Mutual Gelation of Gelatin and Water-in-Oil Microemulsions

Abstract

A thorough understanding of the gelation process is a challenge to colloid and polymer scientists. Thus an experimental study is presented in which the polymer-colloid interactions nicely elucidate some of the subtle details of the gelation phenomenon. – Varying amounts of gelatin were solubilized in thermodynamically stable water-in-oil microemulsions consisting of aqueous «nanodroplets», i.e. nanometer-sized droplets, covered by a monomolecular layer of Aerosol-OT (sodium bis(2-ethylhexyl) sulfosuccinate) and dispersed in isooctane (2,2,4-trimethylpentane). The mutual gelation process of gelatin and such a microemulsion can be resolved into three well distinguishable steps, i.e. (i) the formation of «nanogels», which means gel formation inside the water pools of the nanodroplets, (ii) coagulation of the nanodroplets into an infinite cluster (nucleation step of gelation, formation of a «gel macromolecule»), and (iii) the bulk gelation. The latter is brought about by cross-linking the nanodroplets via gelatin helix-helix interactions. – The resulting weak solids offer many potential applications, e.g. they may be considered as model systems for medical, agro- and food-chemical or pharmaceutical technologies. The transparency of these four-component systems may also stimulate photochemical investigations.