XII.1 Specific Cohesive Energy of Organic Liquids and Polymers Hildebrand Solubility Parameter

To predict the solubility of polymers in various organic solvents, as well as for preliminary estimation of the miscibility of polymers with each other or with plasticizers, the characteristic as the solubility parameter ? is often used. This characteristic has been introduced by Hildebrand for description of solutions of non-electrolytes. The Hildebrand solubility parameters is determined from the correlation

(XII.1)

where ? E ₀ = ? H ₀ - RT; ? H ₀ is the latent heat of liquid evaporation; R is the universal gas constant; T is the absolute temperature; V is the molar volume of the liquid.

The square of the solubility parameter represents specific cohesive energy of the liquid, i.e. the value of cohesive energy divided by the molar volume:

(XII.2)

These notions are also applied to polymers, therewith, estimations are indicated per repeat unit. In this case, the problem is that the value ? may be experimentally determined only for low-molecular liquids evaporating without decomposition. For polymers which cannot be evaporated without decomposition, values of ? are determined by indirect methods or calculated from the constants of energies for separate atoms and groups of atoms [141, 150, 206].

Taking into account the nature of molecules in liquids and polymers leads to the following equation for calculating the specific cohesive energy [25]:

(XII.3)

where ?E* = k ?E ₀ is the...