POLYMERS OF CARBONIC ACID .21. RING-OPENING POLYMERIZATION OF CYCLOBIS(DIETHYLENE GLYCOL CARBONATE) BY MEANS OF BUSNCL3, SNOCT(2) OR BU2SNOAS CATALYSTS

Cyclobis(diethylene glycol carbonate), (DEGC)(2), was synthesized by p olycondensation of diethylene glycol with diethyl carbonate followed b y thermal depolymerization of the crude polycarbonate in vacuo. BuSnCl 3-initiated polymerizations of (DEGC)(2) in chlorobenzene at 100 degre es C gave poor results. Therefore, all further polymerizations were co nducted at 145 degrees C in bulk. Two series of polymerizations were p erformed with BuSnCl3 as catalyst, so that either the time was varied at constant monomer/initiator (M/I) ratio, or the M/I ratio at constan t time. Two analogous series were conducted with SnOct(2). With both c atalysts high yields but only moderate molecular weights were obtained . SnOct, yielded polycarbonates having octoate end-groups, which were detected by H-1 NMR spectroscopy. (DEGC)(2) was also polymerized with Bu2SnO at M/I = 200 or 500 with variation of time. The highest yields and molecular weights were obtained at the shortest time, whereas long er times caused rapid depolymerization. Therefore, Bu2SnO appeared to be the most reactive catalyst. Both H-1 and C-13 NMR spectra proved th at all poly(diethylene glycol carbonates) prepared in this work posses s an alternating sequence of ether and carbonate groups.