Colloids are commonly used as building blocks for the synthesis of advanced functional materials. To realise complex morphologies, accurate control over the specificity and directionality of the colloidal interactions is often required. This can be achieved via the functionalization of colloids with supramolecular moieties, whose interactions are well studied in bulk and dilute solutions, and are strong, directional and reversible by varying the polarity of the solvent, the temperature or by light. In this context, we propose the decoration of colloids with supramolecular moieties for the synthesis of dynamic and responsive complex materials. Our approach consists of silica particles functionalized with o-nitrobenzyl protected benzene-1,3,5-tricarboxamide (BTA) derived molecules. BTA molecules were covalently attached onto the surface of fluorescent silica particles, that remain singlets when dispersed in organic solvents. The cleavage of the protecting group by light allows to activate the short-range hydrogen-bonding interactions of the supramolecular moieties, which in turn triggers the clustering of the particles. The transition from singlets to clusters was evidenced by means of confocal microscopy. Furthermore, the binding strength was tuned with the temperature. The effect of the functionalization degree (controlled during the functionalization step) as well as the amount of active sites (controlled by the light exposure time) on the behavior of the particles was also explored. The behaviour of these supramolecular colloids demonstrates that small surface-grafted molecules can have a dramatic effect on the behaviour of colloidal particles. In summary, we combine supramolecular chemistry with colloid science in a novel approach to control interparticle interactions, which represents an elegant way to realise external control over colloidal phase behavior which could be interesting in fields where stimuli-responsive systems are needed.
n.vilanova.garcia@tue.nl
