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性嵌段共聚物在纤维素纤维界面的自组装产生的。目的是详细阐述纸纤维的尺寸、形状和极性，以及纸的限制作为一个整体，如何影响两亲性嵌段共聚物的结构和孔的形成。在极性纤维界面存在下特定聚合物域的形成将通过聚合物设计和自组装过程中进一步参数的变化来解决，以了解这些功能纸的结构-性能关系。为此目的，将通过活性阴离子聚合或受控自由基聚合制备定制嵌段共聚物，以产生每体积10至50%范围的亲水性嵌段链段。两亲性嵌段共聚物将通过不同的途径与纤维素纤维组合，以提供获得混合嵌段共聚物纤维素膜的途径，从而阐明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性嵌段片段的相互作用将能够与纤维素表面形成氢键。可以预见的是，两亲性嵌段共聚物的经典相图将大大改变纤维素限制的相互作用。此外，自组装和非溶剂诱导相分离（SNIPS）方法将通过改变由二元或三元溶剂混合物浇铸嵌段共聚物的参数（溶剂、粘度、蒸发速率、湿度、浇铸速度、添加剂和其它参数）来实现。通过这种策略，将产生额外的孔结构。最后，均聚物将共价连接在纤维表面和微相分离，孔的形成，和稳定性的影响将进行研究。如果获得成功，该项目将为微流体或传感应用提供一个独立的、柔性的聚合物纤维素基材料的新平台。

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.