Pickering emulsions and dispersions—an early perspective

Pickering stabilization of double emulsions: Basic concepts, rationale, preparation, potential applications, challenges, and future perspectives

Double emulsions (DEs) offer unique compartmentalized structures but are inherently unstable, prompting significant scientific and industrial efforts to enhance their stability. One promising strategy is the use of solid particles-known as Pickering stabilization-resulting in Pickering double emulsions (PDEs), which overcome many limitations of conventional low-molecular-weight (LMW) surfactants. However, the term "Pickering" is often misused in the literature to describe any formulation containing particles, regardless of whether the interface is fully stabilized by them. This review aims to clarify the concept of Pickering stabilization, outline the rationale for its application to DEs, and examine preparation mechanisms, interfacial approaches, potential applications, and current challenges. Particles with dual wettability and high desorption energy irreversibly adsorb at interfaces, forming robust mechanical barriers that inhibit coalescence and reduce diffusion or escape of internal droplets. PDEs can be prepared via two-step emulsification, one-step processes, or advanced microfluidic methods. A variety of Pickering approaches have been developed to engineer particles capable of dual interfacial stabilization, enabling sophisticated functions such as (co-)encapsulation, controlled release, and the formation of hierarchical structures like microspheres, colloidosomes, and antibubbles. To unlock the full potential of PDEs for industrial applications, future research should prioritize eliminating surfactant use, developing safe and sustainable particles, and advancing scalable production methods without compromising emulsion stability or performance.

Analysis of bijel formation dynamics during solvent transfer-induced phase separation using phase-field simulations

Solvent transfer-induced phase separation (STrIPS) is a versatile and scalable method for the fabrication of bicontinuous interfacially jammed emulsion gels (bijels), a soft material with ample potential in membrane separation and energy storage. STrIPS, however, does not facilitate in situ observation of bijel formation, rendering it difficult to relate the phase separation process to the resulting bijel morphology. To address this issue, a phase-field (PF) model is presented that captures the principle components of STrIPS through relatively simple methods. Comparison with experimental results demonstrates that the PF model accurately describes STrIPS, reproducing morphological trends in a complex experimental system. Simultaneously, the model provides insight into the origin of such morphological features, relating the formation of the bijel structure in STrIPS to relatively slow dynamics of phase separation compared to solvent diffusion. Visualising phase separation during the entire STrIPS process, the PF model can therefore help elucidate the formation mechanisms underlying current STrIPS bijel morphologies, in addition to aiding the fabrication of novel ones.

Polymerized and Colloidal Ionic Liquids─Syntheses and Applications

The breadth and importance of polymerized ionic liquids (PILs) are steadily expanding, and this review updates advances and trends in syntheses, properties, and applications over the past five to six years. We begin with an historical overview of the genesis and growth of the PIL field as a subset of materials science. The genesis of ionic liquids (ILs) over nano to meso length-scales exhibiting 0D, 1D, 2D, and 3D topologies defines colloidal ionic liquids, CILs, which compose a subclass of PILs and provide a synthetic bridge between IL monomers (ILMs) and micro to macro-scale PIL materials. The second focus of this review addresses design and syntheses of ILMs and their polymerization reactions to yield PILs and PIL-based materials. A burgeoning diversity of ILMs reflects increasing use of nonimidazolium nuclei and an expanding use of step-growth chemistries in synthesizing PIL materials. Radical chain polymerization remains a primary method of making PILs and reflects an increasing use of controlled polymerization methods. Step-growth chemistries used in creating some CILs utilize extensive cross-linking. This cross-linking is enabled by incorporating reactive functionalities in CILs and PILs, and some of these CILs and PILs may be viewed as exotic cross-linking agents. The third part of this update focuses upon some advances in key properties, including molecular weight, thermal properties, rheology, ion transport, self-healing, and stimuli-responsiveness. Glass transitions, critical solution temperatures, and liquidity are key thermal properties that tie to PIL rheology and viscoelasticity. These properties in turn modulate mechanical properties and ion transport, which are foundational in increasing applications of PILs. Cross-linking in gelation and ionogels and reversible step-growth chemistries are essential for self-healing PILs. Stimuli-responsiveness distinguishes PILs from many other classes of polymers, and it emphasizes the importance of segmentally controlling and tuning solvation in CILs and PILs. The fourth part of this review addresses development of applications, and the diverse scope of such applications supports the increasing importance of PILs in materials science. Adhesion applications are supported by ionogel properties, especially cross-linking and solvation tunable interactions with adjacent phases. Antimicrobial and antifouling applications are consequences of the cationic nature of PILs. Similarly, emulsion and dispersion applications rely on tunable solvation of functional groups and on how such groups interact with continuous phases and substrates. Catalysis is another significant application, and this is an historical tie between ILs and PILs. This component also provides a connection to diverse and porous carbon phases templated by PILs that are catalysts or serve as supports for catalysts. Devices, including sensors and actuators, also rely on solvation tuning and stimuli-responsiveness that include photo and electrochemical stimuli. We conclude our view of applications with 3D printing. The largest components of these applications are energy related and include developments for supercapacitors, batteries, fuel cells, and solar cells. We conclude with our vision of how PIL development will evolve over the next decade.

Recent Advances in Macroporous Hydrogels for Cell Behavior and Tissue Engineering

Hydrogels have been extensively used as scaffolds in tissue engineering for cell adhesion, proliferation, migration, and differentiation because of their high-water content and biocompatibility similarity to the extracellular matrix. However, submicron or nanosized pore networks within hydrogels severely limit cell survival and tissue regeneration. In recent years, the application of macroporous hydrogels in tissue engineering has received considerable attention. The macroporous structure not only facilitates nutrient transportation and metabolite discharge but also provides more space for cell behavior and tissue formation. Several strategies for creating and functionalizing macroporous hydrogels have been reported. This review began with an overview of the advantages and challenges of macroporous hydrogels in the regulation of cellular behavior. In addition, advanced methods for the preparation of macroporous hydrogels to modulate cellular behavior were discussed. Finally, future research in related fields was discussed.