Development of Thermally Stable Novel EO-polymers

Abstract

We have synthesized and evaluated NLO properties of azo dye attached novel NLO polymers with high thermal stability. The NLO polymers containing an azo dye, DR-1, in their side-chain were synthesized using a new approach. Polyacrylic acid or polymethacrylic acid reacted with DR-1 via the intermediate reaction of the acid and N,N′-dicyclohexylcarbodiimide. The DR-1 contents of the products were 39mo1% and 29mo1%, for derivatives from polyacrylic acid and polymethacrylic acid, respectively. Glass transition temperatures of 150°C to 170°C were obtained for Disperse red 1 dye attached polymethacrylic acid. The poled film exhibited second order NLO susceptibilities (χ (2) 33 ) of 48 pm/V to 53 pm/V at 1.3 µm fundamental wave. Due to the high glass transition temperatures of the polymers, long-term stability of the optical nonlinearity at 100°C was observed for 200 hrs or more. However residual carboxyl groups caused absorbance decrease mainly by hydrolysis of the ester bonds of the polymers. These polymers can be further improved to have more thermally stable structure by heat treatment. Through the approach, methacryl imide structure was formed and the polymer has high Tg of 165?. This imidized polymer exhibited χ (2) 33 of 45 pm/V at a wavelength of 1.3 µm and maintained about 90% of the initial value after 230 hrs or more at 100°C.