Influence of the Irregularity of the Molecular Structure on the Chiral Expression of Poly(fluorene)s

Abstract

In this report, the influence of the irregularity of the molecular structure on the chiral expression of 9,9-dialkylpoly(fluorene)s is investigated. For this purpose, different 9,9-dialkylpoly(fluorene)s─one homo-9,9-dialkylpoly(fluorene) and five alternating 9,9-dialkylpoly(fluorene)s─were synthesized according to an A2+B2 polymerization. The side chains of the 9,9-dialkylpoly(fluorene)s were chosen in such a way that a systematical increase in irregularity in the molecular structure of the 9,9-dialkylpoly(fluorene)s was obtained. As the organization of 9,9-dialkylpoly(fluorene)s is governed by an interplay between inter- and intramolecular interactions, we hypothesize that with the increase in molecular irregularity, the organization is more governed by intramolecular interactions and that the intermolecular interactions are suppressed. UV–vis, circular dichroism, and fluorescence measurements confirm this hypothesis. Furthermore, the actual process toward the chiral expression was monitored using a unique setup comprising in situ real-time transmission, optical rotation, static light scattering, third-harmonic scattering, and multiphoton-induced fluorescence experiments, which reveals that different pathways are followed in very regular and very irregular samples.