Synthesis of polymers containing donor-acceptor Schiff base in side chain for nonlinear optics

The Schiff bases 4-(omega -hydroxyalkyloxy)-N-(5-nitro-2-thienylmethylene)aniline with 2, 6 and 8 methylenic units in their alkyl group in which a nitrothienyl group as acceptor and an oxyphenyl group as donor were synthesized by condensation of (omega -hydroxyalkyloxy)anilines with 5-nitro-2-thiophenecarboxaldehyde. The methacrylate monomers 4-(omega -methacryloyloxyalkyloxy)-N-(5-nitro-2-thienylmethylene)aniline with alkylene groups of different lengths were synthesized by two different routes and polymerized using a free radical initiator to produce low molecular weight polymers useful for nonlinear optics, All the obtained compounds were characterized by conventional spectroscopic methods. First-order hyperpolarizability (beta) of 4- (2-hydroxyethyloxy)-N-(5-nitro-2-thienylmethylene) aniline typically was calculated using semiempirical method and the nonlinear optic properties of the same compound was studied by second harmonic generation. (C) 2001 Published by Elsevier Science Ltd.