One-Dimensional Assembly of Silica Nanospheres Mediated by Block Copolymer in Liquid Phase

Abstract

Colloidal silica spheres and their assembly processes are encountered in nature and numerous technological applications. We report here a novel and facile method to prepare highly anisotropic one-dimensional (1D) arrays of silica nanospheres (SNSs) in the liquid phase. Uniform-sized SNSs ca. 15 nm in size assemble into a 1D chain-like structure in the presence of a commercially available block copolymer. The 1D assembly in the liquid phase is evident from Cryo-TEM observations and time-dependent turbidity measurement of the suspension. The mode of the assembly has been systematically controlled by the concentration of the block copolymer, pH of the suspension, and the concentration of a salt added to the system. These results suggest the importance of the balance between electrostatic repulsion and block copolymer-mediated attractive interaction that are operative between particles in the formation of 1D array.

Colloidal Assembly: The Road from Particles to Colloidal Molecules and Crystals

“…This result suggested that the assembly may also be engaged by a synergistic effect, perhaps by hydrogen bonding between colloids and surfactant molecules. [52] Similarly, CdSe/ CdS core-shell colloids that bear a brush-like PEO layer selfassembled into chain-like structures or three-dimensional vesicular aggregates when the surface PEO density was varied. It was suggested that, while a complete PEO coating stabilized the colloids, insufficient amounts of PEO and moderate binding with the nanocrystal surface caused dynamic re-arrangement and introduced certain amphiphilic properties into the colloids, which led to their self-assembly.…”

Ring assembly of silica nanospheres mediated by amphiphilic block copolymers with oxyethylene moieties

“…22 We have previously reported the one-dimensional (1D) chain-like structures obtained from SNSs in the liquid phase mediated by the amphiphilic block copolymers PEO-PPO-PEO, which consist of poly(ethylene oxide) (PEO) and poly (propylene oxide) (PPO). 23,24 The polymers affect the interactions among SNSs by adsorbing to the SNS surface via hydrogen bonding between the ether oxygen and silanol groups. 23,24 The 1D chain-like structure is achieved when the electrostatic repulsion, steric repulsion and hydrophobic attraction between the SNSs with the surfaceadsorbed polymers are properly balanced.…”

Bio-inspired synthesis of polymer–inorganic nanocomposite materials in mild aqueous systems

“…41 It has been found that colloidal silica nanospheres (SNSs) assemble into one-dimensional (1D) chain-like structures in water with the aid of a block copolymer, as described below. 42 Colloidal suspension of SNSs about 15 nm in size was prepared by the method reported by Yokoi et al 43 This method uses a biphasic liquid system containing tetraethoxysilane, water and L-lysine as a catalyst to give monodisperse SNSs. SNSs are colloidally stable at around and above neutral pH because they are electrostatically repulsive (the isoelectric point of silica is pH 2-3).…”