Study On Preparation, Characterization And Crystallization Behavior Of Polymer Nanoblends

Polymer blending has become an important route to develop new materials in the polymer materials field. The properties of these materials primarily depend on the phase morphology of polymer blends. In recent years, the polymer nanoblends have been successfully prepared by in site compatilization/in site polymerization, which exhibited excellent toughness and specific crystallization behavior. Therefore, the study of exploring new routes to prepare nanoblends has profound significance in both theoretical research and practical work.In this thesis, a block copolymers PVA-b-PS and random copolymers PAA-co-PS were synthesizedvia atom transfer radical polymerization (ATRP)and emulsion polymerization methods respectively. Three blends systems of PVA-b-PS/PPO, PVA-b-PS/PEO and PAA-co-PS/PEO were prepared by solution casting methods. The self-assembly behavior of the amphiphilic block copolymer of PVA-b-PS and its blending with PPO to prepare the nanoblends via microphase separation were systematically studied. The specific interaction of hydrogen bonding between both PVA-b-PS and PAA-co-PS with PEO were characterized in detail. The nanoblends of PAA-co-PS and PEO were prepared by adjusting the intensity of hydrogen bonding interaction. The effect of hydrogen bonding interaction both on the melting and crystallization behavior of PVA-b-PS/PEO and PAA-co-PS/PEO blends was further studied. The main results are achieved as follows:1. The block copolymers of PVA-b-PS was synthesized by ATRP, and characterized by using FTIR, ¹H NMR and GPC methods. The results indicated that a well-defined amphiphilic block copolymer with narrow molecular weight distribution was synthesized. The self-assembly behavior of block copolymers in the selective solvents was observed by TEM. It was concluded that the particle size of the micelles formed by self-assembly was related to the ratio of the block segments and the concentration of the blend solutions.2. The two blend systems of PVA-b-PS/PEO and PAA-co-PS/PEO were prepared by solution casting method. The intensity of the hydrogen bonding interaction existed in the blends was characterized by FTIR, which indicated that the specific interaction between PVA-b-PS' and PEO was stronger than that of PAA-co-PS/PEO system. Meanwhile, it was proved that the intrinsic viscosities of the blend solutions and the surface energies of the polymer blends were decreased with the increasing hydrogen bonding interaction forming between the two components; The glass transition temperature(Tg) was changed with the blending ratios, i.e. the change in the density of hydrogen bonding, and showed a negative deviation from the linearity of blends' Tg.3. The nanoblends of PVA-b-PS/PPO and PAA-co-PS/PEO were prepared via two ratios, i.e. microphase separation and adjusting the specific interaction of hydrogen bonding, respectively. The analysis of AFM showed that in the cases of PVA-b-PS/PPO nanoblends, the size of dispersed particles decreased with decreasing the content of PVA-b-PS in the blends. The SEM analysis for PAA₁₅-co-PS/PEO blends indicated that, the dispersed phases could be controlled within nanoscale as the contents of PAA₁₅-co-PS were reached up to 30wt% and 50wt%4. The melting and crystallization behaviors as well as non-isothermal crystallization kinetics were investigated by DSC for blends of PVA-b-PS/PEO and PAA-co-PS/PEO. The results indicated that the melting temperature(Tm), crystallization temperature(Tc),and the relative crystallinity (Xt) decreased as the content of the amorphous component increased in the blends. The kinetics study of non-isothermal crystallization showed that the crystallization rate(Zc) of PEO component in the blends was significantly influenced the hydrogen bonding interaction. However, there was little effect on the nucleation mechanism. According to Kissinger equation, the crystallization activation energy estimated for PS-b-PVA/PEO and PS-co-PAA/PEO were 104.4J/mol and 243.97J/mol respectively, which indicated the stronger in the specific interaction, the higher in the activation energy. The observation with POM showed PEO could grow into integrated spherulites morphology in both blends, but the spherulites grew faster in the blends with weak specific interaction.