Particle monolayer formation with arrayed structure by PMMA-grafted polystyrene Latex at the air-water interface

The structure of the particle monolayer formed by the polymer-grafted latex particle at the air-water interface was estimated mainly by pi--A isotherm measurement and SEM observation to examine the effect of core particle characteristics and to generalize the key factors in determining the polymer-grafted particle monolayer structure. Methyl methacrylate (MMA) was polymerized from the polystyrene latex (PSL) surface by atom transfer radical polymerization to give a PMMA-grafted PSL (PSL-PMMA) with a relatively high graft density of about 0.2 nm-2. We obtained PSL-PMMA with PMMA of different molecular weights but almost the same graft density. The onset area of increasing surface pressure in pi-A isotherm was in agreement with the value of effective radius of PSL-PMMA with quite extended PMMA chains. The particle monolayer structure deposited on the substrate was strongly dependent on the molecular weight of the grafted PMMA. The aggregation size was reduced with increasing molecular weight and a lattice-like structure was observed for PSL-PMMA monolayer with a high molecular weight PMMA. The interparticle distance was decreased and structure becomes ordered with increasing surface pressure. The monolayer structure obtained here was consistent with that of the PMMA-grafted silica particle system. We also synthesized polystyrene (PS)-grafted PMMA latex (PML-PS) and compared the two systems. We confirmed that the lattice-like structure depended on the nature of the grafted PMMA chain, not the core particle characteristics.