The Behavior Of Rheology And Crystallization Study For Polyethylene Oxide Doped With Sodium Iodide

Polymers, due to peculiar properties of low density, easily processing and diverse structure, are widely used in manufacture and life. Most polymers are semicrystalline materials because of long chain and polydispersity. During manufacturing process, polymers undergo injection molding, extrusion, spinning or blow molding, repectively, and this process inevitablely imports in the influence of flow field on polymer crystallization. Polymer chains are to be oriented or extented under flow field, thus the crystallization kinetics are enhanced and polymers form different crystallization morphologies. Flow-induced crystallization has gained a lot of phenomena and theory for half a century, such as the explanation theory for precursor or shish-kebab sturcture, respectively. However, most scholars just directively change flow parameters(such as strain, strain rate or temperature), or molecular parameters in order to investigate crystallization behaviors, respectively. Few researchers have investigated the influence of interaction between polymer chains on rheology and crystallization. The mechanism of entanglement on flow-induced crystallization has not been revealed.This thesis bases on sample system of polyethylene oxide (PEO) and sodium iodide (Nal), altering interaction between polymer chains and importing into new entanglement point, in order to study polymer crystallization under flow field. By Olympus polarized optical microscope (POM) and in situ small angle X-ray scattering (SAXS), the effect of ion on crystallization kinetics and crystallization morphology is investigated; With a combination of differential scanning calorimetry (DSC), extensional rheology and in situ synchrotron radiation SAXS, crystallization of PEO-Nal composites is investigated, aiming to demonstrate versatile roles played by polymer-ion interaction.Effect of Nal on the crystallization behavior of PEO is investigated by POM and in situ SAXS. WAXD indicates that no complex crystal is formed and crystalline structure almost remains the same as pure PEO. A pattern of feather-like lamellar bundles coarsens and arranges around the nuclei loosely, forming immature and imperfect spherulites. Owing to the slow segmental mobility affected by coordination bond, growth rate of spherulites at a given temperature is significantly decreased by addition of Nal owing to the slow segmental mobility.Crystallization of PEO-NaI composites is investigated by differential scanning calorimetry (DSC), extensional rheology and in situ synchrotron radiation SAXS. In the isothermal quiescent crystallization process, the decrease of crystal growth rate is observed for PEO-Nal. In situ SAXS on extensional flow-induced-crystallization (FIC) shows enhanced kinetics and orientation for both PEO and PEO-Nal with increasing strain rate. However an overall weaker strain-rate dependence of FIC is observed for PEO-NaI, which can be interpreted as a synergistic consequence of promoted nucleation under flow and impeded crystal growth by polymer-ion interaction. A possible microscopic mechanism is proposed to account for the experimental observation based on the formation of transient cross-linking points in PEO-Nal and their influences on the entanglement network of polymer under various flow fields. The disclosed strain-rate dependence and various ion effects on behaviors of PEO-salt composites contribute to a comprehensive understanding of polymer-ion solid polyelectrolytes.