Title: large amplitude oscillatory shear behavior at air–water interface

Biography:

Associate Professor (tenure track), Acedemy Research Fellow in Nanocellulosic Biomaterials and chemicals
New cellulose derivatives and their applications - especially fabrication of nano- and microcelluloses and their applications:
Nanocellulose as a novel class of Bionanochemicals: adsorbents, flocculation agents, surfactants, emulsifiers.
Nanocellulose in barriers and films, filters and membranes, nanopapers, smart materials and templated structures.
Deep eutectic solvents and periodate oxidation in cellulose modification.
Surface and colloid chemistry of cellulose systems.

 

 

Abstract

Soft colloidal matters, such as foams and emulsions, are used in our day to day life as well as in industries. These colloids are thermodynamically unstable. Therefore, the interest is paid on their kinetic stability. Presence of particles at the air–water interfaces provides mechanical strength to the interface; consequently, the foams are stable for a longer period.

The stability of foams depends on the stability of thin liquid films separating the two bubbles (or droplets). A thin liquid film consists of two air (or oil)­­–water interfaces. Therefore, the properties of foams (or emulsions) depend on the behavior of the air–water interfaces. Presence of particles at the interfaces tends to have a complex microstructure, which often shows nonlinear response even at low strain (or strain rate). The nonlinearity is due to the change in the microstructure. During the formation of foams, it is routinely exposed to large and fast deformation. Therefore, the study of nonlinear rheological properties of the air–water interface is highly relevant.

              In this study, silica nanoparticles and hexadecyltrimethylammonium bromide (HTAB) were used as stabilizing agents. The air–water interface, containing surfactant-laden particles, was deformed under large amplitude oscillatory shear (LAOS). The LAOS behavior was characterized by analyzing Lissajous–Bowditch curves. These curves were further described by using Fourier transform rheology, Chebyshev polynomial, and sequence of physical processes approach.   

 

Keywords — fluid–fluid interfaces, interfacial shear rheology, large amplitude oscillatory shear, Lissajous–Bowditch curves, nonlinear viscoelastic