Effect of Molecular Weight on Spectroscopic and Spectroelectrochemical Properties of Regioregular Poly(3-hexylthiophene)

Miroslaw Trznadel , Adam Proń , Małgorzata Zagórska , Ryszard Chrzaszcz , Jan Pielichowski

Abstract

Using experimentally established sequence of extractions, we were able to fractionate regioregular poly(3-hexylthiophene) (R-P3HT) into four fractions differing significantly in their molecular weight (Mn) and exhibiting low polydispersity coefficients. 1H NMR analysis of low molecular fractions enabled us to propose the dominant chain termination mechanisms and identify the sources of regioregularity defects. In particular, it turned out that the presence of small amounts of undesired isomer of 2-bromo-3-hexylthiophene, namely, 2-bromo-4-hexylthiophene, strongly influences the molecular weight and to a much lesser extent the regioregularity of the polymer obtained via Grignard type polycondensation. In the reaction with the growing chain, 2-bromo-4-hexylthiophene either causes its termination, lowering in this manner the molecular weight of the resulting polymer, or introduces regioregularity defects of TT?HH (TT = tail to tail; HH = head to head) type. The average conjugation length in R-P3HT increases with the increase of Mn as manifested by a bathochromic shift of the ?max and the appearance of the vibrational structure in the UV?vis?near-IR spectra of the fractions of higher molecular weight. This conclusion is supported by FTIR data. The onset of the oxidative doping of R-P3HT shifts to lower potentials with the increase of the molecular weight as evidenced by cyclic voltammetry and UV?vis?near-IR spectroelectrochemistry.
Author Miroslaw Trznadel
Miroslaw Trznadel,,
-
, Adam Proń KChTP
Adam Proń,,
- Chair Of Polymer Chemistry And Technology
, Małgorzata Zagórska KChTP
Małgorzata Zagórska,,
- Chair Of Polymer Chemistry And Technology
, Ryszard Chrzaszcz
Ryszard Chrzaszcz,,
-
, Jan Pielichowski
Jan Pielichowski,,
-
Journal seriesMacromolecules, ISSN 0024-9297
Issue year1998
Vol31
No15
Pages5051-5058
DOIDOI:10.1021/ma970627a
URL http://dx.doi.org/10.1021/ma970627a
Score (nominal)45
Publication indicators WoS Impact Factor: 2006 = 4.277 (2) - 2007=4.533 (5)
Citation count*257 (2018-01-27)
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