Copolymers containing rigid azobenzene and ester side groups linked by relatively short spacers to the main chain form amorphous films. Such films can be addressed with polarized laser light to produce oriented domains. Birefringence measurements and time dependent infrared spectroscopy are used to analyze the orientation. Two series of copolymers are analyzed in comparison. The first consists of copolymers of 4'-{[2-(methacryloyloxy)ethyl] ethylamino}4-nitroazobenzene (DR1M) and 4-{[2- ((2-methyl-1-oxo-2-propenyl)oxy)ethyl]oxy}benzoate (BEM), where both the azo and the ester rigid groups have similar dipole moments. The second series consists of copolymers of DR1M with a much less polar 4-phenyl-4- {[2-(2-(2-methyl-1-oxo-2- propenyl)oxy)ethyl]oxy}benzoate (NBEM). Birefringence studies clearly suggest that in poly(DR1M-co- BEM), the BEM groups are being oriented by 'sympathy' with the DR1M groups, while in poly(DR1M-co-NBEM) no such cooperative motion is apparent. Time dependent infrared spectroscopy can analyze separately the motions of each of the rigid groups, and it clearly shows that the BEM groups are being moved by the DR1M groups, while the orientation of the NBEM groups is much lower. Thus one can envisage materials where cooperative motion is present (polar groups), or where only the polar azobenzene groups are 'molecularly addressed' by the laser, with the non-polar rigid groups remaining relatively inert. The consequences to formation of surface gratings on these copolymer films are discussed.

Date Published: 23 January 1997
PDF: 10 pages
Proc. SPIE 2998, Photosensitive Optical Materials and Devices, (23 January 1997); doi: 10.1117/12.264180

Published in SPIE Proceedings Vol. 2998:
Photosensitive Optical Materials and Devices
Mark P. Andrews, Editor(s)