Abstract
High internal phase emulsion (HIPE) templated porous materials are attracting increasing interests due to its high porosity and tunable structure. However, large amounts (5-50 vol%) of suitable non-ionic surfactants are commonly required to stabilize conventional HIPE due to the high internal volume fraction of HIPE. In this work, applying frozen polymerization in HIPE, aligned porous beads were prepared with tiny surfactant (~0.1 wt%). These interconnected aligned porous beads were prepared through directional freezing, and frozen ultraviolet (UV) initiation of an oil-in-water (o/w) HIPE. The HIPEs are extruded by needle, and then directionally frozen in liquid nitrogen to form beads. The frozen beads were exposed under UV irradiation in a -20 °C ethanol bath to initiate the monomers in the aqueous phase. Moreover, the morphology of the resulting porous beads were tailored by vary the ratio of oil/water and the amount of emulsifier.
Highlights
Porous polymers are attracting much interest as a result of their application in many areas of advanced materials science [1] including drug delivery, tissue engineering, chromatography and water treatment
Curves reflected the intensity of backscattering became weakened which was consistent with the delamination phenomenon of the High internal phase emulsion (HIPE) (Fig.2 (a) after one day)
All of the results showed that the HIPE prepared with 0.1 wt% is not suitable to be an emulsion template for preparation of polyHIPE
Summary
Porous polymers are attracting much interest as a result of their application (both real and potential) in many areas of advanced materials science [1] including drug delivery, tissue engineering, chromatography and water treatment. High internal phase emulsions (HIPEs) have been found considerable use in materials science as templates to create highly porous structures [3]. Such materials, formed by curing the continuous, or non-droplet, phase of the emulsion, are known as PolyHIPEs. Conventional HIPEs are commonly stabilized by large amounts (550% relative to continuous phase) of suitable non-ionic surfactants due to the high internal volume fraction [4], which is not environmental friendly and is the most cost factor. By using ice-templated assembly and UV-initiated frozen polymerization of O/W HIPEs, the PolyHIPEs beads having both well-defined porous structure and orientation interconnectivity structure in voids’ wall. The morphology of the beads was tuned by changing oil: water ratio and the amount of emulsifier in the continuous phase
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