CHARACTERIZATION OF SURFACE THERMODYNAMIC PROPERTIES OF P-TOLUENE SULFONATE-DOPED POLYPYRROLE BY INVERSE GAS-CHROMATOGRAPHY

p-Toluene sulfonate-doped polypyrrole (PPyTos) powder has been charact erized by inverse gas chromatography at various temperatures. We have used apolar n-alkanes and polar probes of differing acidity and basici ty to interrogate the London dispersive and Lewis acid-base properties of PPyTos, respectively. We have found that the London component of t he surface energy (gamma s(d)) is about 90 mJ . m(-2) at 25 degrees C and the acid-base contribution to the free energy of adsorption (Delta G(a)(AB)) for Lewis bases is higher than 8 kJ . mol(-1). These result s show that PPyTos is a high energy material and is capable of very st rong specific acid-base interactions. Lewis acidity is, however, domin ant and is shown to increase with temperature. The determination of th e heats of adsorption for tetrahydrofuran and ethyl acetate enabled us to determine Drago's E(A), C-A, E(B) and C-B parameters. Whilst E(A) and C-A are similar to those published for chloride-doped polypyrrole and rank PPyTos as a hard acidic species, the E(B) and C-B values sugg est that PPyTos is a very soft Lewis base.