The Synthesis And Catalytic Capability Research Of Heterocycle Derivatives Rare Earth Complexes

In this paper, two novel heterocycle schiff base derivatives and a pyridine amino deravative have been synthesized, then its rare earth complexes have also been prepared as a polmerization catalyst for ring opening polymerization of cyclic ester and coordination polymerization of olefin. These complexes have characterized by 1H NMR and element analysis, and also their catalytic behaviour has been researched. The structure and property of the polymer and copolymer initiated by these complexes have also been characterized, and the postulated mechanism of polymerization has been proposed.An aromatic heterocyclic Schiff base neodymium complex bearing thiazole was synthesized and its activity in the ring opening polymerization ofε-caprolactone (CL) was examined. The conditions of the CL/Nd molar ratio, monomer concentration, polymerization time and temperature were investigated. Activities of ca.171kg/Nd·h were obtained under the optimum condition (CL/Nd=1600(molar ratio), [CL]=2.26mol L^-1, 1h at 50℃), giving a polycaprolactone(PCL) of number molecular weight Mn=5.4×10⁴ and molecular weight distribution MWD=1.96. The conversion of CL monomer as high as 94% was observed after polymerized for one hour. The mechanism of coordination polymerization has also been investigated.Neodymium based thiazole heterocyclic Schiff base complex was prepared and applied for the coordination polymerization of isoprene. This complex polymerized isoprene to afford products featuring high c/s-1,4 stereo specificity (ca.95%) and high molecular weight (ca.10⁵) in the presence of the tri-isobutyl aluminum(AI(iBu)₃) as cocatalyst. The microstructure of obtained polyisoprene was investigated by FTIR, 1H NMR. Two different kinds of active centers in the catalyst system were examined by GPC method.Pyriding Schiff base rare earth complex(Y(DBPP)₂Cl·3THF) can be used as an efficient catalyst for ring opening polymerizaiton of cyclic ester such asε-caprolactone(CL), cyclic carbonic ester and lactide etc. The polymerizaiton of L-lactide under the condition of [LLA]/[Y]=500, 60℃, 40min produced poly(L-lactide) without the convert of chiral center of LLA monomer. The thermal behaviour and crystallinity are coinciding with the reported reference. Through the copolymerization of LLA with CL monomer, the molecualr weight has been increased to 13.5×10⁴ with narrow distribution (1.23). The block copolymer can only be obtained by the sequence of polymerization which initiated CL first. The thermal behaviour and crystallinity of different length of block have been charaterized and the interference of each block has been confirmed.The rare earth samarium complex of N-(trimethylsilyl)pyridin-2-amine is an efficient catalyst of polymerization of polar olefin monomer MMA, giving a syndiotactic PMMA with molecular weight of 12.9×10⁵. Its catalytic behaviour has been researched and the kinetic research proved that the polymerization of MMA in the very beginning (<40min) has a certain character of living polymerization. Through terminal group analysis, a postulated mechanism has been proposed.