Lewis acid-base properties of cellulose acetate butyrate by inverse gas chromatography

The dispersive component of the surface-free energy, gamma(d)(S), of cellulose acetate butyrate (CAB) has been determined using the net retention volume, V-N, of n-alkanes (C-5-C-8) probes in the temperature range 323.15-393.15 K. The gamma(d)(S) S values decrease nonlinearly with increase in temperature, and the temperature coefficients of gamma(d)(S) are -0.32 (mJ/m(2)K) and -0.10 (mJ/m(2)K) in the range 323.15-353.15 K and 353.15-393.15 K, respectively. This variation in d gamma(d)(S)/dT has been attributed to the structural changes that take place on the surface of CAB at similar to 353.15 K. The specific components of the enthalpy of adsorption, Delta H-a(S), and entropy of adsorption, Delta S-a(S), calculated using V-N of polar solutes are negative. The Delta H-a(S) values are used to evaluate Lewis acidity constant, K-a, and Lewis basicity constant, K-b, for the CAB surface. The K-a and K-b values are found to be 0.126 and 1.109, respectively, which suggest that the surface is predominantly basic. The K-a and K-b results indicate for the necessary surface modifications of CAB which act as biodegradable adsorbent material. Copyright (c) 2010 John Wiley & Sons, Ltd.