Solvent properties play a central role in mediating the aggregation and self-assembly of molecular gelators and their growth into fibers. Numerous attempts have been made to correlate solubility parameters of solvents and gelation abilities of molecular gelators, but a comprehensive comparison of the most important parameters has yet to appear. Here, the degree to which partition coefficients (logP), Henry's law constants (HLC), dipole moments, static relative permittivities (er), solvatochromic ET(30) parameters, Kamlet-Taft parameters (b, aand p), Catalan's solvatochromic parameters (SPP, SB and SA), Hildebrand solubility parameters (di), and Hansen solubility parameters (dp, dd, dh) and the associated Hansen distance (Rij) of different solvents (covering a wide range of properties) can be correlated. The approach describes the basis for each of the parameters and how it can be applied. As such, it is an instructional 'blueprint' for how to assess the appropriate type of solvent parameter for use with molecular gelators as well as with molecules forming other types of self-assembled materials. The results reveal several important insights into the factors favoring gelation of solvents. The ability of a solvent to accept or donate a hydrogen bond is much more important than solvent polarity in determining whether mixtures become solutions, clear gels, or opaque gels. Thermodynamically derived parameters could not be correlated to the physical properties of the molecular gels unless they were dissected into their individual HSPs. It is also found that the fate of the molecular gelator, unlike that of polymers, is influenced not only by the magnitude of the distance between the HSPs for the gelator and the HSPs of the solvent, Rij, but also by the directionality of Rij.

Comparing and correlating solubility parameters governing self-assembly of molecular gels

248th National Meeting (2014)

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