Liquid crystal microcapsules

Microcapsules arc used in several film coatings other than carbonless paper. Encapsulated liquid crystal formulations coated on polyester film arc used to produce a variety of display products including ihcrmomelers. Polyester film coated with capsules loaded with leuco dyes analogous to those used in carbonless copy paper is used as a means of measuring line and force pressures. Encapsulated deodorants that release their core contents as a function of moisture developed because of sweating represent... 

On the other hand, the interest towards this field is accounted for by the possibility to create polymeric systems, combining the unique properties of low-molecular liquid crystals and high molecular compounds, making it feasible to produce films, fibers and coatings with extraordinary features. It is well-known that the utilization of low-molecular thermotropic liquid crystals requirs special hermetic protective shells (electrooptical cells, microcapsules etc.), which maintain their shape and protect LC compounds from external influences. In the case of thermotropic LC polymers there is no need for such sandwich-like constructions, because the properties of low-molecular liquid crystals and of polymeric body are combined in a single individual material. This reveals essentially new perspectives for their application. 

Priest C, Quinn A, Postma A et al (2008) Microfluidic polymer multilayer adsorption on liquid crystal droplets for microcapsule synthesis. Lab Chip 8(12) 2182-2187... 

Complex coacervation can be used to produce microcapsules containing flavor, fragrant oils, liquid crystals, dyes, or inks as the core material. Capsules for carbonless paper applications were produced by complex coacervation process. 

Kobayashi T, Saga T (1998) Time response of microcapsulated liquid-crystal particles. Heat Transf Jpn Res 27(5) 390-398... 

Emulsions can behave like microcapsules, microspheres, or mesophasic lyotropic liquid crystals, since the interfacial film is rather thick and, in most cases, multilayered. Increasing the xanthan content in the WPI/xanthan system to 1 wt% in the external aqueous phase decreases droplet diameter from 11.8 to 3.1 pm (Figure 5.17), but no significant improvement in droplet size occurs between ratios of 4 to 0.5 and 4 to 1. It was also found that by increasing the protein-to-polysaccharide ratio, the multiple emulsion droplets were smaller and stability was increased. 

Bryant and Colvin produced a fibre with integral microcapsules with PCMs or plastic crystals. The fibre has enhanced thermal properties at predetermined temperatures. The microcapsules can range in size from about 1 to about 10 microns. In fabricating the fibre, the desired microencapsulated PCMs are added to the liquid polymer, polymer solution or base material and the fibre is then expended according to conventional methods such as dry or wet spinning of the polymer solutions and extrusion of the polymer melts. According to the report, the maximum content of PCM in the polyacrylic fibre is about 10%. The minimum filament denier is 2.2dtex. ... 

In their application in textiles, the paraffins are either in a solid or liquid state. In order to prevent dissolution of the paraffin while in the liquid state, it is enclosed in a small plastic sphere with a diameter of only a few micrometers. The shell polymer should be resistant to mechanical action such as friction, heat and most types of chemicals. When the temperature rises, the miciocapsules absorb heat from the surroundings by melting the PCM in the microcapsules, thus allowing them to store heat energy. When the temperatirre falls, the microcapsules release the heat by crystallizing the PCM in the microcapsttles (Pause, 2000). 

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