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Multiresponsive Core-Shell Microgels Functionalized by Nitrilotriacetic Acid. Biomacromolecules 2024; 25:903-923. [PMID: 38170471 DOI: 10.1021/acs.biomac.3c01056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Stimuli-responsive microgels with ionizable functional groups offer versatile applications, e.g., by the uptake of oppositely charged metal ions or guest molecules such as drugs, dyes, or proteins. Furthermore, the incorporation of carboxylic groups enhances mucoadhesive properties, crucial for various drug delivery applications. In this work, we successfully synthesized poly{N-vinylcaprolactam-2,2'-[(5-acrylamido-1-carboxypentyl)azanediyl]diacetic acid} [p(VCL/NTAaa)] microgels containing varying amounts of nitrilotriacetic acid (NTA) using precipitation polymerization. We performed fundamental characterization by infrared (IR) spectroscopy and dynamic and electrophoretic light scattering. Despite their potential multiresponsiveness, prior studies on NTA-functionalized microgels lack in-depth analysis of their stimuli-responsive behavior. This work addresses this gap by assessing the microgel responsiveness to temperature, ionic strength, and pH. Morphological investigations were performed via NMR relaxometry, nanoscale imaging (AFM and SEM), and reaction calorimetry. Finally, we explored the potential application of the microgels by conducting cytocompatibility experiments and demonstrating the immobilization of the model protein cytochrome c in the microgels.
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Mechanochemical Synthesis of Stimuli Responsive Microgels. Angew Chem Int Ed Engl 2023; 62:e202305783. [PMID: 37177824 DOI: 10.1002/anie.202305783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Revised: 05/12/2023] [Accepted: 05/12/2023] [Indexed: 05/15/2023]
Abstract
Mechanochemical approaches are widely used for the efficient, solvent-free synthesis of organic molecules, however their applicability to the synthesis of functional polymers has remained underexplored. Herein, we demonstrate for the first time that mechanochemically triggered free-radical polymerization allows solvent- and initiator-free syntheses of structurally and morphologically well-defined complex functional macromolecular architectures, namely stimuliresponsive microgels. The developed mechanochemical polymerization approach is applicable to a variety of monomers and allows synthesizing microgels with tunable chemical structure, variable size, controlled number of crosslinks and reactive functional end-groups.
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Structure and Dynamics of Temperature‐Responsive Microgels and Hydrogels by NMR Spectroscopy, Relaxometry, and Diffusometry. MACROMOL CHEM PHYS 2023. [DOI: 10.1002/macp.202200410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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4
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Nanostructuring the Interior of Stimuli-Responsive Microgels by N-Vinylimidazoles Quaternized with Hydrophobic Alkyl Chains. Macromolecules 2022. [DOI: 10.1021/acs.macromol.1c02276] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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5
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Stimuli-responsive microgels with cationic moieties: characterization and interaction with E. coli cells. SOFT MATTER 2021; 17:8678-8692. [PMID: 34518865 DOI: 10.1039/d1sm01007g] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Stimuli-responsive microgel copolymer networks with ionizable functional groups have important applications for encapsulation of drugs, peptides, enzymes, proteins, or cells. Rational design of such networks can be based on characterization of stimuli-induced volume phase transition and spatial distribution of neutral and charged monomer units in crosslinked polymer chains. In this work we successfully synthesized poly(N-vinylcaprolactam-co-1-vinyl-3-methylimidazolium) (poly(VCL-VIM+)) microgels carrying permanent positive charges and demonstrate that 1H high-resolution NMR spectroscopy in combination with transverse (T2) magnetization relaxometry allows investigating separately the behavior of each functional group in the microgel network. The information about comonomer transition temperatures, width of transition, and change in transition entropy were reported and correlated with the concentration of charged functional groups and resulting electrophoretic mobility. A two-state approach was used to describe the temperature-induced volume phase transition separately for neutral and charged polymer segments. The core-corona architecture specific to each functional group was detected revealing that the charged methylated vinylimidazolium groups (VIM+) are concentrated mainly in the corona of the microgel. These biocompatible PVCL-based microgels functionalized with permanent positive charges are shown to serve as an antibacterial system against Gram-negative E. coli strains, due to the positive charge of the incorporated VIM+ comonomer in the polymer network.
