화학공학소재연구정보센터
Thermochimica Acta, Vol.548, 76-80, 2012
Host-guest interactions between 4-sulfonatocalix[8]arene and 1-alkyl-3-methylimidazolium type ionic liquids
The inclusion of 1-alkyl-3-methylimidazolium ions (C(n)mim(+)) in 4-sulfonatocalix[8]arene was studied by isothermal titration calorimetry in aqueous solution at 298 K. Sequential formation of 1:1 and 2:1 complexes occurred in enthalpy driven reactions. The alteration of the molecular structure of the guest barely affected the driving force of the confinement of the first C(n)mim(+). However, the binding affinity of the second C(n)mim(+) went through a maximum when the number of carbon atoms in the side chain was increased. The enthalpy and entropy change diminished linearly with the length of the aliphatic substituent of C(n)mim(+) for 1:1 complexation, but reached a minimum for the hexyl homologue in the case of 2:1 inclusion. Linear entropy-enthalpy correlations were found with smaller slope and intercept for the second binding step. (C) 2012 Elsevier B.V. All rights reserved.