The existence region and composition of a polymer-induced liquid precursor phase for DL-glutamic acid crystals.

The existence region of a polymer-induced liquid precursor (PILP) phase for crystals of an organic compound (DL-glutamic acid, Glu) was determined for the first time in the phase diagram of the Glu-polyethyleneimine-water-ethanol system. The existence region and the amount of PILP phase relative to the thermodynamically stable crystal phase were very small. Other phases detected in the phase diagram were coacervates, homogenous mixtures, and crystals obtained via a clear solution. The PILP phase is rich in the polymeric additive, which helps to explain the long induction period of PILP before crystallization occurs. Volume measurements indicated that its amount is <1 vol%, showing that this precursor phase is only a minor component.