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

The third-order optical nonlinearities of a series of conjugated poly[(aryl ene)(ethynylene)silylene]s, and also of a complementary series of poly[(ary lene)silylene] statistical copolymers without acetylene groups, have been s tudied in chloroform solution by using the degenerate four-wave mixing tech nique with a Q-switched Nd:YAG laser-oscillator at 1064 nm and a pulse dura tion of ca. 6 ns. The polymers contain a variety of arylene groups includin g carbazole and anthracene. The electronic and nuclear contributions of the chi((3)) susceptibility and the thermal nonlinearity of the solutions were separated. The chi((3)) susceptibilities of some poly[(arylene)(ethynylene )silylene]s were found to be as high as \Re chi((3))\=0.95x10(-10) esu for solutions of concentration 50 g l(-1). The results show that the presence o f a single 8-(dimethylamino)naphthyl ligand at silicon affording pentacoord ination has a beneficial effect on the chi((3)) properties. Comparison of t he results for the poly[(arylene)silylene]s with those for the poly[(arylen e)(ethynylene)silylene]s suggests that the absence of acetylene groups in t he former case has in general a deleterious effect on the chi((3)) properti es. Confirmation of the order of magnitude of the non-linear response has b een confirmed by Z-scan measurements with picosecond laser pulses on hybrid sol-gel silica films of two of the poly[(arylene)(ethynylene)silylene]s co ntaining arylene amide groups.