the wagner group















Rich Dombrowski


Curriculum Vitae
B.S. Chemical Engineering, 2003
University of Delaware, Newark, DE

Ph.D. Chemical Engineering, 2007
University of Queensland, Brisbane, Australia

office: 044 Colburn Lab
email: rdombro@udel.edu
phone: 302-831-8919

Rheophysics of Thixotropic Pastes: The Rheology and Microstructure of Systems Containing Crystallizing Surfactants

Complex fluids with high concentrations of crystallizing surfactants are important for consumer skin care products. Research concerning similar systems of fat crystal networks in food products has demonstrated the influence of composition and processing conditions on crystal morphology and, therefore, final product properties, such as spreadability and hardness. The goal of this thesis project, a collaboration between the University of Delaware and Unilever, is to gain a fundamental understanding of the relationships between molecular structure and interactions, crystallization, and macroscopic rheological properties in model systems possessing the important properties of interest for consumer product applications. The systems of interest include surfactants and fatty acids at sufficient concentrations for the coexistence of lamellar and/or hexagonal liquid crystalline phases with needle-like crystals. The formation of a crystal network, influenced by composition and processing conditions, affects the structural and rheological properties of these systems. Methods including polarized light microscopy, scattering, and visual phase behavior studies allow for the characterization of molecular structure and interactions. Differential scanning calorimetry allows for the quantification of model system transition temperatures and energies. Rheology provides a means for measuring macroscopic flow behavior. Ultimately, understanding the relationship between the molecular structure and interactions, crystal morphology, network formation, and macroscopic rheological properties will aid the design of consumer products with specific sensory properties and thermodynamic stability.