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Polymers and Self Assembly: From Biology to Nanomaterials
Thursday Speaker Abstracts
Interfacial Assembly of Synthetic and Natural Nanoparticle
Thomas P. Russell
.
Polymer Science and Engineering Department, University of Massachusetts, Amherst, USA.
Nanoparticles will segregate to the interface between two immiscible fluids to reduce the
interfacial energy. Due to the size of the nanoparticles, the assemblies can range from disordered
energy holding the particle at the interface is small and is, in fact, comparable to thermal
energies. This gives rise to a disordered, liquid-like assembly, as opposed to colloidal particles,
where the assemblies can order and crystallize. This provides a unique platform to probe
assemblies of both synthetic nanoparticles, like cadmium selenide or silica, and natural
nanoparticle, like cow pea mosaic virus an tobacco mosaic virus. In addition, since these
assemblies are at a liquid/liquid interface, the nanoparticles are easily accessed by chemicals
dispersed in one or both of the fluids and chemistries can be performed on the nanoparticles, as
for example, crosslinking chemistries or attachment of ligands that reduce the interfacial tension
further by the formation of nanoparticle surfactants. This reduction in the interfacial energy per
nanoparticle increases the force holding the nanoparticles at the interface and allows the
assemblies to be jammed at the interface when the interfacial area is reduced. This opens the
possibility of shaping the liquid phase by use of an external field, like shear or an electric field,
where, upon removal of the field, the interfacial area decreases, jamming the particles at the
interface and locking-in non-equilibrium shapes of the fluids. Integration of functionality into the
ligands allows the assemblies to be responsive to a range of external stimuli.
Multicomponent Supramolecular Hydrogels
Dave Adams
, Emily R. Draper, Edward Eden, Tom O. McDonald.
University of Liverpool, Liverpool, United Kingdom.
Low molecular weight gelators (LMWG) are molecules that self-assemble into one-dimensional
fibrous structures. Entanglement of these fibres leads to the immobilisation of the solvent and the
formation of a gel. These supramolecular gels are attracting significant interest as they have
unusual properties, for example forming gels at low LMWG concentrations and being able to
reversibly go from a gel to a solution. In most cases, gels are formed from a single LMWG.
Mixing different LMWG (which each form gels independently) is interesting. Conceptually,
depending on how these LMWG assemble, mixing LMWG could be used to adjust the properties
of the final gels, or to prepare systems with higher information content, for example by the
selective positioning of specific functional groups in space. However, for this approach to be
useful, it is not only necessary to simply mix two LMWG, but to be able to finely control the
assembly of both such that, ideally, their location in space is finely controlled. This is extremely
difficult to do. Here, we will describe a range of mixed dipeptide-based LMWG systems. We
will show how fibrous structures form in these systems and show how we can control how
different types of fibrous networks are built up in multicomponent systems. We will show how to
control the type of networks formed, and how this can be used to control the properties of the
gel. We will also show the selective removal of one of the networks.