Colloidal crystallization of C60/polymer-grafted silica particles in organic solvent

Synthesis of fullerene (C60)-tethered polymer-grafted silica and colloidal crystallization of the particles was investigated. The particles were prepared by the reaction of C60 with 4-azidobenzoyl groups introduced in poly(methyl methacrylate-co-2-hydroxyethyl methacrylate), followed by esterification of 2-hydroxyethyl metharylate moieties with 4-azidobenzoyl chloride and grafting onto colloidal silica. The reaction afforded bindings of C60 in the range from 0.44 × 104 to 1.71 × 104 molecules/particle. The C60 amounts did not monotonously increase with 4-azidobenzoyl group on the particles, but decreased with mole fraction of methyl methacrylate in the copolymer. Colloidal crystallizations of the C60-tethered silica particles were observed in acetonitrile with critical volume fractions in the range from 0.018 to 0.024. Inter-sphere distances in the colloidal crystals were consistent with calculated values on assumption of face-centered cubic-closed packing, and then it was suggested that the crystallization took place due to electrostatic repulsion between the particles.