Research Terms
Chemistry Inorganic Chemistry Polymer Chemistry Polymers
Keywords
Catalyst Conducting Polymers Cyclic Polymers Drug Delivery (Protein, Sirna & Dna Delivery) Inorganic Chemistry Organometallic Chemistry Polyolefin Synthesis Teaching And Learning Transition Metal
Highlighted by Synfacts: https://www.thieme-connect.com/products/ejournals/journal/10.1055/s- 00000131.
Expanding iClick to group 9 metals. Polyhedron, 2016, 108, 87-92.
Chemistry World Highlight: http://www.rsc.org/chemistryworld/2014/10/high-spin- square-planar-iron-complex
N-heterocyclic carbene gold(I) and silver(I) complexes bearing functional groups for bio- conjugation. Dalton Trans. 2015, 44, 1914-1923.
http://blogs.rsc.org/dt/2013/09/10/using-click-reactions-to-incorporate-multiple-metals- in-molecules/
“Hot Article” http://blogs.rsc.org/sc/2012/12/10/tetra-anionic-pincer/
“Hot Article” http://blogs.rsc.org/dt/2013/01/30/remarkable-stability-demonstrated-by- tungstenacyclobutadiene-complexes/
“Hot Article” http://blogs.rsc.org/dt/2011/11/25/ligand-duality-in-oxygen-atom-transfer/
44. O’Reilly, M. E.; Del Castillo, T. J.; Falkowski, J. M.; Ramachandran, V.; Pati, M. Correia, M. C.; Abboud, K. A.; Dalal, N. S.; Richardson, D. E.; Veige, A. S.* Autocatalytic O2 cleavage by an OCO3- trianionic pincer CrIII complex: isolation and characterization of the autocatalytic intermediate [CrIV]2(μ-O) dimer. J. Am. Chem. Soc. 2011, 133, 13661-13673.
= PMe3, 4-Picoline), Ta; silox = tBu3SiO. Inorg. Chem. 2003, 42, 6204-6224.
| Director |
Adam Veige |
| Phone | (352)392-9844 |
| Website | http://www.catalysis.chem.ufl.edu/ |
| Mission | To promote research in the area of chemical catalysis and to provide an image to external sources of the University expertise in this area. |
These tethered tungsten-alkylidenes serve as catalysts for the synthesis of cyclic polymers. Cyclic polymers can improve the performance and lifetime of products made from synthetic polymers. The worldwide market for Cyclic Olefin Polymers is expected to reach $1,690 million by 2024. A significant challenge in modern polymer chemistry is the efficient and controlled synthesis of polymers with unique topology. Cyclic polymers have a ring-like topology and, therefore, have no chain ends, unlike their linear counterparts. Because of their topology, cyclic polymers exhibit unique physical and chemical properties in both bulk and solution, such as smaller hydrodynamic volume and radius of gyration, higher glass transition temperature, increased rate of crystallization, and so on. Despite the benefits inherent in cyclic polymers, most commercially available polymers have a linear topology, and the synthesis of cyclic polymers is somewhat limited to research laboratories.
Production of stereoregular, cyclic versions of linear polycyclic alkenes have many potential applications. Producing derivatives like cyclic polynorbornene on a large scale is now synthetically possible, but controlling the specific 3D atomic arrangements remains a crucial challenge. Imparting this stereoregularity is critical to manipulating the polymer’s bulk properties. Researchers at the University of Florida have developed tethered tungsten-alkylidenes as catalysts for the synthesis of cyclic polymers. These catalysts facilitate the efficient production of unique and highly stereoregular ring-shaped polymers, like cis-syndiotactic cyclic polynorbornene.
Catalyst for producing cyclic polymers with very high stereoselectivity
Cyclic polymers have unique physical and chemical properties both in bulk and solution-state compared to their linear counterparts. The differences in the properties may lead to the production of new polymer products. The reaction between tungsten alkylidyne and isocyanate occurs to generate tethered tetraanionic tungsten-imido alkylidene complexes, which polymerize norbornene into cis-syndiotactic cyclic polynorbornene via ring expansion metathesis polymerization. The high stereoregularity provides a more rigid and ordered crystalline structure for the generated polymer, while the cyclic topology provides a higher glass transition temperature. That means more heat is required to change the cyclic polymer into a soft, rubbery state; thus, the constructed cyclic polynorbornene retains greater structural integrity in heated conditions than its linear congeners.