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How Shape Memory Effects can Contribute to Improved Self-Healing Properties in Polymer Materials. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02102] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Poly(vinylamine-co-N-isopropylacrylamide) linear polymer and hydrogels with tuned thermoresponsivity. SOFT MATTER 2020; 16:6549-6562. [PMID: 32617537 DOI: 10.1039/d0sm00408a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The fabrication of functional hydrogels with tuned thermoresponsivity is a major challenge. To meet this challenge we copolymerize N-isopropylacrylamide (NIPAm) with N-vinylformamide (NVF) in different ratios with the formamide group being subsequently selectively hydrolyzed to the corresponding amine (VAm). The copolymers are crosslinked with phenylcarbonate telechelic glycol. The influence of the NIPAm : VAm ratio on the thermoresponsitiviy is investigated in terms of absorbance, rheology, NMR spectroscopy, relaxometry, and diffusometry. Phase transition temperatures, change in the entropy of the polymer-water system, and width of the transition in the process of coil-to-globule and swollen-to-collapsed network transitions were evaluated by a two state model and Boltzmann sigmoidal function.
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Selenium‐Modified Microgels as Bio‐Inspired Oxidation Catalysts. Angew Chem Int Ed Engl 2019; 58:9791-9796. [DOI: 10.1002/anie.201901161] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 03/17/2019] [Indexed: 01/02/2023]
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Functional selenium modified microgels: temperature-induced phase transitions and network morphology. SOFT MATTER 2019; 15:3227-3240. [PMID: 30916678 DOI: 10.1039/c8sm02646g] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Microgels that host selenium and mimic the structure of the enzyme glutathione peroxidase are of great interest for biotechnological and catalytic applications. For this purpose selenium-functionalized thermoresponsive poly(N-vinylcaprolactam) (PVCL) microgels with cleavable diselenide crosslinks have been investigated. Thermodynamic and morphological parameters characterizing the temperature-induced phase transitions of dual crosslinked PVCL microgels were obtained using dynamic light scattering (DLS), 1H high-resolution magic-angle sample-spinning (MAS) NMR spectroscopy, and transverse magnetization (T2) NMR relaxometry. Quantities obtained from Flory-Rehner theory, a two-state model and Boltzmann sigmoidal function were used to relate the phase transitions of the dual crosslinked microgels to the transition temperature, entropy, temperature width of the phase transition, Flory interaction parameters, average number of strands, polymer volume fraction of the collapsed microgels, core-corona fractions and chain dynamics. The morphology of the selenium modified microgels after the oxidation and reduction processes was investigated by 1H T2 NMR and further correlated with the crosslink density.
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Blending of reactive prepolymers to control the morphology and polarity of polyglycidol based microgels. SOFT MATTER 2015; 11:943-953. [PMID: 25515704 DOI: 10.1039/c4sm02116a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The compartmentalization of microgels is a challenging task for synthetic polymer chemistry. Although the complexation with low molecular weight compounds or the use of microfluidic techniques offer attractive possibilities for other length scales, it is difficult to implement compartments in the mesoscale range of 10-100 nm. Herein we show how simple blending of reactive prepolymers is suitable to design new microgel morphologies with tailored compartments. We use poly(EEGE)-block-poly(AGE) as crosslinkable, pro-hydrophilic prepolymer in blends with varying amounts of crosslinkable, yet hydrophobic poly(THF-stat-AllylEHO) or inert and hydrophobic polystyrene, and crosslink the allyl functional prepolymer(s) in a thiol-ene click-type reaction after miniemulsification. Our strategy shows how arrested versus free nanophase separation can be used to control easily the morphology and polarity of microgel particles.
