Coacervates measure 1 to 100 micrometers across, possess osmotic properties and form spontaneously from certain dilute organic solutions. Their name derives from the Latin coacervare, meaning to assemble together or cluster. They were even once suggested to have played a significant role in the evolution of cells and, therefore, of life itself.
The immiscible chemical phases are (i) a liquid manufacturing vehicle phase (ii) a core material phase and (iii) a coating material phase. To form the three phases, the core material is dispersed in a solution of the coating polymer, the solvent for the polymer being the liquid manufacturing vehicle phase. The coating material phase, an immiscible polymer in a liquid state, is formed by utilizing one of the methods of phase separation coacervation, that is,
This is accomplished by controlled, physical mixing of the coating material (while liquid) and the core material in the manufacturing vehicle. Deposition of the liquid polymer coating around the core material occurs if the polymer is adsorbed at the interface formed between the core material and the liquid vehicle phase, and this adsorption phenomenon is a prerequisite to effective coating. The continued deposition of the coating material is promoted by a reduction in the total free interfacial energy of the system, brought about by the decrease of the coating material surface area during coalescence of the liquid polymer droplets.
This is usually done by thermal, cross linking or desolvation techniques, to form a self sustaining microcapsule.
Coacervates were actually suggested by Aleksandr Oparin, as a means by which that first "ur-organism" could have formed from non-living, organic matter. He noted that organic chemicals could be formed by the exposure of natural substances to sunlight (ultraviolet radiation, more specifically), in an oxygen-free atmosphere and then would sometimes recombine into larger molecules, until sufficient to form colloids and, therefore, coacervates. Since these coacervates do superficially resemble living cells, Oparin suggested that they eventually became complex enough to be simple life. While this is vaguely similar to modern theories, regarding the formation of first life, coacervates are no longer thought actually to have become the first cells directly; life is thought to have gone through many intermediate steps before becoming cellular.