DEFORMATION OF A CAPSULE IN A SPINNING DROP APPARATUS

This paper studies the rheological properties of ultrathin aminomethac rylate membranes that are synthesized at the interface between oil and water. We have measured the kinetics of the crosslinking reactions, t he zero shear modulus, and the nonlinear rheological properties of tho se two-dimensional networks. The measurements were performed at a plan ar interface using a special surface rheometer. Once stabilized, the m embranes exhibit rubber-elastic properties. In addition, we have forme d small emulsion droplets using the same type of interfacial polymeriz ation. In order to get more information on the mechanical properties o f the resulting microcapsules, we have developed a new experimental te chnique that consists in measuring the deformation of a capsule in a s pinning drop apparatus. A theoretical analysis of the deformation proc ess allows an interface apparent elastic Young modulus to be calculate d. From a comparison of the surface shear modulus with the Young modul us, it is then possible to estimate the surface Poisson ratio, which i s here approximately zero. These results point to the existence of are a compressible anisotropic membranes. (C) 1998 Academic Press.