Synthesis and Properties of Stereoregular Polymethacrylates with Azobenzene Moiety as a Photoreactive Side-Chain Mesogenic Group

Two kinds of methacrylates having a photoreactive and mesogenic ester group, 6-[4-(4′-methoxyphenylazo)phenoxy]hexyl methacrylate 1 and 6-[4-(4′-butoxyphenylazo)phenoxy]hexyl methacrylate 2, were synthesized and polymerized. Polymerization with phenylmagnesium bromide in CH2Cl2 at 0°C gave isotactic (it-) polymers (mm ∼ 94%) and that with Ph3P-Et3Al in CH2Cl2 at −40°C syndiotactic (st-) polymers (rr ∼ 84%). Syndiotactic poly(1) exhibited a liquid-crystalline (LC) phase, while it-poly(1) did not. Both st-poly(2) and it-poly(2) showed an LC phase, their transition temperatures differing from each other. The trans-to-cis isomerization by UV-light irradiation of the azobenzene moiety of the polymers, except it-poly(1) in the LC phase, induced phase transition of the LC phase into the isotropic phase. Using this phenomenon, image storage was examined. Image storage with a resolution up to 0.5–1 μm was achieved, and the stored image was quite stable at room temperature for at least one year.