Studies of structures and properties of polymeric systems containing bis-(hydroxy-arylidene)alkanones as NLO-active chromophores

NLO-properties of polymer systems containing bis-(hydroxy-arylidene)alkanone chromophores were studied experimentally and analyzed using ab initio quantum chemical calculations. A monoclinic crystal structure (space group P2₁11) of the polyester containing fragments of such chromophores in the backbone was simulated and a reasonable agreement between the experimental and simulated X-ray powder diffraction patterns was achieved. Ab initio quantum-mechanical estimations of the SHG-observable macroscopic second-order non-linearity tensor coefficients, obtained for the polymer crystal structure at the HF SCF level, led to the major d_XZZ-coefficient of 1.9 pm/V. Films of ionic complexes of strongly basic poly-1,10-decamethylene-acetamidine with various bis-(hydroxy-arylidene)alkanone chromophores were prepared and shown to display considerable THG-efficiencies. The molecular structure of these complexes is discussed on the basis of the experimental spectroscopic data and calculated relative stabilities of different forms of the complexes. The formation of the complexes results in a considerable increase of the glass transition temperature by ≈70°C.