Diffusion Of Poly Research Articles

Solute diffusion in poly(vinyl alcohol)/poly(acrylic acid) composite membranes prepared by freezing/thawing techniques

Composite membranes of poly(vinyl alcohol) and poly(acrylic acid) were prepared by freezing and thawing of aqueous solutions of the two components. The ensuing hydrogels and membranes exhibited crystallinity of up to 13.50% (on a swollen basis) due to crystallization of the poly(vinyl alcohol). The membranes prepared under these conditions exhibited size exclusion characteristics. Theophylline and FITC-dextran transport were investigated and the solute diffusion coefficients were correlated with the mesh size of the membranes.

Gas permeation properties of poly(silamine) membrane

The gas permeation characteristics of poly(silamine) membrane, which consists of alternating 3,3-dimethyl-3-silapentane and N,N′-diethylethylenediamine units in the main chain, were investigated. Though poly(silamine) shows high flexibility (glass transition temperature of −88°C), the gas permeabilities were much lower than those of other rubbery polymers such as poly(dimethylsiloxane) and natural rubber. The activation energies of diffusion in poly(silamine) were much higher than that of natural rubber. On the basis of these results, we propose a model such that the interaction between the Si atom and gas molecules (O2 and N2) prevents the free diffusion of the gas molecule in the poly(silamine) membrane. © 1997 John Wiley & Sons, Ltd.

Influence of thermal stabilizers on diffusion of poly(?-caprolactone) in poly(vinyl chloride)/poly(?-caprolactone) blends

The influence of thermal stabilizers on the poly(ϵ-caprolactone) (PCL) diffusion in poly(vinyl chloride) (PVC)/PCL blends was studied with the addition of various concentrations of dibasic lead phthalate and dibutyltin dilaurate. The rate of PCL diffusion was followed by differential scanning calorimetry and IR spectroscopy in three series of experiments: the migration of PCL at the surface of the sample; the extraction of PCL in a fluid surrounding the sample; and the sorption of liquid PCL in the blend. In the last two series, mass losses and mass uptakes were measured as a function of time. As compared to the blend without additive, dibutyltin dilaurate induces an increase of the PCL rate of diffusion whereas dibasic lead phthalate gives a decrease. These trends are explained by: first, the formation of an associative complex between dibutyltin dilaurate and PVC, which can compete with the PVC/PCL interactions in the blend and thus favor the PCL migration; and, second, the modification of the Tg of the blend induced by the addition of a third component, which can modify the diffusion rate by changing the free volume fraction at the diffusion temperature. Tg decreases slightly in the presence of dibutyltin dilaurate but increases with dibasic lead phthalate. © 1996 John Wiley & Sons, Inc.

Cross-Relaxation Effects in Pulsed-Field-Gradient Stimulated-Echo Measurements on Water in a Macromolecular Matrix

Water diffusion in poly[2-hydroxyethyl-methacrylate] hydrogels has been measured by PFG NMR techniques, using both spin-echo and stimulated-echo methods. It is found that the results differ when evaluated using the standard equations for the echo attenuation. Furthermore, an apparent dependence of the diffusion coefficient on the diffusion time was found in stimulated-echo experiments. This effect is shown to be caused by cross relaxation between the protons of the water and those on the polymer matrix. An equation is derived describing the attenuation of a stimulated echo in the presence of cross relaxation. This equation shows that the additional damping due to cross relaxation depends on the gradient amplitude. If this equation is used with the measured cross-relaxation parameters, both methods are found to agree within experimental error, and no diffusion-time dependence is found for the stimulated-echo experiments. The equation predicts the effect of replacing part of the H2O by D2O; this has been experimentally verified. It is concluded that macromolecular systems should be checked for cross relaxation when stimulated-echo methods will be used for self-diffusion measurements.

An Investigation of Polymer Diffusion in Hydrogel Laminates Using Near-Field FTIR Microscopy

The role of diffusion in gel/gel adhesion was examined by near-field FTIR microscopy. Using a near-field FTIR microscopy technique, compositional maps were obtained with improved spatial resolution and enhanced signal to noise ratio. With this technique, the resolution was enhanced by about a factor of 5. Polymer chain diffusion across a gel/gel interface was a substantial mechanism of adhesion. Diffusion of poly(ethylene glycol) (PEG) free chains across poly(acrylic acid) (PAA) gels was investigated. The diffusivity of PEG was on the order of 10-8 to 10-9 cm2/s for these swollen polymer gels. PEG diffusivity in PAA gels scaled to M-0.41. This was similar to values reported for PEG diffusion in aqueous solution.

