Monolayer formation at the air-water interface by polymer-garafted colloidal particles

Poly(methyl methacrylate)-grafted colloidal particles were prepared via atom transfer radical polymerization. Particle monolayers were formed at the air-water interface. Estimation of particle monolayer was performed mainly by surface pressure-area isotherm measurement and SEM observation. PMMA-grafted colloidal silica and PMMA-grafted polystyrene latex with diameter of ca. 100nm formed particle monolayer with lattice-like structure with 300 similar to 500nm intervals when molecular weight of grafted PMMA is over 100,000. With lower molecular weight of grafted PMMA, aggregation was observed on the substrate by SEM images. Even at lower graft densities, however, homogeneous particle monolayer was formed by the PMMA-grafted particle with high molecular weight of grafted PMMA. The key factor in determining particle monolayer structure is the molecular weight of grafted polymer rather than graft density in this system.