Investigation of the relationships between the thermodynamic phase behavior and gelation behavior of a series of tripodal trisamide compounds

Abstract

The solution behavior of a series of tris(2-aminoethyl)amine (TREN) based trisamide derivatives in organic solutions was investigated with a focus on organogelation. First, the general solution behavior of eight compounds was investigated and qualitatively interpreted using the regular solution model and solubility parameter theory. Second, the phase behavior of one trisamide in aromatic solvents, where gels were formed, was investigated in more detail. A correlation was found between the sol–gel transition temperature and the thermodynamic liquidus lines. The prediction of the liquidus lines using the regular solution model and solubility parameter theory reproduced the shape and scaling of the gel transition temperature vs. composition in different aromatic solvent solutions. Good fits of the gel transition temperature vs. composition were obtained using the thermodynamic parameters of the components with one additional fitting parameter to account for entropic contributions to the solution non-ideality. Based on these results the regular solution model was used to calculate the melting temperatures of two different trisamides at the minimum gelation concentration (MGC) in different aromatic solvents. The dependence of the MGC on the minimum undercooling required for gelation is discussed. The assumptions and limitations of the model are also discussed to aid in its more general application to organogelator thermodynamics.