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Structural and interaction parameters of thermosensitive native α-elastin biohybrid microgel. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.08.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Microencapsulation of hydrophobic liquids in closed all-silica colloidosomes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:4253-61. [PMID: 24689512 DOI: 10.1021/la500311y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
A facile approach for the microencapsulation of hydrophobic liquids in closed solid all-silica colloidosomes is reported. The method is based on the formation of oil-in-water emulsions stabilized by silica nanoparticles and subsequent gluing of the particles at the water/oil interface by a silica precursor polymer-hyperbranched polyethoxysiloxane. By this means different oils are successfully enclosed in hence formed all-silica colloidosomes with almost 100% efficiency. Via a systematical study it is demonstrated that this process is a delicate interplay between the emulsion stability, oil polarity, and sol-gel reaction kinetics. This approach allows fabricating microcapsules of hydrophobic liquid substances in a mechanically stable, chemically inert, and biocompatible matrix, silica, with high encapsulation capacity and a controlled release profile.
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Water states and dynamics in perfluorinated ionomer membranes by 1H one- and two-dimensional NMR spectroscopy, relaxometry, and diffusometry. Chem Phys Lett 2014. [DOI: 10.1016/j.cplett.2014.02.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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15
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Correlated Morphological Changes in the Volume Temperature Transition of Core–Shell Microgels. Macromolecules 2013. [DOI: 10.1021/ma400495y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Morphological Heterogeneity by Diffusional Kurtosis NMR Spectroscopy in Perfluorosulfonic Acid/SiO2
Composite Proton-Exchange Membranes. MACROMOL CHEM PHYS 2013. [DOI: 10.1002/macp.201300039] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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18
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Molecular dynamics parameter maps by 1H Hahn echo and mixed-echo phase-encoding MRI. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 227:1-8. [PMID: 23220231 DOI: 10.1016/j.jmr.2012.11.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 10/29/2012] [Accepted: 11/08/2012] [Indexed: 06/01/2023]
Abstract
Residual dipolar couplings and averaged correlation time maps in soft matter were obtained by mixed echo phase-encoding solid imaging (MIPSI). Use of the mixed echo in soft matter NMR imaging experiments has two crucial advantages: the signal intensity is recovered with a weak incoherence losses, and second, the intervals during which the phase-encoding evolution due to the magnetic field gradients takes place can be chosen to be much larger than with all other spin echo experiments and hence, a higher special resolution can be achieved. The parameter maps are compared to those obtained by the Hahn-echo phase-frequency encoding method. For both MRI methods the density operator formalism is applied in the average Hamiltonian approximation to describe the encoding of the spin echoes by the molecular motions. The results of preliminary experiments are presented.
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Water self-diffusion anisotropy and electrical conductivity of perfluorosulfonic acid/SiO2 composite proton exchange membranes. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2012.10.031] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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21
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Copolymer microgels by precipitation polymerisation of N-vinylcaprolactam and N-isopropylacrylamides in aqueous medium. Colloid Polym Sci 2012. [DOI: 10.1007/s00396-012-2659-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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22
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Nanocomposites Based on Layered Silicates and Epoxy Resins: Measurement of Clay Dispersion and Exfoliation using TEM, Solid-State NMR, and X-ray Diffraction Methods. MACROMOL CHEM PHYS 2012. [DOI: 10.1002/macp.201100594] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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23
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Morphology and molecular dynamics of hard α-keratin based micro-tubes by 1H and 13C solid-state NMR. Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2011.10.036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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24
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Heterogeneous Morphology of Random Copolymer Microgels as Reflected in Temperature-Induced Volume Transition and 1H High-Resolution Transverse Relaxation NMR. MACROMOL CHEM PHYS 2011. [DOI: 10.1002/macp.201100340] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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25
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Channel orientation anisotropy in perfluorosulfonic acid/SiO2 composite proton exchange membranes: Water self-diffusion study using NMR. Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2011.08.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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26
