Temperature Effects on the Shell Structure of Micelles Formed by a Polystyrene-Poly(ethylene oxide) Diblock Copolymer in Water

The temperature effects on the shell structure of micelles formed by a deuterated polystyrene-poly(ethylene oxide) diblock copolymer (dPS-b-PEO) in aqueous solution were investigated with small-angle neutron scattering (SANS). SANS data was analyzed using a core-shell model with a structure factor for a hard sphere potential. The shell thickness was obtained from the fits to the SANS data. The shell thickness first decreased with increasing temperature, reached minium at some point and then increased with a further increase of temperature. These structural changes seemed to be due to the combined effects of the decrease in hydrophilicity of the PEO block and the increase in thermal motion of the PEO block with increasing temperature.