SANS study of water sorption and desorption of hygroscopic salt-embedded porous gelatin substrate in a humidity-controlled environment

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Yi Zhang,
ISIS, UK

Biopolymer composites are actively researched as alternatives to synthetic polymer materials owing to their potential advantages in alleviating environment impacts, biodegradability, and cost-effectiveness. The water sorption and desorption behaviours of these materials are of interest in a wide range of research topics, including water retention in biomedical applications and atmospheric water harvesting. Gelatin is an abundant biopolymer in animal resources and is known to be hygroscopic. However, it is not suitable for water harvesting applications in its native forms due to its slow response to changes in humidity in the surrounding. In this work, we introduced pores and embedded hygroscopic salts in the gelatin substrates, and tested their behaviours at various humidity levels, as a model system to study water sorption and desorption in hygroscopic biopolymer composite-based water harvesting devices. SANS was applied in situ to reveal variations in the locations of water through changes in the structures and contrasts at the interfaces and within the gel network. The results help us better understand sorption and desorption events in such composites and would hopefully support more rational design of water harvesting devices with capillary-gel matrices in the future.