Valery G. Babak

Interfacial properties of chitin and chitosan based systems

Chitin and chitosan can be modified to obtain amphiphilic systems with controlled structures and architectures. The hydrophile–lipophile balance (HLB, also called hydrophilic–hydrophobic balance) may be modified with respect to different parameters (pH, degrees of substitution of ionic and alkyl groups), and therefore their properties (especially rheological and interfacial) can be adapted to a specific application. The surface activity of ionic derivatives can be improved either by the addition of an oppositely-charged surfactant, which plays the role of counterion by electrostatic interaction (forming a surfactant–polyelectrolyte complex, SPEC), or by N-alkylation. SPECs are found to be more efficient than alkyl derivatives, and the necessary surfactant concentration to reach tensioactive properties is much lower than its critical micellar concentration in the pure solution. The diversity and the control over such structures and architectures make possible their use in numerous domains, strengthening the current interest in these materials.

Effect of interfacial tension and droplet size on coagulation, adhesion and rheology of concentrated emulsions

Abstract The thermodynamics of microscopic emulsion films, i.e. the thermodynamics of contact interactions between emulsion droplets with radius R and interfacial tension σo, have been systematically analyzed to identify the important role which is played by the deformability of liquid droplets (defined as the ratio ν of the height Πb, of the coagulation barrier, or the depths Π1, or Π2, of the near or far coagulation minima of the disjoining pressure isotherm Π(H), respectively, to the capillary pressure Pc = 2σo/R) in the stability, adhesion and rheological properties of highly concentrated emulsions. It has been demonstrated that increasing the parameter ν at a constant and relatively high coagulation barrier Πb