Holographic gratings in azobenzene side-chain polymethacrylates

Optical storage properties of thin unoriented liquid crystalline and amorph ous side-chain azobenzene polymethacrylate films are examined by polarizati on holographic measurements. The investigated materials are free radical co polymers derived from two photochromic monomers, 6-(4-oxy-4'-cyanoazobenzen e)hex-1-yl methacrylate and 8-(4-oxy-4'-cyanoazobenzene)oct-1-yl methacryla te, and a nonphotochromic optically active comonomer, (-)-menthyl methacryl ate. The thermal behavior and phase transitions of the polymers have been i nvestigated in detail through differential scanning calorimetry and polariz ing optical microscopy. Atomic force microscopy investigations have been ca rried out on the polarization holographic gratings recorded in the polymeth acrylate films. A surface relief grating has been found to appear in all fi lms after irradiation. The copolymers with 50-75% dye content exhibit the l argest surface relief. The stored information seems to be stable up to appr oximately 70 degrees C, except in the case of polymers with low dye content .