Polymers of carbonic acid. XIV. High molecular weight poly(trimethylene carbonate) by ring‐opening polymerization with butyltin chlorides as initiators

Abstract

Abstract Numerous BuSnCl , Bu 2 SnCl , and Bu 3 SnCl‐initiated polymerizations of cyclo(tri‐methylene carbonate) (TMC) were conducted in bulk. In addition to the initiator, reaction time, temperature, and monomer/initiator (M/I) ratio were varied. Yields above 90% were obtained with all three initiators, but their reactivities decrease in the order BuSnCl 3 > Bu 2 SnCl 2 > Bu 3 SnCl. The maximum molecular weights decrease in the same order. With BuSnCl 3 M w s up to 250,000 were obtained. These molecular weights were determined by GPC on the basis of the universal calibration method. In this connection Mark‐Houwink equations for two solvents, tetrahydrofuran (THF) and CH 2 Cl 2 were determined and compared with literature data. Furthermore, mechanistic aspects were studied. 1 H‐ and 13 C‐ NMR spectra revealed that BuSnCl 3 forms complexes with the CO‐group of TMC, whereas Bu 2 SnCl 3 do not cause NMR spectroscopic effects. Kinetic studies in chloroform and nitrobenzene and a comparison with Bu 3 SnOMe suggest that at least BuSnCl 3 initiates a cationic mechanism. However, in contrast to SnCl 4 (or SnBr 4 ), BuSnCl 3 does not cause decarboxylation. Regardless of the initiator 1 H‐NMR spectroscopy revealed CH 2 OH and CH 2 CI endgroups in all cases. © 1995 John Wiley & Sons, Inc.