These cycloaddition reactions (iClick) promote the step-growth of polymerization of metal-containing monomers to produce metallopolymers with advanced photophysical and electronic conducting properties. Metallopolymers are potential replacement materials to improve the efficiency and heat resistance of solar cells and LEDs. Nearly half the lights in the United States are LED lights, and solar energy is one of the most dominant forms of renewable energy. The global solar energy market should reach $223.3 billion by 2026. However, LED and solar energy technologies are hampered by material limitations that cause inefficiencies and heat damage to materials used in these applications.
Researchers at the University of Florida have developed new metallopolymer materials that can be controlled precisely, thus opening new opportunities in heat-resistant solar cells, LEDs, and optical applications.
Materials that combine the beneficial properties of both metals and polymers for application in solar cells and LEDs
These materials are metallopolymers that have combined properties of both metals and polymers and can be used in many applications including solar cells and LEDs. The metallopolymers are synthesized using cycloaddition reactions. The cycloaddition reactions promote the growth of metal-containing monomers to create metallopolymers that combine the conductive properties of metals with the flexible and elastomeric properties of organic polymers. The process enables precise control over the synthesized material properties.
This catalyst polymerizes cyclic alkenes to produce cyclic polymers, utilizing ring expansion metathesis polymerization. Polymerization is the process in which individual monomers are joined together to form polymers. Ring expansion metathesis polymerization allows for the synthesis of high molecular weight cyclic polymers. Polydicyclopentadiene (polyDCPD), a polymer used in many industrial products, is known for its impact resistance at low temperatures. However, the cyclic polymer of dicyclopentadiene has not been discovered. University of Florida researchers have developed an improved catalyst that produces cyclic polymers, which may present substantially different properties from traditional linear polymer structures. The catalyst polymerizes cyclic monomers for the production of cyclic polymers, having potential applications in motor oil as a lubricant and in the construction of industrial grade plastics. In addition, the cyclic polymers obtained can be further functionalized to access new materials with novel properties.
Catalyst as a composition of matter that polymerizes a broader scope of monomers, producing cyclic polymers with very high stereoselectivity.
Cyclic polymers have different physical properties compared to their linear counterparts. The different physical properties have potential to impact the production of new polymer products. The developed catalyst polymerizes cyclic monomers for the production of cyclic polymers, and is more active and long lived. The catalyst produces cyclic polymers that exhibit different characteristics to polyDCPD polymers and polynorbornene.
This metallocyclopropylidene complex catalyzes the conversion of norbornene into cyclic polynorbornene with a high degree of stereoregularity. Polynorbornene, the polymerized form of the norbornene hydrocarbon, serves many purposes in the rubber industry, is beneficial in the fabrication of anti-vibration materials, and has particular use in the railway, construction, and industrial sectors. It often contributes to the formation of personal protective equipment, shoe parts, and bumpers, and can improve adhesion in the tires of cars and toys. Available metallic catalysts frequently produce linear polynorbornene with lower glass transition temperatures and the catalysts require several steps for formation.
Researchers at the University of Florida have developed an organometallic catalyst from molybdenum that converts norbornene into stereoregular, cyclic polynorbornene. The synthesis of this catalyst involves only two steps and the catalyst itself produces cyclic polynorbornene with high stereoregularity.
Organometallic catalyst that promotes highly-stereoregular polymerization of norbornene
This metallocyclopropylidene complex actively catalyzes the polymerization of norbornene into cyclic polynorbornene. The conversion takes place through a ring expansion metathesis polymerization, involving the exchange of ions to construct the stereoregular polymer. Greater stereoregularity enables the polymer to maintain a more rigid and ordered crystalline structure. This crystallinity results in increased glass transition temperatures. Polymers with higher glass transition temperatures require more heating to change into a soft, rubbery state, thus the constructed cyclic polynorbornene retains greater structural integrity in heated conditions than its linear alternatives. The metallocyclopropylidene complex forms from a two-step reaction between a terminal alkyne and a ligand, using molybdenum as the metallic base.
