Novel Core-Shell Structures for Colloids made from Surfactants and Polymers

TL;DR

This paper investigates the formation of colloidal complexes with core-shell structures through electrostatic self-assembly of polyelectrolyte-neutral block copolymers and surfactants, revealing a novel assembly mechanism based on charge complexation.

Contribution

It introduces a new understanding of colloidal core-shell structures formed via charge-driven self-assembly, differing from traditional amphiphilic micelle formation.

Findings

Colloidal complexes have a core-shell microstructure with a dense core and diffuse shell.

The self-assembly mechanism is based on electrostatic complexation, not amphiphilic interactions.

Experimental evidence from scattering techniques confirms the microstructure.

Abstract

We report on the formation of colloidal complexes resulting from the electrostatic self-assembly of polyelectrolyte-neutral block copolymers and oppositely charged surfactants. The copolymers investigated are asymmetric and characterized by a large neutral block. Using light, neutron and x-ray scattering experiments, we have shown that the colloidal complexes exhibit a core-shell microstructure. The core is described as a dense and disordered micro-phase of micelles connected by the polyelectrolyte blocks, whereas the shell is a diffuse brush made from the neutral chains. Colloidal complexes with core-shell structures resemble the well-known amphiphilic block copolymer micelles. The self-assembly mechanism is however different here. It is based on the complexation between opposite charges. This mechanism has recently attracted much interest because it allows to associate components of different nature, such as organic and inorganic or synthetic and biological.