Date of Award

Fall 2023

Document Type

Open Access Dissertation


Chemical Engineering

First Advisor

Nader Taheri-Qazvini


Soft matter, a fascinating class of materials, holds a paramount significance in the realm of material design and engineering. Within this broad category, colloidal gels with their unique characteristics have drawn tremendous attention in a variety of applications, spanning from biomedical engineering to oil and gas recovery. Meeting the specific requirements and criteria of these diverse fields necessitates the development of colloidal gels with highly tunable properties to optimize their performance for a wide range of applications. Hence, both scientific and industrial advancement call for more control over the gel properties by exploring novel practical parameters. This dissertation describes an effort to tailor characteristics of hybrid colloidal gels through employing shape-asymmetrical building blocks to establish a new pathway for deliberate design of desired gels. Here, the focus is on engineering the gels formed through the assembly of positively charged soft nanospheres and negatively charged two-dimensional particles. The primary goal is to explore the untapped potential of these hybrid colloidal gels by manipulating parameters that are not easily accessible in gels composed of single shaped particles. This investigation revealed that the complex interplay of anisotropic interparticle interactions, arising from the shape asymmetry of the building blocks, leads to the formation of gels with remarkably high elasticity at low particle’s volume fraction. Furthermore, by manipulating the interparticle interactions through exploiting innovative yet practical parameters a higher level of control can be achieved. Controlling parameters including charge anisotropy on two-dimensional nanosheets, relative size of the building blocks, and binary assortment of nanosheets provide us this opportunity to tailor hetero-aggregation mechanism, microstructure, elasticity, yielding behavior, stress relaxation, and flowability of the gels. Remarkably, unlike conventional hydrogels, employing shape asymmetrical building blocks provides this opportunity to tune the elasticity and yielding behavior orthogonally. The contribution of this work is to offer a new strategy to design hybrid colloidal gels with desirable characteristics for different applications, specifically 3D printing. While a significant portion of this dissertation is dedicated to investigating hybrid colloidal gels, hybrid membranes, as widely employed soft matter, have also been investigated. Here, we showed that a controlled assembly of asymmetrical soft spherical nanoparticles and two-dimensional nanosheets can yield multifunctional hybrid membranes with robust burst strength and flexibility, enabling their versatile performance across various applications. Taken together, findings accomplished by this study showed the untapped potential of hybrid soft materials, particularly colloidal gels, formed by hetero-aggregation of oppositely charged shape asymmetrical nanospheres and nanosheets building blocks. The insights gained from this research highlight the need for further exploration in this area. The new findings in this dissertation are expected to assist future researchers in rational design of hybrid soft materials based on shape asymmetrical building blocks, open up new possibilities for innovative applications and advancements in the field.


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