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Saturation of the second hyperpolarizability for polyacetylenes

✍ Scribed by Daqi Lu; Bryan Marten; Murco Ringnalda; Richard A. Friesner; William A. Goddard III

Publisher: Elsevier Science
Year: 1996
Tongue: English
Weight: 371 KB
Volume: 257
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(96)00458-7

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✦ Synopsis

Polyacetylene (PA) polymers -(-CH=CH-), lead to large second hyperpolarizabilities (y) that increase with N. For small N the increase is quite rapid, eventually saturating (becoming linear in N) for N > N& Both experimental and theoretical attempts have been made to estimate N,Y,,. In 1994 this led to two Science papers, one obtaining NA, = 20 (semiempirical theory) and the other obtaining N,,, y = 12.5 (experiment, but on a substituted disordered form of PA!). We report here ab initio calculations up through N = 49 (C,,H ,& and show that N,,, y = 45 + 5. The much larger experimental _ value, N,Y,, = 125, is explained in terms of the structural defects and disorder introduced by the synthetic method.

There is a great deal of interest in developing organic non-linear optical (NLO) materials for use in optical processing,

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