Synthesis, characterization, and mechanism studies on novel rare-earth calixarene complexes initiating ring-opening polymerization of 2,2-dimethyltrimethylene carbonate

摘要

Rare-earth (Nd, Y) p-tert-butylcalix[n]arene (n = 4, 6, and 8) complexes without coligands were synthesized from rare-earth isopropoxides in toluene. The products were characterized as the following structures: [C4(OH)03 . CH,C6H5]Nd (4), [C6(OH)(2)O-4 . CH3C6H5](3)Ln(4) [Ln = Nd (5), Y (6)], and [C8(OH)(2)O-6 CH3C6H5]Nd-2 (7). 2,2-Dimethyl trimethylene carbonate (DTC) can be polymerized with complexes 4-7 alone as the initiator. PolyDTC (weight-average molecular weight: 5700, polydispersity index: 1.11, measured by gel permeation chromatography) initiated by complex 5 was obtained with a conversion of 69.1% within 6 h in toluene at 80degreesC. The thermal behavior of polyDTC has been compared with the published data. The DTC ring is opened via acyl-oxygen bond cleavage with end-group examination. NMR analyses of the polymerization reaction mixture indicated that the polymerization proceeds via a coordination-insertion mechanism. (C) 2003 Wiley Periodicals, Inc. [References: 57]