双亲性分级孔结构聚硅氧烷的构筑及其在负载酶催化中的应用

Amphiphilic polymer conetworks (APCNs) are two-component networks of covalently interconnected hydrophilic / hydrophobic (HI/HO) phases of cocontinuous morphology. The swelling degrees of HI/HO phases are independent in water or hydrocarbons. Therefore, the enzyme entrapped into the HI domains of APCNs will improve its activity and stability in hydrocarbons. Meanwhile, it is convenient for the substrates and products to diffuse in HO phases which are swelled in hydrocarbons, and the extremely large HI/HO phases interface can access the biocatalyst. In recent years, the hierarchically porous materials have attracted intensive research interests owing to their high mass- and heat-transfer rates as well as their extremely high surface areas for chemical reaction. In order to further improve the mass-transfer and the activity for biocatalyst in the hydrocarbons, in this project, the three-dimensionally ordered poly(dimethylsiloxane) (3DOM PDMS) with APCN pore-wall will be prepared by a water-soluble colloid crystal template and the method of polymer chemistry and physics to act as enzyme support for preparation of biodiesel in hydrocarbons. More specifically: (1) the preparation and control of the structures of the amphiphilic hierarchically porous PDMS will be investigated to construct a novel porous polymer with high performance, and the relationships between the microstructure (hierarchically porous structures and the HI/HO phases) and the synthesis conditions or confined spaces also will be illustrated; (2) the lipase will be immobilized into the porous PDMS and the immobilization process will be optimized. Meanwhile, the relationship between the microstructure (microenvironment) and the catalytic property will be studied for efficient synthesis of biodiesel in hydrocarbons.

双亲性聚合物共网络（APCNs）由亲水、疏水共连续相通过共价键连接组成，其亲水和疏水相在不同的介质中的溶胀程度不同。将酶固定在亲水相，可显著提高酶在有机溶剂中的活性和稳定性，且疏水相有利于底物和产物的传质。近年来，分级孔结构因其具有高比表面积、高传质、高传热效率等特性而受到广泛关注。为进一步提高非水相酶催化过程的传质和催化效率，本项目提出以水溶性胶体晶为模板，将三维有序大孔（3DOM）结构与APCN相结合，制备孔壁为APCN结构的分级孔聚硅氧烷固定化酶的思路，并将其用于催化制备生物柴油。项目着重考察以下内容：（1）双亲性分级孔聚硅氧烷制备和调控过程，探索分级孔及亲水-疏水相微结构随制备条件、受限空间等因素的变化规律，创制新结构高性能多孔聚合物；（2）调控并优化其固定化酶过程，研究固定化酶在有机溶剂中的催化特性，探究分级孔结构-微环境-酶催化特性间的关系，实现生物柴油的高效制备。

分级孔结构材料由于其在高比表面积、活性位点的高利用性记忆优良的物质传输和扩散性能，近年来，在负载催化、吸附分离、超级电容、以及光子晶体等领域受到日益广泛的关注。其中，将大孔引入到介孔结构中构筑大孔-介孔分级孔结构为降低物质扩散壁垒和在负载催化中潜在的提高活性位点的分布提供了一条有效的途径。本项目以胶体晶为模板，构筑了分级孔聚硅氧烷和具有温敏性质的大孔交联异丙基丙烯酰胺（3DOM PNIPAM）、含酶三维有序大孔氧化硅（3DOM-GOD/SiO2）以及超交联聚苯乙烯分级孔互锁微囊（HPIM-HCL-PS），分别对三种材料进行了详细表征和相应的负载酶催化及检验、固体酸催化等应用，研究结果表明：（1）在制备分级孔结构的聚硅氧烷的过程中，采用先预聚单体再注入的方法，出现了一定的分级孔结构；通过3DOM PNIPAM固定化脂肪酶活性的影响，得出了固定化脂肪酶的最佳浓度为20 mg/mL，最适合的pH为7，重复利用次数高达7次之后，酶活性依旧可以达到50%以上；（2）3DOM-GOD/SiO2具有良好的三维有序大孔结构，且由于溶胶-凝胶作用，材料富含介孔，通过对3DOM-GOD/SiO2进行CLSM表征，表明酶被成功包埋到硅材料中，最适包埋GOD浓度为12 mg/mL；稳定性研究表明，固定化酶在稳定性方面对游离酶有明显优势；动力学参数研究表明，3DOM-GOD/SiO2的大孔及介孔结构对物质的传输有一定的帮助作用，有利于传质阻力的降低；分别以GOD及OPH为模型酶，制备含酶3DOM氧化硅，并将分别其用于溶液中葡萄糖及甲基对硫磷的检测，对极低浓度葡萄糖及甲基对硫磷具有良好的影响。（3）HPIM-HCL-PS经过磺酸基团功能化后（HPIM-HCL-SPS）作为固体酸用于催化苯甲醛和乙二醇的缩合反应，苯甲醛的转化率高达70%，产物2-苯基-1,3-二氧戊环的选择性为98%，TOF值为793 h-1，其值均高于文献报道的同类材料。HPIM-HCL-PS的囊壁分级孔结构可有效降低囊壁与溶液间传质阻力，加快囊腔中液体传质速率，超薄囊壁可大大缩短传质路径，增大催化活性位点利用率，互锁结构可极大提高机械稳定性和循环再利用性，进而使HPIM-HCL-SPS展现出优异的催化活性。