Synthesis of patchy colloids with different chemical functionalities

Abstract

Patchy particles are one of the new frontiers in developing novel functional colloids because of their similarity to molecules in terms of their potential ability to form directional bonds and give rise to complex architecture via self-assembly. Considerable challenges remain in developing effective strategies for synthesizing such complex particles. Most current works have focused on controlling the position of patches, which is already tricky. Still, very few works have tackled the problem of preparing particles with patches bearing different functionalities. In this work, we used an activated swelling method developed in our group to prepare Janus polymer particles with variable Janus balance and used them to synthesize bi-patchy particles with different chemical functionalities. We first created polystyrene/polymethyl methacrylate-glycidyl methacrylate (PS/P(MMA-GMA)) Janus particles with a small methacrylate patch. The epoxy groups were then aminated (PS/P-NH2), leading to a change in the hydrophilicity of the patch. We then used two methods to create patchy particles. In the first case, we mixed unmodified PS/P(MMA-GMA) and PS/P-NH2 Janus particles and fused them by adding THF as a plasticizer. This led to the formation of bi-patchy particles with identical patches and two patches bearing different functionalities, as proved by fluorescence microscopy. In the second case, PS/P-NH2 particles were used as seeds for an additional activated swelling polymerization step with MMA as a monomer to obtain pure bi-patchy particles with differently functionalized patches. This was possible thanks to the incompatibility between the NH2-functionalized first patch and the pure PMMA of the second one. The work opens the path to preparing colloidal molecules capable of forming multiple directional bonds through orthogonal chemical functionalization.