화학공학소재연구정보센터
Journal of Polymer Science Part A: Polymer Chemistry, Vol.48, No.17, 3807-3815, 2010
Ring-Opening Polymerization of 1-Methyltrimethylene Carbonate by Rare Earth Initiators
Ring-opening polymerization of 1-methyltrimethylene carbonate (MTMC) initiated by highly active single-component rare earth tris(2,6-di-tert-butyl-4-methylphenolate)s [Ln(OAr)(3), Ln = La, Dy, Y] or yttrium isopropoxide [Y(OiPr)(3)] is reported for the first time. PolyMTMC (M-w = 8.4 x 10(4), molecular weight distributions = 1.5) initiated by La(OAr)(3) at [MTMC]/[initiator] = 1000 was obtained with the yield over 99% in toluene within 1 h at 30 degrees C. Random and block copolymers of MTMC with epsilon-caprolactone (CL), 2,2-dimethyltrimethylene carbonate (DTC) or polyethylene glycol (PEG) including poly(MTMC-r-CL), poly(MTMC-b-CL), poly(MTMC-r-DTC), poly(MTMC-b-DTC), and poly(MTMC-b-PEG-b-MTMC) were synthesized. The differential scanning calorimetry results show that thermal behaviors of the polymers sensitively depend on their compositions and chain structures. Furthermore, the measurements of H-1-H-1 COSY and density functional theory calculation are applied to investigate the mechanism. The polymerization of MTMC takes place according to a coordination-insertion mechanism, and the ring is opened via acyloxygen bond cleavage resulting in a Ln-O active center. There exist two ring-opening modes of MTMC in which mode b, breaking the CH2O-CO bond, is the major pathway. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3807-3815, 2010