The traditional retraction of the deformed drop method (DDRM) to determine the interfa-cial tension is reformulated to relax the limit the small deformation assumption. The kernel of the new formalism is the calculation of the velocity gradient on the vertex of the ellipsoidal drop. Two models were used for such calculations: the Jackson and Tucker model [J Rheol 47:659 682] and the Yu and Bous-mina model [J Rheol 47:1011 1039]. The method can be used either in the retraction of shear deformed drop, or in the retraction of elongated drops produced by the breakup of a long thread. Comparison with experimental results of the literature showed that conversely to the clas-sical DDRM, good accuracy is ob-tained when the new modeling for the determination of interfacial ten-sion is used both under small and large deformations.

The deformation of a viscoelastic drop suspended in a homogeneous viscoelastic matrix is investigated. The drop and the matrix fluids are assumed to obey linear viscoelastic constitutive equations. Small-deformation analysis is carried out on the basis of the general solution for creeping flow around a spherical drop. The corresponding stress is calculated by extending Batchelor's approach to viscoelastic media for both small and large deformations. Good agreement was found between the model predictions and experimental results available in the literature.

We study the interaction between a surface-anchoring colloidal particle and a liquid-crystalline host, and in particular the formation of orientational defects near the particle. A mean-field theory based on the nonlocal Marrucci-Greco nematic potential is used to represent molecular nteractions in an inhomogeneous orientational field. An evolution equation for the molecular configuration tensor is solved numerically whose steady state minimizes the total free energy of the system. With strong homeotropic anchoring on the particle surface, three types of solutions may appear depending on initial conditions and particle size: Saturn rings, satellite point defects, and polar rings. The Saturn ring remains stable on micrometer-sized particles, contrary to previous calculations but consistent with experiments. A phase diagram is constructed for the three regimes. Based on the free energy, the most stable state is the Saturn ring for smaller particles and the satellite defect for larger ones.

In this study, the dynamic interfacial properties between an isotropic polymer and a thermotropic liquid crystalline polymer (TLCP) were investigated by measuring the time-dependent interfacial tension between them. As a TLCP drop retracts in a flexible polymer matrix, the evolution of its shape is recorded by microscopy. By fitting the ellipsoidal model of Maffettone and Minale, the model of Marrucci and Santo, and large deformation ellipsoidal models by Jackson-Tucker and Yu-Bousmina, the interfacial tension could then be determined. It was found that the retraction of a TLCP ellipsoidal drop in a flexible polymer cannot be described by these models as accurately as in Newtonian systems. The apparent interfacial tension obtained from these models evolves with time; the evolution is ascribed to the slow relaxation of domain orientation within the TLCP drop.

The kinetics of melt intercalation of poly(propylene)/montmorillonite nanocomposites was studied by a rheological approach. The experimental sample was elaborately prepared to investigate the whole intercalating process. The intercalation process was demonstrated by the changes of the viscoelastic response with annealing time. The development of the relative volume fraction of intercalated tactoids was obtained from the rheological characterization. The apparent diffusivities was etermined and the activation energy of melt intercalation was found to be about 80