Handbook of Solvents - George Wypych - ChemTech - Ventech!

250 Valery Yu. Senichev, Vasiliy V. Tereshatov
where:
ϕ 1′
volume fraction of a solvent in a binary mixture of solvents causing a maximum of
equilibrium swelling
ΔHmix experimental value of the mixing enthalpy of components of binary solvent. It can be
taken from literature. 23-24
V12 the molar volume of binary solvent
If there are no volume changes, V12 can be calculated using the additivity method:
V = V ϕ + V ϕ [5.1.19]
12 1 1 2 2
Attempts 25 were made to relate intrinsic viscosity [η] to solubility parameters of mixed
solvents. δ2 of polymer was calculated from the equation: [η]=f(δ1 ). The authors assumed
that the maximum value of [η] is when δ1 = δ2 of polymer. However, studying [η] for
polymethylmethacrylate in fourteen liquids, the authors found a large scatter of experimental
points through which they have drawn a curve with a diffusion maximum. Thus the precision
of δ2 values was affected by 10% scatter in experimental data.
This method was widely used by Mangaray et al. 26-28 The authors have presented [η]as
the Gaussian function of (δ1 - δ2 ) 2 12 /
. Therefore, dependence {( 1/
V1)ln[ η] max / [ η]} = f(
δ1)
can be expressed by a straight line intersecting the abscissa at a point for which δ1 = δ2 . For
natural rubber and polyisobutylene, the paraffin solvents and ethers containing alkyl chains
of a large molecular mass were studied. 26 For polystyrene, aromatic hydrocarbons were
used. For polyacrylates and polymethacrylates esters (acetates, propionates, butyrates)
were used. 27,28 The method was used for determination of δ2 of many polymers. 29-31 In all
cases, the authors observed extrema in the dependence of [η] =f(δ1 ), and the obtained values
of δ2 coincided well with the values determined by other methods. But for some polymers
it was not possible to obtain extremum in dependence of [η] =f(δ1 ). 32
A method of the evaluation [η] in one solvent at different temperatures was used for
polyisobutylene 33 and polyurethanes. 34
For polymers soluble in a limited range of solvents, more complex methods utilizing
[η] relationship are described. 35-37
In addition to the above methods, δ2 of polymer can be determined from a threshold of
sedimentation 38 and by critical opalescence. 39 In recent years the method of inverse gas-liquid
chromatography has been used to evaluate δ2 of polymers. 40,41 One may also use some
empirical ratios relating solubility parameters of polymers with some of their physical properties,
such as, surface tension 42-44 and glass transition temperature. 45
The solubility parameters for various polymers are given in Table 5.1.3.
Table 5.1.4. Solubility parameters of some polymers 36,46
Polymer
(cal/cm 3 ) 1/2
δ
(MJ/m 3 ) 1/2
Polymer
(cal/cm 3 ) 1/2
δ
(MJ/m 3 ) 1/2
Butyl rubber 7.84 16.0 Polydimethylsiloxane 9.53 19.5
Cellulose diacetate 10.9 22.2 Polydimethylphenyleneoxide 8.6 17.6
Cellulose dinitrate 10.6 21.6 Polyisobutylene 7.95 16.2
Polyamide-66 13.6 27.8 Polymethylmethacrylate 9.3 19.0