Preparation and Characterization of Chiral Polyacrylates End-Capped with Bornyl Groups in the Side Chains

Chiral polyacrylates with bornyl end-capped side chains with four kinds of mesogenic moieties (azobenzene, biphenyl, benzoyloxy biphenyl, and phenyl benzoate) were prepared. The phase properties of the polymers were investigated with X-ray diffraction, differential scanning calorimetry, and polarizing optical microscopy. The thermogravimetric characteristics, the glass-transition temperatures and weight-average molecular weights, of the homopolymers were evaluated. The optical properties of the synthesized polymers in diluted solutions and in the thin-film state were also evaluated. The optical behavior of the composite films upon photoirradiation was investigated through the change in the transmittance of the probe light triggered by ultraviolet (365-nm) irradiation. Ultraviolet irradiation and heat treatment caused a reversible intensity change of the probe light at λ = 400 nm. The shrinkage of the photoisomerization of the composite films was also investigated with atomic force microscopy. A spot contraction appeared on the surface when it was irradiated with a laser light spot. The contraction was recovered by heat treatment at 80°C for 10 min.