Sorption of Vapors by High Polymers

Zimm, Bruno H.; Lundberg, J. L.

doi:10.1021/j150538a010

Cited by 849 publications

(916 citation statements)

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“…This is consistent with the analysis of water to cellulose sorption curves using the Zimm and Lundberg (1956) cluster model. This model also predicts a large increase in the cluster size near saturation (Starkweather 1975), and it is found that decreases in magnitude as the w 1 / 2 DM yDt mix humidity increases to 97% RH.…”

Section: Resultssupporting

confidence: 90%

The hydration of paper studied with solid-state magnetisation-exchange 1H NMR spectroscopy

et al. 2006

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The wide-line 1 H nuclear magnetic resonance (NMR) spectrum of paper in equilibrium with ambient humidity consists of super-imposed relatively broad and narrow lines. The narrower line is of the order of 2 kHz wide at half the maximum height, while the broader line is of the order of 40 kHz in width at half height. On the basis of these line widths, the narrow line is assigned to water sorbed to the paper, and the broad line to the polymeric constituents of the paper. It was not possible to distinguish between the various polymeric components of paper contributing to the 1 H NMR spectra. A modified Goldman-Shen pulse sequence was used to generate a spatial magnetisation gradient between the polymer and water phases. The exchange of magnetisation between protons associated with water and those associated with the macromolecules in paper was observed. The exchange of magnetisation is discussed within a heat transfer model for homonuclear dipolar coupling, with exchange being characterised by a spin-diffusion coefficient. Consideration of the magnitude of the initial rate of the exchange process and estimates of the spinspin relaxation times based on 1 H line widths indicate that some water must exist in a sufficiently immobile state as to allow homonuclear dipolar interactions between adjacent polymer and water protons. Thus, water sorbed onto paper must exist in at least two states in mass exchange with each other. This observation allows certain conclusions to be drawn about the ratio of free/bound water as a function of moisture content and the dispersal of water within the polymer matrix.

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Section: Resultssupporting

confidence: 90%

The hydration of paper studied with solid-state magnetisation-exchange 1H NMR spectroscopy

et al. 2006

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“…The mechanism responsible for termination of short chains is less well-understood than for long chains, but has been compared with center-of-mass diffusion where it is expected that a S should equal 0.50-0.66 according to Zimm's treatment 69 of the Stokes-Einstein equation. 70 This postulate is consistent with the results for PSTY, PVAc, and PMMA, but does not agree with the high value of 0.78 determined for PMA.…”

Section: Termination In Dilute Solutionmentioning

confidence: 99%

Bimolecular radical termination: New perspectives and insights

Johnston‐Hall

Monteiro

2008

J. Polym. Sci. A Polym. Chem.

132

216

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ABSTRACT:The reversible addition-fragmentation chain transfer-chain length dependent termination (RAFT-CLD-T) method has allowed us to answer a number of fundamental questions regarding the mechanism of diffusion-controlled bimolecular termination in free-radical polymerization (FRP). We carried out RAFTmediated polymerizations of methyl acrylate (MA) in the presence of a star matrix to develop an understanding of the effect of polymer matrix architecture on the termination of linear polyMA radicals and compared this to polystyrene, polymethyl methacrylate, and polyvinyl acetate systems. It was found that the matrix architecture had little or no influence on termination in the dilute regime.However, due to the smaller hydrodynamic volumes of the stars in solution compared to linear polymer of the same molecular weight, the gel onset point occurred at greater conversions, and supported the postulate that chain overlap (or c*) is the main cause for the observed autoacceleration observed in FRP. Other theories based on \short-long" termination or free-volume should be disregarded. Additionally, since our systems are well below the entanglement molecular weight, entanglements should also be disregarded as the cause of the gel onset. The semidilute regime occurs over a small conversion range and is difficult to quantify. However, we obtain accurate dependencies for termination in the concentrated regime, and observed that the star polymers (through the tethering of the arms) provided constriction points in the matrix that significantly slow the diffusion of linear polymeric radicals. Although, this could at first sight be postulated to be due to reptation, the dependencies showed that reptation could be considered only at very high conversions (close to the glass transition regime). In general, we find from our data that the polymer matrix is much more mobile than what is expected if reptation were to dominate.

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“…Let us now examine the second hypothesis. The isotherm shape can be then analyzed with the ZimmeLundberg theory [11]. These authors define a clustering function f ZL defined by Clusters are present when f ZL > À1.…”

Section: Resultsmentioning

confidence: 99%

Water clustering in polychloroprene

Gac

Roux

Davies

et al. 2014

Polymer

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Water sorption has been studied gravimetrically for polychloroprene rubber samples, first at a fixed hygrometric ratio (98% HR) and several temperatures (25, 40, 60 and 80 C) for samples of 1.8 and 3.8 mm thickness (Constant Temperature and Hygrometry, CTH experiments), then at fixed temperature (40 C) and several hygrometric ratios ranging from 0 to 95% HR on samples of 0.1 mm thickness (DVS experiments). CTH experiments reveal an abnormal sorption behavior: after an apparently fickian transient period, the water absorption continues at almost constant rate, no equilibrium is observed after more than 2500 h, whatever the temperature. DVS experiments reveal a very low Henry's solubility but the formation of clusters at water activities higher than 40%. The water diffusivity is almost independent of activity below 50% HR and decreases rapidly when activity increases above 50%. Contrary to CTH experiments, equilibrium is reached in DVS and the difference is not simply linked to the well-known effect of sample thickness on diffusion rate. The results allow hypotheses such as hydrolysis or osmotic cracking to explain the abnormal sorption phenomenon to be rejected. It is suggested that clusters could be polymerewater complexes having a linear/branched structure able to grow without phase separation that could explain the reversibility of sorptionedesorption cycles. The difference of behavior between thin 0.1 mm and thicker 1.8 or 3.8 mm samples could be due to an effect of swelling stresses. Ó

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Sorption of Vapors by High Polymers

Cited by 849 publications

References 0 publications

The hydration of paper studied with solid-state magnetisation-exchange 1H NMR spectroscopy

The hydration of paper studied with solid-state magnetisation-exchange 1H NMR spectroscopy

Bimolecular radical termination: New perspectives and insights

Water clustering in polychloroprene

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