Stiffening of biopolymer aerogel networks upon wetting: a model-based study

The mechanism behind the stiffening effect observed in the stress-strain response of alginate-starch aerogels upon being exposed to wetting is investigated in this paper, via a physically motivated model approach. A network decomposition concept is introduced, whereby the highly nanoporous network is decomposed into a swollen aerogel network and a hydrogel-like network. The aerogel network is modeled by considering idealized square-shaped microcells of varying sizes. An attempt is made to explain the stiffening of the network, upon wetting, based on changes in the fibril characteristics of the aerogel network upon swelling and formation of a hydrogel-like phase in the microporous region. In this first approach, the aerogel network is described based on a micro-mechanical model, while the hydrogel-like network is described using a phenomenological one. The results of the proposed model idea are in very good agreement with the experimental data of alginate-starch aerogels under different degrees of wetting.