Comparison of the structure and the transport properties of low-set and high-set curdlan hydrogels

Gagnon, Marc‐André; Lafleur, Michel

doi:10.1016/j.jcis.2011.02.033

Cited by 17 publications

(3 citation statements)

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“…9,10 Commonly used techniques to study probe diffusion include source-sink techniques, 11 uorescence recovery aer photobleaching (FRAP), 9 and pulsed eld gradient-NMR (PFG-NMR). [12][13][14][15] Source-sink techniques require the presence of a concentration gradient, the evolution of which is studied over timetypically hours to days, making these techniques experimentally challenging and the results difficult to interpret in terms of the detailed network structure. FRAP and PFG-NMR both work in the absence of concentration gradients, studying instead the chaotic motion of molecules driven by intermolecular collisions.…”

Section: Introductionmentioning

confidence: 99%

“…Studying (averaged) probe/guest molecule diffusion on these short timescales can yield much information on the microscopic structure of porous materials. 13,14,16,17 Soft Matter PAPER One of us recently demonstrated that stable, self-supporting hydrogels were formed upon the addition of aqueous Ca 2+ to 0.5 wt% solutions of naphthalene diphenylalanine (2FF, Fig. 1) at high pH.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of the mesh size in a supramolecular hydrogel by PFG-NMR spectroscopy

2013

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Pulsed field gradient NMR (PFG-NMR) spectroscopy has been used to determine the network mesh size in stable hydrogels formed upon addition of Ca 2+ to solutions of naphthalene diphenylalanine (2FF). At pH 12, the solutions at 0.55 wt% 2FF comprise worm-like micelles. Addition of Ca 2+ results in cross-linking of these micelles. The self-diffusion of dextran guests of nominal 6, 40, 70, 100, 500, 670, 1400 and 2000 kDa, possessing hydrodynamic diameters (2Rh) similar to the expected pore sizes in these systems, was studied both in the precursor micellar solutions and in the hydrogels. The diffusivity of probes with 2Rh < 40 nm is restricted to a similar extent in both types of network with diffusion coefficients scaling as ∼Mr-0.5, where Mr is the nominal mass of the probe, consistent with relatively unrestricted diffusion. Diffusion coefficients fit well the equation Dn/D o = exp(-Rh/ξ), where Dn and Do are the diffusion coefficients in the presence and absence of network respectively and ξ is the mesh size, giving a mesh size of approximately 40 nm. The heaviest ca. 10% of the nominal 2000 kDa dextran fraction having approximate mass and hydrodynamic diameter 3300 kDa and 84 nm respectively was almost immobilised by the gel, consistent with this estimate of the mesh size. The restriction was much weaker in the micellar solution, which is attributed to the transient nature of this micellar network in the absence of Ca 2+. Finally, the mesh size for micellar solutions prepared at 1.1 wt% 2FF is smaller than that of micellar solutions prepared at lower concentrations of 2FF. However, the corresponding gels have a larger mesh size than those prepared at lower concentrations of 2FF. We attribute this to increased fibre aggregation at the higher 2FF concentration. This correlates with lower rheological moduli at higher 2FF concentrations

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of the mesh size in a supramolecular hydrogel by PFG-NMR spectroscopy

2013

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“…The self-diffusion properties of water in hydrated CaAG were characterized as a function of the hydration level of the sample and as a function of the observation time of the diffusion measurement. − The inverse Laplace transformation of the signal decay reveals only one diffusion domain in hydrated CaAG regardless of its water content (Figure ). The explanation is that under the time frame of the diffusion experiment (>10 ms) water molecules localized in the different structural domains of the hydrated aerogel exchange with each other .…”

Section: Resultsmentioning

confidence: 99%

Mechanism of Hydration and Hydration Induced Structural Changes of Calcium Alginate Aerogel

Forgács

Papp

Paul

et al. 2021

ACS Appl. Mater. Interfaces

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The most relevant properties of polysaccharide aerogels in practical applications are determined by their microstructures. Hydration has a dominant role in altering the microstructures of these hydrophilic porous materials. To understand the hydration induced structural changes of monolithic Caalginate aerogel, produced by drying fully cross-linked gels with supercritical CO 2 , the aerogel was gradually hydrated and characterized at different states of hydration by small-angle neutron scattering (SANS), liquid-state nuclear magnetic resonance (NMR) spectroscopy, and magic angle spinning (MAS) NMR spectroscopy. First, the incorporation of structural water and the formation of an extensive hydration sphere mobilize the Caalginate macromolecules and induce the rearrangement of the drystate tertiary and quaternary structures. The primary fibrils of the original aerogel backbone form hydrated fibers and fascicles, resulting in the significant increase of pore size, the smoothing of the nanostructured surface, and the increase of the fractal dimension of the matrix. Because of the formation of these new superstructures in the hydrated backbone, the stiffness and the compressive strength of the aerogel significantly increase compared to its dry-state properties. Further elevation of the water content of the aerogel results in a critical hydration state. The Ca-alginate fibers of the backbone disintegrate into well-hydrated chains, which eventually form a quasi-homogeneous hydrogel-like network. Consequently, the porous structure collapses and the welldefined solid backbone ceases to exist. Even in this hydrogel-like state, the macroscopic integrity of the Ca-alginate monolith is intact. The postulated mechanism accounts for the modification of the macroscopic properties of Ca-alginate aerogel in relation to both humid and aqueous environments.

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FTIR Imaging of Polymeric Materials

Kazarian

Chan

2016

Polymer Morphology

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Comparison of the structure and the transport properties of low-set and high-set curdlan hydrogels

Cited by 17 publications

References 59 publications

Analysis of the mesh size in a supramolecular hydrogel by PFG-NMR spectroscopy

Analysis of the mesh size in a supramolecular hydrogel by PFG-NMR spectroscopy

Mechanism of Hydration and Hydration Induced Structural Changes of Calcium Alginate Aerogel

FTIR Imaging of Polymeric Materials

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