Guohong Gao

Bio: Guohong Gao is an academic researcher. The author has contributed to research in topics: Porous medium & Wetting. The author has an hindex of 1, co-authored 2 publications receiving 6 citations.

Emulsion-templated porous polymers: drying condition-dependent properties.

Abstract: Macroporous materials templated using high internal phase emulsions (HIPEs) are promising for various applications. To date, new strategies to create emulsion-templated porous materials and to tune their properties (especially wetting properties) are still highly required. Here, we report the fabrication of macroporous polymers from oil-in-water HIPEs, bereft of conventional monomers and crosslinking monomers, by simultaneous ring-opening polymerization and interface-catalyzed condensation, without heating or removal of oxygen. The resulting macroporous polymers showed drying condition-dependent wetting properties (e.g., hydrophilicity–oleophilicity from freezing drying, hydrophilicity–oleophobicity from vacuum drying, and amphiphobicity from heat drying), densities (from 0.019 to 0.350 g cc−1), and compressive properties. Hydrophilic–oleophilic and amphiphobic porous polymers turned hydrophilic–oleophobic simply by heating and protonation, respectively. The hydrophilic–oleophobic porous polymers could remove a small amount of water from oil–water mixtures (including surfactant-stabilized water-in-oil emulsions) by selective absorption and could remove water-soluble dyes from oil–water mixtures. Moreover, the transition in wetting properties enabled the removal of water and dyes in a controlled manner. The feature that combines simply preparation, tunable wetting properties and densities, robust compression, high absorption capacity (rate) and controllable absorption makes the porous polymers to be excellent candidates for the removal of water and water-soluble dyes from oil–water mixtures.

HIPEs to PolyHIPEs

Abstract: The aim of this article is to provide a comprehensive and consistent overview of structural transitions during polymerization of high internal phase emulsions (HIPEs). The obtained polymerized HIPEs (known as polyHIPEs) usually have an interconnected porous structure consisting of pores (also called voids) and interconnecting holes, known as pore throats (or windows). We describe how emulsification process and stability of HIPEs affect the pore size of polyHIPEs. The pore throat size is mainly controlled by the interdroplet interaction (affecting flattened area and interdroplet layer thickness between neighboring droplets as well as the interdroplet layer drainage) and interfacial film strength. The processing and molding of polyHIPEs are evaluated from rheological and chemorheological behaviors. It is also discussed how the porogen effect of surfactants, polymerization-induced phase separation, and crystallization induce heterogeneity in polymer phase of polyHIPEs.