Poly(methyl methacrylate) monolayers at the air–water interface

Abstract

Several poly(methyl methacrylate) (PMMA) molecules with various chain numbers has been synthesised using Emulsifier-free emulsion polymerisation method. Langmuir–Blodgett thin film technique is an excellent method to investigate the surface behaviours of organic monolayers at the air–water interface. In this study, PMMA molecules have been studied at the air–water interface using Langmuir–Blodgett thin film method. Area per molecule for several PMMA molecules is found to be between 0.29±0.01 and 0.98±0.01 nm2. The surface pressure–area graphs were taken in two stages i.e. during the first compression of the monolayer and also during the second compression of the same monolayer before the collapsed stage of the monolayer. It is also found that first surface pressure–area graph for the first compressing of the monolayer at the water surface is different than the surface pressure–area graph obtained after a decompression of the monolayer. Isotherm graphs show that long alkyl chain groups of these molecules may cause aggregation behaviours on water surface and a model for the behaviour of PMMA molecules on the air–water interface due to surface interactions has been proposed.