Structure and growth kinetics of zirconium hydrous polymers in organic solutions

Singhal, Amit; Beaucage, Gregory; Harris, Michael T.; Toth, L.M.; Keefer, Keith D.; Lin, J. S.; Hu, Michael Z.; Peterson, J.R.

doi:10.1016/s0022-3093(99)00071-x

Cited by 11 publications

(12 citation statements)

References 19 publications

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“…For this reason, it seemed worth looking for a common framework able to describe different mechanisms of growth, yielding either fractal or non- fractal structures, for different preparation conditions. To do that, we have separated the structural aspects of the aggregates from the kinetic process 11,12 that is related to the growth of the polymeric network. 4.1.…”

Section: Resultsmentioning

confidence: 99%

“…10 In previous studies of similar systems, it was established that the aggregation of monomers in the sol phase leads to cylindrical aggregates that eventually grow and build up complex fractal objects. [11][12][13][14][15][16] The aim of this work is to systematically investigate, using the small-angle X-ray scattering (SAXS) technique, the effects of the variation of several chemical parameters, such as [ HNO 3 ]/[Zr(OPr) 4 ] and [H 2 O]/[Zr(OPr) 4 ] molar ratios and [H 2 SO 4 ]/[Zr(OPr) 4 ] weight ratio concentration, on the mechanisms of aggregation of sulfate zirconia prepared by the sol-gel method. The experimental study was performed by in situ SAXS, using sealed and open sample cells, to verify whether the formation of final products with completely different nanostructural properties can be explained in terms of a unified mechanism of growth.…”

Section: Introductionmentioning

confidence: 99%

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Synchrotron SAXS Study of the Mechanisms of Aggregation of Sulfate Zirconia Sols

et al. 2003

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This is a systematic investigation, using in situ synchrotron small-angle X-ray scattering, of the mechanisms of aggregation of sulfate zirconia sols under different preparation conditions. We have studied the effects of the variations of acid, water, and sulfate contents on the process of aggregate growth. These effects were investigated using open and sealed sample cells. It was observed that two clearly different mechanisms govern the aggregation at the beginning and at advanced stages of the process. In the early stages, small needle-shaped clusters are formed. They have a time independent cross-section and progressively grow by increasing their length. At advanced stages, the initially isolated needle-shaped clusters start to build up a 3D structure, their aggregation being governed by the classical mechanism of diffusion-limited cluster aggregation (DLCA). The experimental results also suggested an effect of sulfate concentration on the structure of the aggregates. Even though the structures of the final sols vary markedly due to differences in the chemical and physical preparation conditions, our experimental results suggest that a single and remarkably simple model explains the aggregation process for all the studied solutions.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synchrotron SAXS Study of the Mechanisms of Aggregation of Sulfate Zirconia Sols

et al. 2003

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“…If there are N = ([NIPA]/[BIS])/2 monomers between the cross-link and the sulfonic group, then where m is the number of monomers involved in the persistent length and a is the length of each monomer. Therefore, The parameter c can be roughly estimated considering that for flexible synthetic polymers the persistent length is around 1−2 nm, ,, e.g., 10 monomers ( m = 10) of 2 Å length ( a = 2 × 10 -10 m). The theoretical value of c is then 0.29.…”

Section: Resultsmentioning

confidence: 99%

“…The parameter c can be roughly estimated considering that for flexible synthetic polymers the persistent length is around 1-2 nm, 36,38,39 e.g., 10 monomers (m ) 10) of 2 Å length (a ) 2 × 10 -10 m). The theoretical value of c is then 0.29.…”

Section: Resultsmentioning

confidence: 99%

A New Approach To Design Imprinted Polymer Gels without Using a Template

2001

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With the aim of developing polymeric gels sensitive to external stimuli and able to reversibly adsorb and release divalent ions, we prepared copolymer gels of N-isopropylacrylamide (NIPA) and N,N′cystaminebis(acrylamide) (BAC) weakly cross-linked with N,N′-methylenebis(acrylamide) (BIS). After polymerization, the -S-S-bonds of BAC mers were broken and oxidized to form pairs of sulfonic groups. The juxtaposition of two anionic groups favors the interaction with a divalent cation. Calcium adsorption experiments showed that the gels prepared in this way memorized the position of the pairs of sulfonic groups after swelling and reshrinking. This "imprinting" effect was tested for several concentrations of adsorbing groups and permanent cross-linkers. The control gels prepared with 2-acrylamido-2-methylpropanesulfonic acid (AMPS), where sulfonic groups were randomly distributed, showed difficulty in forming pairs. Their affinity for calcium ions decayed exponentially as a function of cross-linker concentration. In contrast, the affinity of the imprinted gels was much greater than that of random gels and did not decrease with BIS, showing that memorization has been achieved.

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“…The persistent length had been predicted to be around 2 nm, e.g. ∼ 10 monomers (m ∼ 10) of 2 Å length (a = 2 × 10 −10 m) [92][93][94]. Thus, the obtained result is somewhat reasonable.…”

Section: Cross-linker Concentration Dependencementioning

confidence: 99%

Multiple point adsorption in a heteropolymer gel and the Tanaka approach to imprinting: experiment and theory

Ito

Chuang

Alvarez‐Lorenzo

et al. 2003

Progress in Polymer Science

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Heteropolymer gels can be engineered to release specific molecules into or absorb molecules from a surrounding solution. This remarkable ability is the basis for developing gel applications in extensive areas such as drug delivery, waste cleanup, and catalysis. Furthermore, gels are a model system for proteins, many of whose properties they can be created to mimic. A key aspect of gels is their volume phase transition, which provides a macroscopic mechanism for effecting microscopic changes. The phase transition allows one to control the gel's affinity for target molecules through tiny changes in the solution temperature, salt concentration, pH, or the like. We summarize recent experiments that systematically characterize the gel affinity as a function of adsorbing monomer concentration, solution salt concentration, and cross-linker concentration, on both sides of the phase transition. We provide a physical theory that explains the results and discuss enhancements via imprinting.

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Structure and growth kinetics of zirconium hydrous polymers in organic solutions

Cited by 11 publications

References 19 publications

Synchrotron SAXS Study of the Mechanisms of Aggregation of Sulfate Zirconia Sols

Synchrotron SAXS Study of the Mechanisms of Aggregation of Sulfate Zirconia Sols

A New Approach To Design Imprinted Polymer Gels without Using a Template

Multiple point adsorption in a heteropolymer gel and the Tanaka approach to imprinting: experiment and theory

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