The current synthesis procedures for polymeric aerogels do not offer the freedom to tune their structural or mechanical properties. The density and porosity of an aerogel is usually controlled by changing the polymer concentration. However, decreasing the polymer concentration reduces the number of interactions within the polymer gel that often compromises the mechanical performance of an aerogel. This study describes a novel approach to tune mechanical properties of an aerogel by controlling the swelling properties of the gel preceding the aerogel. The Hansen solubility parameter approach is applied on the cellulose acetate (CA)-acetone-water system to predict the swelling behavior of cross-linked CA gels. The swelled free standing gels are subjected to unidirectional freezing to produce aerogels. The synthesis approach provides a theoretical platform to control gel swelling and subsequently the density and mechanical properties of the aerogel. Using this approach, the density of CA aerogels can be tuned from 25.0 to 113.0 mg/cm<sup>3</sup> without changing the polymer concentration, and the porosity of the corresponding aerogels ranges from 98.1 to 91.3 %. The fine control over aerogel density induces wide range of mechanical properties which are quantified by compression modulus (13-340 kPa), energy of absorption (4-103 kPa) and compressive strength (22-373 kPa). Furthermore, unidirectional freezing induces anisotropy in the aerogel which makes them behave elastic or plastic based on the direction in which the property is measured.<br/>

Anisotropic cellulose ester aerogels with tunable mechanical properties via controlled solvent exchange

253rd National Meeting (2017)

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