PHYSICAL AND DIELECTRIC-PROPERTIES OF SOME NONIONIC SURFACTANTS

Fatty acid esters have been prepared by reacting the acid C-18 with po lyethylene glycols having varying numbers of oxyethylene units (4 simi lar to 88 units) by the direct esterification reaction method. Surface and interfacial tensions are studied at various experimental conditio ns, including, concentration, temperature, and chemical constitution o f the surfactants. Critical micelle concentrations (CMC), surface exce ss Gamma and residual area occupied by each surface active agent molec ule A have been calculated using Gibb's equation. CMC values range fro m 10 to 55x10(-5) mole/L for all studied agents, while the residual ar ea occupied by each molecule varies from 0.6 to 1.5 nm(2) Variation of CMC of some of these agents with temperature have been also examined and data obtained are used to calculate the heat of micellization Delt a H-m and the entropy change during micellization Delta S-m. Values of Delta H-m varies from 14.63 kJ/mole to 2.717 kJ/mole depending on the chemical constitution of the agent under consideration. The apparent dipole moments mu of three surfactants were measured following the Hea dstrand's method. Values of mu are 3.24, 3.14 and 3.02 D for stearates , oleates, and linoleates adducts with polyethylene glycol (1000).