Hydrogel particles (microgels) are colloidal particles with average diameters ranging from several tens of nanometers to single micrometers. In appropriate solvents, these particles become highly swollen with water and demonstrate stimuli responsiveness similar to bulk gels. The swelling/deswelling behavior of these microgels is suitable for various applications such as drug delivery systems, separation carriers, and sensors as the interactions between target molecules and the microgels can be controlled. In particular, the microscopic structure of the microgel is important factor for the molecular uptake behavior.
‘Liquid marbles’ are liquid-in-gas dispersed systems: relatively hydrophobic solid particles adsorbed to air-liquid interface stabilize the liquid marbles. The stability and structure of liquid marbles prepared using stimulus-responsive particles can be controlled by external stimuli, such as pH, temperature, light and magnetic field. Thanks to these stimuli-responsive characters, the liquid marbles have potential encapsulation/release applications.
Droplet-to-Capsule technology using phase separation is a novel process for micro-capsule production. Merging with microfluidics, it upgrades the product to monodisperse micro-capsules with oil or water core. This article demonstrates the rapid production technique of defined micro-capsules by phase separation.
Two novel hybridization methods for the preparation of polymer particles containing of ZrO2 nanoparticles are developed, in order to control the refractive index of polymeric particles. First is based on the mini-emulsion polymerization method by which ZrO2 nanoparticles are incorporated inside of polymer particles. Second is the hetero-coagulation method by which ZrO2 nanoparticles are incorporated outside of polymer particles.
Propagation and scattering of light in a medium is one of the major topics in the study of color materials as well as in many other research fields. Several optical theories dealing with the topic have been developed so far, including geometrical optics and quantum optics. If the minimum length scale of an object of interest is much larger than the wavelength of light, we can discuss the problems of light reflection and refraction by treating the light as rays. For smaller length scales, however, there are some phenomena which cannot be described by geometrical optics. In this case, we need to treat light as scalar or vector waves. The present article presents the theoretical treatment of light phenomena in the context of wave and electromagnetic optics. The finite-difference time-domain method is introduced as a numerical method for analyzing light propagation and scattering in complex media.
Surfactant function is achieved by adsorption to interface and formation of molecular assemblies. Upon increasing surfactant concentration in water, micelles and lyotropic liquid crystals are formed. These phase transitions are generally presented in a phase diagram. The structures of lyotropic liquid crystals formed in a concentrated system are mainly determined by molecular packing of surfactant molecules. Poly(oxyethylene) alkyl ethers, which are a typical type of nonionic surfactant, show structural transitions of lyotropic liquid crystals by changing polymerization degree of the hydrophilic chain due to the change in repulsion between hydrophilic groups. Such structural transitions can be explained by the critical packing parameter. The lyotropic liquid crystals can be applied to the synthesis of mesoporous materials or drug carriers in DDS. The shape of micelles formed in a dilute system also changes depending on the repulsion between hydrophilic groups. Especially wormlike micelles that have an elongated shape like polymer chains increase viscosity of a micellar solution. Wormlike micelles can be applied to DR agents or foam boosters by this feature.