Self-assembling phenomena of benzo-18-crown-6/crowned-spirobenzopyrancopolymers in aqueous solution and controlled release of entrapped organic dyes using external stimuli

Abstract

A novel amphiphilic vinyl copolymer incorporating benzo-18-crown-6 (BC) and crowned spirobenzopyran (cSP) in the side chain [poly(BC-co-cSP)] was synthesized by free radical copolymerization. The spectroscopic measurements made it clear that poly(BC-co-cSP) forms a micelle in water and that its cSP moiety can bind a metal ion in the micelle. Photochromism based on the spirobenzopyran moiety was successfully observed even under conditions of micelle formation. These results indicate that two external stimuli, metal ions and light, can cause significant changes in the assembly state and physical properties of poly(BC-co-cSP). Release behaviors of encapsulated organic dyes from polymeric micelles consisting of poly(BC-co-cSP) were investigated in Tris–HCl buffer solution (pH 7.4) before and after addition of external stimuli. As a result, it was shown that the performances were largely affected by metal-ion addition and photoirradiation. Thus, controlled release of organic dyes from polymeric micelles was realized using a combination of UV-light and visible-light irradiation in water containing BaCl₂.