ABSTRACT
Phase separation techniques are described in all reviews of microencapsulation and have been the mainstay of many studies of drug microencapsulation and release on which a number of clinical investigations have been built. The problem of microcapsule quality, in such applications, has received little attention in spite of known effects of variation of surface area, porosity, membrane thickness, and structure on controlled drug delivery. Liquid-liquid phase transitions may take place by either spinodal or nucleation-growth mechanisms; liquid-solid transitions occur only via the latter. The composition and temperatures of polymer solutions at which one or other of the mechanisms is preferred depends on the underlying free energy diagrams. The aggregation problem is reduced using an additive enlarging the area of liquid coacervate formation. Parameter effects on theophylline microcapsule size showed that at lower production temperature, microscopic mean size fell. Weight frequency distribution by sieving revealed a large increase in aggregation on elevating the temperature.
