Nanoparticle functionalization and grafting-from chemistry for controlling surface properties and nanocomposite behavior

Nanoparticles were functionalized in order to incorporate their unique properties into functional materials. Gold nanoparticles were functionalized to direct their assembly at the oil-water interface, and further modified to achieve cross-linking at the interface, incorporation of charged groups or targeting groups, and extrusion to resize the capsules for potential delivery applications. Capsules were characterized by fluorescence microscopy by encapsulation of a fluorescent dye, and after drying on substrates by scanning force microscopy (SFM) and transmission electron microscopy (TEM). Gold nanoparticles were functionalized for their assembly into a microphase separated block copolymer, polystyrene-b-poly(2-vinyl pyridine) (PS-PVP) and the nanoparticles were directed within the domains by modification of the ligand periphery. Varying the ratio of hydrophobic to hydrophilic ligands allowed for the controlled assembly of the nanoparticles within the PVP domain of the diblock copolymer or at the interface between the two blocks. Thermal annealing resulted in ripening of the particles and migration of all particles to the center of the PVP domain. Location of the nanoparticles was determined by TEM and SFM. Gold nanoparticles were modified with acid-labile groups for potential use in photolithography applications, and with amine groups for incorporation in water purification membranes. Silica particles were modified with a dithiocarbonate chain transfer agent to achieve controlled polymerization by reversible addition fragmentation chain transfer polymerization (RAFT) of vinyl acetate from the particle surface. The poly(vinyl acetate) was hydrolyzed to poly(vinyl alcohol) to achieve particles dispersible in water with potential gas barrier properties. Functionalized silica particles were characterized by thermogravimetric analysis, TEM, and polymer was characterized by size exclusion chromatography

Measuring "Smart" Abilities of Copolymers with PDMAEMA

Color poster with text, graphs, charts, and images.Polymers are composed of covalently bonded repeating units. "Smart" polymers are polymers that can dramatically change their properties in response to a small change in external stimuli. Smart polymers are of interest for their potential use in waste water treatment plants to remove hydrophobic contaminants, such as disperse dyes which are often unrecovered through traditional purification methods.James Larson and Vicki Lord Larson Scholarship; Petroleum Research Foundation (PRF); Grant Number 54467-UNI7 fundamental research; UW-System Applied Research Grant applications research

Tuning Smart Properties of mPEG-block-PDMAEMA Through Polymer Composition

Color poster with text, graphs, and charts.The purpose of this study was to study smart polymers. “Smart” polymers respond to changes in their environment with a measureable change in property. Some smart polymers can change their solubility when the conditions such as pH, temperature, and/or polymer concentration change.University of Wisconsin--Eau Claire Office of Research and Sponsored Programs

Synthesis of Smart Polymer-Grafted Silica and Confocal Microscopy

Color poster with text, images, charts, and graphs.The purpose of this study is to synthesize and characterize smart polymer-grafted colloidal silica particles in order to better understand and tune the smart characteristics and properties.National Science Foundation grant #4160728; NSF-MRI; University of Wisconsin--Eau Claire Office of Research and Sponsored Program

Viscosity Testing of PEG-PDMAEMA and Preliminary ARGET ATRP Synthesis

Color poster with text, images, charts, photographs and graphs.Polymers are present in our everyday life such as clothing, plastics, and electronics. “Smart polymers” are a subset of polymers unique in that they change their properties due to varying external stimuli and can be used in a wide range of applications in the pharmaceutical, environmental, and biomedical fields. This research focuses more on diblock copolymers, which are two separate homopolymers covalently bonded together, of poly(ethylene glycol)-block-poly(2-(dimethylamino)ethyl methacrylate) PEG-PDMAEMA. Solutions of different concentrations of diblock copolymers (1 mg/mL and 10 mg/mL) were paired with different buffer concentrations (.1M and .01M) and different pH (8 and 12) to analyze the specific behavior of each synthesized diblock copolymer to external stimuli. Viscosity, or a fluid’s resistance to flow, was tested on a rheometer for different solutions at different shear rates with stress being measured to determine viscosity. The smart polymer viscosity is expected to substantially increase as temperature increases near the cloud point, which is when the solution becomes cloudy, and is due to the polymer changing from water soluble to water insoluble. The cloud point depends on the molecular weight of the polymer, pH and buffer concentration. The examined smart diblock copolymer PEG-PDMAEMA is currently synthesized by Atom Transfer Radical Polymerization (ATRP). A new synthesis procedure, Activator ReGenerated by Electron Transfer (ARGET) ATRP, was tested because it is able to tolerate being exposed to air and requires less catalyst. Current work includes synthesizing PDMAEMA homopolymers and diblock copolymers. By updating the synthesis and understanding how the viscosity of PEG-PDMAEMA responds to changes in pH and temperature, it can be tailored to specific environments and applications such as enhanced oil recovery.Blugold Commitment Differential Tuition Funds; University of Wisconsin--Eau Claire Office of Research and Sponsored Program

