Synthesis And Properties Of Carbon Dioxide Responsive Waterborne Polyurethane Copolymer Emulsion

Traditional waterborne polyurethane(WPU)has poor water resistance due to the incorporation of permanent hydrophilic group,such as carboxyl group or ammonium salt,into polymer chains.The common-used methods for improving the water resistance of polyurethanes are copolymerization with polyacrylic resin,introduction of hydrophobic groups,and post-crosslinking,However,these methods have not completely solved the problem that WPU contains permanent hydrophilic groups.Therefore,the development of WPU with excellent water resistance and mechanical properties is still a research hotspot.In this study,The functional chain extender(containing tertiary amine groups)that can undergo hydrophilic/hydrophobic transition is introduced into the WPU main chain.And the CO₂-triggered hydrophobic/hydrophilic switchable waterborne polyurethane and its copolymer resin which copolymerized with acrylic units were designed and synthesized.The effect of the molecular structure of the WPU on its performance is explored by analyzing the physical properties of the emulsion and the performance differences of the coating.The main research contents of the paper are as follows:Isophorone diisocyanate(IPDI),polyether diol(PPG),N-(3-dimethylaminopropyl)-N,N-diisopropanolamine(DPA),hydroxyethyl acrylate(HEA),etc.are used as the main raw materials to synthesize the waterborne polyurethane prepolymer with double bond.A series of CO₂-triggered waterborne polyurethane-polymethyl methacrylate were prepared by free radical copolymerization between the polyurethane macromonomer and methyl methacrylate(MMA).The results show that the introduction of polymethyl methacrylate(PMMA)significantly enhances the tensile strength of the film.The initial decomposition temperature of the film is greatly increased,and the material has excellent water resistance performance.When the PMMA content is 10wt.%,the overall performance of the material is the best.Isophorone diisocyanate(IPDI),polyether diol(PPG),N-(3-dimethylaminopropyl)-N,N-diisopropanolamine(DPA),hydroxyethyl acrylate(HEA),etc.are used as the main raw materials to synthesize the waterborne polyurethane prepolymer with double bond.A series of CO₂-triggered waterborne polyurethane-poly2-(dimethyl amino)ethyl methacrylate is prepared by free radical copolymerization between the polyurethane macromonomer and 2-(Dimethylamino)ethyl methacrylate(DMAEMA).The results show that the dual response characteristic of PDMAEMA(which changes when heat or p H changes)accelerates the emulsion response speed when it is stimulated by CO₂.However,the introduction of PDMAEMA structure reduced the mechanical properties,water resistance and heat resistance of the copolymer.