Nonlinear optical properties of polymeric materials

In this paper we discuss the molecular and macroscopic requirements for large second order nonlinear optical effects in polymeric systems. A new enhancement mechanism attributable to cooperative interactions between dipoles in polar polymer chains is proposed and tested by the synthesis and characterization of asymmetric condensation copolymers derived from p‐oxy‐α‐cyanocinnimate derivatives. An enhancement of a factor of 20 in electric field induced second harmonic generation relative to an equivalent concentration of chemically identical nonpolymerized chromophores in solution is obtained. Conformational and perhaps alignment restrictions in the rubbery state result in a reduction in alignment relative to what would be expected for an equivalent concentration of the polymerized chromophores in a moderately viscous medium. A model is proposed to account for the enhancement factors.