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Novel, robust and versatile bijels of nitromethane, ethanediol and colloidal silica : capsules, sub-ten-micron domains and mechanical properties
Bicontinuous, interfacially jammed emulsion gels (bijels) are a class of soft solid materials in which interpenetrating domains of two immiscible fluids are stabilized by an interfacial colloidal monolayer.[1-4] Such structures form through the arrest of the spinodal decomposition of an initially single-phase-liquid mixture containing a colloidal suspension. With the use of hexalmethyldisilazane, the wetting character of silica colloids, ranging in size and dye content, can be modified for fabricating a novel bijel system comprising of the binary liquid ethanediol-nitromethane.[3] Unlike the preceding water-lutidine based system,[2,4] this bijel is stable at room temperature and its fabrication and resultant manipulation are comparatively straightforward. The new system has facilitated three advancements : firstly, we use sub 100 nm silica particles to stabilize the first bijel made from low molecular weight liquids that has domains smaller than ten microns. Secondly, our new and robust bijel permits qualitative rheological work which reveals the bijel to be significantly elastic and self healing whilst it ?s domains are able to break, reform and locally rearrange. Thirdly we encapsulate the ethanediol-nitromethane bijel in Pickering drops to form novel particle-stabilized bicontinuous multiple emulsions that we christen bijel capsules. These emulsions are stimuli responsive - they liberate their contained materials in response to changes in temperature and solvency, and hence they show potential for controlled release applications.
[1] K. Stratford, R. Adhikari, I. Pagonabarraga, J. C. Desplat, M. E. Cates, Science, 2005, 309, 2198.
[2] E. M. Herzig, K. A. White, A. B. Schofield, W. C. K. Poon, P. S. Clegg, Nat. Mat., 6, 971, 2007
[3] J. W. Tavacoli, J. H. J. Thijssen, A. B. Schofield, P. S. Clegg, Adv. Funct. Mater. 2011, in press.
[4] K. A. White, A. B. Schofield, P. Wormald, J. W. Tavacoli, B. Binks, P. S. Clegg, Submitted to J. Colloid Interf. Sci.
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