Effects of main chains on the second order nonlinear optical susceptibility of poled poly(dipropargyloxybenzoates) containing 2-[4-(2-chloro-4-nitrophenylazo)- N-ethyl-phenylamino]ethanol ( Disperse Red 13)

Abstract

A series of isomeric polymers containing hexa-2,4-diynylene-1,6-dioxybenzoate group as the main chain and a polar azo dye ( Disperse Red 13) as in the side chain were synthesized, and their second order nonlinear optical responses were studied. The second order nonlinear coefficients, d 33 were found to be in the range of 50–90 pm/V. The nonlinear response ( d 33) with respect to the positions of main chain was found to be in the order; 3,5-( meta) > 3,4-( ortho) > 2,5- ( para) > 2,4-( meta), but the order of values d 33/ d 31 was 3,5-( meta) > 2,4-( meta) > 2,5- ( para) > 3,4 ( ortho). The higher response of the 3,5-polymer may be attributed to the symmetric substitution on the benzene ring, permitting the main chain conformation with less flexibility, as well as a higher Tg.