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Morphology and molecular dynamics of hard α-keratin under pressure by 1H and 13C solid-state NMR. Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2011.05.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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27
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Free volume of poly(perfluorosulfonic acid)/SiO2 composite proton exchange membranes by 129Xe NMR. Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2011.02.052] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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28
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Microgel Heterogeneous Morphology Reflected in Temperature-Induced Volume Transition and 1H High-Resolution Transverse Relaxation NMR. The Case of Poly(N-vinylcaprolactam) Microgel. Macromolecules 2011. [DOI: 10.1021/ma200103y] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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29
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The heterogeneity of segmental dynamics of filled EPDM by (1)H transverse relaxation NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 208:156-162. [PMID: 21106419 DOI: 10.1016/j.jmr.2010.10.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 10/29/2010] [Accepted: 10/31/2010] [Indexed: 05/30/2023]
Abstract
Residual second moment of dipolar interactions M(2) and correlation time segmental dynamics distributions were measured by Hahn-echo decays in combination with inverse Laplace transform for a series of unfilled and filled EPDM samples as functions of carbon-black N683 filler content. The fillers-polymer chain interactions which dramatically restrict the mobility of bound rubber modify the dynamics of mobile chains. These changes depend on the filler content and can be evaluated from distributions of M(2). A dipolar filter was applied to eliminate the contribution of bound rubber. In the first approach the Hahn-echo decays were fitted with a theoretical relationship to obtain the average values of the (1)H residual second moment <M(2)> and correlation time <τ(c)>. For the mobile EPDM segments the power-law distribution of correlation function was compared to the exponential correlation function and found inadequate in the long-time regime. In the second approach a log-Gauss distribution for the correlation time was assumed. Furthermore, using an averaged value of the correlation time, the distributions of the residual second moment were determined using an inverse Laplace transform for the entire series of measured samples. The unfilled EPDM sample shows a bimodal distribution of residual second moments, which can be associated to the mobile polymer sub-chains (M(2) ≅ 6.1 rad (2) s(-2)) and the second one associated to the dangling chains M(2) ≅ 5.4 rad(2) s(-2)). By restraining the mobility of bound rubber, the carbon-black fillers induce diversity in the segmental dynamics like the apparition of a distinct mobile component and changes in the distribution of mobile and free-end polymer segments.
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Structure and Dynamics of Drawn Gel-Spun Ultrahigh-Molecular-Weight Polyethylene Fibers by 1H, 13C and 129Xe NMR. MACROMOL CHEM PHYS 2010. [DOI: 10.1002/macp.201000455] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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31
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Morphology of Injection-Molded Isotactic Polypropylene/Silica Composites Prepared via in-Situ Sol−Gel Technology. Macromolecules 2010. [DOI: 10.1021/ma1007573] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Morphology and molecular mobility of fibrous hard alpha-keratins by 1H, 13C, and 129Xe NMR. J Phys Chem B 2009; 113:12136-47. [PMID: 19658418 DOI: 10.1021/jp904484r] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The morphology and molecular mobility changes of the side chains for hard alpha-keratin due to oxidative and reductive/oxidative treatments for temperatures around the DSC denaturation peak were investigated by (1)H, (13)C, and (129)Xe NMR spectroscopy and (1)H spin diffusion. Proton wide-line spectra were used to obtain the phase composition (rigid, interface, and amorphous fractions) and molecular dynamics of each phase. Proton spin diffusion experiments using a double-quantum filter and initial rate approximation were employed to obtain the dependence of the rigid domain sizes on chemical treatments and denaturation temperatures. A drastic reduction in the rigid domain thickness takes place for the reductive/oxidative treatment. The keratin mobility gradient in the interfacial region at different denaturation temperatures was measured for hard alpha-keratin from (1)H spin diffusion data. (13)C CPMAS spectra were used to provide a detailed examination of the effects of the chemical treatments especially on the disulfide bonds. Thermally polarized (129)Xe spectra suggest the existence of voids in the hard alpha-keratin induced by the reductive and oxidative treatment. The surface of the hard alpha-keratin fiber surface is probed by the laser hyperpolarized (129)Xe. A qualitative model describing the changes induced in hard alpha-keratin protein by chemical transformation was developed and could be correlated with the changes in domain thickness, phase composition, and molecular dynamics.
