Synthesis of photocrosslinkable non-linear optic polyimides and electro-optic properties

Photocrosslinkable polyimide-type non-linear optical (NLO) polymers were ob tained by multi-step reactions. Polyimide substrate polymer (P05) made From 3,3'-diamino-4,4'-dihydroxybiphenyl (HAB) and aromatic dianhydride (6FDA) had higher molecular weight than other polyimides due to the high nucleophi licity of the amine group in HAB compared to the one in 2,2'-bis(3-amino-4- hydroxyphenyl)hexafluoropropane(Biri-AP-AF) with the electron-withdrawing g roup. The introduction of DR-1 chromophore into the polyimide substrate pol ymers depended on the steric factor between the bulky DR-1 chromophore and the substrate polyimide in the polymer reaction via the Mitsunobu reaction. In the DR-1 substituted NLO polyimides, Tg decreased with the increasing a mount of DR-1 chromophore. Photocrosslinkable NLO polyimide (P05-DR-cin) wa s obtained by the introduction of the photoreactive cinnamoyl group into th e DR-1 substituted polyimides. The electro-optic coefficient (r(33)) Of the NLO polymer was determined with an experimental set-up capable of real-tim e measurement by varying both the poling field and temperature. The electro -optic coefficient (r(33)) of the linear NLO polymer (P05-DR) started to sh ow a decrease of the r(33) value from about 80 degreesC. The photocrosslink ed NLO polymer (P05-DR-cin). however, maintained a high r(33) value up to 1 50 degreesC due to chromophores locked in the polymer matrix with a network structure.