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Photoresponsive polymers IV. Photocontrol of viscosity and pH-value in aqueous systems using poly(methacrylic acid) having spirobenzopyran side groups

1981; Elsevier BV; Volume: 1; Issue: 3 Linguagem: Inglês

10.1016/0144-2880(81)90022-1

1878-2698

Masahiro Irie, Koichiro Hayashi, Akira Menju,

Light effects on plants

Poly(methacrylic acid) having spirobenzopyran side groups has been synthesised to attempt to construct photoresponsive aqueous systems. The viscosity of an aqueous solution of the poly(methacrylic acid) was reversibly reduced by as much as 30% upon irradiation with visible light (λ>470 nm), the initial value being restored in the dark. Reversible photocontrol (up to 0·1) in the pH-value of an aqueous solution has also been achieved by the use of this polymer. Changes of the polymer conformation and the pH-value are caused by the photoisomerisation of the spirobenzopyran attached to the side groups. The difference in hydrophobic nature of the merocyanine and spiropyran form of the spirobenzopyran side groups is considered to alter the balance of the intrachain interaction, resulting in changes in the main chain conformation and pKa value of the carboxylic acid side groups.