Phase separation induced in gelatin-base coacervation systems by addition of water-soluble nonionic polymers II:...

Phase separation, induced in aqueous solutions of gelatin or gelatin-acacia by adding polyethylene oxide (PEO) or polyethylene glycol (PEG) of different molecular weights, was examined. The minimum concentration (Cp) of PEO or PEG required to cause phase separation decreased with an increase in the molecular weight (M2) of the polymer. The dependence of Cp on M2 for a complex coacervation (gelatin-acacia-water) system was larger than for a simple coacervation (gelatin-water) system, in which Cp was approximately proportional to M2-1/2. Elemental analyses indicated that coacervates induced in gelatin-water systems by the addition of PEO (or PEG) did not contain PEO (or PEG); therefore, phase separation may be due to incompatibility.