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Chitosan Hydrogels Based on the Diels-Alder Click Reaction: Rheological and Kinetic Study. Polymers (Basel) 2022; 14:polym14061202. [PMID: 35335533 PMCID: PMC8955920 DOI: 10.3390/polym14061202] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 02/27/2022] [Accepted: 03/09/2022] [Indexed: 02/04/2023] Open
Abstract
The Diels–Alder reaction is recognized to generate highly selective and regiospecific cycloadducts. In this study, we carried out a rheological and kinetic study of N-furfuryl chitosan hydrogels based on the Diels–Alder click reaction with different poly(ethylene)glycol-maleimide derivatives in dilute aqueous acidic solutions. It was possible to prepare clear and transparent hydrogels with excellent mechanical properties. Applying the Winter and Chambon criterion the gel times were estimated at different temperatures, and the activation energy was calculated. The higher the temperature of gelation, the higher the reaction rate. The crosslinking density and the elastic properties seem to be controlled by the diffusion of the polymer segments, rather than by the kinetics of the reaction. An increase in the concentration of any of the two functional groups is accompanied by a higher crosslinking density regardless maleimide:furan molar ratio. The hydrogel showed an improvement in their mechanical properties as the temperature increases up to 70 °C. Above that, there is a drop in G’ values indicating that there is a process opposing to the Diels–Alder reaction, most likely the retro-Diels–Alder.
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2
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Espinosa-Dzib A, Vyazovkin S. Nanoconfined gelation in systems based on stearic and 12-hydroxystearic acids: A calorimetric study. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.116191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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3
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Kissinger Method in Kinetics of Materials: Things to Beware and Be Aware of. Molecules 2020; 25:molecules25122813. [PMID: 32570880 PMCID: PMC7357084 DOI: 10.3390/molecules25122813] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/16/2020] [Accepted: 06/16/2020] [Indexed: 11/17/2022] Open
Abstract
The Kissinger method is an overwhelmingly popular way of estimating the activation energy of thermally stimulated processes studied by differential scanning calorimetry (DSC), differential thermal analysis (DTA), and derivative thermogravimetry (DTG). The simplicity of its use is offset considerably by the number of problems that result from underlying assumptions. The assumption of a first-order reaction introduces a certain evaluation error that may become very large when applying temperature programs other than linear heating. The assumption of heating is embedded in the final equation that makes the method inapplicable to any data obtained on cooling. The method yields a single activation energy in agreement with the assumption of single-step kinetics that creates a problem with the majority of applications. This is illustrated by applying the Kissinger method to some chemical reactions, crystallization, glass transition, and melting. In the cases when the isoconversional activation energy varies significantly, the Kissinger plots tend to be almost perfectly linear that means the method fails to detect the inherent complexity of the processes. It is stressed that the Kissinger method is never the best choice when one is looking for insights into the processes kinetics. Comparably simple isoconversional methods offer an insightful alternative.
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Vyazovkin S. Activation Energies and Temperature Dependencies of the Rates of Crystallization and Melting of Polymers. Polymers (Basel) 2020; 12:polym12051070. [PMID: 32392771 PMCID: PMC7284786 DOI: 10.3390/polym12051070] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 05/04/2020] [Accepted: 05/05/2020] [Indexed: 11/28/2022] Open
Abstract
The objective of this review paper is to survey the phase transition kinetics with a focus on the temperature dependence of the rates of crystallization and melting, as well as on the activation energies of these processes obtained via the Arrhenius kinetic treatment, including the treatment by isoconversional methods. The literature is analyzed to track the development of the basic models and their underlying concepts. The review presents both theoretical and practical considerations regarding the kinetic analysis of crystallization and melting. Both processes are demonstrated to be kinetically complex, and this is revealed in the form of nonlinear Arrhenius plots and/or the variation of the activation energy with temperature. Principles which aid one to understand and interpret such results are discussed. An emphasis is also put on identifying proper computational methods and experimental data that can lead to meaningful kinetic interpretation.
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Affiliation(s)
- Sergey Vyazovkin
- Department of Chemistry, University of Alabama at Birmingham, 901 S. 14th Street, Birmingham, AL 35294, USA
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Espinosa-Dzib A, Vyazovkin S. Nanoconfined gelation of polyacrylonitrile, poly(vinyl alcohol), and isotactic polypropylene probed by calorimetry. SOFT MATTER 2020; 16:3285-3293. [PMID: 32167115 DOI: 10.1039/d0sm00004c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Differential scanning calorimetry is used to obtain insights into the kinetics and thermodynamics of nanoconfined gelation. Gels of polyacrylonitrile in propylene carbonate, poly(vinyl alcohol) in ethylene glycol, and isotactic polypropylene in o-dichlorobenzene and decalin are studied in silica nanopores. Two major effects are observed for nanoconfined gels: a decrease in the heat of gelation and an increase in the gelation temperature. The smaller heat indicates that nanoconfinement of polymer chains results in the formation of fewer ordered crosslinks. The increased gelation temperature suggests acceleration of the gelation kinetics. The kinetics has been treated by an advanced isoconversional method and interpreted in terms of the Fisher-Turnbull model. It is found that acceleration of gelation in nanopores is associated with a decrease in the free energy barrier to nucleation, as one would expect for a change in the process mechanism from homogenous to heterogenous nucleation.
