The Effect of Size Properties and End/Linking Group Chemistry on the Surface Mechanical Properties of Water Spread PS-PEG Micelles on the Water Surface

The surface-mechanical properties of PS-PEG micelles are influenced by the PEG corona structure. Changes in micelle aggregation number as well as changes in the PEG end group and linking group chemistry of the PS-PEG block copolymer are expected to alter PEG corona characteristics and therefore affect surface mechanical properties of the resulting micelle film formed from spreading micelles at the air-water interface. Different sized micelles comprised of PS-PEG block copolymer chains were formulated by equilibrating micelles in different ratios of acetone/water mixtures and subsequently removing acetone using dialysis. Additionally, micelles of a similar size and PS-PEG molecular weight but slightly different chemistry were formulated. The reduction in micelle aggregation numbers results in the subsequent monolayer having higher compressibility moduli and bending stiffnesses and collapsing at lower surface pressures. Micelle hydrophobicity, which is found to change with size and chemistry, does not correlate well with the ability for the monolayer to achieve high surface pressures, but does affect the isotherm shape and the ability for the micelles to respread after collapse.