Design and synthesis of Phenylaminothiophene donor-based chromophore with enhanced electro-optic activity

Three novel chromophores B-D have been synthesized based on thiophene derivatived donors, including 5-(methyl(phenyl)amino)thiophene 5-(bis(4-methoxyphenyl)amino)thiophene 5-((4-methoxyphenyl)(methyl)amino)thiophene groups respectively, with the same isophorone-derived bridge and tricyanovinyldihydrofuran (TCF) acceptors. A new strategy was proposed to improve the electron donating ability of the chromophore, thienyl groups were explored as a replacement for the phenyl unit in the donor part of the chromophore. Density functional theory calculations suggested that the first hyperpolarizability of (arylamino) thiophene donor-containing chromophore B-D is about 20% higher than that of 4-(dialkylamino) phenyl counterpart chromophore A. At least 50% enhancement in bulk nonlinearity (r33) is realized as the donor subunits were changed from alkylaniline to (arylamino) thiophene donors. Polymeric thin films doped with 25 wt% chromophore B-D have been poled to afford large r33 values of 131, 143 and 138 p.m./V at 1.31 μm, respectively, which is much higher than the EO activity of chromophore A (88 pm/V).