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)

Abstract

AbstractThis paper describes the synthesis, characterization and nonlinear optical properties of a series of side chain copolymers prepared by chemical modification of poly[(4,4‐dimethyl‐2‐vinyl‐5‐oxazolone)‐co‐(methyl methacrylate)]s (P(VDM‐co‐MMA)s) with 4,4′‐disubstituted biphenyl. First, a poly(4,4‐dimethyl‐2‐vinyl‐5‐oxazolone) (PVDM) and four P(VDM‐co‐MMA)s were prepared by free‐radical polymerization. Chemical transformation reactions were then performed on these polymer backbones with 4‐cyano‐4′‐(β‐aminoethoxy)biphenyl. This amine was synthesized according to a novel procedure. The functionalized polymers are isotropic and show glass transition temperatures up to 132°C. They can easily be processed by spin‐coating into thin films of optical quality. These films were oriented by a corona discharge process, and ultraviolet spectroscopic measurements were performed to study the axial ordering kinetics as a function of poling conditions. Second‐order nonlinear optical coefficients (d33 and d31) were measured at a fundamental wavelength of 1064 nm. The ratio d33/d31 was found to be close to 3, as expected for amorphous isotropic polymers. No significant relaxation was observed at ambient conditions in 2 months. Hydrogen bonding between CO‐NH groups of neighboring side chains are felt to contribute to the stability of the second‐order nonlinear optical properties in these PVDM systems.