Elastic Paper with Mechanically Switchable Fiber and Pore Structure

该项目的目标是开发可以可逆拉伸超过100%的纸张。随着伸长率的增加，纤维排列的更高顺序应导致片材的孔结构的取向增加。一方面，由熵弹性驱动的变形和择优取向应在所施加的拉伸、压缩或剪切应力结束时立即回归。另一方面，将开发弹性纸，其最初在不施加力的情况下保持明显的伸长/压缩状态，并且仅在施加来自该暂时变形的刺激之后恢复到初始的永久形状关于它们的化学和物理性质，所需弹性纸的纤维应该与常规纸的纤维相似，因此，唯一的区别是新型纸的弹性变形能力。同样，其生产应基于造纸技术的众所周知的组件和过程。主要的挑战是防止纸浆纤维通过氢键直接连接，而是通过纤维之间的弹性的、高度可变形的胶体颗粒间接地实现它们的内聚。一方面，主要的挑战是在适当的尺寸、弹性，变形/松弛特性和化学结构（壳上足够数量的阳离子官能团）。另一方面，纤维应具有优先形成离子键的化学结构（例如连接阴离子基团）。最后，有必要开发一种将同样静电稳定的阳离子弹性体颗粒悬浮液与阴离子纸浆纤维混合并在形成纤维的同时将它们转化成均质纸的方法。在该项目的后期阶段，将生产出更多的胶体颗粒，这些胶体颗粒表现出接近室温的拉伸结晶或玻璃化转变温度。由此，可以生成弹性形状记忆纸。此外，应验证是否可以开发具有纤维优先取向的弹性纸以用于各向异性拉伸。因此，一个基本的理解，以及在理想情况下的建模的结构-性能关系将被开发。因此，分级孔结构的可变性及其在拉伸过程中的取向是特别重要的。

The aim of the project is to develop papers that can be reversibly stretched by more than 100%. With increasing elongation, a higher order of fiber alignment should result in an increasing orientation of the pore structure of the sheet. Deformation and preferential orientation, driven by entropy elasticity, on the one hand should immediately regress when the applied tensile, compressive or shear stress ends. On the other hand, elastic papers are to be developed, which initially retain a distinct state of elongation/compression without application of force and only return to an initial, permanent shape after application of a stimulus from this temporary deformation (i.e. shape-memory papers).With regard to their chemical and physical properties, the fibers of the desired elastic paper should be similar to those of conventional papers, hence, the only difference will be an elastic deformability of the novel paper. Likewise, its production should be based on well-known components and processes of paper making technology. The main challenge is to prevent the otherwise common direct linking of the pulp fibers by means of hydrogen bonding, and instead to achieve their cohesion indirectly via elastomeric, highly deformable colloidal particles in between the fibers.On the one hand, a major challenge is to build up the colloid particles with respect to suitable size, elasticity, deformation/relaxation characteristics and chemical structure (sufficient number of cationic functionalities on the shell). On the other hand, the fibers should be equipped with a chemical structure for preferential formation of the ionic bonds (e.g. attachment of anionic groups).Finally, it is necessary to develop a method of mixing the likewise electrostatically stabilized suspensions of the cationic elastomer particles with the anionic pulp fibers and converting them into homogeneous papers while forming the fiber-bridging ionic bonds between the particles and the surface of the fibers.In the later stage of the project, additional colloid particles are to be produced, which exhibit stretch crystallization or glass transition temperatures near room temperature. By this, elastic shape memory papers can be generated. Furthermore, it should be validated whether elastic papers with preferential orientation of the fibers can be developed for anisotropic extensibilities. Perspectively, a fundamental understanding as well as in ideal case the modeling of the structure-property relationship will be developed. Thereby, the variability of the hierarchical pore structure and its orientation during stretching is of particular importance.