Development of new nonlinear optical polymers based on epoxy- amine oligomers with Bi-chromophore fragments in the side chain

For the first time bichromophore nonlinear optically active compounds, 3,5-bis [2- (N-ethyl-4- (4′-nitrophenylazo) anilino) ethoxy] benzyl alcohol, DF1, and 3,5-bis [6- (N-methyl-4- (4′-nitrophenylazo) anilino) hexaoxy] benzyl alcohol, DF2, have been synthesized. The synthesis of the epoxy-amine oligomers containing DF1 and DF2 dendritic fragments in the side chain was preceded by molecular design which demonstrated that the hexyl groups, binding the chromophores to the branching center in DF2, are able to provide greater mobility of the chromophores compared to the ethyl groups in DF1, thus determining the preference of the former from the viewpoint of NLO activity. Bi-chromophore compounds were introduced into the side chain of epoxy amine oligomers using the esterification reaction under mild conditions by the Steglich method. As a result, oligomers OAB-DF1 (Tg = 122 °C) and OAB-DF2 (Tg = 107 °C) were obtained with good yields, the degree of functionalization was 60 mol% and 45 mol%, respectively. The values of the NLO coefficients, d33, were measured by second harmonic generation technique; they are equal to 29 pm/V for OAB-DF1 and 40 pm/V for OAB-DF2.