Studies of the Cross-Linking Process in Gelatin Gels.

Ferry, I. John D.; Eldridge, J. E.

doi:10.1021/j150466a015

Cited by 61 publications

(20 citation statements)

References 16 publications

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“…These simplifications are made mainly for analytical convenience, although they have direct relevance for the interpretation of impedance spectra. An early analysis of this type was due to Ferry [30], who considered the response of a semi-infinite electrolyte to an oscillating charge density applied at a electrode surface. Ferry's treatment is formally equivalent to the classical theory of dielectric dispersion in bulk electrolytes [74,75].…”

Section: B Microscopic Transport Modelsmentioning

confidence: 99%

Diffuse-charge dynamics in electrochemical systems

2004

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The response of a model microelectrochemical system to a time-dependent applied voltage is analyzed. The article begins with a fresh historical review including electrochemistry, colloidal science, and microfluidics. The model problem consists of a symmetric binary electrolyte between parallel-plate blocking electrodes, which suddenly apply a voltage. Compact Stern layers on the electrodes are also taken into account. The Nernst-Planck-Poisson equations are first linearized and solved by Laplace transforms for small voltages, and numerical solutions are obtained for large voltages. The "weakly nonlinear" limit of thin double layers is then analyzed by matched asymptotic expansions in the small parameter epsilon= lambdaD/L, where lambdaD is the screening length and L the electrode separation. At leading order, the system initially behaves like an RC circuit with a response time of lambdaDL/D (not lambdaD2/D), where D is the ionic diffusivity, but nonlinearity violates this common picture and introduces multiple time scales. The charging process slows down, and neutral-salt adsorption by the diffuse part of the double layer couples to bulk diffusion at the time scale, L2/D. In the "strongly nonlinear" regime (controlled by a dimensionless parameter resembling the Dukhin number), this effect produces bulk concentration gradients, and, at very large voltages, transient space charge. The article concludes with an overview of more general situations involving surface conduction, multicomponent electrolytes, and Faradaic processes.

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Section: B Microscopic Transport Modelsmentioning

confidence: 99%

Diffuse-charge dynamics in electrochemical systems

2004

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“…The excellent review by te Nijenhuis [8] covers these systems in detail, but in this article we shall not restrict ourselves in this way. However, for such thermoreversible gels, Eldridge and Ferry [9] showed, in their work for gelatin gels, that the Concentration C and (weight averagej molecular weight ( M ) dependence of the gel melting temperature could be described by a simple model (essentially that of Flory for the crystalline melting of a polymer). They established that a plot of In(C) versus l/Tm (gel melting temperature in Kelvin) was almost linear, as was ln(M) vs. l/Tm.…”

Section: Equilibrium Aspects Of Physical Gelationmentioning

confidence: 99%

Reversible and irreversible biopolymer gels — Structure and mechanical properties

Ross‐Murphy

1998

Ber Bunsenges Phys Chem

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The majority of synthetic polymer gels are formed by the covalent cross‐linking of linear or branched macro‐molecules using multi‐functional cross‐linking agents. Such gels are networks, or true macromolecules with (nominally) infinite molecular weight and consequently they swell rather than dissolve if immersed in a good solvent. However, there are also a whole class of materials called physical gels where non‐covalent crosslinks occur. These show similarities to covalent networks, but because the cross‐links are not permanent, they will show creep behaviour at very long times. Some of these form on cooling a heated solution, such as gelatin gels, while others form only on heating. Also, some gels are thermoreversible, while others are not. Physical gels can be formed from synthetic or biopolymers. In the latter case non‐covalent cross‐links often comprise more specific and complex mechanisms involving, rather than point‐like cross‐links, “junction zones” of known, ordered secondary structure such as multiple helices. Typically there is a specific, and often intricate, hierarchy of arrangements, which are more familiar to molecular biologists than to polymer physical chemists. In this paper we introduce viscoelastic techniques for characteristing physical gels, and then relate the properties to the underlying structure at the macromolecular and junction zone level. The parallels between synthetic and biopolymer gels will also be illustrated. Finally we describe recent work on the heat‐set gelation of globular proteins, and an attempt to relate the important parameter of the gelation time, tc, to both polymer concentration and temperature.

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“…41-42]. Long ago Ferry and Eldridge [62] treated the nearly stationary values of the GI([)-curve by means of a real chemical equilibrium between the aggregated macromolecules which has been a little modified by the Nijenhuis [63]. At the present time there is no approach which is able to describe the total G(t)-curve including also the range of the percolation theory.…”

Section: The Equilibrium Aggregation Modelmentioning

confidence: 99%

Properties of thermoreversible gels

Borchard¹

1998

Ber Bunsenges Phys Chem

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In a short survey chemical and physical aspects characterising thermoreversibly gelling systems are gathered. Rheological properties of the system gelatin/water for different polymer concentrations at various temperatures and varying angular frequencies are presented. The results are interpreted following the percolation theory. The relevant exponents of the storage and loss modulus are close to the percolation model of Arbabi and Sahimi. The pre‐gel properties favour the Zimm‐limit whereas the post‐gel properties are close to the Rouse‐limit. This controversial behaviour is discussed. The gel‐point has been determined by the divergence criterion of the dynamic viscosity at zero frequency when the storage modulus vanishes. The critical times in the percolation results agree fairly well with the time of gelation but not with the cross over time of the storage and loss modulus curves versus time at zero frequency. An equilibrium aggregation model for the post gelation processes is presented which is based on the percolation approach. The time dependence of the storage modulus can be described in the total time range between gel point and the final equilibrium value after very long times.

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Studies of the Cross-Linking Process in Gelatin Gels.

Abstract: The specific rotations and rigidities of five degraded gelatin samples, with n ranging from 17,000 to 44,000, have been measured over a temperature range

Cited by 61 publications

References 16 publications

Diffuse-charge dynamics in electrochemical systems

Diffuse-charge dynamics in electrochemical systems

Reversible and irreversible biopolymer gels — Structure and mechanical properties

Properties of thermoreversible gels

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