In situ characterization of moisture sorption/desorption in thin polymer films using optical waveguide spectroscopy

Chu, Li‐Qiang; Mao, Hai‐Quan; Knoll, Wolfgang

doi:10.1016/j.polymer.2006.08.031

Cited by 14 publications

(17 citation statements)

References 25 publications

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“…4 suggests that the critical a w for water clustering was not coincident with the a w beyond which the diffusivity decreased. Similar deviation was also reported (Chu et al 2006;Davis and Elabd 2013). This suggests that the beginning of diffusivity decrease does not mean that water clustering will occur immediately.…”

Section: Zimm-lundberg Analysissupporting

confidence: 85%

“…The critical a w values where the MCS Park reached to unity were about 0.85, 0.83 and 0.81 at 10, 20 and 30°C, respectively. Water molecules are randomly mixed within the solid matrix when water activity is lower than the critical values, and begin to cluster when water activity is higher than the critical values (Chu et al 2006). At maximum a w values involved in this study, water molecules formed clusters with an average number of about three.…”

Section: Zimm-lundberg Analysismentioning

confidence: 90%

“…Two possible interpretations of this sharp upturn are the plasticization of the polymer by the water, and the clustering of water molecules. Clustering causes an increase in the average size of a water cluster and hence reduces the diffusion coefficient, while plasticization allows the polymer chains to move more freely leading to faster diffusion (Chu et al 2006). Thus the behavior of the diffusion coefficient can be used to differentiate between plasticization and clustering.…”

Section: Diffusivity Under Isothermal Conditionsmentioning

confidence: 99%

“…The linear relationship can be described by the Henry's law. As an upturn curve at high a w levels, the third region can be described using the Raoult's law (Pascual-Pineda et al 2014), Kelvin's law (Liu et al 2013) and Flory-Huggins theory (Chu et al 2006). Then, a group of isotherm models (called composite models) have been developed in literatures, in which sorbed water are expressed as the sum of the two or three contributing isotherms.…”

Section: Introductionmentioning

confidence: 99%

“…Water clustering is one mechanism proposed to interpret the sharp upturn in an isotherm curve. In order to characterize clustering in waterpolymer mixture, many qualitative or quantitative approaches have been developed, including thermodynamic analysis, Park isotherm model (Chun and Lee 2015), Brown model, Zimm-Lundberg theory, Flory-Huggins theory and engaged species induced clustering (ENSIC) model (Chu et al 2006). In food research, the ZimmLundberg approach was used in several reports (Avital et al 1990;Carrillo et al 1988;Hernaandez-Munz et al 2003).…”

Section: Introductionmentioning

confidence: 99%

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The states of water in glutinous rice flour characterized by interpreting desorption isotherm

et al. 2017

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Water content of glutinous rice flour were determined after equilibrium at water activity (a w ) of 0.06-0.98 and temperature of 10, 20 and 30°C. Distribution of water in different states and its evolution with a w were characterized using four composite models. Interactions of water molecules with solid matrix and themselves were further evaluated. The Park model was a more realistic and mechanism-based approach for describing water desorption of glutinous rice flour. Increased equilibrium water induced by lowering temperature existed mostly as strongly bound water with only a few parts as weakly bound water. The water-polymer thermodynamic incompatibility predominated the water mobility, and resulted in a rapid decrease of diffusion coefficient at a w [ *0.7. Water diffusivity behavior with a w suggested water clustering at high a w levels. The Zimm-Lundberg theory, Park model and Brown analysis all revealed that critical a w of water clustering was of 0.81-0.85, depending on temperature, but gave inconsistent prediction about mean cluster size.

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Section: Zimm-lundberg Analysissupporting

confidence: 85%

Section: Zimm-lundberg Analysismentioning

confidence: 90%

Section: Diffusivity Under Isothermal Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The states of water in glutinous rice flour characterized by interpreting desorption isotherm

et al. 2017

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Vapor Swelling of Hydrophilic Polymer Brushes

Galvin

Genzer

2017

Polymer and Biopolymer Brushes

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Electrocontrolled Swelling and Water Uptake of a Three‐Dimensional Conducting Polypyrrole Hydrogel

et al. 2016

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Polypyrrole 3D hydrosponges of tubular structure were synthesized and electrochemically characterized. The Fourier transform infrared attenuated total reflection (FTIR‐ATR) spectroscopy technique was employed to study the water uptake of the hydrosponges under different conditions. This technique presents several advantages over conventional swelling measurements due to its specificity that allows analyzing the kinetics of water uptake at the molecular level. In combination with mathematical modeling, FTIR‐ATR spectroscopy also enables the calculation of the water diffusion coefficients in the hydrogels. The experimental setup also allows electroswelling of the hydrosponges to be studied. The results presented herein are complementary to those obtained with the electrochemical quartz crystal microbalance with dissipation (EQCM‐D) technique and make it possible to determine the actual role played by water in the ionic exchange occurring in conducting polymers during their redox processes. Whereas EQCM‐D shows the whole mass change in the film provoked by injection/ejection of ions and solvent molecules, FTIR‐ATR spectroscopy follows water flux only, which thus allows separation of the solvent contribution.

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In situ characterization of moisture sorption/desorption in thin polymer films using optical waveguide spectroscopy

Cited by 14 publications

References 25 publications

The states of water in glutinous rice flour characterized by interpreting desorption isotherm

The states of water in glutinous rice flour characterized by interpreting desorption isotherm

Vapor Swelling of Hydrophilic Polymer Brushes

Electrocontrolled Swelling and Water Uptake of a Three‐Dimensional Conducting Polypyrrole Hydrogel

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