spinodal

https://doi.org/10.1351/goldbook.ST07274
Curve defining the region of composition and temperature for a binary mixture across which a transition occurs from conditions where single-phase mixtures are metastable to conditions where single-phase mixtures are unstable and undergo phase separation by spinodal decomposition.
Notes:
  1. The spinodal curve for a binary mixture is defined as the geometrical locus of all states with \[\left ( \frac{\delta^{2}\Delta _{\text{mix}}G}{\delta\phi ^{2}} \right)_{T,p} = 0\].
  2. In the @U06569@ region bounded by the spinodal curve, @PT07286@ separation is spontaneous, i.e., no nucleation step is required to initiate the separation process.
Source:
PAC, 2004, 76, 1985. 'Definition of terms related to polymer blends, composites, and multiphase polymeric materials (IUPAC Recommendations 2004)' on page 1998 (https://doi.org/10.1351/pac200476111985)