Modified-PVK-based Photorefractive Three-Component Low-T_g Composites

Two modified poly(N-carbazole), poly (2-carbazolylethyl methacrylate) (PCEMA) and poly(3-carbazolylpropyl methacrylate) (PCPMA), were synthesized. Doped with electro-optic (EO) chromophore 1-n-butoxyl-2,5-dimethyl- 4-(4'-nitrophenylazo)benzene and the photosensitizer 2,4,7-trinitro-9-fl uorenone, the EO response and photore- fractive (PR) effect were studied experimentally. Due to the shorter spacer between the carbazolyl and the main-chain and thus a higher glass-transition-temperature T_g, PCEMA-based composite exhibited an effective EO coefficient as only a quarter as that in PCPMA-based composite. However, a slight higher two-beam coupling coefficient and much faster PR response were observed in the former. It was suggested that both the spacer length and the polymerization degree changed the T_g and the number density of traps, which decided the EO and PR