Preparation of Asymmetric Thermosensitive Double-layer Gel

Abstract

AbstractHeterogeneous amidation of poly(acrylic acid) gel-1,8-diazabicyclo-[5,4,0]-7-undecene salt (DAA) in N-methyl-2-pyrrolidone containing an excess of alkylamine and triphenylphosphite occurred from the surface to give the corresponding DAA-poly(N-alkylacrylamide) (PNAA) core-shell type gel, consisting of an unreacted DAA core and a quantitatively amidated shell layer. Further amidation of the DAA-PNAA core-shell type gel with a second alkylamine afforded a novel core-shell type gel consisting of two PNAA layers: PNAA(2) and PNAA(1). The resulting cylindrical PNAA(2)-PNAA(1) core-shell type gels were resistant to marked deformation caused by swelling/de-swelling because of their axial symmetry. This paper proposes a new approach to the preparation of asymmetric thermosensitive PNAA(2)-PNAA(1) double-layer gels by several procedures using the synthetic method of the core-shell type gels containing of poly(N-isopropylacrylamide) and poly(N-n-propylacrylamide) layers. Among the obtained asymmetric double-layer gels the model I type gel (cylindrical grooved PNNPA-PNIPA core-shell type gel) was markedly bent in water at temperatures between the lower critical solution temperatures of both layers.