Solubility properties in polymers and biological media: 10. The solubility of gaseous solutes in polymers, in terms of solute-polymer interactions

A general equation. SP=SP₀+l log L¹⁶+s(π₂^*+dδ₂) + aα₂ + bβ₂. has been used to describe solubility properties of a wide range of gaseous solutes in polymers. The property, SP, may be a log V_G value, an enthalpy of solution, etc., and the explanatory variables are solute parameters: L¹⁶ is the Ostwald solubility coefficient of the solute on hexadecane at 25°C, π*₂ is the solute dipolarity, δ₂ a polarizability correction term, α₂ the solute hydrogen-bond acidity, and β₂ the solute hydrogen-bond basicity. Solubilities may then be discussed in terms of the various solute-solvent interactions that are reflected by the coefficients of the various terms. These are cavity effects and dispersion forces (l), dipole-dipole and dipole-induced-dipole interactions (s), and hydrogen-bonding between solute acid and polymer base (a) or between solute base and polymer acid (b). For non-dipolar solutes in all non-aqueous solvent phases, and for weakly dipolar solutes in weakly dipolar phases, the general equation reduces to a more specific equation that includes only the term due to cavity effects and dispersion forces. SP=SP₀+l log L¹⁶.