Self-assembly of pluronic block copolymers in aqueous dispersions of single-wall carbon nanotubes as observed by spin probe EPR

Marc Florent, Rina Shvartzman-Cohen, Daniella Goldfarb, Rachel Yerushalmi-Rozen

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

The self-assembly of Pluronic block copolymers in dispersions of single-wall carbon nanotubes (SWNT) was investigated by spin probe electron paramagnetic resonance (EPR) spectroscopy. Nitroxide spin labeled block copolymers derived from Pluronic L62 and P123 were introduced in minute amounts into the dispersions. X-band EPR spectra of the SWNT dispersions and of native polymer solutions were measured as a function of temperature. All spectra, below and above the critical micelle temperature (CMT), were characteristic of the fast limit motional regime. The temperature dependence of the 14N isotropic hyperfine coupling, aiso, and the rotational correlation time, τc, were determined. It was observed that, below the CMT, EPR does not distinguish between chains adsorbed on SWNT and free chains. Above CMT, substantial differences were observed: in the native solution, the Pluronics spin labels experience only one environment, Sm, assigned to spin labels in the corona of the Pluronic micelle, whereas in the SWNT dispersions, in addition to Sm, a second population of nonaggregated, individual chains, Si, is observed. The relative amounts of S m and Si were found to depend on the relative concentrations of the Pluronic and SWNT. Furthermore, the aggregates formed in the SWNT dispersions do not show the typical increase in chain-end mobility as a function of temperature, observed in the post-CMT regime of the native Pluronic solutions. This suggests a larger dynamical coupling among aggregated chains in the presence of the SWNT as compared to the native micelles. The overall findings are consistent with the formation of a new type of aggregates, composed of a SWNT-polymer hybrid.

Original languageEnglish
Pages (from-to)3773-3779
Number of pages7
JournalLangmuir
Volume24
Issue number8
DOIs
StatePublished - 15 Apr 2008

ASJC Scopus subject areas

  • Materials Science (all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Fingerprint

Dive into the research topics of 'Self-assembly of pluronic block copolymers in aqueous dispersions of single-wall carbon nanotubes as observed by spin probe EPR'. Together they form a unique fingerprint.

Cite this