Controlled self-assembly of amphiphilic monotailed single-chain nanoparticles

Abstract

In the field of materials science, one of the current challenges is to organize nanoparticles with various sizes, geometries and compositions into specific structures for constructing functional materials and devices. In this research, the self-assembly of the monotailed single-chain nanoparticles with different charge densities was investigated. Poly(2-(dimethylamino)ethyl methacrylate)-block-polystyrene (PDMAEMA-b-PS) was synthesized by reversible addition–fragmentation chain transfer polymerization, and amphiphilic monotailed PDMAEMA single-chain nanoparticles were prepared by intramolecular cross-linking of PDMAEMA blocks. The cross-linking degree was controlled at about 20%. The surface charge densities on the single-chain nanoparticles were controlled by reactions of the single-chain nanoparticles with varying amounts of iodomethane. The surface charge density has a significant influence on the self-assembly of the monotailed single-chain nanoparticles. The monotailed single-chain nanoparticles made from PDMAEMA₇₄-b-PS₁₀₀ self-assemble into spherical micelles in aqueous solutions, and the average size of the micelles increases with the charge density. With an increase in the charge density, the morphology of the aggregates self-assembled by the monotailed single-chain nanoparticles changes from spherical micelles to vesicles, and to a mixture of worm-like cylinders and vesicles. In a cyclohexane–THF mixture, the monotailed single-chain nanoparticles made from PDMAEMA₇₄-b-PS₂₉₇ self-assemble into bunchy micelles, or a mixture of vesicles and large compound vesicles, depending on the charge densities.