Grating diffraction of blends involving NLO random copolymers

Dielectrophoresis can be employed to create a grating-like microstructure in phase-separated polymer blends. Typically, this process produces a morphology of pearl chain-like and/or elongated column-like entities spaced rather regularly throughout a matrix. In addition, these microstructures are generally waving and not uniform in terms of column size, shape, and spacing; i.e., they lack periodicity. Our recent work shows that it is possible to obtain an improved quality of elongated column-like entities in field-modified blend films. In this study, a nonlinear optically active (NLO) random copolymer, with hyperpolarizable chromophores as side groups, is mixed with a linear optical (LO) polymer. Important blend parameters, such as blend composition, polymer concentration, molecular weights of dispersed phase and matrix phase, and electric field strength, are carefully controlled to optimize the periodicity of the field-modified microstructure. The resulting unique morphology is capable of creating a grating diffraction pattern from light at 632.8 nm.