Self-Assembly of Amphiphilic Block Copolymers in Dispersions of Multiwalled Carbon Nanotubes As Reported by Spin Probe Electron Paramagnetic Resonance Spectroscopy

Abstract

Self-assembly (SA) of amphiphilic block copolymers (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)) was investigated in dispersions of multi-walled carbon nanotubes (MWNT) as a function of temperature using spin probe electron paramagnetic resonance (EPR) spectroscopy. Nitroxidelabeled Pluronic with a short poly(ethylene oxide) block, L62-NO, and a small molecular probe, 4-hydroxy-TEMPO-benzoate, 4HTB, were used for probing the local dynamic and polarity of the polymer chains in the presence of the nanostructures. It was found that MWNT modify the temperature, and the dynamic behavior of polymer SA and comparison between the MWNT and single-walled nanotube (SWNT) showed that the structure and dynamical behavior of the nanostructure-polymer hybrids formed depend on the size matching between the diameter of the native micelles and the additives. While SWNT induced the formation of hybrid polymer-SWNT micelles, MWNT (with a diameter of 20-40 nm) induced the assembly of polymer aggregates at the surface of the MWNT.

Low-temperature Electronic Paramagnetic Resonance Measurements of TEMPO and 4-Hydroxy-TEMPO Benzoate for Purity Analyses by the Effective Magnetic-moment Method

“…Paramagnetic resonance results of 4HTB near temperatures of liquid-He temperature have not reported within our knowledge, although 4HTB has been used as a spin probe for studies of concerning the formation mechanism of mesoporous materials. [11][12][13] For TEMPO and TEMPOL, some researchers had reported magnetic resonance behaviors until near-liquid-He temperature for TEMPO [14][15][16] and TEMPOL. [14][15][16][17][18] However, it has not been clear whether the effective g-values for TEMPO from liquid-N2 temperature to near liquid-He temperature is temperature-independent.…”

Presence of vacuoles in natural rubber–Cloisite 15A nanocomposites

“…Local chain dynamics, environment, interactions, and free volume variations on the timescale from 10 −11 s to 10 −7 s were investigated with conventional electron spin resonance (ESR) spectroscopy, either with the spin‐label or spin‐probe method. In the spin‐label method, stable free radicals are covalently bonded to the site of interest.…”

EPR Spin Probe Study of Molecular Mobility and Structure of Aqueous Solutions and Gels of Polydiphenylenesulfophthalide

“…Despite its long history, this method continues to be in constant development [4,5] and active use for investigating polymers in their solid state as well as their gels, solutions, and polymer micelles [6][7][8][9][10][11][12][13].…”