Thiophene-Based π-Conjugated Emitting Polymers:  Synthesis and Photophysical Properties of Poly[2-(dodecyloxy)-5-methyl-m-phenyleneethynylene] and Poly[2-(dodecyloxy)-5-methyl-m-bis(ethynyl)phenyleneoligo-thienylene]s

Abstract

A series of copolymers, poly[2-(dodecyloxy)-5-methyl-m-phenyleneethynylene] and poly[2-(dodecyloxy)-5-methyl-m-bis(ethynyl)phenyleneoligothienylene]s, in which ethynylene units are inserted into both of the meta positions of every phenylene for the elimination of the steric hindrance around the meta linkages, was synthesized by a Heck type coupling reaction. The resulting polymers were characterized by infrared and nuclear magnetic resonance spectroscopy and by elemental analysis and gel permeation chromatography. Their optical spectra show that the absorption and emission maxima regularly shift to lower energy with increasing number of the thiophene units between the consecutive m-phenylene linkages. It is confirmed that the role of the m-phenylene as an interrupting block does not come from the steric hindrance around the linkage but from the intrinsic property, e.g., the MO of the m-phenylene moiety. The quantum yields of their emissions gradually decrease with a decrease in concentration of the ethynylated m-phenylene units on the polymer backbone and the Stockes shifts increase. Both of the trends indicate that a nonradiative decay of the excited states increases with an increase in the possible configurations of thiophene rings within the repeating active block.

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“…A 1 H NMR dilution investigation (3–0.5 mM) revealed no important intermolecular interactions (<0.02 ppm). Similar observations have been reported for other kinds of intramolecularly π‐stacking oligomers and polymers 30, 31. The broadening of the aromatic signal for m ‐PPY would reflect the slowness of its molecular motion in the ordered structure 38, 39.…”

“…The trimethylsilyl group was removed by a treatment with tetrabutylammonium fluoride to afford compound 3 . The polymer, m ‐PPY, was synthesized by a Sonogashira–Hagihara polycondensation reaction between 3 28 and 9 29 with a 4% yield 30. The molecular weight of the amphiphilic polymer was estimated by GPC, which gave M n = 5373 and M w = 7457 with a polydispersity index of 1.26.…”

The Synthesis of Electroluminescent Polymers

“…Most PAEs investigated to date have been poly(p-phenylene ethynylenes) (PPEs) with alkoxy-(red-orange emitting) or alkyl substituents (green emitting). Blue emission has been seen from PPEs with meta -or ortho-phenylene units [78,79], or with bulky substituents that reduce interchain interactions [80].…”

Synthesis, characterization, and optical properties of new pyridine- and thiophene-based copolymer bearing bulky naphthyl group

“…In fact, it appears to be widely accepted that meta-linkages in polymers are something to be avoided if one wishes to produce systems with high conductivity that is generally associated with delocalized carriers. However, there are some reports about using meta-linkages, to produce highly conductive polymers [19][20][21][22]. Polythiophene and its derivatives are the most widely studied conducting polymers [3,23].…”