Transport of penetrants in the macromolecular structure of coals

Barr-Howell, Barbara D.; Howell, John M.; Peppas, Nicholas A.

doi:10.1016/0040-6031(87)88175-3

Cited by 6 publications

(7 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Often, there has been interest in diffusing organic solvents into coal, as in direct liquefaction or as part of some pretreatment step. As a result, over the past decade there have been a number of studies of the factors that influence diffusion in solid coals. − The cited studies have been mostly concerned with transport of organic solvents. Others have been concerned with the transport of gases, such as methane, but these are not considered here.…”

Section: Introductionmentioning

confidence: 99%

“…The process of relaxation of coal structure by the solvents plays an important role in determining how fast the coal can take up additional solvent. The rates of solvent uptake are strongly influenced by factors such as the nature of the coal, the size of the coal particles, the strength of the solvent, ,, the size and shape of the solvent molecules, ,, the temperature, ,,− , the moisture content of the coal, and other features of its pretreatment. ,,,− …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Temperature Dependence of Solvent Swelling and Diffusion Processes in Coals

Otake

Suuberg

1997

Energy Fuels

View full text Add to dashboard Cite

The rates of solvent swelling of the Argonne Premium Sample coals have been measured in various organic solvents at various temperatures. The results show that the extents of swelling, when experiments are carried out in liquid solvents, are independent of the temperature, within the temperature range studied here (10−60 °C). Thermodynamically, this requires that equilibrium swelling should occur with a near-zero enthalpy, as generally required for absence of a temperature effect on equilibrium. This conclusion is consistent with a number of other recently published results. The rates of swelling of the coals do not correlate with rank. The nature of the swelling process varies from relaxation controlled to Fickian diffusion controlled. The activation energies for the kinetics of swelling are consistent with other recently published values, but again, a correlation with rank could not be substantiated. The activation energies all fall in the range from 20 to 60 kJ/mol, suggesting that the activation barrier may be associated with the breakage of internal electron donor−acceptor (e.g., hydrogen bonding) interactions. Thermal pretreatment of some of the coals to 350 °C had significant effects on their swelling behaviors. The effect was generally to increase the rate of swelling, and in some cases, the extent of swelling. The activation energies for swelling were, however, unaffected. This is interpreted as consistent with the hypothesis that the activation energy barrier is determined by donor−acceptor interactions which are unaffected by pretreatment but that other thermally dissociable coal−coal interactions may serve to stiffen its structure.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Temperature Dependence of Solvent Swelling and Diffusion Processes in Coals

Otake

Suuberg

1997

Energy Fuels

View full text Add to dashboard Cite

show abstract

“…Equation is generally applicable for tetra‐functional cross‐linking units as derived in the original Flory–Rehner model. However, several cases of network polymers exist in which the functionality of the cross‐link junctions needs to be taken into account: highly cross‐linked systems, hydrogels synthesized from multi‐functional cross‐linkers, and free radical photopolymerization where the functionalities of cross‐linked junctions could be heterogeneous rather than possessing a single, well‐defined functionality . In this work, hydrogel networks modeled are ideal with a homogeneous functionality ( F = 6); thus, the number of links/chain ( N ) is given by

\frac{3 M_{C}}{M_{r}}

instead of

\frac{2 M_{C}}{M_{r}}

used in the original Peppas–Merrill model.…”

Section: Resultsmentioning

confidence: 99%

“…The encapsulation and delivery of drugs has been achieved in a controlled manner by swelling, degradation of the network structure, or by application of a mechanical force. The network structure of hydrogels is one of the important factors in determining the efficiency of drug delivery for target applications . Several factors including molecular weight and solution concentration of the monomers/macromers, synthesis technique, cross‐linking time, temperature, pH, viscosity, and the specificity of bioactive molecules incorporated can modify the network structure and thereby the macroscopic gel properties, including stiffness, volumetric swelling, and diffusivity of drug molecules through the network.…”

