Employing polymer-polymer incompatibility for oil microencapsulation by coacervation

Abstract

© 2010 by Nova Science Publishers, Inc. All rights reserved. Microencapsulation by coacervation is a common method for microcapsules production. It can be achieved by employing different methods, where the most common one is formation of an insoluble complex of two oppositely charged polymers and its subsequent deposition at surface of dispersed particles (e.g. emulsified oil droplets). In this way, microcapsules with coacervate shell are formed. Composition and microstructure of the coacervate shell are key to determine properties and application of microcapsules. In this chapter, novel method for microencapsulation by coacervation is presented. The method employs polymer-polymer incompatibility taking place in a ternary system composed of sodium carboxymethyl cellulose (NaCMC), hydroxypropylmethyl cellulose (HPMC), and sodium dodecylsulfate (SDS). In the ternary system, various interactions between HPMC-NaCMC, HPMC-SDS and NaCMC-(HPMC-SDS) take place. The interactions were investigated by carrying out detailed conductometric, tensiometric, turbidimetric, viscosimetric, and rheological study. The interactions may result in coacervate formation as a result of incompatibility between NaCMC molecules and HPMC/SDS complex, where the ternary system phase separates in HPMC/SDS complex rich coacervate and NaCMC rich equilibrium solution. By tuning the interactions in the ternary system coacervate of controlled rheological properties was obtained. Thus obtained coacervate was deposited at the surface of dispersed oil droplets in emulsion, and oil-content microcapsules with a coacervate shell of different properties were obtained. Formation mechanism and stability of the coacervate shell, as well as stability of emulsions depend on HPMC-NaCMC-SDS interaction. Emulsions stabilized with coacervate of different properties were spray dried and powder of microcapsules was obtained. Dispersion properties of microcapsules, and microencapsulation efficiency were investigated and found to depend on both properties of deposited coacervate and the encapsulated oil type.