Structure and Thermodynamics in Associating Model Ionomer Solutions

Karayianni, Eleni; Cooper, Stuart L.

doi:10.1021/ie00034a034

Cited by 7 publications

(9 citation statements)

References 48 publications

(60 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This picture of ionic aggregation is consistent with the results obtained from this study that support the formation of self-loops in the dilute regime with extension of chains due to bridging between different micelles as concentration increases. It should be noted that the fact that the chain dimensions measured increase with concentration and are larger than those expected from a cyclization of the polymer chains is consistent with our observations from total SANS 14 and dynamic light scattering measurements . These results showed that the aggregates were in an extended rather than a contracted conformation as revealed by the rather small fractal dimension of the aggregates.…”

Section: Data Evaluation and Analysissupporting

confidence: 90%

“…It should be noted that the fact that the chain dimensions measured increase with concentration and are larger than those expected from a cyclization of the polymer chains is consistent with our observations from total SANS 14 and dynamic light scattering measurements. 52 These results showed that the aggregates were in an extended rather than a contracted conformation as revealed by the rather small fractal dimension of the aggregates.…”

Section: Single Chain Conformation Of Telechelic Ionomer Solutionsmentioning

confidence: 87%

See 1 more Smart Citation

Small-Angle Neutron Scattering Studies of Low Polarity Telechelic Ionomer Solutions. 2. Single Chain Scattering

1997

Self Cite

View full text Add to dashboard Cite

A direct probe of the single chain conformation in associating low polarity model telechelic ionomer solutions has been obtained using small-angle neutron scattering. A contrast matching technique was employed utilizing a solution of hydrogenated and deuterated ionomer chains in a mixture of labeled and unlabeled solvent molecules. The scattering data at all concentrations and ionic levels examined show an excellent fit to the wormlike chain model. Single chain scattering patterns were obtained for two sodium-neutralized carboxy−telechelic polystyrene ionomers that differ by a factor of 2 in their molecular weight, in a concentration range from the dilute to the concentrated solution regime. The single chain dimensions were found to be influenced by both the ionic interactions and the extent of association. Both ionomer systems showed a contraction of the chain dimensions in the dilute solution regime which is more pronounced for the lower molecular weight telechelic ionomer. As concentration increases, the single chain dimensions increase until they reach a plateau value in the concentrated solution regime. This plateau value is very close to the chain dimensions of the ionomer in the bulk, as was found from a previous SANS study on similar ionomer systems. This plateau value chain dimension is also the same as the unperturbed dimension of the nonionic parent polymer in the bulk. The effect of concentration on the ionomer chain dimensions is attributed to the influence of ionic interactions as the nonionic form of the material shows larger chain dimensions in the concentration regime studied. These results indicate that intramolecular interactions with the formation of self loops prevail in the dilute solution regime. Intermolecular interactions with ionic groups connecting to different chains prevail in the concentrated solution regime, as evidenced by an extension of the chain dimensions.

show abstract

Section: Data Evaluation and Analysissupporting

confidence: 90%

Section: Single Chain Conformation Of Telechelic Ionomer Solutionsmentioning

confidence: 87%

Small-Angle Neutron Scattering Studies of Low Polarity Telechelic Ionomer Solutions. 2. Single Chain Scattering

1997

Self Cite

View full text Add to dashboard Cite

show abstract

“…To verify large cations reduce physical cross-linking, or ionic aggregation, we turn to X-ray scattering, a common tool for identifying ionic aggregates. ,− Ionic aggregation can be identified through the wavevector q of ionomer peaks, where q = (4π/λ) sin(θ/2), with X-ray wavelength, λ and scattering angle, θ. Typical ionomers with similar ion contents have been reported to show peaks near q = 0.15−0.2 Å −1 corresponding to Bragg spacing of d = 2π/ q ≈ 3 nm between ion aggregates. ,− Figure shows the X-ray results for our polyester ionomers shifted vertically for clarity. The sodium ionomer has the most scattering in the 0.02 Å −1 < q < 0.17 Å −1 range, suggesting that the ionomer with Na counterions has the most extensive ion aggregation.…”

Section: Resultsmentioning

confidence: 99%

Counterion Dynamics in Polyester−Sulfonate Ionomers with Ionic Liquid Counterions

et al. 2011

View full text Add to dashboard Cite

Conventional sodium cations (Na+) in sulfonated polyester ionomers were replaced with ammonium-based ionic liquid counterions. Counterion dynamics were measured by dielectric spectroscopy and linear viscoelastic response via oscillatory shear. Ion exchange from sodium counterions to ionic liquid counterions such as tetramethylammonium and tetrabutylammonium showed an order of 104 increase in conductivity compared with sodium counterions, primarily attributed to weaker ionic interactions that lower the glass transition temperature. Electrode polarization was used in conjunction with the 1953 Macdonald model to determine the number density of conducting counterions and their mobility. Conductivity and mobility exhibit Vogel−Fulcher−Tammann (VFT) temperature dependences and both increased with counterion size. Conducting counterion concentrations showed Arrhenius temperature dependences, with activation energy reduced as counterion size increased. When ether−oxygen was incorporated into the mobile cation structure, self-solvating ability notably increased the conducting ion concentration. Weakened ion pairing interactions prove favorable for fundamental design of single-ion conductors for actuators, as ionic liquid counterions can provide both larger and faster strains, required by such electro-active devices.

show abstract

“…The aggregation results in an increase in viscosity by orders of magnitude over that of unneutralized materials which makes ionomers useful as viscosity enhancers in low-polarity solvents. This thickening ability in the semidilute region depends on the ion content, − neutralizing cation, − and solvent quality. ,, Further, nonpolar ionomer solutions often exhibit shear-thickening and shear-thinning behavior, − making them useful as rheology modifiers.…”

Section: Introductionmentioning

confidence: 99%

Effect of Water on Viscosity and Shear-Thickening Behavior of Telechelic Ionomers in Nonpolar Solvents

Bhargava

Cooper

1998

Macromolecules

View full text Add to dashboard Cite

Quantitative effects of water on the viscosity and rheology of magnesium- and sodium-neutralized dicarboxy-terminated polybutadiene in toluene are reported. A change in the water concentration from 50 to 500 ppm led to a viscosity decrease of 2 orders of magnitude for solutions near the gel concentration. Because of the hygroscopic nature of ionomer solutions, rheological experiments were conducted in a humidity-free environment. The dynamic measurements show that the viscosity reduction is related to a reduction in both the plateau modulus and the terminal relaxation time. The magnitude of shear-thickening decreases and the onset of shear-thickening shifts to higher shear rates with increasing water content.

show abstract

Structure and Thermodynamics in Associating Model Ionomer Solutions

Cited by 7 publications

References 48 publications

Small-Angle Neutron Scattering Studies of Low Polarity Telechelic Ionomer Solutions. 2. Single Chain Scattering

Small-Angle Neutron Scattering Studies of Low Polarity Telechelic Ionomer Solutions. 2. Single Chain Scattering

Counterion Dynamics in Polyester−Sulfonate Ionomers with Ionic Liquid Counterions

Effect of Water on Viscosity and Shear-Thickening Behavior of Telechelic Ionomers in Nonpolar Solvents

Contact Info

Product

Resources

About