Studies on conjugated
polymers seldom report on their NMR characterization
in solution. This paper shows how NMR experiments, both
1
H NMR and routine 2D NMR spectra, can help in gaining a further insight
into the aggregation behavior of conjugated polymers and could be
used to flank the more employed solid-state NMR and other spectroscopy
and microscopy techniques in the understanding of the aggregation
processes. NMR spectroscopy allows distinguishing, within the class
of poorly solvatochromic conjugated polymers, those highly prone to
form π-stacked aggregates from the ones that have a low tendency
toward π-stacking.
Six new aminoalkylsulfanyl polythiophenes (PTs), namely PTNHBoc, PTNMeBoc, PTNH2,PTNHMe, PTNMe2, and PTN+Me3, were synthesized. Four of them were obtained through Stille coupling, whereasPTNH2 and PTNHMe were obtained through deprotection via N-Boc precursors. The solubility changes goingfrom the protected amines to the quaternary ammonium salt. All the polymers are soluble in DMSO and DMF.PTNHBoc and PTNMeBoc are also soluble in CHCl3, CH2Cl2, THF, and DMPU; PTNH2 and PTNHMe aresoluble in CH3OH, whereas PTNMe2 and PTN+Me3 are soluble both in CH3OH and in H2O. These PTs show atendency toward microaggregation in solution that does not represent an obstacle to their solubility. NMR, UV-vis,and XRD results prove that they are able to reach very high conjugation lengths and ordered conformations, notonly in the solid state but also in solutions of good solvents
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