Converting a Dilute Slurry of Hollow Tube-like Papermaking Fibers into Phase-reversible, Self-healable, and Stretchable Hydrogels

Commercially, assembly-directed packing of hollow tube-like papermaking fibers with diameters of roughly 10-50 μm into sustainable micro-fibrous bio-assemblies (i.e., cellulosic paper) starts with a dilute fiber slurry. In this process, a huge amount of water is required to disperse and transport fibers, which also facilitates colloidal interactions and formation of inter-fiber bonds. To form bio-assemblies in their dry states, unit operations associated with dewatering and drying are routine practices and treatment of the generated wastewater is a necessity. We herein present a facile, scalable concept of converting fiber slurry into dynamic hydrogels by using chemical additives (similar to papermaking wet-end additives), but without water removal. We used a typical group of additives as an example in an attempt to demonstrate the applicability of the concept. With boron-based dynamic chemistry as a key theoretical foundation, the combination of crosslinking and hydrogen bonding led to the formation of phase-reversible, self-healable, and stretchable hydrogels. Essentially, the characteristics of hydrogels can be facilely tunable, and process parameters such as polymer dosage are rather critical. It is worth noting that fibers can act as a structural skeleton or mechanical support for tailorable design of hydrogels. The concept demonstrated in this study would provide useful insights into value-added utilization of mass-producible biopolymeric fibers in accordance with existing mill facilities. Fiber-based hydrogels would find use in diversified applications:toys, 3D/4D printing materials, soft robots, drug delivery systems, among others.