基于嵌段共聚物受限微相分离的阶层式贯穿多级孔材料的制备与性能研究

Various strategies including "top-down" and "bottom-up" have been developed to target porous materials since they captured the interest of scientists and engineers for more reasons than their visual appeal. However, there are still some open problems in preparing them. For instance, it is a challenge to obtain "hierarchical", "connected", "controllable" porous structures with high "mechanical strength". In this proposal, we will demonstrate two routes to fabricate materials with structures discussed above by combination of "top-down" and "bottom-up" strategies. Therefore, electrospinning and AAO (anodic aluminium oxide) together with confined block copolymer will be employed to enable the fabrication and control of one-dimension (1D) microstructures with varied nanostructures in them. In microscale, pores resulted from fibers (in electrospinning) and rods (in AAO) can be controled through electrospinning parameters (e.g. viscosity of solution, Voltage) or AAO parameters (e.g. size and distance of holes), while nanapores resulted from microphase separation can be tuned by the fraction of blocks and annealing temperature. On the other hand, to increase the strength of porous materials, gyroid-tube structure will be designed and fabricated based on the investigation of surface (or interface) effect during microphase separatin and formation of porous structures. Finally, applications of the prepared materials in Dye Sensitized Solar Cell (DSSC), Li-ion Batteries will be investigated. Our results will not only help to understand experimentally the basic physical mechanism of microphase separation of confined block copolymer, but also serve as important starting point of establishing new methods to prepare 3D-connected hierarchically porous structures.

近年来，介孔材料的制备方法获得快速发展（主要包括"自上而下"和"自下而上"两种策略），但仍缺乏制备"贯穿"、"可控"、"阶层式"和"高强度"多孔材料的有效方法。针对这一问题，本项目提出将"自上而下"和"自下而上"两种成孔策略进行有效结合以获得阶层式三维贯穿的多孔材料。即采用"自上而下"的静电纺丝（或AAO模板）构建来自单根纤维间（或AAO的孔间）的微米孔结构，利用"自下而上"的嵌段共聚物微相分离构建每根纤维（或棒）内部的纳米孔结构。我们将重点研究含无机前驱体的嵌段共聚物在不同受限尺寸（纺丝直径及AAO孔径）下的微相分离行为，对微相分离及其诱导的多孔结构进行主动调控。最后，考察所得多孔材料在染料敏化太阳能电池、锂离子电池等领域的应用。通过本研究，一方面总结受限情况下嵌段共聚物微相分离的规律，理解其尺寸依赖性；另一方面建立利用"自上而下"和"自下而上"结合制备阶层式贯穿多孔材料的新方法。

高分子和无机介孔材料在多个领域有着重要的应用。其制备方法主要包括“自上而下”和“自下而上”两种策略，但仍缺乏制备“贯穿”、“可控”、“阶层式”和“高强度”多孔材料的有效方法。针对这一问题，本项目提出将“自上而下”和“自下而上”这两种成孔策略进行有机结合获得阶层示三维贯穿的多孔材料。同时，本项目还在研究相容结晶/结晶高分子多层次结构的基础上，创新的利用共混物结晶相互穿插实现高分子纳米多孔材料的制备。借助静电纺丝、反相复制等模式获得了多种具有多级孔结构、功能的有机和无机纳米孔材料。项目主要成果如下：1）通过结合自上而下的静电纺丝模板法和自下而上的聚苯乙烯/聚氧乙烯（PS/PEO）相分离以及PS-PEO嵌段共聚物的微相分离得到各种各样结构新颖的TiO2纳米纤维。特别是成功获得光电性能优异的、带有外壳和内部连续孔隙的雪茄状结构TiO2纳米纤维。明确了在有限的几何空间中PS-PEO嵌段共聚物的微相分离是造成包含连续的TiO2框架和连续孔隙的内部双连续结构的原因。2）系统研究了熔体相容的结晶/结晶聚乳酸/聚甲醛（PLLA/POM）共混体系的结晶行为。发现了基于“片晶穿插”和“晶纤穿插”的球晶复制行为，首次观察到两组份分别的环带球晶的结晶形态。3）共混物中PLLA与POM的片晶相互穿插，形成POM和PLLA晶体间纳米尺度高度连续的“双连续相”结构。通过选择性溶剂刻蚀去除PLLA组份（或者POM组份），即可制得三维贯通纳米多孔结构POM材料（PLLA材料）。制备得到多孔材料的孔结构，可以通过结晶条件、组份比例实现调控。此外，所得多孔材料还可作为结构模板，制备具有环带球晶结构的无机多孔材料。（4）在PLLA/POM/MWCNT纳米复合体系中，POM在MWCNT表面先发生结晶形成纳米杂化串晶，仍处于无定形状态的PLLA分子链，则主要分布在POM“碟状”片晶之间。PLLA发生结晶时，MWCNT表面形成PLLA与POM晶体交替生长的特殊结构。通过选择性刻蚀纳米复合体系中的PLLA组份，可以制备得到导电多孔纳米多孔材料。项目共在Macromolecules (3篇), ACS Appl. Mat. Interfaces (5篇), Polymer 等重要杂志上发表于本项目相关的SCI 论文30余篇，获得国家发明专利3项。其中聚甲醛纳米多孔中空纤维及薄膜已由企业中试，探索其工业应用。