Abstract
A series of thermally stable side-chain second-order nonlinear optical (NLO) poly(amide–imide)s via sequential self-repetitive reaction (SSRR) have been developed. This SSRR is based on carbodiimide (CDI) chemistry. Three difunctional azo chromophores (DR19, NDPD and DNDA) were, respectively, reacted with excessive amount of 4,4′-methylene-diphenylisocyanate (MDI) to form poly-CDI, and subsequently trimellitic anhydride (TMA) was added to obtain an intermediate, poly(N-acylurea). Poly(N-acylurea) exhibits excellent organosolubility, which enables the fabrication of high quality optical thin films. Moreover, its moderate glass transition temperature (Tg) characteristic allows the NLO-active polymer to exhibit high poling efficiency. After in situ poling and curing process, N-acylurea moieties were converted to amide–imide structures via SSRR, and the Tgs of the polymers were elevated significantly up to 70°C higher than that of the poly-CDI sample. Electro-optical coefficients, r33 of about 5.2–25.2pm/V at 830nm were obtained. Good temporal stability (80°C) and waveguide optical losses (3.8–6.6dB/cm at 830nm) were also obtained for these polymers.
Published Version
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