This metallocyclopropylidene complex catalyzes the conversion of norbornene into cyclic polynorbornene with a high degree of stereoregularity that remains stable after hydrogenation. Polynorbornene, the polymerized form of the norbornene hydrocarbon, serves many purposes in the rubber industry, is beneficial in the fabrication of anti-vibration materials, and has particular use in the railway, construction, and industrial sectors. Polynorbornene also often contributes to the production of personal protective equipment, shoe parts, and bumpers, as well as facilitates tire adhesion improvements. Available metallic catalysts frequently produce linear polynorbornene with lower glass transition temperatures, but they require several steps for their synthesis. Researchers at the University of Florida have developed an organometallic catalyst from molybdenum that converts norbornene into stereoregular, cyclic polynorbornene in only two steps. Additionally, synthesis of this catalyst involves the catalyst, itself, producing cyclic polynorbornene that maintains its high stereoregularity throughout the conventional hydrogenation processes.
Organometallic catalyst that promotes highly-stereoregular polymerization of norbornene
A two-step reaction between a terminal alkyne and a ligand with molybdenum as the metallic base forms this metallocyclopropylidene complex that actively catalyzes the polymerization of norbornene into cyclic polynorbornene. The conversion takes place through a ring expansion metathesis polymerization. Greater stereoregularity provides a more rigid and ordered crystalline structure for the polymer. The crystallinity results in increased glass transition temperatures. Since polymers with higher glass transition temperatures require more heating to change into a soft, rubbery state, the constructed cyclic polynorbornene retains greater structural integrity in heated conditions than its linear alternatives. After formation, the cyclic polynorbornene can undergo hydrogenation via standard H2/Pd/C procedures or tosylhydrazine decomposition all while maintaining its stereoregularity.
These aptamers, conjugated with N-heterocyclic carbene metal complexes, deliver therapeutic doses of the cytotoxic metal ion to targeted cancer cells. These complexes avoid toxicity to healthy cells while being highly effective for destruction of cancer cells. Malignant tissue growth accounted for approximately 7.5 million deaths worldwide in 2008, and that number is projected to increase to 13.2 million by 2030. Patient responses to specific drugs vary widely, calling for a more individualized treatment process. One potential approach to individualized treatment is to exploit cancer-specific biomarkers to deliver chemotherapeutic agents to the cancer cell. Available metal-based drugs are non-discriminatory, causing detrimental effects due to heavy metal buildup in the kidneys and liver, but University of Florida researchers have developed an NHC aptamer that specifically targets cancer cells and prevents dispersal of the metal ion to healthy cells in the body.
NHC metal complexes for cancer therapeutics and targeted drug delivery
Aptamers are formed by a relatively easy and reproducible DNA synthesis. Their molecular specificities are easily modified, they have low toxicity, and they are easily stored. Metal ions are highly toxic to cancer cells and combining them with aptamers provides an effective method of cancer treatment. Current metal-based drugs have detrimental side-effects due to heavy metal buildup in the kidneys and liver, but N-heterocyclic carbene aptamers are highly selective, targeting delivery only to specific cancer cells, thus requiring low dosages and reducing side effects. The aptamers target the cell surface of cancer cells and are internalized carrying the NHC metal ion that disrupts cell activity. The strong M-C bond of the NHC prevents the loss of the metal ion in the body prior to cell recognition.
This catalyst has the ability to transform cyclic alkynes into cyclic polyalkynes, which have different functional properties than the linear polymer. Catalysts are important in creating compounds for the energy industry such as motor oil, biofuels, and flexible electronics. The escalating demand for catalysts from applications including chemical synthesis, petroleum refining, polymers and petrochemicals, and environmental is driving demand for process optimization, yield improvement, cost-saving, and energy-saving amongst manufacturers globally. The global catalyst market size was valued at $33.9 billion in 2019 and is expected to grow at a compound annual growth rate (CAGR) of 4.4 percent.
Researchers at the University of Florida have discovered a catalyst and its respective product, cyclic polyalkynes, that may be useful in the chemical synthesis of more conducting polymers, photoactive materials, solar cells, and flexible electronics.
Various uses in the catalyst industry, including flexible electronics, polymers, solar cells, and conducting polymers
The catalyst is composed of a tethered alkylidyne and catalyzes the ring expansion alkyne metathesis polymerization (REAMP) of cyclic alkynes to produce cyclic polyalkynes. The functional properties of these molecules have not been tested yet, as its synthesis is novel.
