Polymers containing backbone acetylene, anthracene and tetra-, penta- or hexa-coordinate silicon units: UV–visible, photoluminescence and solution χ(3) non-linear optical properties

Degenerate four-wave mixing measurements of the ?(3) non-linear optical properties of poly(arylene-ethynylenesilylene)s

“…As previously reported, 9 for the series of polymers 2-4 containing naphthyl (Np) or naphthylamine (NpN) groups at silicon, smooth trends in the 29 Si and SiCC 13 C NMR chemical shifts as well as the energy of the n(CC) IR absorbance are observed with increasing coordination number at silicon, reflecting the change in the electronic environment. However, in the case of the w (3) results no such trend is observed, the effect increasing from 2 to 3 and then decreasing on going from 3 to 4, whereas the value for 1 (with phenyl groups at silicon) is very large.…”

“…Z-scan w (3) measurements on some similar silicon-containing polymers of general 8 and 1064 nm in the near-resonant region [Re (1 (3) ) = 4.0 Â 10 À13 esu]. 9 Here, we report the considerably higher values obtained by using the DFWM technique for solutions of a variety of poly(arylene-ethynylenesilylene)s. Following the route previously described, 9-11 polymers 1-8 (Table 1) were prepared by palladium-catalysed cross-coupling polymerization between the appropriate diethynylsilane (obtained from the corresponding dichlorosilane) and dibromoarene (Eqn [1]). Polymers 3, 4 and 8 contain the 8-(dimethylamino)naphthyl ligand, which gives stable hypercoordinate species.…”

“…13 For polymers 1, 3 and 4, the Im(w (3) ) and Re(w (3) ) values determined by the Z-scan method at 1064 nm (pulse duration 140 ps, intensity 20 GW cm À2 ) in CHCl 3 solution (50 g l À1 ) have been previously reported. 9 DFWM experiments were made with a Qswiched Nd:YAG laser-oscillator at 1064 nm and both co-and cross-polarized pumps, the pulse duration being 6 ns unless otherwise stated ( Table 1). The pulse energy of each pumping wave was up to 10 mJ.…”

“…The results obtained are greater by more than two orders of magnitude than those previously reported for 1 and 4 in concentrated solutions as determined by the Z-scan technique at 1064 nm. 9 However, in this previous study the values of n 2 were extracted from the Z-scan results with large uncertainties since the data could not be fitted well; indeed, for 3 no satisfactory result could be obtained and apparently identical results were obtained for 1 and 4. Not only is comparison of results obtained using the two techniques difficult 5,16 but also it should be noted that a much lower light beam intensity (%1 MW cm À2 ) was used in the present study than for the Z-scan determination (20 GW cm À2 ).…”

“…Not only is comparison of results obtained using the two techniques difficult 5,16 but also it should be noted that a much lower light beam intensity (%1 MW cm À2 ) was used in the present study than for the Z-scan determination (20 GW cm À2 ). 9 At the greater intensities used in the Z-scan experiment, higherorder non-linear susceptibilities (w (5) and w (7) ) giving negative contributions could decrease the overall non-linear effect of phase modulation. 8 Other reasons for the small values of n 2 obtained by Z-scan measurement include possible competing effects such as two-photon absorption and stimulated scattering appearing at high beam intensity.…”