Aggregation of polythiophene homopolymer and block copolymer in solution utilizing the characteristics of pyridine at the side chain

Abstract

Poly[3-(5 0 -hexylpyridine-2 0 -yl)thiophene] (P3PT) (M n 5 13900, H-T content 5 90%) was prepared by the regioselective Grignard metathesis reaction and the subsequent Kumada coupling polymerization. Likewise, poly(3-hexylthiophene)-b-poly[3-(5 0 -hexylpyridine-2 0 -yl)thiophene] (P3HT-b-P3PT) (M n 5 17,300) was synthesized in the one-pot and successive monomer addition protocol, in which the segment ratio was calculated to be 56 (P3HT)/44 (P3PT) base on the 1 H NMR spectrum. The absorption and emission spectra of homopolymer P3PT(H), obtained by the protonation of the pyridine nitrogen, in THF/cyclohexane shifted to the longer wavelength as compared with those collected in THF, suggesting the aggregation in poor solvent. The aggregation of P3PT induced by the addition of Sc(OTf) 3 could be controlled by the molar ratio of pyridine and scandium complex. The protonated block copolymer P3HT-b-P3PT(H) was also subjected to the aggregate formation. The absorption maximum in THF/CH 3 OH showed a bathochromic shift and the fluorescence emission was almost quenched. From the 1 H NMR spectra and DLS measurements, P3HT-b-P3PT(H) forms nanometer scale aggregates particularly with the insolubility and stacking of non-ionic P3HT in alcohol as the driving force.

Optical properties of amphiphilic copolymer-based self-assemblies

“…On the other hand, J-aggregation displays larger molecular displacement along the long molecular axis with higher k r which usually induces a red shifted absorption spectrum and the formation of an aggregation-induced emission enhancement (AIEE) system [67,68]. In addition, the aggregation tendency of the conjugated polymers depends on the chemical structures as well as the environmental conditions, such as concentration, solvent polarity, and temperature [69].…”

Hydrodynamic properties and conformation of poly(3-hexylthiophene) in dilute solutions

“…Furthermore, a lot efforts have been devoted to the studies of the aggregation processes in poly(thiophene) solutions by dynamic light scattering (DLS), SEC, UV–vis spectroscopy, and photoluminescence; the authors have found combinations of solvents which can be used to obtain the P3HT aggregates of various structural order. In the work by McCulloch et al, characteristics of poly(3‐hexylthiophene) and other poly(3‐alkylthiophene)s, including the persistence lengths of the macromolecules, were obtained by small‐angle neutron scattering, SEC, and NMR spectroscopy.…”