No abstract

A novel Y‐type polyurethane (polyurethane 3) containing 4‐(4‐nitrophenylazo)resorcinoxy groups as nonlinear optical (NLO) chromophores, which constitute part of the polymer backbone, was prepared and characterized. Polyurethane 3 is soluble in common organic solvents such as acetone and N,N‐dimethylformamide. It shows thermal stability up to 270 °C from thermogravimetric analysis with a glass transition temperature obtained from differential scanning calorimetry of 102 °C. The second harmonic generation (SHG) coefficient (d33) of the poled polymer film at 1064 nm fundamental wavelength is 2.06 pm V−1. Polymer 3 exhibits thermal stability up to Tg, and no significant SHG decay is observed below 100 °C, which is acceptable for nonlinear optical device applications. Copyright © 2012 Society of Chemical Industry

Novel X‐type polyurethane 5 containing 4‐(2′,2′‐dicyanovinyl)‐6‐nitroresorcinoxy groups as nonlinear optical (NLO) chromophores, which constitute parts of the polymer backbone, was prepared and characterized. Polyurethane 5 is soluble in common organic solvents such as acetone and N,N‐dimethylformamide. It shows thermal stability up to 280 °C from thermogravimetric analysis with a glass transition temperature (Tg) obtained from differential scanning calorimetry thermogram of around 120 °C. The second harmonic generation (SHG) coefficient (d33) of poled polymer film at 1064‐nm fundamental wavelength is around 6.12 × 10−9 esu. The dipole alignment exhibits a thermal stability even at 5 °C higher than Tg, and there was no SHG decay below 125 °C due to the partial main chain character of the polymer structure, which is acceptable for NLO device applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

No abstract

We derive the collisionless Landau damping in a plasma by satisfying the causal requirement that the susceptibility function of the plasma for time t < 0 should be nil. The causality condition should be satisfied by the susceptibility function of a plasma no matter what equations we employ to describe the plasma. Thus we conclude that the fundamental reason of the collisionless damping can be traced to the causality. As an example, we derive the collisionless damping of ion acoustic wave in a plasma by employing fluid equations.