TETRAPHENYLPORPHYRIN-ALUMINUM COMPOUNDS AS INITIATORS FOR THE RING-OPENING POLYMERIZATION OF 2,2-DIMETHYLTRIMETHYLENE CARBONATE - SYNTHESIS OF HOMOPOLYMERS AND COPOLYMERS WITH EPSILON-CAPROLACTONE, ETHYLENE-OXIDE AND PROPYLENE-OXIDE

Insertion polymerization of 2,2-dimethyltrimethylene carbonate (DTC) with initiators based on tetraphenylporphyrin-aluminium (TPPA1-R) results in high yields of poly(2,2-dimethyltrimethylene carbonate) without cyclic oligomers being formed. This indicates that back biting does not take place. The polymerization reaction is slow in methylene chloride or toluene at room temperature; the reaction rate increases with increasing temperature. Tetraphenylporphyrin-alkoxides (TPPA1-OR), the most active initiators for DTC polymerization, from a mixture of DTC and epsilon-caprolactone (ECL) yield a statistical copolymer, indicating poor selectivity towards these monomers. The initiator, however, is well suited for block copolymer synthesis upon stepwise addition of the monomers, e.g. poly(ECL-block-DTC), poly(ethylene oxide-block-DTC) and poly(propylene oxide-block-DTC). The thermal properties of poly(propylene oxide-block-DTC) as a function of composition are reported. Copolymers with a high propylene oxide content show a pronounced glass transition temperature for the polyether block; all copolymers show only one melting transition which is assigned to that of the polycarbonate block.