1989 Volume 17 Issue 2 Pages 86-93
1, 3; 2, 4-p, p′-ditoluyliden sorbitol (PDTS) is an excellent gelling agent. A great variety of organic solvents and oligomers can be gelled by addition of small amount of PDTS. We studied thermoreversible sol-gel transitions in PDTS/organic solvent systems and PDTS/oligomer systems by means of a falling-ball (FB) method.
Sol-gel transition temperature (Tfg) was obtained as a function of PDTS concentration (C) for several PDTS/organic compound systems by the FB method. We found a linear relationship between lnC and l/T fg and that Ferry-Eldridge equation for sol-gel transition of polymeric gelling agent systems is applicable to the PDTS/organic compound systems. The heat evolved in the sol-gel transition (ΔH) was found to be in the range of 10.3-26.2 kcal/mol depending upon the solubility parameter (SP) of the organic compounds. |ΔH| decreases with increasing SP due to the solvation effect, if the SP for the organic compounds is smaller than that for PDTS, SP for PDTS being 12.5. We also found that the gel formation by PDTS was stopped by vitrification of the matrix organic compound and that the gel structure preexisting in the system was not destroyed by crystallization or vitrification of the matrix.