97,848 research outputs found
Oscillations in the concentration of phenylacetylene and its carbonylation products
No full textThe oscillatory nature of the palladium catalysed phenylacetylene oxidative carbonylation (PCPOC) reaction was first reported by Temkin and colleagues1-4. It was demonstrated that the PCPOC reaction in a catalytic system (PdI2, KI, O2, NaOAc in methanol) exhibits oscillations in redox potential, pH and the rate of CO/O2 gas mixture consumption. Later on, Novakovic and colleagues5-8 investigated the characteristics of the PCPOC reaction and carried out this reaction in a calorimeter for the first time. They reported simultaneous oscillations in pH and rate of heat evolution (Qr)5, the influence of oscillations on product selectivity as well as the dynamics of product formation6 and the influence of the reaction temperature on the period and amplitude of oscillations7. In addition, the products resulting from this reaction have been reported.8 To make use of all observations the reaction mechanism responsible for the oscillations needs to be understood. In this quest, the reaction network responsible for the initial reactions of PdI2 in this system were studied.9 Subsequently, the role of water in this oscillatory system, as well as the importance of the order of reactant addition and its effect on product formation have been reported.10 This recent study enabled the proposal of a prospective theory to describe the oscillatory behaviour. In this work the existence of oscillatory behaviour in the concentration of phenylacetylene and carbonylation products (E-3-phenylacrylic acid methyl ester, Z-2-phenylbut-2-enedioic acid dimethyl ester, E-2-phenylbut-2-enedioic acid dimethyl ester, 5,5-dimethoxy-3-phenylfuran-2(5H)-one and 3-phenylfuran-2,5-dione) is uncovered. The amplitude of the oscillations in phenylacetylene was as high as 34% relative to the initial amount of phenylacetylene added to the system. 1. A.V. Malashkevich, L.G. Bruk and O.N. Temkin, J. Phys. Chem. A, 1997, 101 (51), 9825-9827; 2. S.N. Gorodskii, A.N. Zakharov, A.V. Kulik, L.G. Bruk and O.N. Temkin, Kinet. Cat., 2001, 42 (2), 251-263; 3. S.N. Gorodskii, E.S. Kalenova, L.G. Bruk and O.N. Temkin, Russ. Chem. Bull., 2003, 52 (7), 1524-1543; 4. O.N. Temkin and L.G. Bruk, Kinet. Cat., 2003, 44 (5), 601-617; 5. K. Novakovic, C. Grosjean, S.K. Scott, A. Whiting, M.J. Willis and A.R. Wright, Chem. Phys. Lett., 2007, 435, 142–147; 6. K. Novakovic, C. Grosjean, S.K. Scott, A. Whiting, M.J. Willis and A.R. Wright, Phys. Chem. Chem. Phys., 2008, 10, 749-753; 7. K. Novakovic, A. Mukherjee, M. Willis, A. Wright and S. Scott, Phys. Chem. Chem. Phys., 2009, 11, 9044-9049; 8. C. Grosjean, K. Novakovic, S.K. Scott, A. Whiting, M.J. Willis and A.R. Wright, J. Mol. Cat. A, 2008, 284, 33-39; 9. K. Novakovic, J. Parker, Int. J. Chem. Eng, 2011; 10. K. Novakovic, J. Parker, Submitted
Joshua Davis: Author of Spare Parts
Get PDFCitation: K-State First (2016). Joshua Davis: Author of Spare Parts [Flier]. Manhattan, Kansas: K-State First.Flyer advertising Joshua Davis's author talk at Kansas State University
Polymeric substrates and polymeric catalysts in oscillatory carbonylation reactions
No full textAiming to produce fully self-oscillatory materials [1], materials that act life-like, materials that are able to carry and dispense their content in predefined rhythm we have made number of advancement in the area of polymeric oscillators in lab conditions. In addition to demonstrating polymeric alkyne-terminated substrates as viable in the oscillatory palladium-catalysed carbonylation reaction [2] we have now shown that polymer-bound catalytic species can also yield oscillations in pH. [3] Moving towards autonomous rhythmic materials we now developed chitosan-based palladium catalyst fully capable of delivering oscillatory pH behaviour in a batch-like carbonylation reaction set-up.1. Isakova A, Novakovic K. Oscillatory Chemical Reactions In The Quest For Rhythmic Motion of Smart Materials. European Polymer Journal 2017, 95, 430-439.2. Donlon L, Novakovic K. Oscillatory carbonylation using alkyne-functionalised poly(ethylene glycol). Chemical Communications 2014, 50, 15506-15508.3. Isakova A, Murdoch B, Novakovic K. From small molecules to polymeric catalysts in the oscillatory carbonylation reaction: multiple effects of adding HI. Physical Chemistry Chemical Physics, 2018, 20, 9281-928
Development of a Smart Hydrogel Oscillator
