Solution DFWM χ(3) non-linear optical properties of poly[(arylene)silylene]s and poly[(arylene)(ethynylene)silylene]s containing tetra- or hypercoordinate silicon

Abstract

The third-order optical nonlinearities of a series of conjugated poly[(arylene)(ethynylene)silylene]s, and also of a complementary series of poly[(arylene)silylene] statistical copolymers without acetylene groups, have been studied in chloroform solution by using the degenerate four-wave mixing technique with a Q-switched Nd:YAG laser–oscillator at 1064 nm and a pulse duration of ca. 6 ns. The polymers contain a variety of arylene groups including carbazole and anthracene. The electronic and nuclear contributions of the χ⁽³⁾ susceptibility and the thermal nonlinearity of the solutions were separated. The χ⁽³⁾ susceptibilities of some poly[(arylene)(ethynylene)silylene]s were found to be as high as ∣Re χ⁽³⁾ ∣=0.95×10⁻¹⁰ esu for solutions of concentration 50 g l⁻¹. The results show that the presence of a single 8-(dimethylamino)naphthyl ligand at silicon affording pentacoordination has a beneficial effect on the χ⁽³⁾ properties. Comparison of the results for the poly[(arylene)silylene]s with those for the poly[(arylene)(ethynylene)silylene]s suggests that the absence of acetylene groups in the former case has in general a deleterious effect on the χ⁽³⁾ properties. Confirmation of the order of magnitude of the non-linear response has been confirmed by Z-scan measurements with picosecond laser pulses on hybrid sol–gel silica films of two of the poly[(arylene)(ethynylene)silylene]s containing arylene amide groups.