New chiral photochromic menthone-containing homopolymers and copolymers-synthesis, phase behaviour and photo-optical properties

A new approach for the preparation of photosensitive materials for coloured data recording and storage is advanced. This approach involves the synthes is of copolymers containing nematogenic and combined (-)-arylidene-p-mentha n-3-one chiral photochromic fragments in one monomer unit. The conditions f or the formation of an LC phase in the chiral photochromic homopolymers as a function of the structure of the side groups have been identified; for a new series of copolymers, the effect of their composition on the phase beha viour and photo-optical properties is considered. Planarly oriented films o f the copolymers show selective light reflection in the UV, visible, and ne ar IR spectral regions. The photochemical behaviour of the homopolymers and copolymers in dilute solution and as films has been studied. In these syst ems, under UV radiation, the E-Z isomerization of the (-)-arylidene-p-menth an-3-one fragment is the dominating process. The kinetic features of the ph otoprocess are revealed, and the effective quantum yields calculated. The i somerization process leads to dramatic changes in the anisometry of the chi ral side groups, and the helical twisting power decreases. Therefore, as a result of UV radiation of films of the copolymers, the selective light refl ection peak is shifted to a longer wavelength spectral region. This means t hat such polymeric films can be considered as promising materials for colou r data recording and as storage media.