Materials prepared by Freezing-Induced Self-Assembly of Dispersed Solutes: A Review

Abstract

Crystallization demands structural regularity. Therefore, when a solvent is frozen to form a crystalline solid, it forces the dispersed solute to partition out of the crystalline phase. This forms the basis of ice-templating, wherein a solvent (often water) containing dispersed particles and/or macromolecules is frozen so that the dispersed solute phase is expelled by the ice crystals and is consolidated at their boundaries, when the ice crystals impinge. Removal of the ice crystals results in the formation of a macroporous material, whose pores are bounded by walls formed by the freezing-induced self-assembly of the solute. This versatile technique can be applied to a wide variety of solutes since their expulsion and aggregation due to solvent freezing is largely independent of solute chemistry. Ice-templating has therefore become an increasingly popular synthetic tool in the materials science community. In this review, we summarize the process of freezing and the interaction of the solute with the freezing solvent. We specifically review the literature on how solute–solute interactions influence the self-assembled structure that results from ice templating, and identify lacunae in our current understanding of ice-templated materials synthesis.