Handbook of Solvents - George Wypych - ChemTech - Ventech!

5.2 Prediction of solubility parameter 253
5.2 PREDICTION OF SOLUBILITY PARAMETER
Nobuyuki Tanaka
Department of Biological and Chemical Engineering
Gunma University, Kiryu, Japan
5.2.1 SOLUBILITY PARAMETER OF POLYMERS
For the purpose of searching for the solvents for a polymer, the solubility parameter of polymers,
δp , is defined as: 1-11
( / )
δ p h v
= 0
12 /
[5.2.1]
where:
h0 the cohesive enthalpy per molar structural unit for a polymer (cal/mol)
v the volume per molar structural unit for a polymer (cm 3 /mol)
because δp is equivalent to the solubility parameter of solvents, δs, that shows the minimum
of the dissolution temperature 7 or the maximum of the degree of swelling 1,2 for the polymer.
For δs,h0is the molar energy of vaporization that is impossible to measure for polymers decomposed
before the vaporization at elevated temperatures, and v is the molar volume of a
solvent. The measurements of the dissolution temperature and the degree of swelling are
only means to find the most suitable solvents for a polymer by trial and error.
In order to obtain easily the exact value of δp at a temperature, T, the possibility
of δp prediction from the thermal transition behaviors such as the glass transition and the
melting has been discussed. 9-11 Consequently, it was found that the sum of their transition
enthalpies gave h0 in equation [5.2.1] approximately:
for crystalline polymers,
h0 hg hx hu
≈ + + T ≤Tg [5.2.2]
h0 hx hu
≈ + Tg