ChE PhD Dissertation Defense: Alexander Kaltashov

Name:
Alexander Kaltashov

Title:
Temporal and Spatial Control of Structure and Rheology in Binary Colloidal Gels

Date:
08/06/2026

Time:
01:00:00 PM

Committee Members:
Prof. Safa Jamali (Advisor)
Prof. Sara Hashmi
Prof. Craig Maloney
Prof. Steven Lustig

Location:
Hayden Hall 424

Abstract:
Colloidal gels are soft materials formed when attractive interactions between nanometer-to-micrometer scale particles dispersed in a fluid phase drive their self-assembly into a percolated network. Traditionally, the structure and mechanical properties of single-component colloidal gels are tuned through control of inter-particle interactions and particle concentration. The introduction of additional components into a system expands the range of accessible gel architectures, which can be further tailored through multiple coexisting inter-particle interaction types, as well as size disparity and component stoichiometry. Beyond these conventional control parameters, the design space can be expanded further by treating the self-assembly pathway itself as an independent variable. Specifically, temporal control through sequential gelation protocols and spatial control through prescribed composition gradients enable binary colloidal gel architectures with structural characteristics beyond those achievable through conventional controls alone. Yet, despite their promise as routes to engineering novel materials, these concepts remain underexplored in colloidal gels. This dissertation presents a series of computational studies that explore pathway-dependent design strategies for binary colloidal gels. Sequential gelation is first examined as a temporal control mechanism for programming network formation and structural evolution, followed by an investigation of composition gradients as a spatial control strategy for creating heterogeneous gel architectures. Collectively, these studies establish the self-assembly pathway as an independent design parameter for engineering multicomponent colloidal materials with tailored morphologies and properties.

Alexander I. Kaltashov is a doctoral candidate in Chemical Engineering at Northeastern University, where he conducts computational studies of the structure, dynamics, and rheology of multicomponent colloidal gels. His doctoral research focuses on understanding how temporal and spatial controls over self-assembly pathways can be used to control the architecture and mechanical properties of binary colloidal networks. His work combines particle dynamics simulation, rheological modeling, and structural analysis to investigate the relationship between colloidal interactions, self-assembly processes, and structural/material properties. Prior to his doctoral studies, Alexander received a Bachelor of Chemical Engineering from McGill University in Montreal, Canada, in 2020. During his undergraduate studies, he conducted research across a variety of fields, including the development of a low-cost, large-area UV photolithography system, investigation of protein phase separation, and oxygen mass transfer studies in laboratory-scale bioreactors. His current research interests broadly include soft materials, colloidal assembly, rheology, and computational modeling.