Polymers of carbonic acid. XXVII. Macrocyclic polymerization of trimethylene carbonate

2,2-Dibutyl-2-stanna-1,3-dioxepane (DSDOP) was used as cyclic initiator for the polymerization of trimethylene carbonate (TMC). The polymerizations we re either conducted in concentrated chlorobenzene solution at 50 and 80 deg rees C or in bulk at 60 and 120 degrees C. With monomer/initiator ratios le ss than or equal to 100 the conversion was complete within 2 h at 80 degree s C and within 12 h at 50 degrees C. Variation of the reaction time reveale d that the rapid polymerization is followed by a relatively rapid (backbiti ng) degradation even at 80 degrees C. The polymerizations in bulk at 60 deg rees C were somewhat slower than those at 80 degrees C in solution, but the influence of degradation reactions was less pronounced. With optimized rea ction time the number average molecular weight (M-n) roughly parallels the monomer/initiator ratio and M-n's up to 100,000 were obtained. In contrast to a classical living polymerization broader polydispersities (1.5-1.7) wer e found. In the case of 5,5-dimethyltrimethylene carbonate rapid degradatio n and chain transfer reactions prevented the formation of high molecular we ight polymers. (C) 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 3 7: 2179-2189, 1999.