“…The error bars represent standard deviations. For flux measurements through polymer composites, relative standard deviations of ≤10% are good, with ±20% not uncommon. − 2 Dependence of the effective flux of hydroquinone through neutron track-etched polycarbonate membrane/20% cross-linked poly(4-vinylpyridine) composites on the pore radius. The cross-linked agent is 1,6-dibromohexane.…”
Section: Resultsmentioning
confidence: 99%
“…Neutron track-etched polycarbonate membranes (Poretics Corp.) are transversed with parallel cylindrical pores (pore densities of (0.3-6) × 10 8 pores/cm 2 ). Composites were formed by soaking 12,14 the polycarbonate membranes in the poly(4-vinylpyridine) solution for approximately 30 min. The membranes were touched against the rim of the container to remove excess polymer solution from the outer surface of the membrane.…”
Section: Methodsmentioning
confidence: 99%
“…Flux through heterogeneous matrices has been an important issue in microstructured ion exchange polymers, as well as in the design of ion-selective systems. − Fitch and co-workers − have characterized the impact of micro- and nanostructural heterogeneity on flux through clay layers. For composites of Nafion and neutron track-etched polycarbonate, a correlation between a characteristic dimension of the composites (pore radius) and the measured flux has been demonstrated. − …”
Section: Introductionmentioning
confidence: 90%
“…A solution of 5% w/v poly(4-vinylpyridine) (Scientific Polymer Products, Inc.) in 2-propanol (EM Science) was prepared, and sufficient cross-linking agent was added to obtain 26% crosslinking. For most of the experiments, the cross-linking agent was either Composites were formed by soaking 12,14 the polycarbonate membranes in the poly(4-vinylpyridine) solution for approximately 30 min. The membranes were touched against the rim of the container to remove excess polymer solution from the outer surface of the membrane.…”
Section: Methodsmentioning
confidence: 99%
“…For composites of Nafion and neutron track-etched polycarbonate, a correlation between a characteristic dimension of the composites (pore radius) and the measured flux has been demonstrated. [12][13][14] If the local flux is influenced by the heterogeneity of the matrix, the measured flux will correlate with the dimensions which characterize the heterogeneity of the matrix. In the study of Nafion/neutron track-etched composites, a simplistic model for the dependence of the measured flux on a characteristic dimension of the composites (pore radius) was developed.…”
For any heterogeneous matrix with a parametrizable geometry, a model is provided to determine a microscopic, local flux profile within the matrix from the macroscopic, experimentally measured flux of a probe species. By analyzing the dependence of the measured flux on the geometric parameters that describe the matrix, a mathematical function describing a local flux profile within the matrix is obtained. Example applications of the model include composites of Nafion and neutron track-etched polycarbonate membranes. Composites of neutron track-etched polycarbonate membranes and 20% cross-linked poly(4-vinylpyridine) are also described. The measured flux of hydroquinone through the composites varies with r o -1 , where r o is the pore radius, a characteristic dimension of the matrix. The measured flux is characterized by a second-order polynomial in r o -1 . The local flux profile is found by application of the model and is shown to be higher toward the center of the pore. Poly(4-vinylpyridine) is cross-linked with various dibromoalkanes, with 2-8 and 12 carbons. A quadratic relationship is found between the measured flux and the chain length of the cross-linking agent, with a minimum for 1,6-dibromohexane. Effects of inter-and intrachain cross-linking are discussed.
“…The error bars represent standard deviations. For flux measurements through polymer composites, relative standard deviations of ≤10% are good, with ±20% not uncommon. − 2 Dependence of the effective flux of hydroquinone through neutron track-etched polycarbonate membrane/20% cross-linked poly(4-vinylpyridine) composites on the pore radius. The cross-linked agent is 1,6-dibromohexane.…”
Section: Resultsmentioning
confidence: 99%
“…Neutron track-etched polycarbonate membranes (Poretics Corp.) are transversed with parallel cylindrical pores (pore densities of (0.3-6) × 10 8 pores/cm 2 ). Composites were formed by soaking 12,14 the polycarbonate membranes in the poly(4-vinylpyridine) solution for approximately 30 min. The membranes were touched against the rim of the container to remove excess polymer solution from the outer surface of the membrane.…”
Section: Methodsmentioning
confidence: 99%
“…Flux through heterogeneous matrices has been an important issue in microstructured ion exchange polymers, as well as in the design of ion-selective systems. − Fitch and co-workers − have characterized the impact of micro- and nanostructural heterogeneity on flux through clay layers. For composites of Nafion and neutron track-etched polycarbonate, a correlation between a characteristic dimension of the composites (pore radius) and the measured flux has been demonstrated. − …”
Section: Introductionmentioning
confidence: 90%
“…A solution of 5% w/v poly(4-vinylpyridine) (Scientific Polymer Products, Inc.) in 2-propanol (EM Science) was prepared, and sufficient cross-linking agent was added to obtain 26% crosslinking. For most of the experiments, the cross-linking agent was either Composites were formed by soaking 12,14 the polycarbonate membranes in the poly(4-vinylpyridine) solution for approximately 30 min. The membranes were touched against the rim of the container to remove excess polymer solution from the outer surface of the membrane.…”
Section: Methodsmentioning
confidence: 99%
“…For composites of Nafion and neutron track-etched polycarbonate, a correlation between a characteristic dimension of the composites (pore radius) and the measured flux has been demonstrated. [12][13][14] If the local flux is influenced by the heterogeneity of the matrix, the measured flux will correlate with the dimensions which characterize the heterogeneity of the matrix. In the study of Nafion/neutron track-etched composites, a simplistic model for the dependence of the measured flux on a characteristic dimension of the composites (pore radius) was developed.…”
For any heterogeneous matrix with a parametrizable geometry, a model is provided to determine a microscopic, local flux profile within the matrix from the macroscopic, experimentally measured flux of a probe species. By analyzing the dependence of the measured flux on the geometric parameters that describe the matrix, a mathematical function describing a local flux profile within the matrix is obtained. Example applications of the model include composites of Nafion and neutron track-etched polycarbonate membranes. Composites of neutron track-etched polycarbonate membranes and 20% cross-linked poly(4-vinylpyridine) are also described. The measured flux of hydroquinone through the composites varies with r o -1 , where r o is the pore radius, a characteristic dimension of the matrix. The measured flux is characterized by a second-order polynomial in r o -1 . The local flux profile is found by application of the model and is shown to be higher toward the center of the pore. Poly(4-vinylpyridine) is cross-linked with various dibromoalkanes, with 2-8 and 12 carbons. A quadratic relationship is found between the measured flux and the chain length of the cross-linking agent, with a minimum for 1,6-dibromohexane. Effects of inter-and intrachain cross-linking are discussed.
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