The degradation reactions of aliphatic polycarbonates formed in coordination copolymerization of 1,2-propylene oxide and carbon dioxid
Polimery 1994, No 7-8, 449
The degradation and depolymerization reactions of poly(l,2- propylene carbonate) effected by ethylzinc phenolates and alcoholates were investigated. By using the methods of 1H-NMR-, 13C-NMR- and IR-spectroscopy, it was demonstrated that donor-acceptor complexes of the carbonate group of polymer and zinc compound are formed and these complexes contribute to polymer degradation. An analysis of the degradation products revealed that in the case of using ethylzinc phenolate the degradation reaction proceeds via the stage of zinc orthocarbonate compound and chains of degraded polymer with zinc alcoholate end-groups are formed which in their turn depolymerize easily to propylene carbonate (cf. Table 1). In the case of degradation effected by ethylzinc alcoholate, it was demonstrated that degradation proceeds with the formation in degraded polymer of chains with relatively stable zinc carbonate end-groups. These chains eliminate CO2 and are transformed into chains with zincalcoholate end-groups which depolymerize easily to propylene carbonate. The role of the investigated degradation reactions in the copolymerization of alkylene oxide and carbon dioxide catalyzed by ethylzinc compounds and leading to macromolecular aliphatic polycarbonates was also discussed.
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