Expression of Chirality in Tailor-Made Conjugated Polymers
2018
Van Den Eede, Marie-Paule | Van Gestel, Lore | Koeckelberghs, Guy
The supramolecular organization and chiral expression in tailor-made conjugated polymers (CP) are investigated. The polymers were synthesized in a controlled way, providing (almost) perfect control over the molecular structure. This allowed to understand the effect of different parameters in the molecular structure. The polymers were analyzed by gel permeation chromatography (GPC) and ¹H NMR. Solvatochromism experiments were performed on all polymers, using UV–vis spectroscopy and circular dichroism (CD). Two new parameters influencing the supramolecular organization and chiral expression were found. First, in block copolymers consisting of an (S)-chiral and (R)-chiral block of equal length, end-groups are required to break the symmetry. If no end-group is present, the polymer chains do not aggregate. Second, if one single (head-to-head) HH-coupling is present in regioregular poly(thiophene), the supramolecular aggregation is completely disrupted, which is in contrast to the presence of one (tail-to-tail) TT-defect. The obtained results were confirmed by differential scanning calorimetry (DSC).
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