Molecular design and degradation mechanism of biodegradable polymer

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Molecular design of biodegradable polycarboxylate-type functional polymers was studied on the following two approaches.(1) Introduction of pendant functional groups susceptible to microbial reaction,such as hydroxyl, carboxymethoxyl or sulfonate groups, to non-biodegradable polymer chain.(2) Introduction of ether or ester linkages to the main chain of functional polymer. polycarboxylates bearing pendant hydroxyl, methoxyl, sulfonate or carboxymethoxyl groups, obtained by the copolymerization of acrylic acid with vinyl acetate, methyl vinyl ether, methyl vinyl sulfide, vinyl sulfonate or vinyloxyacetic acid, were found to show better biodegradability with activated sludge or soil bacteria, comparing to those of polycarboxylates without such pendant functional groups.Several kinds of poly(sodium vinyloxyacetate) (PVOA) and poly(vinyl alcohol) assimilable microbial strains, such as Bacillus cereus and Pseudomonas sp. were isolated from soil by the enrichment culture technique.Also acrylate copolymers bearing carboxymethoxyl groups were subjected to microbial degradation by PVOA assimilable strains. It was suggested that the introduction of pendant groups susceptible to microbial degradation to non-biodegradable water soluble polymers was improved their biodegradability.Polycarboxylates containing ether linkages were prepared by the ring-opening polymerization of the corresponding oxirane derivatives. Polymers containing ester groups were prepared by the ring-opening polymerization of corresponding malolactonate, by direct polymerization of malic acid, or by the radical copolymerization of acrylamide with 2-methylene-1,3-dioxepane. Introduction of ether or ester linkages to the main chain of the polymer was found to improve their biodegradability, and polymers containing ester groups on the main chain, such as poly(malic acid) were readily biodegraded by activated sludge or soil bacteria.