The properties of multiphase colloidal systems such as foams and emulsions are critically dependent on capillary effects at interfaces and stability of thin liquid films. We will discuss how embedding magnetic field-responsive particles in such systems allows making novel responsive classes of soft matter, including smart foams, emulsions and gels. In the first part of the talk we will present the design and characterization of magnetically responsive Pickering foams that remain stable at ambient conditions, but can be rapidly destroyed upon exposure to a gradient of magnetic field. These foams are stabilized by particles from hydrophobically modified cellulose with magnetic responsiveness imparted through incorporation of carbonyl iron particles into the films. We will also discuss how these systems can be made photo- as well as thermally sensitive, to make new photo-thermo-magneto responsive foams (<i>Chem. Sci.</i> 4:3874, 2013). In the second part of the talk, we will describe a new smart gel system containing ultraflexible chains of magnetically responsive nanoparticles formed in multiphase water-oil systems. Liquid lipid shells condensed on the nanoparticles lead to directed assembly of microfilaments and networks via nanocapillary bridges. These liquid bridges allow for particle rolling and sliding, and the resulting chain flexibility was measured to be orders of magnitude higher than any other linear structures reported to date (<i>Nature Mater.</i> 14:1104 2015). The physical properties of filaments and gel structures formed by the nanocapillary binding of particles depend on the bridge fluidity, type and lipid composition. The nanoparticles’ binding through soft, "snappable" capillary forces provides a facile means of creating self-repairing networks (illustrated below). The nanocapillary bridging could be applied as a tool for multiscale assembly of temperature-responsive and self-repairing gels, complex lattices from Janus and patchy particles, and new types of responsive multiphase composites.

Design of new classes of responsive soft matter by embedding nanoparticle structures in Pickering foams and multiphasic gels

251st National Meeting (2016)

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