No full textOscillatory palladium-catalysed oxidative carbonylation reactions, named the BT-GN reactions after their core contributors Bruk, Temkin, Gorodsky and Novakovic, have garnered attention due to their ability to under batch-like conditions produce long lasting (minutes to weeks) oscillations in pH, redox potential, turbidity, and heat of the reaction. [1] This makes the BT-GN reactions an attractive prospect for use as a driving force in smart materials, such as pH responsive hydrogels. The BT-GN reactions take place under lab conditions where complex products are formed from simple starting materials. In many of the studies phenylacetylene is used as a substrate and palladium iodide as a catalyst. [2] To use them in polymeric smart materials such as a hydrogels the BT GN reaction must be adapted to produce oscillations in pH within a polymeric framework, therefore the substrate and catalyst must be replaced with polymeric analogues. In our recent studies we shown that other palladium catalysts and a polymeric alkyne-based substrate PEGA (poly(ethylene glycol) methyl ether acetylene) can produced oscillations in pH. Furthermore a proof-of-concept study demonstrated a self oscillating chitosan macrogel with phenylacetylene as a substrate. [3], [4] This talk will cover advances in the BT-GN reaction with reactions between the polymeric catalyst, chitosan-2-pyridylimine palladium chloride (Chi-IM-PdCl2) and polymer substrate (PEGA) in both solution and hydrogels. References [1] K. Novakovic, L. Bruk, and O. Temkin, “History, versatility and future prospects of oscillatory carbonylation reactions of alkynes.,” RSC Adv., vol. 11, no. 39, pp. 24336–24344, Jul. 2021, doi: 10.1039/d1ra03810a. [2] O. N. Temkin and L. G. Bruk, “Palladium(II, I, 0) Complexes in Catalytic Reactions of Oxidative Carbonylation,” Kinet. Catal., vol. 44, no. 5, pp. 601–617, 2003, doi: 10.1023/A:1026161103700. [3] L. Donlon and K. Novakovic, “Oscillatory carbonylation using alkyne-functionalised poly(ethylene glycol),” Chem. Commun., vol. 50, no. 98, pp. 15506–15508, 2014, doi: 10.1039/c4cc01548g. [4] A. Isakova and K. Novakovic, “Pulsatile release from a flat self-oscillating chitosan macrogel,” J. Mater. Chem. B, vol. 6, no. 30, pp. 5003–5010, 2018, doi: 10.1039/c8tb00781k
Steven Johnson Author Talk Poster
No full textK-State Book NetworkA poster advertising an author talk by Steven Johnson at Kansas State University on September 3, 2014. Steven Johnson's book "The Ghost Map" was the 2014-2015 common book
From food waste to high value transformative healthcare solutions
No full textChitosan, a linear, cationic copolymer, produced from the deacetylation of chitin found in fungal cell walls and crustaceans, with the latter being a major waste product of the fishing industry, is gaining momentum in efforts towards sustainable healthcare. Chitosan has been designated ‘Generally Recognized As Safe (GRAS)’ by the FDA and is approved for use in dietary supplements as well as applications in wound dressings and gels, but ambition goes well beyond this and includes formulations of intelligent stimuli responsive scaffolds for tissue engineering and advanced drug delivery systems. In this talk, we will present key findings from our studies ranging from chitosan purification and endotoxin removal [1], biodegradation and biocompatibility [1-3], to novel injectable, implantable [4] and recently developed transdermal formulations for drug delivery of both small drug molecules and biologics. 1. Effective Endotoxin Removal from Chitosan That Preserves Chemical Structure and Improves Compatibility with Immune Cells, Sophie L Reay, Emma L Jackson, Daniel Salthouse, Ana Marina Ferreira, Catharien MU Hilkens, Katarina Novakovic, Polymers, 2023. 2. In vitro evaluation of the biodegradability of chitosan–genipin hydrogels, Sophie L Reay, Emma L Jackson, Ana M Ferreira, Catharien MU Hilkens, Katarina Novakovic, Materials Advances, 2022. 3. Genipin‐crosslinked chitosan hydrogels: Preliminary evaluation of the in vitro biocompatibility and biodegradation, Nga TN Vo, Lei Huang, Henrique Lemos, Andrew L Mellor, Katarina Novakovic, Journal of Applied Polymer Science, 2021. 4. Poly (ethylene glycol)‐interpenetrated genipin‐crosslinked chitosan hydrogels: Structure, pH responsiveness, gelation kinetics, and rheology, Nga TN Vo, Lei Huang, Henrique Lemos, Andrew Mellor, Katarina Novakovic, Journal of Applied Polymer Science, 2020
Oscillatory Chemical Reactions in the World of Polymers
