Microcapsules containing dyes

Microcapsules containing dyes are usually prepared by dispersion jiolymerization. Dyes may be dissolved in the monomer, which is further polymerized [29]. This technique usually results in poor polymer conversion and particles having a broad size distribution. In another method, blank polymer particles are first produced as an... 

These two seemingly dissimilar applications have a common basis—both are examples of the pressure-sensitive release of a chemical. How are these products designed Tiny spherical capsules (microcapsules or microspheres) with a glass or polymer shell are filled with a liquid core and glued onto paper. For a scratch-and-sniff ad, the core of the microcapsules contains a liquid with the desired scent for carbonless paper, a liquid ink or dye is encapsulated within the... 

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. 

FIGURE 61.1 Schematic representation of a microcapsule containing pigment substance and SEM image of spray-dried microcapsules loaded with dye. 

Aim of this worit was to demonstrate a particular example of a sensor system, which combines catalytic activity for urea and at the same time, enabling monitoring enzymatic reaction by optical recording. The proposed sensor system is based on multilayer polyelectrolyte microcapsules containing urease and a pH-sensitive fluorescent dye, which translates the enzymatic reaction into a fluorescendy registered signal. 

N. Zydowicz, E. Nzimba-Ganyanad, N. Zydowicz, PMMA microcapsules containing water-soluble dyes obtained by double emulsion/solvent evaporation technique, Polym. Bull. 2002, 47,457-463. 

Usami, T. Shimomura, T. Thermal recording material containing dye-precursor-incorporated microcapsules and a dispersion of color developing base. Jpn. Kokai Tokkyo Koho JP 01145190, 1989 Chem. Abstr. 1990,112, 169163. 

Interesting smart coatings are based on microcapsules containing a marker dye that can be released when the coating is damaged by cutting, by abrasions, and by... 

The amount of active urease immobilized into the polyelectrolyte microcapsules was determined under assumption that the enzyme retains its activity while encapsulated. Free urease had 100 U/mg according to the data sheets. The activities of free and encapsulated enzyme were determined from the decomposition of urea into two ammonia molecules and CO using a pH-sensitive d e Bromocresol purple [24], The urease aliquot solutions were added to a reaction mixture contained a necessary amount of urea and 0.015 mM Bromocresol, whose pH was aprioiy brought up to 6.2. The reaction kinetics was recorded as a change in the optical absorption of the dye at 588 run to obtain the linear calibration plot. Then, the known number of microcapsules containing urease and SNARF-1 dextran was added to the reaction solution. The revealed activity of enzyme was compared with amount of free urease. 

Pressure-sensitive recording materials are obtained by dissolving a triphenylmethane leuco dye in a solvent composed of paraffin oils. The microcapsules are formed from a water-soluble106 or water-dispersible material.107,108 Leuco dyes dissolved in sunflower oil are microencapsulated in a solution containing a melamine-HCHO precondensate and coated on the back side of a paper sheet. Contact of the microcapsule-coated sheet with an acid-coated receptor sheet allows the color formation to occur. 

The CB sheet is coated on the back with microcapsules 5 to 10 pm in diameter, in which leuco dye solution in a nonvolatile solvent is contained. The CF sheet is coated on the front with an acidic coreactant such as reactive clay, zinc salt of salicylic acid derivatives, zinc-modified phenolic resin, etc. On the application of pressure, the microcapsule is ruptured in the area delineated by the pressure pattern, and the leuco dye solution is thereby transferred to the CB sheet to bring about a color-forming reaction with acidic coreactant resulting in a distinct image on the surface of the CF sheet. By inserting a middle sheet (or sheets) called the CFB sheet, which is coated on the front and back with acidic coreactant and microcapsules, respectively, multiple copies can be obtained. 

An imaging system based on photopolymerizable microcapsules has recently been developed (8-101. The microcapsules (Figure 1) contain photoinitiators, acrylic monomers, and a colorless dye precursor. 

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