Polymers of carbonic acid. XVII. Polymerization of cyclobis(tetramethylene carbonate) by means of BuSnCl3 and Sn(II) 2-ethylhexanoate

Dimeric cyclotetramethylene carbonate (TeMC)2 was polymerized in bulk at 185°C. Either nBuSnCl3 or Sn(II)2-ethylhexanoate (SnOct2) were used as catalysts. SnOct2 proved to be somewhat less reactive, but high yields (up to 93%) and high viscosities (νinh up to 0.85 dL/g) were obtained with both catalysts. Viscosity-average molecular weights (Mv) in the range of 50–75 × 103 were determined. The isolated crystalline poly(tetramethylene carbonate)s were characterized by IR, 1H- and 13C-NMR spectra, DSC measurements and WAXD powder pattern. CH2OH and octoate end groups were detected by means of 1H-NMR spectroscopy when SnOct2 was used as initiator, but ether groups were absent. DSC measurements revealed that poly(tetramethylene carbonate) is a slowly crystallizing polymer with a degree of crystallinity below 50% and a melting temperature in the range of 64–69°C depending on the molecular weight. Thermogravimetric analyses proved that polyTeMC decomposes completely between 240 and 340°C without leaving a residue. CO2 and tetrahydrofuran were the main degradation products.