Bondi’s tables

The molecules must be divided into groups as defined by the UNIFAC method. The segment surface areas and the segment volumes are calculated from Bondi s tables according to... 

Many attempts have been made to improve the UNIFAC-frf model which cannot be listed here. A comprehensive review was given by Fried et al. An innovative method to combine the free-volume contribution within a corrected Flory-Huggins combinatorial entropy and the UNIFAC concept was found by Elbro et al. and improved by Kontogeorgis et al. These authors take into account the free-volume dissimilarity by assuming different van der Waals hard-core volumes (again from Bondi s tables ) for the solvent and the polymer segments... 

Low molecular weight PS was mixed vdth poly(methyl phenyl siloxane), PMPS, to form an immiscible blend with an upper critical solution temperature (UCST) [199]. The viscoelastic properties were studied by dynamic and steady-state shearing the neat polymers showed Newtonian behavior. Within the miscible region the blend viscosity followed the Mertsch and Wolf equation, Eq. (2.35), but with the parameter /fit = calculated from Bondi s tables. The phase separation created a rheolog-ically complex behavior. 

Bondi s calculation method is simple. The van der Waals volumes are the sum of the van der Waals volumes of fragments, as given in Table 6.3. The calculated van der Waals volumes are summarized in Table 6.4. However, these volumes are different from those calculated using the MOPAC-BlogP program, even though the correlation is excellent. 

Table 6.3 Bondi s group contributions to the van der Waals volume of hydrocarbons...

Figure 6.4 Relationship of log k values measured on ODS-bonded silica gel to Bondi s van der Waals volumes. Column, Develosil ODS, 15 cm x 4.6 mm i.d. eluent, 70% aqueous acetonitrile at 30 °C. Numbers beside symbols see Table 6.4 <>, Polycyclic aromatic hydrocarbons x, alkylbenzenes O, halogenated benzenes A, alkanols and , alkanes.

The "predicted" values in Table 5.6 have average deviations from the experimental values of 11% for AHm and of 7% of ASm. In accordance with Bondi s statement the "additivity" of ASm is better than that of AHm. 

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