Study On Synthesis Of Polycaprolactone And Poly(butylene Adipate)Tri-block Copolymer And Its Epitaxial Behavior On Oriented Polyethylene Substrate

Epitaxial crystallization is an effective method to control the crystalline structure of semi crystalline polymers.Although multitudinous studies have been made on the epitaxial crystallization characterization of homopolymers,such as poly(butylene adipate)(PBA),poly(s-caprolactone)(PCL),poly(L-lactide)and so on,such studies on copolymers are still rare.In this research:1.By adjusting ingredients ratio and time of polymerization,a series of block copolymers of polycaprolactone and poly(butylene adipate)(PCL-b-PBA-b-PCL)with different molecular weights and different weight fraction ratios was synthesized.2.The bulk crystallization behaviors of block copolymers from both solution and melt were studied.The results showed that the isothermal crystallization rate of the triblock copolymer decreased along with the molecular weight.Some of the triblock copolymers formed ring spherulites both from isothermal crystallization and crystallization with certain cooling rates.The size of the ring spherulites increased when the crystallization temperature increased in isothermal crystallization but the influence of cooling rate on the formation of ring spherulites was relatively small.3.The epitaxial behavior of block copolymers on highly oriented high-density polyethylene substrate from both solution and melt was studied.The microscopic results clearly indicated the occurrence of heteroepitaxy of the triblock copolymers on the PE substrate.The electron diffraction patterns confirmed that both PCL segments and PBA segment formed heteroepitaxy on highly oriented PE substrate with their molecular chains parallel to PE molecular chains and that ?-form PBA instead of a-form PBA was formed in the triblock copolymer.