Segmental Relaxation Dynamics of the Core and Corona in a Single Dry Micelle

Abstract

The segmental relaxation dynamics of the core and the corona in a single dry spherical micelle comprising a polystyrene (PS) or poly(methyl methacrylate) (PMMA) core and a poly(acrylic acid) (PAA) corona, along with the effects of the micelle density and the chain length of the core-forming and corona-forming polymers, were investigated by AFM. The results showed that the segmental relaxation temperature in the micelle core was close to its bulk Tg and independent of the micellar structure, such as micelle size, density, and corona thickness. By contrast, the segmental relaxation temperature in the micelle corona is dependent on the micellar structure. The depressed chain mobility in the corona was enhanced as the micelle density and the length of both the corona-forming and core-forming blocks increased. This phenomenon was attributed to conformational entropy loss in the micelle corona because of the chain adopting a conformation more perpendicular to the core as the micelle size and density increased.