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*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

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

Funding

We acknowledge support of Northwestern University via discretionary funds associated with a Walter P. Murphy Professorship (J.M.T.), ISEN Fellowships (L. L.; X. C.), and Terminal-Year Fellowships (L. L.; X. C.; K. J.). We also thank 3M for supporting this work through a 3M fellowship (X. C.). Z. Q. and M. W. acknowledge the donors of the American Chemical Society Petroleum Research Fund for partial support of this research. This work made use of the SPID facility of Northwestern University's NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the MRSEC program (NSF DMR-1720139) at the Materials Research Center, the International Institute for Nanotechnology (IIN), the Keck Foundation, and the State of Illinois through the IIN. Northwestern University; American Chemical Society Petroleum Research Fund; Northwestern University Funding information We acknowledge support of Northwestern University via discretionary funds associated with a Walter P. Murphy Professorship (J.M.T.), ISEN Fellowships (L. L.; X. C.), and Terminal‐Year Fellowships (L. L.; X. C.; K. J.). We also thank 3M for supporting this work through a 3M fellowship (X. C.). Z. Q. and M. W. acknowledge the donors of the American Chemical Society Petroleum Research Fund for partial support of this research. This work made use of the SPID facility of Northwestern University's NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS‐1542205), the MRSEC program (NSF DMR‐1720139) at the Materials Research Center, the International Institute for Nanotechnology (IIN), the Keck Foundation, and the State of Illinois through the IIN.

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
  • Polymers and Plastics
  • Materials Chemistry

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