The Structure And Properties Of The The Aryloxy Rare Earth Catalyst For Ring-opening Polymerization Preparation Of Aliphatic Polyesters And Polycarbonate

Ring opening polymerization of e-caprolactone (CL) at low temperature catalyzed by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) (La(OAr)3) has been studied for the first time. It was found that the monomer conversion and polymer molecular weight all increase with polymerization time. The second addition of monomer after a period of reaction makes the polymer chains extend. The block copolymers of CL and cyclic carbonates can be synthesized.A series of random copolymers of CL and 2,2-dimethyltrimethylene carbonate (DTC) with varied molar ratios were prepared by La(OAr)3. Their physical properties and crystalline characters were described in detail. Compared to those of PCL homopolymer, the thermal properties of random copolymers have many changes. Their Tgs comply with Fox equation; Their Tds increase with increasing the content of CL in the copolymers; Their Tms decrease with the increase of DTC amount as DTC amount less than 50%, otherwise, they increase as DTC amount over than 50%. The isothermal crystallization kinetics of random copolymers shows that the crystallization rate decreases with the increase of DTC amount.The blends of PCL and PDTC with different molar ratios were prepared by solution mixing. Their thermal and crystalline properties were studied by DSC, WAXD and PLM methods. The isothermal crystallization rate increases with increasing PDTC content in blend. The PCL/PDTC(80/20) blend is miscible with a single Tg.A series of PDTC homopolymers with different molecular weights were prepared and their thermal and crystalline properties were analyzed by DSC method. It has a quite different crystallization pattern crystallized from solution comparing to that crystallized from melt.A series of PCL homopolymer with different molecular weights were also prepared. Their physical properties and crystalline characters were studied in detail. The tensile strength and elongation all increase with the increase of molecular weight ofPCL.