Impact of bottlebrush chain architecture on Tg-confinement and fragility-confinement effects enabled by thermo-cleavable bottlebrush polymers synthesized by radical coupling and atom transfer radical polymerization

Lingqiao Li, Zhe Qiang, Xi Chen, Kailong Jin, Muzhou Wang, John M. Torkelson

Research output: Contribution to journalArticlepeer-review

Abstract

Thermo-cleavable bottlebrush polymers were synthesized by a facile grafting-to method via radical coupling and atom transfer radical polymerization (ATRP) without small-molecule synthesis involved. Bottlebrushes were achieved by coupling backbones of poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl), which contain nitroxide radicals, and ATRP-synthesized side chains, which can be halogen-abstracted to generate carbon-centered radicals. Bottlebrushes were prepared using homopolymer or block copolymer side chains. Alkoxyamine covalent bonds resulting from radical coupling are thermo-reversible at high temperature, and grafting density may be tuned by annealing of post-synthesis bottlebrush, with the bottlebrush regime going from loose bottlebrush to dense comb and loose comb. The effects of confinement on the Tg and fragility of films of polystyrene bottlebrush were studied by ellipsometry; comparisons were made to thermally cleaved linear components obtained directly after annealing. Relative to linear polymer, bottlebrush topology reduces bulk fragility and suppresses Tg- and fragility-confinement effects. The correlation between the strengths of the confinement effects is consistent with other film studies of linear and non-linear polymers and supports the notion that fragility is a fundamental property underlying perturbations to Tg. Besides providing a platform for advancing fundamental scientific understanding, our synthetic strategy may afford novel applications of bottlebrushes via incorporated dynamic chemistry.

Original languageEnglish (US)
Pages (from-to)2887-2905
Number of pages19
JournalJournal of Polymer Science
Volume58
Issue number20
DOIs
StatePublished - Oct 15 2020

Keywords

  • ATRP
  • chain topology
  • comb polymer
  • dynamic chemistry
  • glass transition temperature
  • nanoscale confinement
  • nitroxide radical
  • thin film

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Materials Chemistry
  • Polymers and Plastics

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