Non‐ionic surfactant effects on polymer diffusion in poly(butyl methacrylate) latex films

AbstractThe influence of non‐ionic surfactant molecules on polymer interdiffusion in poly(butyl methacrylate) (PBMA) latex films was investigated using the non‐radiative energy transfer technique. It was found that nonylphenoxypoly(ethylene oxide) surfactants such as NP‐20 and NP‐100 act as plasticizers to enhance the polymer diffusion rate. The increase in diffusion rate with the increase in surfactant concentration is in complete accord with the Fujita‐Doolittle free volume model. This suggests that by the time the latex dispersion is dry, the surfactant has diffused uniformly into the latex polymer.

Settling characteristics of microparticles modified by hydrophilic semi‐interpenetrating polymer networks

AbstractMicroparticles of 2‐hydroxyethyl methacrylate cross‐linked with ethylene glycol dimethacrylate were produced by suspension polymerization. Semi‐interpenetrating polymer networks were prepared by diffusion of poly(ethylene oxide) (PEO) solution into the particles. The PEO was allowed to diffuse into the dried particles and the resulting swollen particles were treated with an excess of acetone to collapse them. The ensuing networks consisted of the collapsed particles and the trapped PEO. The modified particles were allowed to settle in water, and characteristic settling times were measured as a function of swelling time. The settling times were compared to those of the unmodified particles. It was found that the settling time changes with volume fraction, particle size, degree of functionality, and amount of swelling. An increased volume fraction in both unmodified and modified particles causes a slower settling rate. The smaller particle sizes fall more slowly, and size difference plays a more significant role in hindering the settling for lower amounts of trapped PEO. As the amount of PEO increases, the settling rate decreases dramatically. Swelling also slows the settling rate, until the particles reach equilibrium. Equilibrium swelling occurs near 10 min for both unmodified and modified particles. Optical photo‐microscopy verified the amount of swelling and demonstrated the process of PEO penetration. © 1995 John Wiley & Sons, Inc.

Polymer/probe interaction in probe diffusion through a polymer matrix: methyl red diffusion in poly(vinyl acetate)/toluene solutions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolymer/probe interaction in probe diffusion through a polymer matrix: methyl red diffusion in poly(vinyl acetate)/toluene solutionsJaeyoung Lee, Kaapjoo Park, Taihyun Chang, and Jin Chul JungCite this: Macromolecules 1992, 25, 25, 6977–6979Publication Date (Print):December 1, 1992Publication History Published online1 May 2002Published inissue 1 December 1992https://doi.org/10.1021/ma00051a039RIGHTS & PERMISSIONSArticle Views133Altmetric-Citations25LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (375 KB) Get e-Alerts Get e-Alerts

Studies of oxygen diffusion in poly(styrene-co-1-naphthyl methacrylate) by phosphorescence quenching

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStudies of oxygen diffusion in poly(styrene-co-1-naphthyl methacrylate) by phosphorescence quenchingJames E. Guillet and Mark AndrewsCite this: Macromolecules 1992, 25, 10, 2752–2756Publication Date (Print):May 1, 1992Publication History Published online1 May 2002Published inissue 1 May 1992https://doi.org/10.1021/ma00036a029RIGHTS & PERMISSIONSArticle Views128Altmetric-Citations28LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (564 KB) Get e-Alerts Get e-Alerts

Laser interferometry: A measurement technique for diffusion studies in thin polymer films

AbstractLaser interferometric techniques have many applications in the area of thin film science and technology due to their sensitivity, simplicity, and low cost. Typically, changes in thickness and/or refractive index of a transparent polymer film sample are detected from changes in film reflectivity, as measured by variations in the intensity of reflected laser light. Diffusion related properties such as solvent uptake/swelling, dissolution, and drying rates are accessible with laser interferometry since each of these processes involves a change in the film's thickness and/or refractive index. The principles and basic experimental considerations common to these three applications will be discussed. Illustrative examples from our lab will include n‐methyl‐2‐pyrrolidone diffusion in polyimide, and methanol diffusion in poly(methyl methacrylate).

Investigation of the mutual diffusion in poly(ethylene oxide)/poly(methyl methacrylate) blends by photon correlation spectroscopy

Photon correlation spectroscopic studies of the mutual diffusion of poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) blends are carried out. The experimental investigation deals with the measurement of the mutual diffusion coefficient of the PEO/PMMA blend by varying the molecular weight of PEO but keeping the molecular weight of PMMA fixed. At 20% volume fraction of PEO, and high PMMA molecular weight, the mutual diffusion coefficient linearly decreases with M−1PEO. The temperature dependence of the mutual diffusion coefficient is non-Arrhenius. The Onsager coefficient of mutual diffusion is obtained as a function of temperature.

