Boronate Microparticles: Preparation, Characterisation, and Functionalisation
There is great interest in materials science in the development of hierarchical self-assemblies with well-defined topologies, because their properties are greatly modified or completely different from those of the molecular modules, as clearly observed in biology. Reversible boronate esterification can be used to build well-ordered microparticles through supramolecular polymerization of benzene-1,4-diboronic acid with tetraols. This chapter mainly focuses on our recent progress in developing boronate-based microparticles and their functionalisation. Orthogonal boron and phenyl π-interactions between the resultant polymers can induce nucleation of aggregates. Growth then proceeds as a function of time to give well-dispersed particles. For example, when pentaerythritol is used as the tetraol component for boronate ester-based self-assembly, thermodynamically stable flower-like microparticles of average diameter 2.3 ± 0.3 µm are produced. Notably, surface functionalisation enables the fabrication of not only nanometal-deposited heterogeneous catalysts but also white-light-emissive chemosensors that work in water. Inspired by these results, we further investigated the use of aggregation-induced-emission-active luminogens, a series of propeller-shaped luminescent molecules, as components for boronate assembly for the development of fluorescent boronate particles through restriction of their intramolecular rotation. This chapter focuses on the pivotal engineering of boronic acid-inspired hierarchical systems.