Photoactive polyamideimides synthesized by the polycondensation of azo-dye diamines and rosin derivative

New rosin-based photoactive polyamideimides (PAI-a and PAI-b) with a large second-order nonlinear optical coefficient and photoinduced birefringence were synthesized by the polycondensation of rosin-maleic anhydride adduct (RMA) with azo-dye diamines, 2-(2-{ethyl-[4-(4-nitrophenylazo)phenyl]aminoethoxy)benzene-1,4- diamine (4a) or 2-(2-{ethyl-[4-(4- methylsulfonylphenylazo)phenyl]amino}ethoxy)benzene-1,4-diamine (4b). Due to the bulky alicyclic structure of the rosin, these polymers were highly soluble in organic solvents and could easily be processed by spin-coating into thin films of high optical quality. Fabricated polymer films were very smooth, tough, adhesive to the substrate, and optically clear. Second-order nonlinear optical coefficients (d₃₃) of the corona-poled PAI-a and PAI-b films were 83 and 54 pm/V, respectively, at the fundamental wavelength of 1064 nm. Birefringences as high as 0.072 for PAI-a and 0.035 for PAI-b could be induced and erased repeatedly by the irradiation of linearly polarized and circularly polarized 532-nm light, respectively.