Copolymers of -caprolactone (CL) and trimethylene carbonate (TMC) have been synthesized through ring-opening polymerization using a novel initiator of scandium tris (2,6-di-tert-butyl-4-methylphenolate). CL and TMC polymerizations proceed via the "coordination anionic mechanism" with acyloxygen bond cleavage. Five kinds of copolymers with different structures of X, XB, AXB, AB, and BAXB are synthesized under different polymerization conditions and characterized by 1H NMR, GPC, and DSC, where X, A, and B denote as random blocks of CL and TMC, PTMC blocks, and PCL blocks, respectively.

The ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC) initiated with highly active single rare earth tris(2,6-di-tert-butyl-4-methylphenolate) (Ln(OAr)3, Ln=La, Nd, Dy, Y) is reported for the first time. The catalytic activities of various Ln(OAr)3 systems are decreasing in the following sequence: La>Nd>Dy～Y. PolyDTC (Mw=17.1×104, MWD=2.79) initiated by La(OAr)3 at [DTC]/[initiator]=1000 was obtained with a conversion of 97.9% within 1 h in toluene at 15℃. 1H NMR, GPC, and DSC are used to characterize the polymer's structure and to investigate the polymerization mechanism. PolyDTC obtained has no ether unit developed from CO2 elimination. The polymerization of DTC occurs according to a coordination anionic mechanism, and the ring is opened via acyl-oxygen cleavage leading to an Ln-O active center.

tically suppress the transesterification reactions by screening linear polymer chains from the active center during the polymerization of є-caprolactone (CL) with rare earth alkoxide. Therefore, isopropoxy rare earth diethyl acetoacetate ((EA)2LnOiPr Ln=Nd, Y) and Nd(OiPr)3-donor adducts (1,10-phenanthroline, 2,2¢-bipyridyl, 18-crown-6 ether) are excellent catalysts for the living polymerization of є-caprolactone, giving poly(є-caprolactone) (PCL) with a narrow molecular weight distribution. Block copolymerizations of є-caprolactone with trimethylene carbonate (TMC) and D,L-lactide (LA) have been attained successfully using (EA)2LnOiPr as catalyst. The characterizations by GPC, NMR, DSC, and polarizing microscope showed that the block copolymers, P(CL-b-TMC) and P(CL-b-D,L-lactide), have well-controlled sequences without random placement.

Ring-opening polymerization of є-caprolactone catalyzed by rare earth halides and rare earth halide-epoxide has been carried out for the first time. It was found that rare earth halides have low activities for the polymerization of є-caprolactone, but in the presence of epoxide, rare earth halides are highly active for the bulk and solution polymerization of є-caprolactone, with high molecular weight poly-(-caprolactone) (PCL) formed. With the NdCl3-20PO system, PCL with a molecular weight of 22.4×104 can be easily obtained at 30℃, and the molecular weight of PCL can be increased to 42×104 at 60℃ with a catalyst efficiency of 100×104g of PCL/mol of NdCl3. The catalytic activities of the rare earth halides are affected by the kind of rare earth element, halogen, epoxide, amount of added epoxide, catalyst concentration, and polymerization temperature. It has been found that rare earth halides react with epoxide and produce halogen rare earth alkoxides: (X3-xLn{[OCH(R)CH2]yX}x, X=Cl, Br, I). A study on the polymerization mechanism showed that the resulting rare earth alkoxide bond initiates the polymerization of є-caprolactone via a "coordination-insertion" mechanism with acyl-oxygen bond cleavage of the monomer during the є-caprolactone polymerization catalyzed by rare earth halide-epoxide.

Copolymerzation of proplene oxide and carbon dioside was successfully carried out by using new rare-earth catalytic systems for the first time. It has been found that ternary rare-earth coordination catalysts composed of rare-earth phosphonat, triisobutylaluminum, and glycerine are effective catalysts for the copolymerixation. The system Y(P204)3-Al(i-Bu)3-glycerine shows the highest activity. The yield and interinsic viscosity of the copolymer depend significantly on the molar ratio of catalyst components and the reaction condition. The copolymers prepared were characterizaed by IR, 1HNMR, GPC. and DTA-TGA. It is showed that the copolymers obtained have a high molecular weight with a narrow molecular weithg distribution is showed that the copo;ymers obtained have a high molecular weitht with a narrow molecular weith distribution and a high thernmal stsbility. The carbonat unit content of the methanol-insoluble copolymer is as high as 30-40%.