Adsorption of sodium cyclododecylmethanoate and cycloundecylmethanoate at the air/water interface

Abstract

JAN J. SPITZER. Can. J. Chem. 62, 2359Chem. 62, (1984. Surface tension measurements on aqueous solutions of sodium cyclododecylmethanoate and sodium cycloundecylmethanoate in sodium carbonate/bicarbonate buffers and at constant sodium ion concentration at 25OC were used to obtain the standard free energies of adsorption, the saturation areas per surfactant ion, and the critical "micelle" concentrations of these compounds. Similar measurements were done for solutions of sodium dodecanoate for comparisons.The standard free energies of adsorption of CH2 group that is located in a macrocyclic cycloalkyl ring appears to follow the "mle of two" (-RT In 2) that is also valid for straight chain ionic surfactants. The sat;ration areas of both cyclododecylmethanoate and cycloundecylmethanoate are about 52 A2/ion as compared to about 32 A2/ion for normal dodecanoate.For large ring cycloalkylmethanoates the critical "micelle" concentrations appear to decrease by a factor of about 415 for each CH2 group added to the ring as compared to the factor of about 112 for each CH2 group added to the chain of normal alkanoates. The data suggest that large cycloalkyl rings have "collapsed ring", or "double chain", conformation in aqueous solutions and in the adsorbed state.

Interfacial properties of poly(maleic acid-alt-1-alkene) disodium salts at water/hydrocarbon interfaces

“…In fact, in the present case there are two carboxylate groups per comonomer unit, whose electrostatic repulsive interaction acts to desorb the polyelectrolyte from the interface, whereas in the case referred to [1] there is only one carboxylate group per comonomer unit. At the air/water surface, −1.72 kJ/mol has been reported as the contribution to G 0 ads for the adsorption of each methylene group [13]. On the other hand, the contribution to G 0 ads per methylene group in poly(4-vinylpyridine) N -alkyl quaternized from chloroform to chloroform/water interface is just 0.13 kJ/mol, reflecting that methylene groups act to stabilize this type of polyelectrolyte in the chloroform phase.…”

Surface properties of inclusion complexes between α-cyclodextrin and poly(ethylene oxide)

“…To obtain the thermodynamic parameters for the adsorption process of the IC and PEO studied here, the standard free energy of adsorption, G 0 ads , was determined using the equation [30] (7) G 0 ads = −2.303RT log(A) − 1.74 , where A is one numerically empirical fitting parameter related to G 0 ads . Values of G 0 ads are also listed in Table 1.…”