Smart Polymer-Grafted Silica: Synthesis and Characterization

Color image with text, images, and graphs.Colloidal particles have properties based on size and have the potential to better explain molecular systems. Smart polymers are chains of repeating subunits that have the unique ability to change properties based on an external stimulus such as temperature of pH. Our goal is to synthesize and characterize smart polymer-grafted colloidal silica particles in order to observe a combination of properties from both systems. Silica particles were synthesized using the Stober growth process, which allowed for controlled particle growth around a fluorescent dye. Atom transfer radical polymerization (ATRP) was used to graft the smart polymer, poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), from functionalized silica particles. PDMAEMA is a known smart polymer that changes its polarity based on temperature, pH, and molecular weight. To confirm polymer synthesis, infrared spectroscopy and gel permeation chromatography were completed. The use of confocal laser scanning microscopy allowed imaging for the polymer-grafted particles through both time-scans and z-scans. These scans enabled observation of particle movement in 3D as the temperature and pH were changed. Observations concerning the synthesis and behavior of smart polymer-grafted silica can be used for applications ranging from 3D printing to enhance oil recovery.University of Wisconsin--Eau Claire Office of Research and Sponsored Program

Examining the Smart Properties of mPEG-block-PDMAEMA Using Interfacial Tension

Color poster with text, graphs, images, and charts.“Smart” polymers are defined by their adaptability to their surrounding environment. Their properties such as solubility can respond to differences in pH, temperature, ionic strength, and/or polymer concentration. Variables can affect the interfacial tension of PEG-PDMAEMA making it of interest for a wide range of potential applications such as enhanced oil recovery and wastewater treatment.Applied Research Grant for Instrumentation- Petroleum Research Foundation (PRF). Grant Number 54467-UNI7; Blugold Differential Tuition; University of Wisconsin--Eau Claire Office of Research and Sponsored Programs

Synthesizing and Characterizing Triblocks of the Smart Polymer PDMAEMA

Color poster with text, images, charts, and graphs.Polymers are covalently bonded molecules, or monomers, that have repeating units. The polymer composition of interest is linear triblock copolymers consisting of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) on both ends of poly(ethylene glycol) (PEG). The tertiary amine group on the PDMAEMA gives rise to these “smart” polymers. Smart polymers can switch their properties depending on the external stimuli. The external stimuli which can affect the properties of the polymer are temperature, pH, ionic strength and polymer concentration. Properties that are tested and observed are viscosity, interfacial tension, and water solubility. These properties are caused by the stimuli-responsive PDMAEMA. Synthesizing PDMAEMA-containing block copolymers with controlled architecture can lead to unique structures which result in various properties.NSF RUI DMR Award #1809532; NSF REU grant Award #1460728; NSF LSAMP Award #1400815; University of Wisconsin--Eau Claire Office of Research and Sponsored Program

Synthesis and Characterization of a Reversible and Tunable Smart Polymer

Color poster with text, images, and graphs.Polymers are made of covalently bonded repeat units, called monomers, which make up long chains. The structure can be controlled to achieve a diblock copolymer with two different repeat units connected in blocks. “Smart” polymers are polymers that can change their properties under certain conditions. Solubility is one property that can change when the conditions such as pH, temperature, and/or polymer concentration change. Cloud point is the temperature above which the thermoresponsive smart polymer will change its solubility and form aggregates. What is a “smart” polymer? Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) is a smart polymer that changes its cloud point when conditions change, such as temperature, pH, polymer concentration, and ionic strength. When combined into a diblock copolymer with poly(ethylene glycol), the newly formed polymer, PEG-PDMAEMA, retains the smart polymer properties of PDMAEMA and acquires properties based on its new diblock structure.Petroleum Research Foundation (PRF) Grant Number 54467-UNI7; University of Wisconsin--Eau Claire Office of Research and Sponsored Program

UV-Vis and DLS Characterization of Smart Properties of PEG-PDMAEMA Block Copolymers Synthesized by ARGET ATRP

Color poster with text, images, charts, and graphs.The purpose of this project is to synthesize and characterize smart polymers that have controlled polymer architecture. Smart polymers are polymers that respond to a change in environment; the polymer becomes insoluble with an increase in temperature depending on the pH of the solution. Poly((2-dimethylamino) ethyl methacrylate) (PDMAEMA) was synthesized via Activator Regenerated by Electron Transfer Atom Transfer Radical Polymerization (ARGET ATRP) because it reduces cost, and it is more environmentally friendly than traditional ATRP. To determine the effect of polymer structure on smart properties, each smart polymer composition is tested using Dynamic Light Scattering (DLS) and Ultraviolet–visible spectroscopy (UV-Vis) to assess the pH and temperature sensitive behaviors. DLS is used to test the size of polymer because as solubility changes with temperature, the polymer switches from individual polymer chains to aggregates or micelles. UV-Vis measures the transmittance of light through the polymer 94 solution, and the transmittance drops suddenly at the cloud point, or the temperature where the polymer solution becomes cloudy due to the change in solubility. These smart polymers have potential for use in drug delivery and enhanced oil recovery.National Science Foundation Award; University of Wisconsin--Eau Claire Office of Research and Sponsored Program