Self-assembly of molecular building blocks into ordered architectures, polymers and materials opens exciting avenues in nanoscience and applications in biomedical technologies, optoelectronics and catalysis. One of our major goals is to control and manipulate self-assembly mechanisms, and to design supramolecular synthons for the programmable self-assembly of functional materials in water.
Inspired by protein functionality in their native biological setting, we have designed electrostatic- and pH-regulated supramolecular polymerisations in water (Angew. Chem. 2013, Chem. Eur. J. 2015, Polym. Chem. 2015; for a mini-review see Macromol. Rapid Commun. 2015).
β-sheet encoded anionic and cationic amphiphiles form supramolecular alternating copolymers when self-assembled in a 1:1 feed ratio of the monomers. These materials are designed for on-off polymerisation in response to pH triggers: the self-assembly is switched on at a physiologically relevant pH value and can be switched off by increasing or decreasing the pH value. The pH-driven transition from copolymers to monomers, or hetero-copolymers to homopolymers can be tuned by the careful design of the supramolecular comonomer. This unique approach for the pH-regulated reactivity and selectivity has important implications for the preparation of stimuli-responsive organic materials and biomedical applications.
In another strategy, we use frustrated self-assembly (the balance of attractive supramolecular interactions with repulsive forces) to prepare responsive, organic nanorods with a well-defined shape, size and stability (J. Mater. Chem. B 2013).
Using steric constraints or electrostatic forces, we induce frustration in the supramolecular polymerisation and restrict the one-dimensional assemblies into well-defined nanorods. Electrostatic repulsive forces based on acidic side chain functional groups can be tuned by the pH and ionic strength of the environment. In order to understand the multi-stimuli responsive character we build state diagrams, analogous to self-assembled natural spherical or filamentous viruses, and show that the monomer to polymer transition can be shifted between pH 5.0 and pH 7.4 (Org. Biomol. Chem. 2015).
The aqueous self-assembly into well-defined rod-like structures has large potential for biomedical technologies, in view of recent reports that anisotropic shapes in the carrier design outperform conventional isotropic materials. With these tools in hand, our goal is to explore new avenues for applications in molecular imaging and diagnostics, responsive and switchable drug delivery vehicles.
Our most recent research involves the design of a new class of Au(I)-bioinorganic hybrid materials (Chem. Commun. 2015; for a mini-review see Tetrahedron 2013).
Structurally and functionally the aurophilic interaction between Au(I)-centres is at the heart of these systems: the aqueous self-assembly of Au(I)-metalloamphiphiles into hierarchically ordered materials with short interatomic gold contacts creates unique functional properties for applications in photoluminescence, electronics and catalysis.
We characterise the supramolecular materials with a range of experimental techniques, TEM & cryoTEM, SLS & DLS, SAXS, steady state & transient CD and photoluminescence spectroscopy, PFG & MAS-NMR spectroscopy, in combination with multi-scale molecular modelling studies.
See the lab page for more information.