interpolymers (ESIs). These polymers have narrow molecular weight distribution, homogeneous comonomer distribution. These features make the new copolymers excellent vehicles for looking into fundamental issues in structure-property relationships of polymers.; The basic properties of these copolymers were described in Chapter 1. Based on the combined observations from melting behavior, density, dynamic mechanical response, and tensile deformation, a classification scheme with 3 distinct categories was proposed. In Chapter 2, crystalline ESIs were compared with ethylene-octene copolymers (EOs) based on comonomer content. This comparison revealed the effect of side chains on the structure and property relationships in ethylene copolymers.; Amorphous ESIs provide an excellent model system for testing classical and contemporary molecular dynamics for polymer viscoelasticity. The creep behavior of ESIs in Chapter 3 revealed that the entanglement molecular weight of the ESIs calculated from the plateau modulus was much closer to that of polyethylene than to that of polystyrene. This was attributed to the unique chain microstructure of the ESIs. The linear relaxation master curves of ESIs above glass transition temperature (T_g) were correlated with the molecular weight distribution by using double reptation theory in Chapter 4. The nonlinear relaxation behavior above T_g was successfully described by the Doi-Edwards theory, and a two entanglement network model was developed to describe the instantaneous recovery after large strain stress relaxation in Chapter 5.; Blends of ESIs with different styrene content can be a basis for probing the copolymer composition effect on polymer miscibility. A miscibility and cocrystallization map for binary ESI blends was determined from morphology as imaged with atomic force microscopy, glass transition behavior, and melting behavior in Chapter 6. Blends of some ESIs that were close to 8 wt% difference in styrene content exhibited evidence of partial miscibility. A unique approach for constructing the phase diagram using AFM was developed to characterize partial miscibility in Chapter 7. An analysis that considered the molecular weight distribution was used to extract the χ interaction parameter from the phase volume fraction and blend composition.