NOVEL SIDE-CHAIN LIQUID-CRYSTALLINE POLYESTER ARCHITECTURE FOR REVERSIBLE OPTICAL STORAGE

New side-chain liquid crystalline polyesters have been prepared by mel t transesterification of diphenyl tetradecanedioate and a series of me sogenic 2-[omega-[4-[(4-cyanophenyl)azo]phenoxyl] alkyl]-1,3-propanedi ols, where the alkyl spacer is hexa-, octa-, and decamethylene in turn . The polyesters have molecular masses in the range 5000-89 000. Solut ion C-13 NMR spectroscopy has been employed to identify carbons of pol yester repeat units and of both types of end groups. Polyester phases and phase transitions have been investigated in detail by polarizing o ptical microscopy and differential scanning calorimetry for the hexame thylene spacer architecture with different molecular masses. Using FTI R polarization spectroscopy, the segmental orientation in unoriented p olyester films induced by argon ion laser irradiation has been followe d and an irradiation-dependent order parameter for the cyanoazobenzene mesogens calculated. FTIR is also utilized to follow the temperature- dependent erasure of the induced orientation. Optical storage properti es of thin unoriented polyester films are examined through measurement s of polarization anisotropy and holography. A resolution of over 5000 lines/mm and diffraction efficiencies of about 40% have been achieved . Lifetimes greater than 30 months for information stored have been ob tained, even though the glass transition temperatures are about 20 deg rees C. Complete erasure of the information can be obtained by heating the films to about 80 degrees C, and the films can be reused many tim es without fatigue.