XPS investigations of acid–base interactions in adhesion. Part 4.—Use of trichloromethane as a molecular probe for the quantitative assessment of polymer basicity

Trichloromethane has been used as a molecular probe for the assessment of acid–base properties of polymers in the solid state. It is shown in this paper that when CHCl3 is sorbed in polymers it undergoes a negative XPS chemical shift as a result of acid–base interactions. Following the FTIR approach of Fowkes, we determined ΔHAB, the enthalpy of acid–base adduct formation, for the different polymer–CHCl3 adducts, and found that the XPS binding energy (Eb) of the Cl 2p3/2 line is linearly related to ΔHAB. The relationship is of the form –ΔHAB/kcal mol–1= 228.8–1.14 Eb/eV.