Controlling swelling in mixed transport polymers through alkyl side-chain physical cross-linking

Nicholas Siemons, Drew Pearce, Hang Yu, Sachetan M. Tuladhar, Garrett S. LeCroy, Rajendar Sheelamanthula, Rawad K. Hallani, Alberto Salleo, Iain McCulloch, Alexander Giovannitti, Jarvist M. Frost, Jenny Nelson

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Semiconducting conjugated polymers bearing glycol side chains can simultaneously transport both electronic and ionic charges with high charge mobilities, making them ideal electrode materials for a range of bioelectronic devices. However, heavily glycolated conjugated polymer films have been observed to swell irreversibly when subjected to an electrochemical bias in an aqueous electrolyte. The excessive swelling can lead to the degradation of their microstructure, and subsequently reduced device performance. An effective strategy to control polymer film swelling is to copolymerize glycolated repeat units with a fraction of monomers bearing alkyl side chains, although the microscopic mechanism that constrains swelling is unknown. Here we investigate, experimentally and computationally, a series of archetypal mixed transporting copolymers with varying ratios of glycolated and alkylated repeat units. Experimentally we observe that exchanging 10% of the glycol side chains for alkyl leads to significantly reduced film swelling and an increase in electrochemical stability. Through molecular dynamics simulation of the amorphous phase of the materials, we observe the formation of polymer networks mediated by alkyl side-chain interactions. When in the presence of water, the network becomes increasingly connected, counteracting the volumetric expansion of the polymer film.

Original languageEnglish (US)
Article numbere2306272120
JournalProceedings of the National Academy of Sciences of the United States of America
Volume120
Issue number35
DOIs
StatePublished - 2023
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • conjugated polymers
  • mixed electronic-ionic conductors
  • organic electrochemical devices
  • soft materials
  • structure-property relationships

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