Tayssir Hamieh*, Khaled Chawraba, Jacques Lalevee and Joumana Toufaily
Many studies were devoted in our Laboratory to the determination of physico-chemical and thermodynamic properties of polymers and/or oxides by using the inverse gas chromatography (IGC) at infinite dilution. More particularly, we studied the interactions of solid substrates with some model organic molecules and their acid-base properties, in Lewis terms, by determining the acidic and basic constants. We proposed in this paper to study the surface thermodynamic energetics, transition phenomena, specific interactions and acid-base properties of both the conducting polyaniline (PANI-HEBSA) and the non-conducting form (PANI-EB) on the light of the new progresses of IGC methods. This technique was used to obtain the net retention volume Vn and then the dispersive free enthalpy of n-alkanes adsorbed on PANI. The curves of the dispersive component of the surface energy of n-alkanes adsorbed on PANI, as a function of the temperature highlighted the presence of two transition temperatures on 383K and 430K respectively for PANI-HEBSA and PANI-EB. There results were confirmed by the curves of RTlnVn =f(1/T) of n-alkanes. The determination of the specific free enthalpy of polar molecules adsorbed on PANI proved a shift of 4K in the value of the glass transition of PANI-EB. From the variation of as a function of the temperature, one deduced the values of the specific enthalpy of the various polar molecules and determined the acidic constant KA and basic constant KD, the two constants characterizing the solid substrate. It was showed that PANI is highly more basic than acidic (about 2.6 times more basic) and an increase of the acid-base character was highlighted near the glass transition for PANI-EB.
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