Molecular design and degradation mechanism of biodegradable polymer

采用以下两种方法研究了生物可降解聚羧酸型功能聚合物的分子设计。(1)将易受微生物反应的悬垂官能团，如羟基、羧基甲氧基或磺酸基，引入到不可生物降解的聚合物链中。(2)在功能聚合物的主链上引入醚或酯键。通过丙烯酸与醋酸乙烯、甲基乙烯醚、甲基乙烯硫醚、乙烯磺酸或乙烯氧乙酸共聚而得到的含有悬垂羟基、甲氧基、磺酸或羧基甲氧基基团的聚羧酸酯，与没有这些悬垂官能团的聚羧酸酯相比，在活性污泥或土壤细菌中表现出更好的生物降解性。采用富集培养技术从土壤中分离出几种可吸收聚乙烯氧乙酸钠（PVOA）和聚乙烯醇的微生物菌株，如蜡样芽孢杆菌和假单胞菌。含有羧基甲氧基的丙烯酸酯共聚物也被PVOA可同化菌株降解。结果表明，引入易被微生物降解的悬垂基团可提高非生物降解水溶性聚合物的生物降解性。用相应的氧环烷衍生物开环聚合法制备了含醚键的聚羧酸酯。采用相应的丙二酸酯开环聚合、苹果酸直接聚合或丙烯酰胺与2-亚甲基-1,3-二氧基丙烷自由基共聚制备了含酯基的聚合物。研究发现，在聚合物主链上引入醚或酯键可以提高其生物降解性，而在主链上含有酯基团的聚合物，如聚苹果酸，很容易被活性污泥或土壤细菌降解。

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.