Scattering and swelling properties of inhomogeneous polyacrylamide gels

Mallam, Simon; Horkay, Ferenc; Hecht, Anne‐Marie; Geissler, Erik

doi:10.1021/ma00198a029

Cited by 174 publications

(150 citation statements)

References 12 publications

Supporting

Mentioning

146

Contrasting

Order By: Relevance

“…II. Elsewhere, similar slope dependence has been reported for inhomogeneous polyacrylamide gels and is also interpreted in terms of cross-link density [43].…”

Section: Resultssupporting

confidence: 82%

Network structure of polyfluorene sheets as a function of alkyl side chain length

et al. 2011

View full text Add to dashboard Cite

The formation of self-organized structures in poly(9,9-di-n-alkylfluorene)s ∼1 vol % methylcyclohexane (MCH) and deuterated MCH solutions was studied at room temperature using neutron and x-ray scattering (with the overall q range of 0.000 58-4.29Å−1 ) and optical spectroscopy. The number of side chain carbons (N ) ranged from 6 to 10. The phase behavior was rationalized in terms of polymer overlap, cross-link density, and blending rules. For N = 6−9, the system contains isotropic areas and lyotropic areas where sheetlike assemblies (lateral size of >400Å) and free polymer chains form ribbonlike agglomerates (characteristic dimension of >1500Å) leading to a gel-like appearance of the solutions. The ribbons are largely packed together with surface fractal characteristics for N = 6−7 but become open networklike structures with mass fractal characteristics for N = 8−9, until the system goes through a transition to an isotropic phase of overlapping rodlike polymers for N = 10. The polymer order within sheets varies allowing classification for loose membranes and ordered sheets, including the so-called β phase. The polymers within the ordered sheets have restricted motion for N = 6−7 but more freedom to vibrate for N = 8−9. The nodes in the ribbon network are suggested to contain ordered sheets cross-linking the ribbons together, while the nodes in the isotropic phase appear as weak density fluctuations cross-linking individual chains together. The tendencies for macrophase separation and the formation of non beta sheets decrease while the proportion of free chains increases with increasing N. The fraction of β phase varies nonlinearly, reaching its maximum at N = 8.

show abstract

“…II. Elsewhere, similar slope dependence has been reported for inhomogeneous polyacrylamide gels and is also interpreted in terms of cross-link density [43].…”

Section: Resultssupporting

confidence: 82%

Network structure of polyfluorene sheets as a function of alkyl side chain length

et al. 2011

View full text Add to dashboard Cite

show abstract

“…[20], [6]- [8]) is similar to the problem solved by Ochoa et al (63) involving diffusion and reaction in cellular media; however, the present system includes three relaxation terms and the adsorption factor, P.…”

Section: Volume Averaging In V T and The One-equation Modelmentioning

confidence: 78%

“…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%

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

“…Experimentally, small-angle X-ray scattering (SAXS) 28 and small-angle neutron scattering (SANS) have been extensively employed to elucidate the inhomogeneities in polymer gels. [29][30][31][32][33][34] As a matter of fact, inhomogeneities are one of the most interesting topics in SANS of polymer gels.…”

Section: What Are Structure Inhomogeneities In Gels?mentioning

confidence: 99%

Universality and Specificity of Polymer Gels Viewed by Scattering Methods

Shibayama¹

2006

Bulletin of the Chemical Society of Japan

107

112

View full text Add to dashboard Cite

Concentration fluctuations in polymer gels are composed of dynamic thermal fluctuations and frozen inhomogeneities. Particularly, the latter is a characteristic of gels and is due to cross-linking. The frozen inhomogeneities manifest unique properties in polymer gels. Speckle patterns are commonly observed in gels. The time-correlation function of the scattering intensity entails a power-law behavior at the sol-gel transition. The appearance of speckle patterns is related to the nonergodicity of gels, and the power-law behavior corresponds to the self-similarity of clusters at the gelation threshold. In this review, it will be demonstrated that light scattering is one of the most powerful tools for structure characterization of polymer gels. Then, the universality and specificity of polymer gels will be examined for various types of gels, including physical gels, composite gels, and gelators.

show abstract

Scattering and swelling properties of inhomogeneous polyacrylamide gels

Cited by 174 publications

References 12 publications

Network structure of polyfluorene sheets as a function of alkyl side chain length

Network structure of polyfluorene sheets as a function of alkyl side chain length

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

Universality and Specificity of Polymer Gels Viewed by Scattering Methods

Contact Info

Product

Resources

About