A HIPE is formed by mixing two immiscible liquids to form a stable emulsion, and the EHA/IBOA copolymer HIPE was prepared according to a published procedure.29 (link) Briefly, a HIPE was prepared by mixing the monomers isobornyl acrylate (IBOA, 3.66 g) and 2-ethylhexyl acrylate (EHA, 1.56 g) with the crosslinker trimethylolpropane triacrylate (TMPTA, 1.41 g) using an overhead stirrer. The surfactant Hypermer B246 (0.21 g, Croda) was added, and the solution was mixed until it was dissolved. The photoinitiator diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide/2-hydroxy-2-methylpropiophenone blend (0.35 ml) was added before the addition of water.
To prepare a HIPE with an aqueous content of 80%, 28 ml of deionised water was added over 5 min in a drop-wise fashion into a 100 ml capacity beaker containing the oil phase, stirred at a specific stirring speed using an overhead stirrer (Lab Egg, IKA). The emulsion was stored in an amber glass vial (Supelco) and used within 6 h of preparation. The stirring speeds used to investigate processing conditions were 320, 540, 765, 870, and 1260 rpm. To investigate the effect of temperature on porosity, the aqueous temperature was stabilised at 4, 15, and 30 °C before addition to the monomer.
To prepare a HIPE with an aqueous content of 80%, 28 ml of deionised water was added over 5 min in a drop-wise fashion into a 100 ml capacity beaker containing the oil phase, stirred at a specific stirring speed using an overhead stirrer (Lab Egg, IKA). The emulsion was stored in an amber glass vial (Supelco) and used within 6 h of preparation. The stirring speeds used to investigate processing conditions were 320, 540, 765, 870, and 1260 rpm. To investigate the effect of temperature on porosity, the aqueous temperature was stabilised at 4, 15, and 30 °C before addition to the monomer.