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. Nitroxide-labeled 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...