Showing papers by "James E. Martin published in 1986"
TL;DR: Static and dynamic light scattering and small-angle x-ray scattering measurements are reported for vapor-phase aggregates of silica, and the Rayleigh linewidth is found to vary as the 2.7 power of the momuntum transfer for large momentum transfer.
Abstract: Static and dynamic light scattering and small-angle x-ray scattering measurements are reported for vapor-phase aggregates of silica. From the static scattering data the fractal dimension is found to be approx.1.84 +- 0.08, in agreement with the prediction of the cluster-cluster aggregation model. The Rayleigh linewidth is found to vary as the 2.7 power of the momuntum transfer for large momentum transfer.
78 citations
TL;DR: The static scattering exponent for the diluted sol was found to be in good agreement with the percolation prediction of 16, and the quasielastic scattering measurements demonstrate the flexibility of the sol clusters as discussed by the authors.
Abstract: Solutions of tetramethoxysilicon are reacted until very near the sol-gel transition At this point the sol is diluted and elastic and quasielastic light scattering measurements are made at intermediate momentum transfer The static scattering exponent for the diluted sol is found to be in good agreement with the percolation prediction of 16, and the quasielastic scattering measurements demonstrate the flexibility of the sol clusters
33 citations
TL;DR: In this article, a combination of static and dynamic data was used to show that lattice animal-like structures are formed which break apart and swell on dilution, and they observed a threshold for large-scale polymerization when there are 2.5 bridging groups per A1.
Abstract: Alumina polymers are studied at various degrees of branching using X-ray and light scattering. A combination of static and dynamic data shows that lattice animal-like structures are formed which break apart and swell on dilution. We observe a threshold for large-scale polymerization when there are 2.5 bridging groups per A1. Below this value only polynuclear species occur whereas above this value the system gels.
24 citations
TL;DR: The linewidth and relaxation time are found to be fractional powers of the momentum transfer if the distribution of fractal sizes is a power law, in agreement with recent experimental findings.
Abstract: A theory is given for the momentum-transfer dependence of the quasielastic-scattering linewidth and relaxation time for solutions of surface and mass fractals. The linewidth and relaxation time are found to be fractional powers of the momentum transfer if the distribution of fractal sizes is a power law, in agreement with recent experimental findings.
23 citations
TL;DR: Le polymere marque est dilue (polystyrene) and le polymere solvant/polymethylvinylether est semidilue as mentioned in this paper, i.e.
Abstract: Le polymere marque est dilue (polystyrene) et le polymere solvant/polymethylvinylether est semidilue
18 citations
TL;DR: In this article, light scattering measurements of the relaxation times of internal modes of single polymer chains in semidilute solution are reported for dilute high molecular weight polystyrene in a semi-linear poly(vinylmethylether)/toluene host.
Abstract: Dynamic light scattering measurements of the relaxation times of internal modes of single polymer chains in semidilute solution are reported for dilute high molecular weight polystyrene in a semidilute poly(vinylmethylether)/toluene host. Since PVME is index matched by toluene, these light scattering measurements probe the dynamics of the isolated polystyrene chains and are insensitive to the collective fluctuations of the PVME host. The principle result is that the Rayleigh linewidth scales like the third power of the momentum transfer regardless of the concentations of the semidilute polymer. This is in apparent contradiction to current theories of hydrodynamic screening in semidilute solutions, which predict a fourth power dependence for the linewidth.
11 citations
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TL;DR: In this paper, the dynamics of colloidal aggregates were studied in a dilute suspension by quasi-elastic light scattering and the results for polymers and colloidal particles were reviewed.
Abstract: Apart from linear polymers, the dynamic properties of fractal structures are essentially unexplored. This paucity of data is due to the fact that dynamic light scattering, the technique of choice for such studies, is expected to display unique features only for objects which are fractal over dimensional scales comparable to the wavelength of light (5000A). Recently, however, colloidal aggregates were shown 1 both to be fractal over lengths up to and to display interesting dynamics. (2) Our purpose here is not only to discuss the dynamics of such aggregates, but also to review the results for polymers and colloidal particles. In all cases, these systems are studied in a dilute suspension by quasi-elastic light scattering.
1 citations