No full textPolymeric oscillators in lab conditions are a new concept primarily associated with only two research groups worldwide, Professor Ryo Yoshida’s research group, Tokyo University and the Novakovic research group, Newcastle University.1-5 The ultimate aim in linking oscillatory chemical systems with polymer science is the development of useful materials and devices that otherwise would not be feasible. The vision includes fully self-oscillatory materials, materials that act life-like, materials that are able to carry and dispense their content in predefined rhythms, and materials which can be made into an artificial heart. Here we present most recent developments in Novakovic lab ranging from first ever mono- and poly-functional polymeric substrate oscillatory chemical reactions (employing alkyne-terminated poly(ethylene glycol)) to recently expanded family of polymeric catalysts successfully applied to oscillatory systems (using polymer-bound palladium catalysts).1 Yoshida, Sakai, Hara, Maeda, Hashimoto, Suzuki, Murase, J. Control Release 2009, 140, 186; 2Yoshida, Adv. Mater.2010, 22, 3463; 3; Donlon, Novakovic, Chem. Commun.2014, 50, 15506; 4Isakova, Novakovic, Eur. Polym. J.2017, 95, 430; 5 Isakova, Murdoch, Novakovic, PCCP2018, In Press
Spatial and temporal regulation of signaling pathways in hESCs using microfluidic technologies
No full textDiffusion-driven instabilities in the BT-GN oscillatory carbonylation reaction network
Get PDF\ua9 2024 Author(s).This study explores the role of diffusion in creating instabilities in the Bruk Temkin-Gorodsky Novakovic (BT-GN) oscillatory carbonylation reaction network. Stoichiometric network analysis and numerical methods revealed the presence of two destabilizing feedback cycles responsible for these instabilities. Analysis of a spatially uniform system showed that the saddle-node bifurcation can be simulated within the reaction network. The introduction of diffusion results in two types of instabilities: one occurs when a spatially uniform system is already unstable, leading to a reaction-diffusion front; and another involves diffusion-driven instabilities where introducing diffusion destabilizes a stable spatially uniform system. Slower PdI2 diffusion plays a key role in inducing these instabilities. Equations describing conditions for the emergence of the instabilities in both cases were derived
Genipin-crosslinked chitosan-poly(vinyl pyrrolidone) hydrogel for coupling with pH oscillators
No full textSmart polymer gels are macromolecular networks that can exhibit significant and reversible conformational rearrangements upon variable changes in the local environment. Hydrogels are examples of such materials that can swell or deswell in aqueous solutions upon application of an external stimulus such as temperature or pH.1 Oscillatory chemical reactions (e.g. Belousov Zhabotinsky) exhibit the relevant stimuli to induce a simultaneous volume change within a responsive hydrogel if both environments are compatible.2 Pronounced oscillations in reaction heat output (e.g. 0.6 kJ/oscillation at 40\ub0C) and pH (1-6) are exhibited by the phenylacetylene oxidative carbonylation (PCPOC) reaction studied in our group.3,4 It is therefore desirable to couple the PCPOC reaction with a cationic hydrogel able to swell in acidic media. Chitosan, a cationic polysaccharide, is known to be biocompatible, non-toxic, biodegradable, antimicrobial, mucoadhesive and a strong candidate for drug release. However, owing to its fragility and uncontrollable porosity, it has limited use. To overcome this, it is often chemically crosslinked with agents such as glutaraldehyde, formaldehyde or epoxy compounds, although all are cytotoxic and are inappropriate for biomedical applications. Genipin is an alternative natural crosslinking agent that is 10,000 times less cytotoxic than glutaraldehyde, has a slower degradation rate and fluoresces upon forming crosslinks. Poly(vinyl pyrrolidone) (PVP) is a haemocompatible, water soluble polymer that can control the porosity of chitosan structures. In this work, chitosan has been crosslinked with PVP using genipin to form smart hydrogels. Following initial experimental studies, the gel composition that produces stable structures is established. The degree of swelling and the rate at which equilibrium is reached are experimentally studied as a function of polymerisation temperature, polymerisation time and pH. Polymerisation temperatures considered were 37 and 50 \ub0C with polymerisation times ranging from 24 to 72 h. In all experiments acidic environments were investigated. (1) Tanaka, T.; Fillmore, D.; Sun, S. T.; Nishio, I.; Swislow, G.; Shah, A. Physical Review Letters 1980, 45, 1636. (2) Yoshida, R. Adv. Mater. 2010, 22, 3463. (3) Novakovic, K.; Grosjean, C.; Scott, S. K.; Whiting, A.; Willis, M. J.; Wright, A. R. Chemical Physics Letters 2007, 435, 142. (4) Novakovic, K.; Mukherjee, A.; Willis, M.; Wright, A.; Scott, S. Physical Chemistry Chemical Physics 2009, 11, 9044
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