Saturation of the hyperpolarizability of oligothiophenes

Abstract

We report the observation of saturation with chain length of the second hyperpolarizability of a series of long, well-defined, conjugated oligothiophenes. This saturation occurs at the same length as that of the band gap and of the polarizability, and is attributed to a saturation of the effective conjugation length. Solvatochromic and thermochromic measurements indicate that conformational effects play a role.