Kinetics of Dopant Diffusion in Poly(3-alkylthiophene) Films Studied by Chronoabsorptometric Method

The kinetics of dopant diffusion in poly(3-alkylthiophene) films is studied by the determination of apparent diffusion coefficient from chronoabsorptometric curves. The diffusion coefficient during oxidation DOx increases with increasing electrolyte concentration and applied potential. On the other hand, the diffusion coefficient during reduction DRed is not dependent on the electrolyte concentration. Both DOx and DRed decrease with increasing alkyl chain length. From the experimental results, a model of charge-transport in poly(3-alkylthiophene) films during doping and undoping processes is proposed.

Investigation of diffusion processes in poly(ethylene oxide)/poly(methyl methacrylate) blends by laser light scattering spectroscopy

Mutual diffusion in poly(ethylene oxide)/polymethyl methacrylate blends is investigated by using the photon correlation spectroscopic technique. The mutual diffusion coefficient and the static structural factor are measured as a function of concentration for various temperatures. The Onsager coefficient is obtained by simultaneous measurements of the diffusion coefficient and static structural factor. The result is employed to test theoretical predictions on the concentration dependence of the mutual diffusion coefficient of the polymer blend. The experiment results are found not in agreement with theoretical predictions.

Polymer-probe interactions in forced Rayleigh scattering measurements of probe diffusion in poly(vinyl acetate) solutions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolymer-probe interactions in forced Rayleigh scattering measurements of probe diffusion in poly(vinyl acetate) solutionsJ. A. Lee and T. P. LodgeCite this: J. Phys. Chem. 1987, 91, 22, 5546–5548Publication Date (Print):October 1, 1987Publication History Published online1 May 2002Published inissue 1 October 1987https://doi.org/10.1021/j100306a010RIGHTS & PERMISSIONSArticle Views139Altmetric-Citations34LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (415 KB) Get e-Alerts

Oxygen diffusion in poly(dimethyl siloxane) using fluorescence quenching. I. Measurement technique and analysis

AbstractThe transport properties of oxygen in poly(dimethyl siloxane) have been measured using the method of quenching of fluorescence. This paper discusses the uniqueness of this method and its use in measuring the diffusion coefficient of oxygen in unfilled PDMS. The results show (1) a large value for the diffusion coefficient of oxygen in pure PDMS at 25°C, D = 3.55 × 10−5 cm2/s, (2) a low value of the acitivation energy, ED = 4.77 kcal/mole, which was not temperature dependent in the ranges evaluated, and (3) a large value of the preexponential term, D0 = 0.115 cm2/s. The diffusion coefficient was found to be independent of both the oxygen concentration and fluorophor concentration in the pressure and temperature ranges used in these experiments. The import of these experiments lies in their application to a unique biomedical oxygen sensor which is fast, sensitive, and does not consume oxygen.

Dye Diffusion in Poly(ethylene Terephthalate) Fibers

Temperature dependence of dye diffusion in poly(ethylene terephthalate) (PET) fibers heat set under slack and taut conditions at various temperatures (in the range 100-240°C) was investigated. The observed temperature dependence of diffusion coefficient was more appropriately represented by the Williams-Landel-Ferry approach rather than the Arrhenius equation. Values of the parameter Bd were determined.

Solvent diffusion in amorphous polymers

AbstractNew diffusivity data are presented for solvent diffusion in poly(vinyl acetate), poly(methyl methacrylate), and polystyrene. These data are used to test the predictive and correlative capabilities of a recently proposed free‐volume theory of diffusion. Comparisons of data and theory showed that the proposed theory provided an accurate description of diffusion in concentrated polymer solutions.

Diffusion in polymers: Optical techniques

AbstractOptical techniques have been applied to study gas diffusion in poly(methyl methacrylate) and Lexan polycarbonate resin[poly(diphenyl‐2,2‐propane carbonate)] for temperatures ranging from 20°C. to the glass transition temperatures. One method consists of observing the movement of a sharp colored diffusion boundary which occurs when certain radical scavenging gases (e.g., O2, I2) penetrate a polymer which has been exposed to high energy irradiation. The theoretical basis and physical interpretation of the moving boundary are discussed. In essence, the color center concentration (produced by irradiation) is greater than the normal equilibrium concentration of scavenger molecules in the polymer so that the latter are trapped before they can move very far inward. The result is approximately a step‐function distribution of the remaining color centers. For O2 penetration into Lexan below Tg, D (cm.2/sec.) ⋍ 0.014 exp {7100 cal./mole/RT}. This relation accounts for the effect of O2 partial pressure on the penetration rate. For O2 penetration into PMMA, below Tg, an activation energy of 10 kcal./mole was observed. A spectrophotometric method was used to measure the uptake of J2 vapor in polycarbonate films. The data indicate a large change (∼50 kcal./mole) in apparent activation energy near 114°C. Several possible applications of the moving boundary technique are mentioned and the results of its use to investigate the effect of stress on the diffusion rate in the polycarbonate are presented. Tensile stresses near the yield point produce a two‐fold increase in D, whereas compressive stresses of comparable magnitude cause only a slight reduction.