Complex formation of amphiphilic polymers with azo dyes and their photoviscosity behavior

Abstract

The hydrophobic interaction of amphiphilic copolymers, which contain 2‐hydroxyethyl methacrylate(HEMA) and 1vinyl‐2‐pyrrolidone (VPy), with Methyl Orange (MO) was compared with that of HEMA‐acrylamide (AAm) copolymers to deduce the correlation between their complexation ability in a photochromic azo dye and the photoviscosity effect in aqueous copolymer/dye complex solution. On the basis of the dialysis data and fluorometric analysis it appeared that the complexation dependence on HEMA content in the copolymers was due to the hydrophobic interaction between the polymer and the dye. For a comparable HEMA content AAm copolymers bound less MO than VPy copolymers. It was confiied by photoviscosity measurements that the conformation of the complex composed of photochromic azo dye and HEMA copolymer changed reversibly in response to the photo‐ and thermal isomerization of the dye. In HEMA‐AAm copolymer systems the photoviscosity effect was small compared with that of HEMA‐VPy copolymer systems. From these results it was concluded that the complexation ability of polymers due to the hydrophobic interaction was an important factor in producing a large photoinduced conformational change in water.

Highly efficient sensitization of titanium dioxide

“…product is obtained upon similar hydrolysis and dehydration of bis(4-bromobutoxy)(2,4,6-tri-?er?-butylphenyl)borane (5), obtained by the reaction of 4 with boron tribromide in tetrahydrofuran (eq 3)•8 4 -W-B(OCH2CH2CH2CH2Br)2 1 Compound 1 reacts with water and oxygen; when heated to 85 °C it decomposes with loss of two molecules of 2-methylpropene to form a second diboradioxetane, 6, also a pale yellow oil (eq 4).9 Both 1 and 6 show rather positive UB chemical shift values, Irradiation of 1 at -196 °C in 3-methylpentane glass led to formation of a weak UV absorption band at 314 nm which may be due to free 2. Further investigations of this new species are being carried out.…”