Effect of surfactants on the porous structure of poly(N-isopropylacrylamide) hydrogels prepared by an emulsion templating method

Stimuli-sensitive porous hydrogels prepared with an emulsion templating method developed by the authors are potentially applicable in the medical and pharmaceutical fields; thermosensitive N-isopropylacrylamide (NIPA) hydrogels having randomly distributed sphere-like cavities have been prepared by the polymerization in an aqueous phase in an oil-in-water (O/W) emulsion, followed by the washing of oil (oleyl alcohol) microdroplets. The surfactant plays a dominant role in the preparation of porous hydrogels and the pore size. This study concerns with the surfactant effects on the stability of pre-gel O/W emulsions. The porous NIPA hydrogels were successfully prepared using the surfactants forming the stable emulsion and their internal structures and swelling properties were characterized. The O/W emulsions and the porous hydrogels prepared using various amounts of oil and surfactant were characterized. The information obtained serves for preparation of porous hydrogels having suitable porous structure for their applications.