Porosity Modulation of Cellulose Fiber Mats by Phase Inversion of Block Copolymers

在该项目中，功能性孔结构是通过两亲嵌段共聚物在纤维素纤维界面上的自组装而产生的。目的是详细阐述纸纤维的大小、形状和极性，以及纸的限制作为一个整体，对两亲性嵌段共聚物的结构和孔形成的影响。为了了解这些功能纸的结构-性能关系，将通过聚合物设计和自组装过程中其他参数的变化来解决在存在极性纤维界面的情况下特定聚合物结构域的形成。为此，将通过活性阴离子聚合或受控自由基聚合来制备量身定制的嵌段共聚物，以获得每体积亲水嵌段10%至50%的范围。两亲性嵌段共聚物将通过不同的路径与纤维素纤维结合，从而获得杂化嵌段共聚纤维素膜，并阐明其微相分离和孔形成的结构关系。定制的和通过合成可调节的亲水嵌段之间的相互作用将能够与纤维素表面形成氢键。预计两亲嵌段共聚物的经典相图将因纤维素限制下的相互作用而发生巨大变化。此外，自组装和非溶剂诱导相分离(SNIPS)过程将通过改变从二元或三元混合溶剂浇注嵌段共聚物的参数(溶剂、粘度、挥发速率、湿度、浇注速度、添加剂和其他参数)来完成。通过这一策略，将产生额外的孔结构。最后，均聚物将以共价方式附着在纤维表面，并将研究它们对微相分离、孔形成和稳定性的影响。如果获得成功，该项目将为微流控或传感应用带来一种新型的独立、灵活的聚合物-纤维素材料平台。

In the project, functional pore structures are generated by self-assembly of amphiphilic block copolymers at the cellulose fiber interfaces. The aim is to elaborate how the size, shape and polarity of the paper fibers in detail, but also the paper confinement as a whole, affect the structure and pore formation of amphiphilic block copolymers. The formation of specific polymer domains in the presence of polar fiber interfaces will be addressed by polymer design and by variation of further parameters during the self-assembly process, in order to understand the structure-property relationship of these functional papers. For this purpose, tailor-made block copolymers will be prepared by means of living anionic polymerization or controlled radical polymerizations in order to yield a range of 10 to 50 % per volume of the hydrophilic block segment. The amphiphilic block copolymers will be combined with cellulose fibers by different pathways ion order to provide access to hybrid block copolymer cellulose films, for which structure-relationships for microphase separation and pore formation will be elucidated. The interaction of the tailor-made and - by synthesis - adjustable hydrophilic block segments will be capable of forming hydrogen bondings with the cellulose surface. It is expected that the classical phase diagram for amphiphilic block copolymers will tremendously be changed by interactions in the cellulose confinement. Moreover, the self-assembly and non-solvent induced phase separation (SNIPS) process will be accomplished by varying the parameters of casting the block copolymers from binary or ternary solvent mixtures (solvents, viscosity, rate of evaporation, humidity, casting speed, additives and other parameters). By this strategy, an additional pore structure will be generated. Finally, homopolymers will be covalently attached at the fiber surface and their influence on microphase separation, pore formation, and stability will be investigated. If crowned by success, this project lead to a novel platform of free-standing, flexible polymer-cellulose-based materials for e.g. microfluidic or sensing applications.