Dilational surface viscoelasticity of hydroxypropyl methyl cellulose and CnTAB at air–water surface

Using oscillating barriers method, the dilational surface viscoelasticity of nonionic hydroxypropyl methyl cellulose (HPMC)/CnTAB adsorbed layers are measured at air–water surface. The evaluation of such measurements shows the information about the influence of CnTAB surfactant on the dilational surface viscoelastic properties of HPMC. The dilational viscoelasticity of HPMC/CnTAB adsorbed layers depends on the surfactant chain length, bulk concentration of HPMC or CnTAB, as well as the oscillation frequency. The frequency dependent of dilational viscoelasticity for HPMC/CnTAB surface layer is weaker than that of pure HPMC and CnTAB systems. For HPMC/C12TAB surface layer, its dilational elasticity and stability are the lowest comparing with HPMC/C16TAB and HPMC/C14TAB surface layers. However, the dilational elasticity of HPMC/C14TAB surface layer shows a remarkably higher value than that of HPMC/C16TAB. This phenomenon is ascribed to more HPMC molecules adsorb on the surface except some C14TAB molecules at this C14TAB concentration.