Soft self-assembled nanoparticles with temperature-dependent properties.

Lorenzo Rovigatti,Christos N Likos,Barbara Capone

doi:10.1039/c5nr04661k

Abstract

The fabrication of versatile building blocks that reliably self-assemble into desired ordered and disordered phases is amongst the hottest topics in contemporary materials science. To this end, microscopic units of varying complexity, aimed at assembling the target phases, have been thought, designed, investigated and built. Such a path usually requires laborious fabrication techniques, especially when specific functionalisation of the building blocks is required. Telechelic star polymers, i.e., star polymers made of a number of f di-block copolymers consisting of solvophobic and solvophilic monomers grafted on a central anchoring point, spontaneously self-assemble into soft patchy particles featuring attractive spots (patches) on the surface. Here we show that the tunability of such a system can be widely extended by controlling the physical and chemical parameters of the solution. Indeed, under fixed external conditions the self-assembly behaviour depends only on the number of arms and on the ratio of solvophobic to solvophilic monomers. However, changes in temperature and/or solvent quality make it possible to reliably change the number and size of the attractive patches. This allows the steering of the mesoscopic self-assembly behaviour without modifying the microscopic constituents. Interestingly, we also demonstrate that diverse combinations of the parameters can generate stars with the same number of patches but different radial and angular stiffness. This mechanism could provide a neat way of further fine-tuning the elastic properties of the supramolecular network without changing its topology.

Highlights

Designing novel materials on the nanometer scale requires a careful choice of the microscopic building blocks.[1]
A simple yet very successful toy model with a built-in limited valence is provided by the socalled patchy particles, e.g., colloids decorated with attractive spots on their surface.[6,7,8,9]
Np ≈ 0 in the good solvent limit (λ → 0), since the attractive nature of the entropic-solvophilic monomers does not play any significant role in the self-aggregating behaviour that is instead driven by the enthalpic-solvophobic part of the molecule

Summary

Introduction

Designing novel materials on the nanometer scale requires a careful choice of the microscopic building blocks.[1]. Paper self-assembling nature of the particles makes them inherently soft and floppy, providing additional control over the target structure and its properties.[32,33] such a subtle dependence of the bulk properties on the single-star conformation calls for a precise determination of the latter. We demonstrate that different combinations of the parameters can generate stars with the same number of patches but different radial and angular stiffness. This mechanism could provide a neat way of tuning the elastic properties of the supramolecular network without changing its topology

Models and methods

Results

Characterisation of the patches

Characterisation of the shape

Conclusions