Synthesis and characterization of Bi-functional photorefractive polymers with high molecular weight and low glass transition temperature

Abstract

Carbazole-based bi-functional photorefractive polyacrylates were prepared via free radical polymerization and post-azo-coupling reaction. The structure of polymers was characterized by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The differential scanning calorimetry (DSC) and the thermal gravimetric analysis (TGA) were used to characterize the thermal property of polymers. The results indicate that though the glass transition temperature (T g) of polymers increases with increasing the ratio of NLO groups, the polymers with different ratios of NLO groups still all show low glass transition temperatures around 60 °C, and good thermal stability, which are favorable to the practical application of these polymers. The gel permeation chromatographic (GPC) result indicates that these polymers all have high-molecular-weight which is favorable to the long term stability of the material. Further, these polymers have good solubility in chloroform solvent, and the solutions can easily be fabricated into optically transparent films. Gain coefficients of 75 cm−1, 185 cm−1 and 66 cm−1 can be observed at zero external electric field without any addition agent or pre-poling for polymers P-2, P-3 and P-4 respectively. The different contents of NLO groups result in the different properties of polymers P-2, P-3 and P-4.