Dr. Pengxiang Si November 20, 2020 @ 1 pm.
Abstract
Polyurethanes (PUs) are a class of versatile polymers; their structure and morphology can be readily tailored to exhibit various mechanical, physical, chemical and biological properties. PUs have been employed in a variety of industrial applications including foams, coatings, textiles, machinery, sporting, transportation, vehicles and construction. Water-based PU was developed to reduce the usage of volatile organic compounds (VOCs) in the synthesis of conventional solvent based PU, and exhibits advantages of superior material properties (e.g. flexibility, stretchability, elasticity, mechanical strength), processability (e.g. 3D printing, inkjet printing, screen printing, spray coating, molding) and sustainability (e.g. low VOCs, degradable). Water-based PU combines the superior mechanical properties of PU with the excellent stability of colloids. The current research trend of PU is shifting from traditional industrial applications to state-of-the-art fields such as soft and wearable electronics, energy storage devices, biosensors, actuators, photovoltaic devices and stimuli-responsive materials. Due to the existence of a variety of functional groups such as urethane, aliphatic or aromatic hydrocarbons, esters, ethers, amides and urea, water-based PU can be physically or chemically incorporated with functional materials to form PU colloidal composites towards various applications.
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Remi Casier December 3, 2020 @ 1pm
The Hierarchy of Protein Folding
Abstract
Proteins are biological macromolecules composed of linear polypeptide chains. Often, a specific three-dimensional arrangement of the constituting polypeptide chains is required to provide the protein a biological function. Despite all the advancements in protein science, a simple, yet fundamental question remains: How do proteins fold so quickly? A polypeptide chain has near infinite conformational space, yet many proteins are capable of rapidly navigating from a structureless state to their native conformation on the order of milliseconds to seconds. Therefore, it is clear that proteins cannot exhaustively probe their entire conformational space, and instead must somehow explore a more limited conformational space as they fold.
This presentation will provide an introduction to the concepts involved in protein folding. It will cover the underlying physical forces governing folding, the experimental evidence used to understand the folding behavior of proteins on a macroscopic and microscopic scale, and how the microscopic behavior of proteins can circumvent the time-scale folding problem.
Biography
Remi Casier obtained his BSc in honours chemistry in 2013 followed by his MSc in polymer chemistry in 2015 from the University of Waterloo. Under the supervision of Prof. Jean Duhamel, Remi is currently pursuing his PhD in polymer science. Currently, his research focuses on using advanced fluorescence techniques to probe the conformational state and internal dynamics of polypeptides in solution in order to provide insight to the dynamic behavior of proteins.
Damin Kim February 25th, 2021 @ 1pm
Discussion on some Polysaccharides: Their Structures, Properties, and Applications
Abstract
Polysaccharides are natural polymers that can be divided into two categories depending on whether they are used for storage or structure. Animals and plants can store glucose as a primary energy source by polymerizing it into polysaccharides. Many different polysaccharides are also present in cell walls, where they serve as structural components. As polysaccharides play important roles in many fields, carbohydrate chemistry has been the focus of intense research for decades. The fundamental study of a polysaccharide begins by characterizing its structure. Different structural models have been proposed for some polysaccharides. In turn, these structural models help better understand the properties of polysaccharides and their applications. The fact, that polysaccharides are abundant, cost effective, and biodegradable, combined with current environmental concerns increases the demand for replacing synthetic polymers with polysaccharides. The hydroxyl groups of polysaccharides provide an easy route for chemical modification with a variety of functional groups to reinforce the properties of polysaccharides in a controlled manner and widen their range of industrial applications.
The structures, properties, and applications of some polysaccharides will be discussed in the presentation. Various techniques including acid hydrolysis, enzyme treatment, and methylation will be reviewed since these techniques were applied to determine the fundamental structures of polysaccharides. The different building blocks of polysaccharides will be presented as they lead to different structures and, ultimately, properties, that are unique for each polysaccharide. As a result, different polysaccharides can be used in various fields depending on the properties desired for a given application. The current industrial use of polysaccharides will be reviewed and some current research on polysaccharides will be presented.
