Structural inhomogeneities in the range 2.5-2500 .ANG. in polyacrylamide gels

Hecht, Anne‐Marie; Duplessix, R.; Geissler, Erik

doi:10.1021/ma00153a018

Cited by 164 publications

(167 citation statements)

References 6 publications

Supporting

Mentioning

158

Contrasting

Unclassified

Order By: Relevance

“…Deviations from the ideal gel lead to clustering and clumping of microscopic regions of the less water-soluble bisacrylamide. Further support for the existence of microscopic (i.e., on the nanometer length scale) heterogeneities within polyacrylamide gels has been provided by light scattering studies (3,5,6). These studies indicate the existence of heterogeneous domains whose sizes vary with the amount of crosslinker.…”

Section: Introductionmentioning

confidence: 95%

“…2). This model is based upon previously published experimental and theoretical results (3,5,26) that indicate that the crosslinker can form a separate, less water-soluble phase.…”

Section: Derivation Of Magnetization Recovery Equations For Proton Rementioning

confidence: 99%

“…In addition, hydrogels have potential as experimental models of biological tissue. Hydrogel structures in general have been analyzed by a number of methods including dynamic light scattering (1-3), electron microscopy, laser light scattering (4), small angle X-ray scattering (3,5), osmotic swelling (6 -8), atomic force microscopy (9), NMR imaging (10), NMR T 1 and T 2 relaxation methods (11)(12)(13)(14), and magnetization transfer methods (15)(16)(17). Despite the wide range and number of these studies, there remain some very important unresolved issues concerning the structure of these gels and the relationships between gel structure and diffusive transport within the gel.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Proton Diffusion andT1Relaxation in Polyacrylamide Gels: A Unified Approach Using Volume Averaging

Penke

Kinsey

Gibbs

et al. 1998

Journal of Magnetic Resonance

View full text Add to dashboard Cite

The structure of polyacrylamide gels was studied using proton spin-lattice relaxation and PFG diffusion methods. Polyacrylamide gels, with total polymer concentrations ranging from 0.25 to 0.35 g/ml and crosslinker concentrations from 0 to 10% by weight, were studied. The data showed no effect of the crosslinker concentration on the diffusion of water molecules. The Ogston-Morris and Mackie-Meares models fit the general trends observed for water diffusion in gels. The diffusion coefficients from the volume averaging method also fit the data, and this theory was able to account for the effects of water-gel interactions that are not accounted for in the other two theories. The averaging theory also did not require the physically unrealistic assumption, required in the other two theories, that the acrylamide fibers are of similar size to water molecules. Contrary to the diffusion data, T 1 relaxation measurements showed a significant effect of crosslinker concentration on the relaxation of water in gels. The model developed using the Bloch equations and the volume averaging method described the effects of water adsorption on the gel medium on both the diffusion coefficients and the relaxation measurements. In the proposed model the gel medium was assumed to consist of three phases (i.e., bulk water, uncrosslinked acrylamide fibers, and a bisacrylamide crosslinker phase). The effects of the crosslinker concentration were accounted for by introducing the proton partition coefficient, K eq , between the bulk water and crosslinker phase. The derived relaxation equations were successful in fitting the experimental data. The partition coefficient, K eq , decreased significantly as the crosslinker concentration increased from 5 to 10% by weight. This trend is consistent with the idea that bisacrylamide tends to form hydrophobic regions with increasing crosslinker concentration.

show abstract

Section: Introductionmentioning

confidence: 95%

“…2). This model is based upon previously published experimental and theoretical results (3,5,26) that indicate that the crosslinker can form a separate, less water-soluble phase.…”

Section: Derivation Of Magnetization Recovery Equations For Proton Rementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Proton Diffusion andT1Relaxation in Polyacrylamide Gels: A Unified Approach Using Volume Averaging

Penke

Kinsey

Gibbs

et al. 1998

Journal of Magnetic Resonance

View full text Add to dashboard Cite

show abstract

“…Moreover, poly(acrylamide) gels and networks are known to possess an inhomogeneous distribution of crosslinking points, with highly crosslinked domains embedded in a less densely crosslinked matrix. [29] Thus, upon sample preparation, especially during the drying step, residual stress built up in the sample, e.g. due to different deswelling ratios of the domains.…”

Section: Mechanical Deformation Of Samples and Self-reporting Of Damamentioning

confidence: 99%

Self-Reporting Materials: Protein- Mediated Visual Indication of Damage in a Bulk Polymer

Bruns

Clark

2011

Chimia

View full text Add to dashboard Cite

Damage self-reporting materials are able to indicate the presence of microscopic damaged regions by easy to detect signals, such as fluorescence. Therefore, these smart materials can reduce the risk of catastrophic failure of load-bearing components, e.g. in aerospace and construction applications. We highlight here our proof-of-concept paper and we present some additional data, which shows that proteins can be used as mechanophores in solid polymeric materials. Macroscopic mechanical forces were transferred from the polymer to the embedded proteins. The biomolecules act as molecular strain sensor, giving the material the desired selfreporting property. Poly(ethylene glycol) and poly(acrylamide) (PAAm) networks were doped with small amounts of thermsosome (THS), a protein cage from the family of chaperonins, that encapsulated a pair of fluorescent proteins. THS acts as a scaffold which brings the two fluorescent proteins into distance suitable for fluorescence resonance energy transfer (FRET). Moreover, THS can be distorted by mechanic forces so that the distance between the fluorescent proteins changes, leading to a change in FRET efficiency. Using the brittle PAAm as a model system, we were able to visualize microcracks in the polymers by FRET microscopy and by fluorescence lifetime imaging. THS also stabilizes the encapsulated guest proteins against thermal denaturation, increasing their half-live at 70°C by a factor of 2.3.

show abstract

“…These characteristics of AFM and NMR limit the utility of these tools for the characterization of cross-link density gradients in gels and networks. Inhomogeneities in cross-link density in polyacrylamide gels using a combination of visible light scattering, small-angle neutron scattering, and smallangle X-ray scattering has also been described, 17 but of course, these methods only provide bulk averaged information. Another method one might consider for analysis of heterogeneity in cross-link structure in hydrogels is cryofracture techniques coupled with transmission electron microscopy (TEM).…”

Section: Introductionmentioning

confidence: 99%

Quantitative Characterization of Microscopic Variations in the Cross-Link Density of Gels

et al. 2001

View full text Add to dashboard Cite

We report the visualization and quantitative analysis of the cross-link structure in model core/shell hydrogel polymers on the microscopic scale, in a fully swollen state, using soft X-ray microscopy. The cross-link density in these materials and their microscopic or even nanoscopic variation critically influence materials characteristics, yet the cross-link density is difficult to characterize by conventional methods. By the use of soft X-ray microscopy, one can investigate these materials in a fully swollen state and thus directly visualize and quantitatively determine the cross-link structure on a microscopic scale. Materials that were cross-linked by different methods were shown to give rise to differently shaped profiles. Abrupt and gradient cross-link density profiles have been investigated, and the spatial variation in their cross-link density has been determined quantitatively.

show abstract

Structural inhomogeneities in the range 2.5-2500 .ANG. in polyacrylamide gels

Cited by 164 publications

References 6 publications

Proton Diffusion andT1Relaxation in Polyacrylamide Gels: A Unified Approach Using Volume Averaging

Proton Diffusion andT1Relaxation in Polyacrylamide Gels: A Unified Approach Using Volume Averaging

Self-Reporting Materials: Protein- Mediated Visual Indication of Damage in a Bulk Polymer

Quantitative Characterization of Microscopic Variations in the Cross-Link Density of Gels

Contact Info

Product

Resources

About