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State of water in hybrid sulfonated poly(ether ether ketone) – silica membranes by 1H solid-state NMR. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2009.03.063] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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36
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Distributions of transverse relaxation times for soft-solids measured in strongly inhomogeneous magnetic fields. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2009; 196:178-190. [PMID: 19083248 DOI: 10.1016/j.jmr.2008.11.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Revised: 11/09/2008] [Accepted: 11/12/2008] [Indexed: 05/27/2023]
Abstract
The single-sided NMR-MOUSE sensor that operates in highly inhomogeneous magnetic fields is used to record a CPMG (1)H transverse relaxation decay by CPMG echo trains for a series of cross-linked natural rubber samples. Effective transverse relaxation rates 1/T(2,short) and 1/T(2,long) were determined by a bi-exponential fit. A linear dependence of transverse relaxation rates on cross-link density is observed for medium to large values of cross-link density. As an alternative to multi-exponential fits the possibility to analyze the dynamics of soft polymer network in terms of multi-exponential decays via the inverse Laplace transformation was studied. The transient regime and the effect of the T(1)/T(2) ratio in inhomogeneous static and radiofrequency magnetic fields on the CPMG decays were studied numerically using a dedicated C++ program to simulate the temporal and spatial dependence of the CPMG response. A correction factor T(2)/T(2,eff) is derived as a function of the T(1)/T(2) ratio from numerical simulations and compared with earlier results from two different well logging devices. High-resolution T(1)-T(2) correlations maps are obtained by two-dimensional Laplace inversion of CPMG detected saturation recovery curves. The T(1)-T(2) experimental correlations maps were corrected for the T(1)/T(2) effect using the derived T(2)/T(2,eff) correction factor.
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Surface UV aging of elastomers investigated with microscopic resolution by single-sided NMR. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2008; 192:1-7. [PMID: 18294890 DOI: 10.1016/j.jmr.2007.10.017] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2007] [Revised: 10/27/2007] [Accepted: 10/30/2007] [Indexed: 05/25/2023]
Abstract
Depth profiles taken from the surface of UV irradiated natural rubber sheets have been measured with microscopic resolution using a Profile NMR-MOUSE. An NMR observable related to the sum of the spin echoes in the Carr-Purcell-Meiboom-Gill pulse sequence was used to characterize the cross-link density changes produced by the action of UV radiation in each sheet. The aging process was investigated as function of irradiation time and penetration depth. An exponential attenuation law with a space dependent absorption coefficient describes the change in the NMR observable with penetration depth. An Avrami model is used to describe the dependence of the absorption coefficient on the aging time. The method can be applied to investigate the effect of various aging agents on the surfaces of elastomers.
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Proton exchange in hybrid sulfonated poly(ether ether ketone)–silica membranes by 1H solid-state NMR. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.03.048] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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41
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Study of Uniaxially Stretched Isotactic Poly(propylene) by 1
H Solid-State NMR and IR Spectroscopy. MACROMOL CHEM PHYS 2008. [DOI: 10.1002/macp.200700503] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Abstract
Tendons are composed of a parallel arrangement of densely packed collagen fibrils that results in unique biomechanical properties of strength and flexibility. In the present review we discuss several advanced magnetic resonance spectroscopy (MRS) and imaging (MRI) techniques that have allowed us to better understand the biophysical properties of tendons and ligaments. The methods include multiple quantum and T(2) filtering combined with NMR and MRI techniques. It is shown in detail how these techniques can be used to extract a number of useful parameters: 1) the (1)H-(1)H and (1)H-(2)H dipolar interactions; 2) the proton exchange rates between water and collagen, and between water molecules; 3) the distribution of fibril orientations; and 4) the anisotropy of diffusion. It is shown that relaxation data as a function of angular dependence can be obtained in vivo using mobile NMR sensors. Finally, this article describes how double quantum filtered (DQF) MRI can be used to image and monitor the healing process in injured tendons.
