Novel Sustainable chemical recycling of green polymers using environmentally benign catalytic process

在这项研究中，可持续的化学回收的可生物降解的聚（乳酸）和生物基聚合物，这是从可再生资源中产生的，使用环境友好的催化剂，如酶和固体酸。此外，还对生物聚硫酯的酶催化合成和化学回收进行了研究。结果总结如下。（1）生物基聚合物向可再聚合环状齐聚物的转化研究了酶催化下聚己二酸丁二醇酯的环状齐聚反应。结果表明，在一定的有机溶剂中，脂肪酶能快速地进行环化齐聚反应。对脂肪酶的亲和力以及重聚合产物的分子量显着影响的环状低聚物的大小。（2）利用固体酸对聚L-乳酸进行化学回收的新方法研究发现，蒙脱土可以有效地将聚L-乳酸降解为低聚物。所得乳酸低聚物通过固态聚合容易地再聚合以再生分子量大于100，000的聚乳酸。基于这些结果，提出了生物基聚合物的可持续化学回收。（3）聚硫酯的新型酶促合成及性质首次发现巯基羧酸在酶作用下容易聚合生成分子量为数万的聚硫酯。与相应的聚氧酯相比，由此产生的聚硫酯显示出更高的熔融温度和对有机溶剂的耐受性。此外，一系列的聚硫酯的烷二硫醇与烷二羧酸的缩聚反应，并建立了使用酶的化学回收。

In this study, sustainable chemical recycling of biodegradable poly(lactic acid) and bio-based polymers, which were produced from renewable resources, were developed using environmentally benign catalysts, such as enzymes and solid acids. Also, enzyme-catalyzed synthesis and chemical recycling of biopolythioesters were also studied. Summaries of the results are as follows.(1)Transformation of bio-based polymers into repolymerizable cyclic oligomersEnzyme-catalyzed cyclic oligomerization of poly(butylene adipate) was studied with respect to the basic reaction parameters. It was found that in certain organic solvents cyclic oligomerization was quickly occurred by lipase. The affinities toward lipase as well as the molecular weight of the repolymerization products were significantly influenced by the cyclic oligomer size.(2)Developing of novel chemical recycling of poly(L-lactic acid) using solid acidIt was found that poly(L-lactic acid) was efficiently degraded into oligomers by montmorillonite. The obtained lactic acid oligomer was readily repolymerized by solid state polymerization to regenerate the polylactic acid with a molecular weight of greater than 100,000. Based on these results, sustainable chemical recycling of bio-based polymers was proposed.(3)Novel enzymatic synthesis and properties of polythioestersIt was first found that mercaptocarboxylic acid was readily polymerized by enzyme to produce polythioester with a molecular weight of several ten thousands. Thus produced polythioester showed a higher melting temperature and resistance against organic solvents comparing to those of the corresponding polyoxyesters. Also, a series of polythioesters were produced by the polycondensation of alkanedithiol with alkanedicarobxylic acid, and their chemical recycling was established using an enzyme.