具有立构规整性的可持续发展聚合物的催化合成

As petroleum resources continue to be depleted, polymer chemists face the challenge of gradually replacing existing petroleum-based polymeric materials with those derived from naturally renewable feedstocks in a technologically and economically competitive fashion. In this context, naturally renewable methylene butyrolactones, such as MBL (α-methylene-γ-butyrolactone) and MMBL (γ-methyl-α-methylene-γ-butyrolactone), are of particular interest in exploring the prospects of substituting the petroleum-based methacrylate monomers for specialty chemicals or polymers production. As the cyclic analog of MMA, MBL and MMBL exhibit greater reactivity in chain-growth addition polymerization than MMA, attributable to the presence of the nearly planar five-membered lactone ring. Importantly, owing to the conformational rigidity of the polymer chain through incorporation of the butyrolactone moiety, the resulting polymers, PMBL and PMMBL, exhibit enhanced materials properties over the petroleum-based PMMA. We have already achieved significant successes for the synthesis of sustainable polymers from renewable feedstocks using several different catalytic systems. However, up to date, all catalysts employed for such synthesis are achiral, producing atactic, amorphous polymer products. Accordingly, the central objective of this proposal is to develop catalyst site-controlled stereoselective polymerization of renewable feedstocks by specifically designed chiral silylium or N-heterocyclic carbene catalysts. Accomplishing this major objective will enable the synthesis of highly stereoregular sustainable polymers, which will undoubtedly lead to new or enhanced materials properties, thereby significantly expanding the application of such superior polymeric materials. The investigation of the relationship between the catalyst structures and the stereomicrostructures of polymers will be carried out to advance the knowledge and technology of new catalyst design and synthesis of high performance polymers.

随着石油资源的不断被消耗，人类社会将面临的一个巨大挑战就是如何利用自然界中的可再生资源来替代传统的石油基聚合物。作为MMA的环状类似物，乙烯基环丁内酯MBL和MMBL这两种从生物质衍生的可再生单体不但可以用来替代MMA，而且该类单体由于具有环状结构使其聚合活性更高，所得聚合物的材料性能较PMMA更为优越。申请人在前期工作中已经成功的利用多种催化体系实现了对上述单体的高效聚合。然而，目前的催化体系还未能对该类单体进行立体选择性聚合。本课题拟合成一系列具有特殊结构的手性酯基烯醇硅醚和氮杂环卡宾催化体系。利用催化剂的手性和空间位阻来控制单体的立体选择性聚合，生成具有立构规整性的聚合物，从而改变聚合物的性能，拓宽该类聚合物的应用范畴。同时深入考察催化剂结构与聚合物微结构之间的关系，为新型催化剂的设计和高性能高分子材料的制备提供技术与理论依据。

项目围绕着可再生单体的催化聚合展开研究。具体包括以下三个方面：（1）手性硅烷化合物的合成及其催化可再生单体的聚合；（2）聚合物链结构的精准合成；（3）糠醛到ϒ戊内酯高效转化的研究。.具体内容如下：（1）我们合成了含有联奈基团的单核以及双核的硅烷化合物，并将其成功的应用于可再生单体MMBL的催化聚合当中，聚合结果显示，该类联奈催化剂并不能很好的控制所得聚合物的立构规整性；（2）利用酯基烯醇硅醚化合物和Lewis酸体系实现了可再生单体MBL和MMBL的活性可控聚合，同时可以实现两种单体的嵌段共聚。利用氮杂环烯烃NHO与Lewis酸体系实现了可再生单体己内酯的活性可控聚合，体系可以有效的控制副反应酯交换的发生。（3）利用RuCl3与壳聚糖组成的非均相催化剂与Amberlyst-15组成的复合催化剂体系实现了糠醛到ϒ戊内酯的高效一锅法合成，产率可以高达79%。这一反应为可再生单体MMBL的合成打下基础。相关研究工作目前发表SCI论文7篇，申请中国发明专利3项。