Tunable Sponge‐Like Hierarchically Porous Hydrogels with Simultaneously Enhanced Diffusivity and Mechanical Properties. Issue 20 (8th April 2021)

• Record Type: Journal Article
• Authors: Alsaid, Yousif; Wu, Shuwang; Wu, Dong; Du, Yingjie; Shi, Lingxia; Khodambashi, Roozbeh; Rico, Rossana; Hua, Mutian; Yan, Yichen; Zhao, Yusen; Aukes, Daniel; He, Ximin
• Is Part Of: Advanced materials. Volume 33:Issue 20(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-04-08
• Subjects: 3D printing -- diffusion -- hierarchical structures -- hydrogels -- stimuli‐responsive materials; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.202008235
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: Crosslinked polymers and gels are important in soft robotics, solar vapor generation, energy storage, drug delivery, catalysis, and biosensing. However, their attractive mass transport and volume‐changing abilities are diffusion‐limited, requiring miniaturization to avoid slow response. Typical approaches to improving diffusion in hydrogels sacrifice mechanical properties by increasing porosity or limit the total volumetric flux by directionally confining the pores. Despite tremendous efforts, simultaneous enhancement of diffusion and mechanical properties remains a long‐standing challenge hindering broader practical applications of hydrogels. In this work, cononsolvency photopolymerization is developed as a universal approach to overcome this swelling–mechanical property trade‐off. The as‐synthesized poly( N ‐isopropylacrylamide) hydrogel, as an exemplary system, presents a unique open porous network with continuous microchannels, leading to record‐high volumetric (de)swelling speeds, almost an order of magnitude higher than reported previously. This swelling enhancement comes with a simultaneous improvement in Young's modulus and toughness over conventional hydrogels fabricated in pure solvents. The resulting fast mass transport enables in‐air operation of the hydrogel via rapid water replenishment and ultrafast actuation. The method is compatible with 3D printing. The generalizability is demonstrated by extending the technique to poly( N ‐tertbutylacrylamide ‐co‐ polyacrylamide) and polyacrylamide hydrogels, non‐temperature‐responsive polymer systems, validating the present hypothesis that cononsolvency is a generic phenomenon driven by competitive adsorption. Abstract : A general approach is developed to produce hierarchically structured hydrogels with highly interconnected pores, resulting in unprecedented simultaneously enhanced mass transport and mechanical properties. This approach is applied to several polymer systems and is compatible with 3D printing. This universal technique should greatly benefit the fundamental study of co‐nonsolvency and the development of functionalized porous materials with mitigated diffusion limits.