Molecular structure of azopolymers and photoinduced 3D orientational order",

The combination of transmission null ellipsometry (TNE) and attenuated total reflection (ATR) methods supported by absorption measurements is shown to be an effective tool to study spontaneous and photoinduced 3D order in azopolymers. We investigated a series of azobenzene containing side-chain polyesters differing by the length of the main-chain spacer (CH 2 ) m (m ) 2, I. Introduction Presently, in the era of information technologies, there is an increasing interest in photonic processes allowing the improvement of devices for information storage, processing, displaying, and transfer. The phenomenon of photoinduced anisotropy (PIA) is one of the best candidates for this purpose. Photoinduced anisotropy (also named Weigert 1 effect) produces optical dichroism and birefringence in various materials by generating an orientational order. This order is centrosymmetric (quadrupolar) and should be more correctly named alignment, in contrast with the orientation induced by poling methods (photoassisted electrical poling (PAEP) 2 and all-optical poling (AOP) 3-5 ), which generate a noncentrosymmetric (dipolar and octupolar) orientational order, producing nonlinear effects ( (2) ). Azobenzene-containing polymers are known to be among the most effective materials for PIA generation. The microscopic explanation of PIA in azopolymers is based on two properties of azochromophores: 6,7,10 the trans-ci

Surface tension and dilation rheology of DNA solutions in mixtures with azobenzene-containing cationic surfactant

The surface tension and dilational surface visco-elasticity of the individual solutions of the biopolymer DNA and the azobenzene-containing cationic surfactant AzoTAB, as well as their mixtures were measured using the drop profile analysis tensiometry. The negatively charged DNA molecules form complexes with the cationic surfactant AzoTAB. Mixed DNA + AzoTAB solutions exhibit high surface activity and surface layer elasticity. Extremes in the dependence of these characteristics on the AzoTAB concentration exist within the concentration range of 3 x 10(-6)-5 x 10(-5) M. The surface tension of the mixture shows a minimum with a subsequent maximum. In the same concentration range the elasticity shows first a maximum and then a subsequent minimum. A recently developed thermodynamic model was modified to account for the dependence of the adsorption equilibrium constant of the adsorbed complex on the cationic surfactant concentration. This modified theory shows good agreement with the experimental data both for the surface tension and the elasticity values over the entire range of studied AzoTAB concentrations. (C) 2016 Elsevier B.V. All rights reserved