About the speaker
Damin Kim received her B.Sc in Chemistry with specialization in Material Chemistry from the University of Waterloo in 2014. She then joined the Duhamel Laboratory for her graduate studies. She completed her MSc thesis in 2016, which focused on the characterization of hydrophobically modified starch nanoparticles. She is now finalizing her PhD thesis, which expanded her MSc research to characterize various polysaccharides using different fluorescence techniques. Damin Kim has had many opportunities to present her work at various conferences and she has received a few internal graduate scholarships from the University of Waterloo.
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Janine Thoma Friday March 12, 2021 at 1pm
PEGylation and Polymeric Brushes for Drug Delivery
Abstract
PEGylation has been utilized since the late 1970s in the biomedical industry to confer water solubility, non-immunogenicity, and targeted tissue delivery to hydrophobic and/or toxic drug molecules. Through careful drug and peptide-conjugate engineering, researchers have been able to use PEGylation in the preparation of many FDA approved drugs over the last 30 years to treat different diseases including severe combined immunodeficiency, acute lymphoblastic leukemia, febrile neutropenia, and Crohn’s disease. Unfortunately, with the increased use of PEG with drug and peptide conjugates, there has been reports of patients generating anti-PEG antibodies causing an autoimmune response. Researchers have determined that by introducing PEG via a branched architecture reduces the autoimmune response induced by anti-PEG antibodies. This presentation aims to briefly introduce and discuss PEGylation as well as the physiological considerations, that need to be considered, when designing a drug or peptide conjugate. Finally, the incorporation of PEG into different polymeric bottle brush (PBB) drug conjugates will be explored and three specific research articles will be discussed in more detail.
About the Speaker
Janine Thoma is currently pursuing her PhD in polymer chemistry studying the backbone and sidechain dynamics of polymers with branched architectures in solution using fluorescence under the supervision of Prof. Jean Duhamel. She received her BSc in biochemistry from the University of Waterloo in 2015 and then began her MSc in the Duhamel lab. In 2016 she transferred directly into the PhD program. In 2018 and 2019 she was awarded a Nanofellowship from the Waterloo Institute for Nanotechnology (WIN) and in 2020 she won the Institute of Polymer Research (IPR) award as well as the Graduate Student Excellence Award from the department of chemistry. Currently she is working on probing the backbone conformation and determining the persistence length of poly(oligo(ethylene glycol) methacrylate) (PEGMA) polymers in solution.
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Jiaxin Xu Friday March 26, 2021 at 1pm
Nanogels
Abstract
Nanogels are described as hydrophilic three-dimensional crosslinked polymeric particles that can absorb large amounts of water or physiological fluids while maintaining their internal network. As a distinctive class of material that combines both the properties of hydrogels and nanomaterials, nanogels provide long term colloidal stability and biocompatibility. Due to the advantages and unique properties mentioned above, nanogels can be easily tailored and applied in many fields, such as drug delivery systems, controlled release, tissue engineering, and environmental remediation applications. In this presentation, nanogels will be introduced based on different types of classifications, synthesis methods and, applications. Emulsion polymerization, a traditional method employed for nanogel fabrication, will be introduced too. A pH responsive, methacrylic acid and ethyl acrylate (MAA/EA) crosslinked nanogel will be used as an example for elucidating different characterization techniques, including: Dynamic light scattering/ static light scattering (DLS/SLS), Zeta potential measurement, Transmission electron microscopy and potentiometric-conductometric titration.