Section: Introductionmentioning

confidence: 99%

An Insight into Structural and Mechanical Properties of Ideal‐Networked Poly(Ethylene Glycol)–Peptide Hydrogels from Molecular Dynamics Simulations

Rukmani

Anstine

Munasinghe

et al. 2020

Macro Chemistry & Physics

View full text Add to dashboard Cite

Simulations of local structure and interactions in stimuli‐responsive hydrogel networks at atomistic resolution has the capability to compliment experimental efforts by providing insight into current soft materials design challenges. This work simulates ideal hexafunctional networks of poly(ethylene glycol) (PEG)‐diacrylate (PEGDA) and PEG–peptide hydrogels with two enzyme‐responsive peptide sequences, Gly‐Leu‐Lys (GLK) and Gly‐Pro‐Gln‐Gly‐Ile‐Phe‐Gly‐Gln‐Lys (GPQGIFGQK), using molecular dynamics (MD) simulations at water contents from 84% to 90%. This presents the first atomistic MD study of a PEG–peptide hydrogel. The mesh sizes obtained are compared to common swelling theories and the available micropore space for diffusion is compared to the sizes of a family of matrix metalloproteinases (MMPs) to predict size‐based exclusion. The effects of interactions between PEG, peptide, and water on the chemical environment surrounding the cleaving site of peptides are investigated by examining partial radial distribution functions and solvent accessible surface areas. The chemical environment around the peptide sequence is found to be more hydrophobic in PEG‐9‐peptide hydrogels, thereby favoring cleavage by the hydrophobic binding pocket of MMPs. Furthermore, the mechanical moduli of the hydrogels is also examined, and an increase with the incorporation of peptide sequences and a general decrease with increasing water concentration is observed.

show abstract

“…As it is widely reported in literature, the equilibrium swelling data can be used to evaluate the network property of the polymeric hydrogels. In particular, the structure of hydrogels that do not contain ionic moieties can be analyzed using the Peppas–Merrill equation, a modification of the Flory–Rehner equation that takes into account the presence of a solvent during the gel preparation 39, 40. Through this equation, one can evaluate an average value for the molecular weight of the polymer chain between two consecutive crosslinking points ( M c ) and the corresponding mesh size ξ, also referred to as the pore size.…”

Section: Resultsmentioning

confidence: 99%

Radiation synthesis and characterization of poly(ethylene oxide)/chitosan hydrogels

Branca

Auditore

Loria

et al. 2012

J of Applied Polymer Sci

View full text Add to dashboard Cite

Recent advances in hydrogel technology have focused on finding more biocompatible, nontoxic materials intended for pharmaceutical and biomedical applications. In this study, a series of pH-sensitive hydrogels were prepared from poly(ethylene oxide) (PEO) and chitosan in aqueous solutions by electron beam irradiation. This method is a suitable tool for the formation of biocompatible hydrogels because in radiation processing no initiators or crosslinkers, potentially toxic and difficult to remove, are needed. In this frame, also the PEO and chitosan choice was based on their characteristic of low toxicity. The properties of the prepared hydrogels were investigated in terms of the gel fraction and of the swelling behavior in solutions at different pHs. Some swelling kinetic and diffusional parameters were also determined. The observed properties show that increasing the chitosan content, or lowering the pH, the crosslinking density of these networks increases inducing the formation of more stable, but less swellable, hydrogels.

show abstract

Transport of penetrants in the macromolecular structure of coals

Cited by 6 publications

References 4 publications

Temperature Dependence of Solvent Swelling and Diffusion Processes in Coals

Temperature Dependence of Solvent Swelling and Diffusion Processes in Coals

An Insight into Structural and Mechanical Properties of Ideal‐Networked Poly(Ethylene Glycol)–Peptide Hydrogels from Molecular Dynamics Simulations

Radiation synthesis and characterization of poly(ethylene oxide)/chitosan hydrogels

Contact Info

Product

Resources

About