Synthesis And Properties Of Isotactic Polypropylene Ionomers

Polypropylene is one of the largest volume thermoplastic materials and widely used in our daily life.However,the lack of polar group limits its application in certain areas.Introduction of polar group on polypropylene chain to obtain functionalized polypropylene can effectively improve its poor interactive performance.Polypropylene ionomer containing a certain amount of ionic group in its side chain has high hydrophilicity,thermal stability and mechanical properties.In this paper,a series of polypropylene ionomers containing up to 6.47 mol%ionic groups with high molecular weight,narrow molecular weight distribution and high isotacticity were synthesized.The propylene/11-iodo-1-undecene（PP/IUD）copolymers were prepared by dimethyl（pyridylamino）hafnium catalyst.Taking PP/IUD copolymers as an intermediate,iodine groups underwent nucleophilic substitution reaction with triamines,to successfully obtain triethylamine ionomers and N-methylimidazole ionomers.N-methylimidazole polypropylene ionomers with different counter ions（I^-,Tf₂N^-,BF₄^-,PF₆^-）were obtained by ion exchange reaction.First,the thermogravimetric analysis（TGA）results showed that the thermal stability of N-methylimidazole polypropylene ionomers withoutβ-H was significantly higher than that of triethylamine polypropylene ionomers.Second,the hydrophilicity of polypropylene ionomers was improved compared with that of PP.Third,the elongation at break of polypropylene ionomers was significantly increased to 900%.In addition,counter ions had an influence on mechanical properties,the polypropylene ionomers possessing I^-anion had the highest yield strength and breaking strength than those with other counter ions（Tf₂N^-,BF₄^-,PF₆^-）.Furthermore,we used PP/IUD copolymers as intermediate,iodine groups underwent click chemistry reaction with thiol reagents to get o-mercaptoaniline hydrochloride polypropylene ionomers and sodium thioglycolate polypropylene ionomers.The TGA results showed that the thermal stability of polypropylene ionomers was enhanced after functionalization.The contact angle test demonstrated that the functionalization improved the surface hydrophilicity.The toughness of polypropylene ionomers was remarkably increased compared with PP.