Novel mechanism of fast relaxation of photo-induced anisotropy in a poly(malonic esters) containing p-cyanoazobenzene

The relaxation behavior of photo-induced anisotropy has been investigated i n a side-chain liquid crystalline(LC) poly(malonic ester) (PCN). Abnormal p henomenon, increment of the induced birefringence, in decaying process was observed just after the pumping beam polarized perpendicularly to the recor ding beam was illuminated in the relaxation process. This is difficult to e xplain using the present models, the thermal cis-trans isomerization or the free volume effect for the relaxation process. We suggest a new model cons idering the elastic force between the side-chain and the backbone in the po lymeric film. According to our model, the backbone can be reoriented togeth er with the side-chain, and fast relaxation is associated with the elastic force. (C) 2000 American Institute of Physics. [S0021-9606(00)51642-0].