About the Speaker
Jiaxin (Sara) Xu is currently pursuing her PhD in chemical engineering (water institute) studying the development of versatile nanogel hybrid materials applied for drinking water purification, antimicrobial/bioimaging, and catalytic systems under the supervision of Professor Michael Tam. She received her BSc at Dalian Jiaotong University in Chemical and Software engineering (2009-2014) and then her MSc with Professor Leonardo Simon for the evaluation of mechanical properties of recycled polyamide-cellulose fiber composites (2015-2016). She started her PhD studies with Professor Xianshe Feng and Zhongchao Tan for membrane-based flue gas denitrification and desulfurization projects. From 2018 she transferred to Professor Tam’s lab perusing her PhD studies on beta-cyclodextrin functionalized magnetic particles applied for drinking water purification. She was a speaker at the 2017 American Filtration and Separations Society conference and presented at the UW Research Spotlight: the Grand River Watershed workshop. She received a University of Waterloo Graduate Scholarship in 2020, and Ontario Graduate Scholarship and President’s Graduate Scholarship in 2020-2021.
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Frankin Frasca Friday, March 11, 2022 at 2pm
Polymeric Oil Additives: Their Chemistry and Applications
Abstract
Oil additives have been used in lubricating oils for almost a century, providing longer-lasting and greener lubricants which help to increase the lifetime of both the lubricant and lubricated equipment. Lubricants are employed in a large variety of equipment spanning multiple industries, from automobile engines and metalworking fluids to even hard drive disks like the one that this abstract is written on. Since a lubricant is comprised of a mixture of base oils and additives, which enhance the performance of the lubricant, the increasing assortment of modern devices and machinery requiring lubrication means that no one lubricant will perform optimally for all possible applications. Hence, lubricant formulations require the judicious selection of additives for the task at hand, while their effects on both the overall lubricant performance and compatibility with other additives in the mixture need to be carefully monitored.
Among the many additives incorporated into lubricants, polymeric oil additives have become increasingly popular since their introduction as pour-point depressants, viscosity index improvers, dispersants, and for other applications in the mid 1900’s. These macromolecular additives can be tailored to impart highly specific properties to a lubricant or even combine the functions of multiple additives into one macromolecule, thus reducing the cost of formulation.
Despite the impressive body of work conducted since their inception in the design of new and improved oil additives and formulations, there is still considerable research being carried out to both discover new additives and gain a better understanding of both the properties of the additives currently in use and their mechanisms of action. This talk will discuss some of the basic properties expected from different lubricating fluids designed to target specific applications before delving into more specialized effects encountered with the more popular additives, with a particular focus on those additives that are polymeric in nature.
About the Speaker
Franklin Frasca completed his BSc in Chemistry at the University of Waterloo in 2018 after gaining some hands on experience with oils and oil additives in a co-op placement at Oleo Energies in 2017. In 2018, he also conducted a senior undergraduate research project in the Duhamel Lab, where he determined the intrinsic viscosity of poly(stearyl methacrylate) in different solvents as a function of solvent temperature. He then decided to join the Duhamel Lab for graduate school. His MSc project was to characterize polyisobutylene-based dispersants used as oil additives by applying pyrene excimer fluorescence (PEF). He finalized his work in an MSc thesis defended near the end of 2020. He continued his graduate studies by joining the PhD program at the University of Waterloo in January 2021. As part of his PhD research, Franklin is expanding his application of PEF to characterize the chemical composition, conformation, and internal dynamics of polymeric oil additives .
Weinan Zhao Friday, March 25, 2022 at 2pm
Sustainable Superhydrophobic surface with tunable nanoscale hydrophilicity for water harvesting
Abstract
Superwettable surfaces show great potential in water harvesting applications, however, a scalable water harvesting surface remains elusive due to the trade-off between water deposition and transport. Herein, we report a unique superhydrophobic surface with tunable nanoscale hydrophilicity constructed by structured Pickering emulsions. Preferential exposure of the cellulose nanocrystal’s outer surface and wax microspheres accelerates droplet deposition allowing for the manipulation of droplet mobility. Appropriate tuning of the wetting characteristics of the surfaces, optimizing the hydrophobicity and density of the water affinity nanodomains enhance the water deposition rate without the sacrifice of water transport rate, achieving an optimal water harvesting flux of 3.402 L m-2h-1 for a plate and 5.02 L m-2 h-1 for a mesh. This hydrophilic/Superhydrophobic surface allows the controllable manipulation of droplet nucleation and removal to enhance the water harvesting efficiency.
