Abstract
The influence of the regioregularity on the second-order nonlinear optical response of polythiophenes in solution was investigated. A series of chiral poly((S)-3,7- dimethyloctylthiophene)s with varying degrees of regioregularity from 54 to 100% were studied. To a large extent, the changes in second-order nonlinear optical properties with varying degree of regioregularity are caused by electronic effects. More specifically, the second-order nonlinear optical response increases with increasing regioregularity, as this corresponds to a rising conjugation length. However, a regioregularity of 80% suffices for a maximized second-order nonlinear optical response.