A diol 1

3-di(2-hydroxyethyl) 5-hydroxyl isophthalate (DHHI) was synthesized through the nucleus substitution reaction of 5-hydroxyl isophthalic acid(HIA)．The monomer was characterized by 1H-NMR

FTIR

elemental analysis and differential scanning calorimetry (DSC)．Then a precursor polymer (PU-OH) containing hydroxyl groups was prepared by step polymerization of DHHI and 4

4′-diphenylmethane-di-isocyanate (MDI).By PU-OH’s functionalization with cinnamoyl chloride

a polyurethane (PU) with cinnamate side-groups (PU-CI) was obtained．The polymers synthesized were characterized with 1H-NMR

DSC

IR spectroscopy and elemental analysis．The photosensitive polymer PU-CI was found to be cross-linked under the irradiation of UV light through a cyclo [2+2] reaction．After processed by Linear Polarized Polymerization (LPP)

the spin-coating films of PU-CI were changed into photo alignment layers．Then sandwich-type liquid crystal cells (LC cells) of a 50-μm-thick were assembled via a capillary action using nematic liquid crystal 5CB．The microscopic photographs were obtained which showed the LC-aligning ability of PU-CI photo alignment layers．Therefore

the photosensitive polymer PU-CI synthesized has potential application as photo alignment layer in liquid crystal cells．