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Affiliation(s)
- Alejandra Espinosa-Dzib
- Department of Chemistry, University of Alabama at Birmingham, 901 S. 14th Street, Birmingham, AL 35294, USA.
| | - Sergey Vyazovkin
- Department of Chemistry, University of Alabama at Birmingham, 901 S. 14th Street, Birmingham, AL 35294, USA.
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6
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Pham QT, Yao ZH, Chang YT, Wang FM, Chern CS. LCST phase transition kinetics of aqueous poly(N-isopropylacrylamide) solution. J Taiwan Inst Chem Eng 2018. [DOI: 10.1016/j.jtice.2018.07.045] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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7
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Gelation of Poly(Vinylidene Fluoride) Solutions in Native and Organically Modified Silica Nanopores. Molecules 2018; 23:molecules23113025. [PMID: 30463293 PMCID: PMC6278663 DOI: 10.3390/molecules23113025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Revised: 11/08/2018] [Accepted: 11/16/2018] [Indexed: 12/03/2022] Open
Abstract
The purpose of this study is to highlight the surface and size effects of the nanopores on the thermodynamics and kinetics of gelation. The effects have been probed by applying differential scanning calorimetry to poly(vinylidene fluoride) solutions in tetraethylene glycol dimethyl ether (tetraglyme) and γ-butyrolactone. Nanoconfinement has been accomplished by introducing gels into native and organically modified silica nanopores (4–30 nm). Nanoconfinement has produced two major effects. First, the heat of gelation has decreased three to four times compared to that for the bulk systems. Second, the temperature of gelation has increased by ~40 °C (tetraglyme based systems) and ~70 °C (γ-butyrolactone based systems), the increase being stronger in native nanopores. The effects are discussed in terms of acceleration of gelation due to heterogeneous nucleation at the confining surface, and retardation of gelation due to constricted polymer chain mobility in the middle of the pore volume. Calorimetric data have been subjected to isoconversional kinetics analysis. The obtained temperature dependencies of the activation energies of gelation have been interpreted in the frameworks of the nucleation model of Turnbull and Fisher. The results suggest that nanoconfinement leads to a lowering of both the free energy of nucleation and activation energy of diffusion.
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Payne C, Dolan EB, O'Sullivan J, Cryan SA, Kelly HM. A methylcellulose and collagen based temperature responsive hydrogel promotes encapsulated stem cell viability and proliferation in vitro. Drug Deliv Transl Res 2017; 7:132-146. [PMID: 27924469 DOI: 10.1007/s13346-016-0347-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
With the number of stem cell-based therapies emerging on the increase, the need for novel and efficient delivery technologies to enable therapies to remain in damaged tissue and exert their therapeutic benefit for extended periods, has become a key requirement for their translation. Hydrogels, and in particular, thermoresponsive hydrogels, have the potential to act as such delivery systems. Thermoresponsive hydrogels, which are polymer solutions that transform into a gel upon a temperature increase, have a number of applications in the biomedical field due to their tendency to maintain a liquid state at room temperature, thereby enabling minimally invasive administration and a subsequent ability to form a robust gel upon heating to physiological temperature. However, various hurdles must be overcome to increase the clinical translation of hydrogels as a stem cell delivery system, with barriers including their low tensile strength and their inadequate support of cell viability and attachment. In order to address these issues, a methylcellulose based hydrogel was formulated in combination with collagen and beta glycerophosphate, and key development issues such as injectability and sterilisation processes were examined. The polymer solution underwent thermogelation at ~36 °C as determined by rheological analysis, and when gelled, was sufficiently robust to resist significant disintegration in the presence of phosphate buffered saline (PBS) while concomitantly allowing for diffusion of methylene blue dye solution into the gel. We demonstrate that human mesenchymal stem cells (hMSCs) encapsulated within the gel remained viable and showed raised levels of dsDNA at increasing time points, an indication of cell proliferation. Mechanical testing showed the "injectability", i.e. force required for delivery of the polymer solution through devices such as a syringe, needle or catheter. Sterilisation of the freeze-dried polymer wafer via gamma irradiation showed no adverse effects on the formed hydrogel characteristics. Taken together, these results indicate the potential of this gel as a clinically translatable delivery system for stem cells and therapeutic molecules in vivo.
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Affiliation(s)
- Christina Payne
- School of Pharmacy, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland.,Tissue Engineering Research Group, Department of Anatomy, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland
| | - Eimear B Dolan
- School of Pharmacy, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland.,Tissue Engineering Research Group, Department of Anatomy, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland
| | - Janice O'Sullivan
- Tissue Engineering Research Group, Department of Anatomy, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland
| | - Sally-Ann Cryan
- School of Pharmacy, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland.,Tissue Engineering Research Group, Department of Anatomy, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland.,Trinity Centre for Bioengineering, Trinity College Dublin, Dublin 2, Ireland.,Centre for Research in Medical Devices (CÚRAM), National University of Ireland Galway, Galway, Ireland
| | - Helena M Kelly
- School of Pharmacy, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland. .,Tissue Engineering Research Group, Department of Anatomy, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland.
