Ice-templated additive-free porous starches with tuned morphology and properties

Biodegradable anisotropic neat porous starch materials without any additional cross-linking, plasticizer or any extra matter have been fabricated via facile ice-templating method. Waxy maize was dissolved in water followed by unidirectional freezing and ice sublimation. The influence of process parameters (starch concentration and retrogradation time) on the morphology, density, mechanical properties under the uniaxial compression and thermal conductivity were investigated. The internal morphology and the shape of the pores, from lamellar to sponge-like, was shown to be governed by starch concentration. All porous starches have very low density (0.07–0.15 g/cm3), anisotropic mechanical properties and low thermal conductivity, in particular in transverse direction (0.037–0.048 W/(m·K)). Interestingly, when compressing the ice-templated starches in the transverse direction, the thermal conductivity was further decreased reaching the values of 0.033 W/(m·K). This work provides the guidelines for making fully biobased porous starch materials with controlled morphology and properties.