| Popis: |
A novel photoresponsive polymer containing organic chromophores which possess thermal stability as well as substantial and reversible responsiveness upon external photostimulus has been developed. trans-2{4-[2-(Dimethylcarbamoyl)vinyl]phenoxy}ethyl methacrylate (1) was synthesized and copolymerized by free-radical methods with methyl methacrylate giving a copolymer poly[(methyl methacrylate)-co-1] (poly(MMA-co-1)) (2) with cinnamamide moiety chromophores randomly attached as side groups. Photoisomerization and ultraviolet absorbance were used to examine the photostationary states and solubility changes upon photoirradiation. Poly[(methyl methacrylate)-co-1] (90,7 : 9,3 mol%) with 9,3 mol-% cinnamamide content has better solubility in a polar solvent such as acetonitrile (theta temperature ΘPMMA = 30°C) than in a nonpolar solvent such as carbon tetrachloride (ΘPMMA = 27°C). Photoisomerization of the trans-cinnamamide to cis-cinnamamide units significantly shifts the cloud point of poly[(methyl methacrylate)-co-1] (90,7 :9,3 mol-%) in carbon tetrachloride; this cloud point shift is reversible by photoisomerization back to the trans state. However, in a hydrogen-bonding solvent such as tert-butyl alcohol, while photoirradiation of poly[(methyl methacrylate)-co-1] (90,7 :9,3 mol%) yields a significant shift in cloud point, this is not reversible by photoirradiation as hydrogen-bond formation between the tertiary amide and the hydroxylic solvent reduces the isomerization efficiency. Fatigue of the photoreversibility of the copolymer, which is not present in dilute solutions of the cinnamamide chromophore, is noted. |
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