1977 Volume 1977 Issue 7 Pages 1035-1040
In order to elucidate the influence of hydrophobic interaction on photomechanical effect in water, copolymers, consisting of 2-hydroxyethyl methacrylate (HEMA) and N-vinylpyrrolidone (VPy), were prepared. As to the amphiphilic HEMA-VPy copolymer, which is water soluble non-polyelectrolyte, the hydrophobic interaction markedly increased with increasing HEMA composition. The study on the influence of hydrophobic interaction on the photoviscosity dehavior was made in the aqueous copolymer-dye solution.
The copolymer-dye complex was formed upon addition of anionic azo dye to the aqueous coplymer solution, and the viscosity behavior of the complex was quite similar to that of polyelectrolytes. The copolymer chain expanded because of the electrostatic repulsion between the negative charges of the dye, and the extent of the copolymer chain remarkably increased with increasing HEMA composition in the copolymer. This showed that the hydrophobic interaction contributed to the complex formation.
When the complex solution was exposed to and then screened from the light, alternately, the reversible conformational change in the complex was observed, being accompanied by isomerization of the dye. Such photoinduced conformational changes increased with increasing HEMA composition in the copolymer. These results suggested that photomechanical effect in water increased with increasing hydrophobic interaction of the polymer.
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