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Light and oxygen induce chain scission of conjugated polymers in solution

Louis, Boris LU ; Caubergh, Stéphane; Larsson, Per Olof LU ; Tian, Yuxi LU and Scheblykin, Ivan G. LU (2018) In Physical Chemistry Chemical Physics 20(3). p.1829-1837
Abstract

Conjugated polymers have been widely studied as flexible, versatile semiconductors in organic electronics. However, the material stability is one of the problems limiting their applications. Thus, understanding the degradation process of conjugated polymers is crucial. In this work, we monitored the chain scission of the model polymer MEH-PPV in chloroform solutions under different conditions by assessing its molecular weight using gel permeation chromatography and optical spectral measurements. We showed that changes in the UV-VIS spectrum can be seen only when the degradation has already progressed substantially. The fluorescence spectrum was found to be almost totally insensitive to the degradation stage of the polymers. We... (More)

Conjugated polymers have been widely studied as flexible, versatile semiconductors in organic electronics. However, the material stability is one of the problems limiting their applications. Thus, understanding the degradation process of conjugated polymers is crucial. In this work, we monitored the chain scission of the model polymer MEH-PPV in chloroform solutions under different conditions by assessing its molecular weight using gel permeation chromatography and optical spectral measurements. We showed that changes in the UV-VIS spectrum can be seen only when the degradation has already progressed substantially. The fluorescence spectrum was found to be almost totally insensitive to the degradation stage of the polymers. We demonstrate that chain scission in solutions happens even in the dark leading to a 15% decrease of the molecular weight after just one day of storage. If exposed to room light, the chain length decreases by about 10 times over one day of exposure. Using stronger light intensity or enriching the solution with oxygen accelerates the degradation process dramatically. The rate of the reaction follows approximately a square root dependence with light intensity and oxygen concentration. We conclude that some extent of polymer degradation is difficult to avoid in common laboratory practices since to prevent it, one needs to work in an oxygen-free atmosphere in the dark. Preparation of polymer films from partially degraded solutions might lead not only to losing the connection between the molecular weight and the opto-electronic properties but also to unintentional doping of the semiconductor by products of chain scission reactions.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Chemistry Chemical Physics
volume
20
issue
3
pages
9 pages
publisher
Royal Society of Chemistry
external identifiers
  • scopus:85041049403
ISSN
1463-9076
DOI
10.1039/c7cp07347j
language
English
LU publication?
yes
id
432c96b8-2f6f-48a9-826d-0767b7f53555
date added to LUP
2018-02-06 10:30:38
date last changed
2018-02-07 03:00:02
@article{432c96b8-2f6f-48a9-826d-0767b7f53555,
  abstract     = {<p>Conjugated polymers have been widely studied as flexible, versatile semiconductors in organic electronics. However, the material stability is one of the problems limiting their applications. Thus, understanding the degradation process of conjugated polymers is crucial. In this work, we monitored the chain scission of the model polymer MEH-PPV in chloroform solutions under different conditions by assessing its molecular weight using gel permeation chromatography and optical spectral measurements. We showed that changes in the UV-VIS spectrum can be seen only when the degradation has already progressed substantially. The fluorescence spectrum was found to be almost totally insensitive to the degradation stage of the polymers. We demonstrate that chain scission in solutions happens even in the dark leading to a 15% decrease of the molecular weight after just one day of storage. If exposed to room light, the chain length decreases by about 10 times over one day of exposure. Using stronger light intensity or enriching the solution with oxygen accelerates the degradation process dramatically. The rate of the reaction follows approximately a square root dependence with light intensity and oxygen concentration. We conclude that some extent of polymer degradation is difficult to avoid in common laboratory practices since to prevent it, one needs to work in an oxygen-free atmosphere in the dark. Preparation of polymer films from partially degraded solutions might lead not only to losing the connection between the molecular weight and the opto-electronic properties but also to unintentional doping of the semiconductor by products of chain scission reactions.</p>},
  author       = {Louis, Boris and Caubergh, Stéphane and Larsson, Per Olof and Tian, Yuxi and Scheblykin, Ivan G.},
  issn         = {1463-9076},
  language     = {eng},
  number       = {3},
  pages        = {1829--1837},
  publisher    = {Royal Society of Chemistry},
  series       = {Physical Chemistry Chemical Physics},
  title        = {Light and oxygen induce chain scission of conjugated polymers in solution},
  url          = {http://dx.doi.org/10.1039/c7cp07347j},
  volume       = {20},
  year         = {2018},
}