Research progress of bicontinuous interfacially jammed emulsion gel (Bijel)

Abstract

In 2005, a bicontinuous arrangement of domains was explored by large-scale computer simulations. In a binary liquid host, the behaviors of neutrally wetting particles were simulated following an instantaneous quench into the demixed region. As the two mutually immiscible liquids phase separate, particles can be swept up by the freshly created interface and jam together as the domains coarsen, forming a particle-stabilized interface between two continuous liquid phases. This type of material is known as “bicontinuous interfacially jammed emulsion gel” (Bijel), and has been demonstrated experimentally using water-lutidine mixture in 2007. It is believed that Bijels have rich potential applications in diverse areas including healthcare, food, energy and reaction engineering due to their unique structural, mechanical and transport properties.As a new class of soft materials, Bijels have received great attention in recent years, and have been developed by using different liquids and non-spherical particles. However, a wide gap remains between the experimental systems and the industrial applications. This short review will critically assess current progress of Bijels and relevant studies including the attempts and challenges to use them in industry; the creation of Bijels by direct mixing at room temperature will be highlighted specifically.Chapter 1 presents the theoretical background. For binary-liquid systems containing dispersed colloidal particles, arrested composites can be created via the stabilization of convoluted fluid-fluid interfaces. Based on this, different morphologies of Pickering emulsions would be obtained. Chapter 2 first focuses on some complex emulsions, including Janus droplets and multiple emulsions, and then induces the bi-continuous structures. Such structures were originally formed through spinodal decomposition, which catches the phase demixing of an initially single-phase liquid mixture containing a colloidal suspension, and normally needs to control the temperature carefully. In Chapter 3, the mechanism of spinodal decomposition is presented. Chapter 4 shows some recent research progress of Bijels, including the studies with different liquid systems, nonspherical particles and some chemical property measurements. This chapter also summarizes the challenges in using Bijels in industry. In Chapter 5, a new method of creating Bijels by direct mixing at room temperature is demonstrated. This method simply needs high viscosity liquids, nanoparticles and a surfactant; it not only bridges the gap between conventional Bijel production (see Chapter 3) and that of particle stabilized bicontinuous structures using bulk polymers, but also bypasses the careful particle modification and phase separation steps for conventional Bijels. In Chapter 6 some conclusions are drawn and a general outlook is also provided.