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Vyazovkin S. Isoconversional Kinetics of Polymers: The Decade Past. Macromol Rapid Commun 2016; 38. [PMID: 28009078 DOI: 10.1002/marc.201600615] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 11/02/2016] [Indexed: 01/17/2023]
Abstract
This article surveys the decade of progress accomplished in the application of isoconversional methods to thermally stimulated processes in polymers. The processes of interest include: crystallization and melting of polymers, gelation of polymer solutions and gel melting, denaturation (unfolding) of proteins, glass transition, polymerization and crosslinking (curing), and thermal and thermo-oxidative degradation. Special attention is paid to the kinetics of polymeric nanomaterials. The article discusses basic principles for understanding the variations in the activation energy and emphasizes the possibility of using models for linking such variations to the parameters of individual kinetic steps. It is stressed that many kinetic effects are not linked to a change in the activation energy alone and may arise from changes in the preexponential factor and reaction model. Also noted is that some isoconversional methods are inapplicable to processes taking place on cooling and cannot be used to study such processes as the melt crystallization.
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Affiliation(s)
- Sergey Vyazovkin
- Department of Chemistry, University of Alabama at Birmingham, 901 S. 14th Street, Birmingham, AL, 35294, USA
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Vyazovkin S. A time to search: finding the meaning of variable activation energy. Phys Chem Chem Phys 2016; 18:18643-56. [PMID: 27137352 DOI: 10.1039/c6cp02491b] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This review deals with the phenomenon of variable activation energy frequently observed when studying the kinetics in the liquid or solid phase. This phenomenon commonly manifests itself through nonlinear Arrhenius plots or dependencies of the activation energy on conversion computed by isoconversional methods. Variable activation energy signifies a multi-step process and has a meaning of a collective parameter linked to the activation energies of individual steps. It is demonstrated that by using appropriate models of the processes, the link can be established in algebraic form. This allows one to analyze experimentally observed dependencies of the activation energy in a quantitative fashion and, as a result, to obtain activation energies of individual steps, to evaluate and predict other important parameters of the process, and generally to gain deeper kinetic and mechanistic insights. This review provides multiple examples of such analysis as applied to the processes of crosslinking polymerization, crystallization and melting of polymers, gelation, and solid-solid morphological and glass transitions. The use of appropriate computational techniques is discussed as well.
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Affiliation(s)
- Sergey Vyazovkin
- Department of Chemistry, University of Alabama at Birmingham, 901 S. 14th Street, Birmingham, AL 35294, USA.
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11
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Vyazovkin S, Yancey B, Walker K. Nucleation-Driven Kinetics of Poly(ethylene terephthalate) Melting. MACROMOL CHEM PHYS 2013. [DOI: 10.1002/macp.201300443] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Sergey Vyazovkin
- Department of Chemistry; University of Alabama at Birmingham; 901 S. 14th Street Birmingham AL 35294 USA
| | - Benjamin Yancey
- Department of Chemistry; University of Alabama at Birmingham; 901 S. 14th Street Birmingham AL 35294 USA
| | - Kahleah Walker
- Department of Chemistry; University of Alabama at Birmingham; 901 S. 14th Street Birmingham AL 35294 USA
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Chan A, Orme RP, Fricker RA, Roach P. Remote and local control of stimuli responsive materials for therapeutic applications. Adv Drug Deliv Rev 2013; 65:497-514. [PMID: 22820529 DOI: 10.1016/j.addr.2012.07.007] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 06/28/2012] [Accepted: 07/06/2012] [Indexed: 12/25/2022]
Abstract
Materials offering the ability to change their characteristics in response to presented stimuli have demonstrated application in the biomedical arena, allowing control over drug delivery, protein adsorption and cell attachment to materials. Many of these smart systems are reversible, giving rise to finer control over material properties and biological interaction, useful for various therapeutic treatment strategies. Many smart materials intended for biological interaction are based around pH or thermo-responsive materials, although the use of magnetic materials, particularly in neural regeneration, has increased over the past decade. This review draws together a background of literature describing the design principles and mechanisms of smart materials. Discussion centres on recent literature regarding pH-, thermo-, magnetic and dual responsive materials, and their current applications for the treatment of neural tissue.
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Guigo N, Sbirrazzuoli N, Vyazovkin S. Gelation on Heating of Supercooled Gelatin Solutions. Macromol Rapid Commun 2012; 33:698-702. [DOI: 10.1002/marc.201100748] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Revised: 12/12/2011] [Indexed: 11/10/2022]
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14
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Dranca I, Vyazovkin S. Thermal stability of gelatin gels: Effect of preparation conditions on the activation energy barrier to melting. POLYMER 2009. [DOI: 10.1016/j.polymer.2009.06.070] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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