This process efficiently synthesizes pure, highly-conjugated cyclic polyacetylene in film, bulk, and soluble form, producing conductive cyclic polymers for many applications. A cyclic polymer binds together the chain ends of a linear polymer, dramatically changing its physical properties, often for industrial advantage. However, cyclic polymers are very difficult to synthesize. Linear polyacetylene is a known conductive polymer. Its cyclic counterpart, which would offer superior electrical conductivity, remains unavailable.
Researchers at the University of Florida have developed a catalytic process that synthesizes cyclic polyacetylene, a polymer with high electrical conductivity suitable for use in functional thin films. Functional polymer thin films benefit many energy applications due to their conductivity and processability, providing a better material alternative for separation membranes in fuel cells, electrodes in batteries, and various components in solar power systems.
Cyclic polyacetylene synthesis for creating low-cost, electrically conductive functional polymer thin films
This is the first synthesis of cyclic polyacetylene ever reported. Unlike the synthesis of linear polyacetylene, this cyclic polyacetylene synthesis is versatile to polymerization temperature ranging from -90 to 70 °C, producing exclusively trans polyacetylene as a high-quality polymer, with low crosslinking defects, less than 1 percent. A UF catalyst enables cyclic polymerization of acetylene to form trans-cyclic polyacetylene in film, powder, or soluble form.
This catalyst selectively polymerizes the acetylene contained in ethylene gas, purifying streams more easily for the production of polyethylene. Analysts project the global polyethylene market to exceed $140 billion in value by 2026. Synthesizing polyethylene gas for its many industrial applications requires ethylene gas significantly free of acetylene, which most manufacturers remove by hydrogenating it into ethylene. This step requires excess ethylene and a catalyst to avoid hydrogenating the ethylene into ethane, but available catalysts have limited stability and selectivity.
Researchers at the University of Florida have developed a catalyst that polymerizes the acetylene in ethylene gas streams into solid cyclic polyacetylene without reacting with the ethylene. Removing acetylene via selective catalysis rather than hydrogenation enables more efficient purification and processing of ethylene gas streams in the production of polyethylene.
Catalytic removal of acetylene from ethylene gas for more efficient polyethylene manufacturing
Ethylene gas bubbles through a solution of this catalyst, polymerizing the acetylene without reacting with the ethylene. The catalytic solution converts acetylene into insoluble cyclic polyacetylene, which readily separates from the stream to purify ethylene gas for polyethylene production. Direct catalytic removal of acetylene replaces the standard hydrogenation reaction to facilitate more efficient processing and reduce energy required in polyethylene synthesis.
These catalytic metal complexes can initiate the synthesis of polymers with unique cyclic topologies. Only a few techniques are available to create cyclic polymers. A common synthesis route involves intramolecular coupling of polymer chain ends. However, this route has inherent limitations in that it requires dilute conditions and long reaction times. Ring closing synthesis attempts to produce samples of unique ring-shaped polymers, yet it is difficult to product at a large scale.
Researchers at the University of Florida have developed compounds known as metallacyclopentadienes for initiating polymerization of alkynes to produce cyclic polymers efficiently and on large scales for the first time. These catalytic intermediates apply ring expansion metathesis polymerization (REMP) to speed up the reaction time and allow the polymers to have new physical properties.
Metal complexes that polymerize alkynes by ring expansion metathesis polymerization (REMP) to yield cyclic polyalkenes. Subsequent hydrogenation provides the corresponding cyclic version of cyclic polyolefins.
These metallacyclopentadiene complexes serve as catalytic initiators for cyclic polymer synthesis from alkynes. Specifically, they can initiate polymerization of alkynes to give cyclic polymers. The compounds have a carbon composition and include a site for a transition metal. Critical to their design is the presence of a unique supporting ligand containing a tethered M=C double bond that ensures the polymer chain ends remain attached to the metal ion. These initiators permit the synthesis of polymers with unique topologies such as cyclic dendronized polymers, cyclic brush polymers, and stereoregular cyclic polymers. Cyclic polymers are now finding potential application in drug delivery, low friction materials, viscosity modifiers, optical devices, anti-fouling surface modifiers, plasticizers, and melt flow modifiers.
