Photoalignment Films of Polyesters with Photoreactive Main Chain

The photoreactive thin films of poly(oxyalkyleneoxy-1,4-phenylenediacryloyl), a PDA-n polyester (n=2–5), were prepared. Their photoreactions and the liquid crystal (LC) photoalignment by irradiation of linearly polarized UV light (LPL) were investigated. The PDA-n polyesters have photoreactive sites in the polymer main chain and not in the side chain which is different from poly(vinyl cinnamate) (PVCi), a well-known photoalignment polymer. These PDA-n thin films show different photoreactivities depending on the number of methylene units, n. Odd-numbered PDA-n polyesters with higher photosensitivity than even-numbered PDA-n polyesters show a dichroism due to irradiation with LPL which results in a homogeneous alignment of the nematic LC.