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Segmental dynamic heterogeneity of short-chain grafted-poly(dimethylsiloxane) by 1H spin-diffusion NMR. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.09.092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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45
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Segmental mobility in short-chain grafted-PDMS by homo- and heteronuclear residual dipolar couplings. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2006; 30:45-54. [PMID: 16516447 DOI: 10.1016/j.ssnmr.2006.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Revised: 01/26/2006] [Accepted: 01/27/2006] [Indexed: 05/06/2023]
Abstract
Different homo- ((1)H-(1)H) and heteronuclear ((1)H-(13)C) multiple quantum solid-state NMR experiments were applied to a series of short poly (dimethylsiloxane) (PDMS) chains grafted onto hydrophilic silica. The existence and clear separation of a strongly dipolar coupled region which is attributed to the silica-PDMS interface and a weakly dipolar coupled region attributed to the mobile chain portions outside the interface is evident in all experiments. In a sample series with different average chain lengths the residual dipolar couplings and with that the average order parameters are constant for the interface part and correlate for the mobile part linearly with the average chain length. Temperature dependent studies using (1)H double quantum experiments indicate the different stages of immobilization of the polymer chains. Solid-state NMR techniques therefore can give detailed information about the microscopic structure of this material and especially the effect of chain anchoring. It is also demonstrated that sample rotation influences the mobility of the mobile component and therefore the analysis of such materials should always be done under static conditions.
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Self-diffusion measurements by a mobile single-sided NMR sensor with improved magnetic field gradient. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2006; 180:229-35. [PMID: 16545589 DOI: 10.1016/j.jmr.2006.02.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2006] [Revised: 02/24/2006] [Accepted: 02/26/2006] [Indexed: 05/07/2023]
Abstract
A simple and fast method of measuring self-diffusion coefficients of protonated systems with a mobile single-sided NMR sensor is discussed. The NMR sensor uses a magnet geometry that generates a highly flat sensitive volume where a strong and highly uniform static magnetic field gradient is defined. Self-diffusion coefficients were measured by Hahn- and stimulated echoes detected in the presence of the uniform magnetic field gradient of the static field. To improve the sensitivity of these experiments, a Carr-Purcell-Meiboom-Gill pulse sequence was applied after the main diffusion-encoding period. By adding the echo train the experimental time was strongly shortened, allowing the measurement of complete diffusion curves in less than 1min. This method has been tested by measuring the self-diffusion coefficients D of various organic solvents and poly(dimethylsiloxane) samples with different molar masses. Diffusion coefficients were also measured for n-hexane absorbed at saturation in natural rubber with different cross-link densities. The results show a dependence on the concentration that is in good agreement with the theoretical prediction. Moreover, the stimulated-echo sequence was successfully used to measure the diffusion coefficient as a function of the evolution time in systems with restricted diffusion. This type of experiment proves the pore geometry and gives access to the surface-to-volume ratio. It was applied to measure the diffusion of water in sandstones and sheep Achilles tendon. Thanks to the strong static gradient G(0), all diffusion coefficients could be measured without having to account for relaxation during the pulse sequence.
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Segmental orientation of thermoplastic polyurethanes investigated by 1H double-quantum NMR. Correlation with thermodynamic and mechanical properties. POLYMER 2006. [DOI: 10.1016/j.polymer.2006.01.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Abstract
The principal values of the diffusion tensor of free water in the pores of sheep Achilles tendon were determined. For this purpose, the azimuthally angular dependence of the self-diffusion coefficient was measured using a radiofrequency tilt coil and pulsed-field-gradient stimulated-echo (PFGSE) NMR. Combining the PFGSE with multiple acquisitions of Hahn echoes using the Carr-Purcell-Meiboom-Gill pulse sequence reduced the measuring time. The diffusion measurements revealed two diffusion process characterized by a fast and a slow effective diffusion coefficient. A model which describes the stimulated-echo amplitude, encoded by the water diffusion and magnetization transfer, was used for evaluation of the fast diffusion coefficients. The fast diffusion process characterizes the water molecules in pores surrounding the collagen fibrils. The diffusion coefficients characterizing the fast process show a well-defined anisotropy. The principal values of the diffusion tensors were determined assuming the elongated pores to be oriented parallel to the tendon fibrils and thus the orientation distribution function of the pores followed that of the collagen fibrils. The average aspect ratio of pores was estimated from the principal values of the water diffusion tensor and is suitable to characterize quantitatively the changes in tendon morphology due to healing or aging. The methods in this investigation can also be applied to measurements of the diffusion anisotropy using ex situ NMR sensors.
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