Preparation of porous honeycomb monolith from UV-curable monomer/dioxane solution via unidirectional freezing and UV irradiation

A well-ordered micrometer-scale honeycomb monolith porous polymeric material with aligned channels was successfully prepared from UV-curable urethane diacrylate monomer and 1,4-dioxane solutions by conducting unidirectional freezing, photopolymerization, and sublimation of the frozen solvent. UV light was irradiated into the frozen solution, and the monomer was photopolymerized and solidified in a template of 1,4-dioxane crystals. The effects of monomer concentration, freezing rate, and viscosity of the solution on the porous structure were investigated. High monomer concentration increases the solution viscosity, decreases the diffusivity of solute, and consequently, increases the degree of the supercooling. Thus, the pore size was decreased, and the channel wall feature was changed from smooth to dendrite as the solution viscosity increased. Pre-UV irradiation was also conducted before the unidirectional freezing process so as to control the solution viscosity and change the porous structure. Experiments elucidated that the solution viscosity is one of the key factors of determining the cell structure in the unidirectional freezing technique. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012