1984
DOI: 10.1126/science.225.4666.1021
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Periodic Interfacial Precipitation in Polymer Films

Abstract: Interfacial precipitation of silver halides in water-swollen polymer films occurred in complex, multilayered patterns if the concentrations of counterdiffusing reactants were unequal or decreased at different rates. Development of the rapidly forming Liesegang rings, which extend the phenomenon of periodic precipitation to the submicrometer range, is attributable to the combined effect of a moving reaction zone and periodic immobilization of colloidal silver halide.

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Cited by 42 publications
(12 citation statements)
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“…Cross sections of the film prepared at 125 °C show a number of layers of PbS aggregates parallel to the film surface of variable thickness near 1 gm, with variable spacings of tens of micrometers, which is undoubtedly the Liesegang ring phenomenon,19 but with the usual centimeter spacing and millimeter thickness in aqueous media reduced to micrometer size because of the much higher viscosity of the E-MAA copolymer. 20 We found the activation energy of aggregation of 0.25 M PbS (<2.5 nm PbS -4.5 nm PbS) in E-MAA to be 76 kcal. This coincides with an estimate for the energy of flow of the E-MAA copolymer.…”
Section: Sirmentioning
confidence: 81%
“…Cross sections of the film prepared at 125 °C show a number of layers of PbS aggregates parallel to the film surface of variable thickness near 1 gm, with variable spacings of tens of micrometers, which is undoubtedly the Liesegang ring phenomenon,19 but with the usual centimeter spacing and millimeter thickness in aqueous media reduced to micrometer size because of the much higher viscosity of the E-MAA copolymer. 20 We found the activation energy of aggregation of 0.25 M PbS (<2.5 nm PbS -4.5 nm PbS) in E-MAA to be 76 kcal. This coincides with an estimate for the energy of flow of the E-MAA copolymer.…”
Section: Sirmentioning
confidence: 81%
“…This is regarded as a spatial periodic precipitation controlled process, which usually means a series of concentric rings or bands that are parallel to the diffusion front and formed by crystallization. [27][28][29] These phenomena can be seen as various processes in nature such as the formation of gallstones, mother of pearl, rings of trees, and zebra rocks. [30][31][32][33] Therefore, a multistep build-up process controlled by a spatially periodic precipitation mechanism is proposed here to explain the formation of multilayers (Fig.…”
mentioning
confidence: 99%
“…C, the initial separation of reactants leads to the formation of a dynamic reaction front. The presence of such a reaction interface is characteristic of many processes in nature [17][18][19][20][21][22]. Interesting properties of the front are the global reaction rate R͑t͒, the location of the center of the reaction front x f ͑t͒, the width of the front w͑t͒, and the local reaction rate at the center of the front R͑x f , t͒.…”
mentioning
confidence: 99%