The influence of the end-group on the chiral self-assembly of all-conjugated block copolymers

Abstract

This research demonstrates the influence of the end-group on the self-assembly of conjugated polymers.

Harmonic light scattering study reveals structured clusters upon the supramolecular aggregation of regioregular poly(3-alkylthiophene)

“…Simultaneously, the fluorescence is quenched and a strong bisignate CD spectrum appears in the visible part of the spectrum (Fig. 2) in line with earlier observations 2,4,45,48 . The generally accepted view is that the polythiophene undergoes a transition from an isolated disordered structure to a (semi-)microcrystalline aggregated structure in which the planarized polythiophene backbone stacks in a helical fashion giving rise to the strong CD response 3,44,[48][49][50] .…”

“…1) supramolecular aggregation process using a combination of UV/Vis and CD spectroscopy. Initially when the polymer is in a good solvent, the polymer is generally assumed to be present in a non-aggregated state where it prefers an extended conformation owning to its rigid backbone 2,4,7,[43][44][45][46][47] . The featureless absorption band with a maximum at 448 nm is typically taken as a sign that aggregation is absent.…”

“…In our experiments we used a regioregular poly(3-(3(S),7-dimethyloctyl) thiophene) of 34 monomeric units (8.2 kDa) and dispersity 1.1 (Fig. 1) that was reported by Van den Eede et al 2 using a Ni(bisdiphenylphosphinopropane)mediated Kumada catalyst transfer condensative polymerization reaction. We opted for this particular polymer as it can serve as a model system for many other polythiophene derivatives that have been investigated for applications.…”

“…Hence, supramolecular organization of conjugated polymers has been a topic of great interest and debate. For example, numerous studies have been devoted to their supramolecular aggregation in good or poor solvents [1][2][3][4] and in thin films 5,6 , and to the influence of parameters such as temperature [7][8][9] , pH or molecular structure [10][11][12][13] . A particularly popular polymer system is polythiophene and its derivatives 14 .…”

“…This decrease in solubility triggers a supramolecular aggregation process, the onset of which is typically visualized by a color change resulting from a red-shift of the UV/Vis absorption spectrum or a change in fluorescence emission spectrum. For chiral polymers, circular dichroism (CD) is often used to obtain additional information on the aggregation process 2 . These spectral changes are generally attributed to a phase separation resulting in two distinct phases in solution, i.e.…”