Third trans-polyacetylenes

Large third order susceptibilities have recently been observed for trans-polyacetylene, heteroaromatic polymers, and poly[p-phenylene vinylene] (4-11). Such nonlinear phenomena in electroactive polymers due to intense laser irradiation has been linked to the photogeneration of charged solitons on time scales of the order 10 s, and values of (3w-w+w+w)—4x 10 esu for... 

The highest value of 7 found in a study of quadrupolar examples (THG at 1,907 nm) was 229 x 10 esu for 225, which was the longest system studied. The third-order susceptibility, (DFWM, 532 nm), for the polymer, 226, was found to be over 1,000 times that of all-trans polyacetylene, although this value is presumably dispersion enhanced and very far from the static value. " ... 

It must be noted that the values reported in the literature vary over broad ranges. Therefore, the values listed here reflect only the general behavior of several classes of compounds. It can be seen in Table 3.5 that trans-polyacetylenes (PAs) and polydiacetylenes (PDAs) exhibit the largest third-order NLO susceptibilities. The x value of cis-PA (not shown) is more than an order of magnitude smaller than that of trans-PA. Derivatives of poly-p-phenylene, poly(phenyl-ene vinylene), and polythiophene also exhibit NLO activity, but to a much lesser extent than PAs and PDAs. As pointed out above, polysilanes also possess quite large x values. This is explained by the cr-conjugation of the silicon chain, which implies a pronounced delocalization of cr-electrons. A very large x value... 

Oxidative polymerization of trans-bis-deprotected 79 under Hay coupling conditions [54] yielded, after end-capping with phenylacetylene, the high-melting and readily soluble oligomers 80a-e with the poly (triacetylene) backbone [87,106] (Scheme 8). Poly(triacetylene)s [PTAs,-(C=C-CR=CR-C=C) -] are the third class of linearly conjugated polymers with a non-aromatic allcarbon backbone in the progression which starts with polyacetylene [PA,... 

To explore more fully the nature of the defects induced by the n>doping of polyacetylene with divalent cations, optical absorption experiments have been carried out (17). Spectra were obtained on thin semitransparent films of polyacetylene grown on fiat glass. The 2000A thick films were synthesized using one-third the normal catalyst concentration and a five second exposure to 60 torr of acetylene gas (10). After washing and drying the thin c/s-rich polyacetylene films, they were thermally isomerized to trans-... 

It is of interest to compare the present results with those obtained by the SE method. The Young s modulus of the trans film (40 GPa) prepared by the INS method is about one third smaller than that (100 GPa) prepared by the SE method, but the tensile strength (2100 MPa) from the former method is about twice that (900 MPa) from the latter. This means that the polyacetylene film synthesized by the INS method is more easily elongated but less breakable than the film prepared by the SE method. 

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