About the Speaker
Weinan obtained his BSc in applied chemistry in 2016 and followed by his MSc in Chemical engineering in 2019 from China University of Petroleum. Under the supervision of Prof. Michael Tam, Weinan is currently pursuing his PhD in materials science. Currently, his research focuses on using sustainable nanomaterials to build super-wetting system in order to collect fresh water and harvest osmotic energy.
Sanjay Patel Friday, November 24, 2023 at 1 pm
Nanogels
Abstract
Ultimately the conformation of macromolecules in solution governs their solution and physical properties. Therefore, polymer scientists must have access to experimental tools capable of probing macromolecular conformations. The current techniques used to characterize macromolecular conformations can be broadly divided into four categories depending on whether they are based on microscopy, computation, scattering, or spectroscopy. Each category of experiments has provided useful insights on macromolecular conformations, but like any experimental method, each one comes with its own set of advantages and limitations.
For example, there exists a wide array of microscopy-based experiments, such as scanning electron (SEM), transmission electron (TEM), atomic force (AFM), etc microscopy, all of which excel at generating images of macromolecules. Depending on the specific instrument, experimental approach, sample type, and preparation applied, different features about a macromolecule can be detected. Microscopy images allow us to predict what conformation a macromolecule will adopt in solution. However, such deductions must be carefully considered since the conformation of a macromolecule adsorbed onto a 2D surface might not be fully representative of the 3D conformation of the macromolecule in solution or in the bulk.
Computation-based experiments, in contrast to microscopy-based experiments, yield 3D macromolecular structures with atomic resolution. The experimentalist imposes the type and length/time scale of interactions, which occur in the system. Consequently, computational methods enable one to account for any interaction which may occur, which is an admirable feature. However, this strength is also a major limitation. Due to the multitude of potential interactions, accounting for all of them in any given system is computationally impossible. Instead, assumptions, custom restraints, and simplifications are required. But since the outcome of these approximations is unknown, they must be benchmarked against experimental data collected from other techniques before being released for wide application.
In comparison, scattering techniques such as small angle X-ray (SAXS), small angle neutron (SANS), and static light (SLS) scattering are well-suited for probing the local density of macromolecules. This, in turn, provides insight on the macromolecules size, shape, and surface. However, scattering experiments typically require high concentrations of monodisperse samples, a feat which can be difficult to achieve for many synthetic macromolecules.
Spectroscopy-based experiments, such as nuclear magnetic resonance (NMR), rely on the ability of a macromolecule to interact with electromagnetic radiation. Specifically, NMR probes the local environment of a given nucleus and its proximity to adjacent nuclei, which, in turn, can be used to generate 3D images of the macromolecular structure. Unfortunately, the minute difference in the local environment experienced by synthetic macromolecules coupled with their broad signals limits the structural information that can be extracted for polymers from NMR experiments.
The purpose of the present seminar is to discuss the advantages and disadvantages of the current experimental techniques used to probe macromolecular conformations, with an emphasis on their fundamental principles. These advantages and disadvantages will then be compared to those encountered when using pyrene excimer formation (PEF) as a novel methodology for probing macromolecular conformations.
About the Speaker
Sanjay Patel completed his BSc in Biochemistry with a biotechnology specialization at the University of Waterloo in 2016. During his undergraduate degree he decided to apply for a senior undergraduate research project in the Duhamel Lab, where he focused his efforts on quenching experiments using various nitroaromatics and pyrene labeled starch nanoparticles. During his MSc project he was able to further extend these studies by developing a paper-based sensor with pyrene labeled starch nanoparticles for nitroaromatic detection, which resulted in a provisional patent. In 2019, he continued his graduate studies in the Duhamel Lab with a focus on using pyrene excimer formation (PEF) to characterize the conformation of different pyrene labeled macromolecules on different length scales.