Third-Order Optical Nonlinearity of Poly(1,6-Heptadiyne) Derivatives Containing Mesogenic Moiety

Abstract

Poly (1,6-heptadiyne) derivatives with side group liquid crystalline mesogens were prepared by the metathesis polymerization with transition metal catalyst. It was found that the MoCl⁵-based catalyst systems were very effective for the polymerization of 1,6-heptadiyne monomers with various mesogenic groups. Polymerization of these monomers gave to the conjugated polyenes that contain cyclic recurring unit in the polymer backbone. Resulting polymers with electron donating mesogenic groups exhibited good solubility in common organic solvents and were easily spin coatable on fused silica substrate. Copolymerization of the mesogen-containing monomers with diethyl dipropargyl malonate (DEDPM) was also attempted to improve their physical properties. The third-order nonlinear optical susceptibility, x ⁽³⁾, was evaluated by the optical third-harmonic generation measurement. The near-resonant x ⁽³⁾ value was found to be in the range of 1.75 ∼ 8.22 × 10⁻¹¹ esu at the fundamental wavelength of 1.907 μm.