Polymers of carbonic acid, 28 - SnOct(2)-initiated polymerizations of trimethylene carbonate (TMC, 1,3-dioxanone-2)

SnOct(2) (Sn(II) 2-ethylhexanoate) initiated polymerizations of TMC were st udied either in cone. chlorobenzene solution at 80 degreesC or in bulk at t emperatures greater than or equal to 120 degreesC. Benzyl alcohol added as coinitiator accelerated the polymerization process and allowed a control of the number-average molecular weight ((M) over bar (n)) via the monomer/ co initiator ratio (M/C). The formation of benzyl carbonate endgroups allowed in turn the determination of ((M) over bar (n)) via H-1 NMR endgroup analys es. Model reactions suggest that at 80 degreesC intermediately formed Sn-al koxide groups play the role of the true initiator. At 140, 160 or 180 degre esC neat SnOct(2) polymerized TMC in such a way that polyTMC having octanoa te endgroups was formed. Variation of the monomer/initiator (M/I) ratio at 160 degreesC enabled again a proper control of (M) over bar (n) via the M/I -ratio and high molecular weight polyTMC was obtained. The influence of bac k-biting degradation on the molecular weight was also studied at 160 degree sC to find the optimum time-temperature window.