Synthesis of thermosensitive double-layer gel by polymer reaction

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The purpose of this study is to establish synthetic method of asymmetric, thermosensitive double-layer gel by amidation of poly(acrylic acid) gel-1,8-diazabicyclo-[5,4,0]-7-undecene salt (DAA) with alkylamine.1. The first amidation of DAA with alkylamines proceeded nearly quantitatively at 80℃ in the presence of triphenylphosphite to give the corresponding DAA-poly(N-alkylacrylamide) (PNAA) core-shell type gels. The thickness of the shell layer was controlled by the reaction time. PNAA(2)-PNAA(1) core-shell type gels were prepared by the second amidation of the DAA-PNAA core-shell type gel with another alkylamine under the similar conditions as the first amidation.2. The swelling/de-swelling of shell layers and cores in the PNAA(2)-PNAA(1) core-shell type gels occurred almost independently in response to the temperature changes.3. The semi-cylindrical, double-layer gels were prepared by cutting the cylindrical PNAA(2)-PNAA(1) core-shell type gels into halves.4. The resulting semi-cylindrical, double-layer gels were markedly bent in water at temperatures between the lower critical solution temperatures (LCSTs) of PNAA(2) and PNAA(1). The reversible bending behavior was observed in response to stepwise temperature changes cross the LCSTs. However, the destruction on the boundary occurred gradually, since the shape of the bent gel was extremely distorted.5. A new approach to the preparation of asymmetric thermosensitive PNAA(2)-PNAA(1) double-layer gels, which were not damaged by this deformation, by several procedures was proposed.6. A thin long, asymmetric, thermosensitive double-layer gel was prepared. This gel can be bent in zigzag with high-speed response.