On the measurement of phase transition temperatures in physical molecular organogels

Methods of measurement of the phase transition temperatures in physical mol ecular gels are analyzed. The "falling ball" technique, NMR, and rheology a re compared. Temperature versus concentration phase diagrams can be easily obtained, and the reliability and workability of the methods are discussed. It appears that rheology is the more accurate and convenient technique whi le the falling ball method provides acceptable Delta H, Delta S values, but the melting temperature values are significantly altered. With NMR, kineti c information associated with the molecular aggregation process can also be extracted. (C) 2000 Academic Press.