SYNTHESIS AND CHARACTERIZATION OF POLYMERS CONTAINING 4-CYANOBIPHENYL-BASED SIDE-GROUPS FOR NONLINEAR-OPTICAL APPLICATIONS .4. POLY[(4,4-DIMETHYL-2-VINYL-5-OXAZOLONE)-CO-(METHYL METHACRYLATE)]S

This paper describes the synthesis, characterization and nonlinear opt ical properties of a series of side chain coprohemins prepared by chem ical modification of poly[(4,4-dimethyl-2-vinyl-5-oxazolone)-co-(methy l methacrylate)]s (P(VDM-co-MMA)s) with 4,4'-disubstituted biphenyl. F irst, a poly(4,4-dimethyl-2-vinyl-5-oxazolone) (PVDM) and four P(VDM-c o-MMA)s were prepared by free-radical polymerization. Chemical transfo rmation reactions were then performed on these polymer backbones with 4-cyano-4'-(beta-aminoethoxy)biphenyl. This amine was synthesized acco rding to a novel procedure. The functionalized polymers are isotropic and show glass transition temperatures up to 132 degrees C. They can e asily be processed by spin-coating into thin films of optical quality. These films were oriented by a corona discharge process, and ultravio let spectroscopic measurements were performed to study the axial order ing kinetics as a function of poling conditions. Second-order nonlinea r optical coefficients (d(33) and d(31)) were measured at a fundamenta l wavelength of 1064 nm. The ratio d(33)/d(31) Was found to be close t o 3, as expected for amorphous isotropic polymers. No significant rela xation was observed at ambient conditions in 2 months. Hydrogen bondin g between GO-NH groups of neighboring side chains are felt to contribu te to the stability of the second-order nonlinear optical properties i n these PVDM systems.