The Formation and Elasticity of a Hydroxypropyl Cellulose Film at a Water–Air Interface

Abstract

The kinetics of spreading of aqueous hydroxypropyl cellulose (HPC) solutions with different concentrations over a water surface and the rheological properties of films formed at the water–air interface have been studied. The performed experiments are distinguished by the fact that the solvent in the polymer solutions is identical to the liquid subphase, while, beginning from a certain concentration, the aqueous HPC solutions are capable of forming a liquid-crystalline phase. The chosen initial polymer solution concentrations correspond to different regions of the phase diagram for the HPC–water system. The contact of a solution droplet with water yields a time-stable spot of an HPC solution layer. In spite of the fact that some solution concentrations correspond to the existence range of a lyotropic liquid-crystalline phase, an isotropic layer is formed on the water surface irrespective of the concentration and phase state of the solution in the droplet. The dynamic dilatational storage modulus of such an interfacial layer at a frequency of 0.03 Hz is equal to 43 ± 2 mN/m; i.e., it almost coincides with the surface tension of the formed interfacial layer.