This simpler, more efficient alkene polymerization and selective alkene oligomerization catalyst can result in substantial savings for the user. The market for polymerization of ethylene and propylene – common in the development of highly commercial thermoplastics – exceeds 100 million tons, and is growing at an annual rate of about 5 percent. The catalyst industry that supports these products has sales approaching a billion dollars in the United States alone. Additionally, the oligomerization of ethylene to provide 1-hexene or 1-octene selectively, has tremendous market value. The polymerization process typically relies on the use of stoichiometric or greater (sometimes >1000) equivalents of expensive activators to initiate the catalyst. To combat this market inefficiency, researchers at the University of Florida have created a simpler, more efficient single-component catalyst for polymerization and selective oligomerization that can work without a co-catalyst or stoichiometric activator, resulting in substantial savings.
Cost-effective olefin polymerization and oligomerization to streamline the production process and cost
This product has the potential to improve the polymerization and selective oligomerization process of ethylene, offering unparalleled competitive advantages in a multibillion-dollar industry. Besides cost savings from the elimination of expensive activators, the single-component catalyst also presents the potential for an overall improvement in the development of polymers. The new technology involves the use of cheap Cr metal ions bound by a new class of ligands called trianionic pincer ligands. A provisional patent has been filed for this technology.
These metal complexes supported by carbene ligands are cheaper and more effective alternatives to phosphine ligands for catalyzing chemical reactions. Phosphine ligands attached to transition metals are common catalysts in the pharmaceutical industry and in other chemical applications. Unfortunately, phosphine ligands can be toxic and are often unstable. Thus, there is always a need for cheaper, cleaner, more stable, efficient, and selective catalysts.
Researchers at the University of Florida have developed catalysts that meet this need using carbene ligands. These catalysts are far less expensive and toxic, as well as modular and more selective than phosphine ligands.
Carbene ligand compounds that catalyze chemical reactions
These carbene ligands combine with transition metals to catalyze a wide variety of reactions to produce safer and less toxic products. For example, in pharmaceutical drug production, these ligands produce only one enantiomer of a chiral compound. This is advantageous because drugs typically have two enantiomers, with the non-toxic one being responsible for healing effects and the toxic one causing harmful side effects. Eliminating the toxic one thus eliminates side effects. Furthermore, these carbene ligands increase the efficiency of chemical reactions when compared to phosphine ligands because they give higher yields and catalyze a wider variety of reactions.
This catalyst enhances the efficiency and stability of photovoltaic solar cells and other light-reactive materials. Photovoltaic cells, which convert photons from light into voltage, form the foundation of solar energy technologies. Renewable, sustainable, and producing zero emissions, solar is one of the world's fastest-developing energy technologies: more than 100 American companies manufacture solar cells and modules, according to the United States Energy Information Administration. Despite its rapid growth and clear benefits, solar energy has been hampered by inefficiency, particularly related to overheating; the voltage output of a solar panel system drops when a certain temperature threshold is crossed. University of Florida researchers have created a technology to synthesize conducting organometallopolymers with previously unattainable compositions. Organometallopolymers marry the desirable high conducting properties of metals and the flexible and elastomeric properties of organic polymers to make advance functional materials with distinct properties. Enabling exquisite control over materials properties, the technology provides more efficient and more heat resistant solar cells and optical applications, including light-emitting diodes.
Advanced catalyst to link metal ions for use in photovoltaics and other light-reactive materials
"Click" reactions are chemical reactions that operate in a wide range of solvents and pH conditions, are functional group tolerant, and provide product in quantitative yield. These properties are highly desirable for the mass production of functional materials. Despite these appealing characteristics, Click reactions thus far have had few applications in organometallic and inorganic chemistry. The inventors created a class of reactions known as iClick chemistry that employs metal ions as discrete building blocks for materials synthesis. Employing iClick technology permits rapid access to materials with diverse properties. Next-generation photovoltaics with high efficiencies that are flexible will require iClick technology for their synthesis. Access to iClick technology to synthesize organometallopolymers will provide a competitive advantage as current state of the art materials that employ metals or organic polymers alone reach their maximum efficiency.
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