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Full-Text Articles in Chemical Engineering
On The Generalized Borel Transform And Its Application To The Statistical Mechanics Of Macromolecules, Marcelo Marucho, Gustavo A. Carri
On The Generalized Borel Transform And Its Application To The Statistical Mechanics Of Macromolecules, Marcelo Marucho, Gustavo A. Carri
College of Polymer Science and Polymer Engineering
We present a new integral transform called the generalized Borel transform (GBT) and show how to use it to compute distribution functions used to describe the statistical mechanics of macromolecules. For this purpose, we choose the random flight model (RFM) of macromolecules and show that the application of the GBT to this model leads to the exact expression of the polymer propagator (two-point correlation function) from which all the statistical properties of the model can be obtained. We also discuss the mathematical simplicity of the GBT and its applicability to macromolecules with other topologies. (C) 2003 American Institute of Physics.
Yieldlike Constitutive Transition In Shear Flow Of Entangled Polymeric Fluids, Prashant Tapadia, Shi-Qing Wang
Yieldlike Constitutive Transition In Shear Flow Of Entangled Polymeric Fluids, Prashant Tapadia, Shi-Qing Wang
College of Polymer Science and Polymer Engineering
We describe an unexpected constitutive transition in entangled polymer solutions. At and beyond a critical stress, the initial spatially homogeneous and well-entangled sample transforms from its entangled (coiled) state into a fully disentangled (stretched) state over a period during which the resulting shear rate increases in a spatially inhomogeneous fashion. In the mode of controlled shear rate, the sample exhibits a stress plateau over three decades. Flow birefringence and normal stress observations unravel additional features of these flow phenomena.
Observation Of Novel Liquid-Crystalline Phase Above The Bulk-Melting Temperature, Keshav S. Gautam, Satyendra Kumar, Didier Wermeille, Doug Robinson, Ali Dhinojwala
Observation Of Novel Liquid-Crystalline Phase Above The Bulk-Melting Temperature, Keshav S. Gautam, Satyendra Kumar, Didier Wermeille, Doug Robinson, Ali Dhinojwala
College of Polymer Science and Polymer Engineering
In this paper, we show that a noncrystalline but ordered smectic-like phase exists above the bulk-melting temperature (T-m) at poly(n-alkyl acrylates)-air interface. The surface ordered phase is one monolayer thick and undergoes a sharp transition from order to disorder 10degreesC above T-m for n=22. The presence of a surface phase that does not exist in the bulk has important implications in the design of thermally responsive adhesives.
Relaxation Of A Rubbed Polystyrene Surface, Alexander D. Schwab, Ali Dhinojwala
Relaxation Of A Rubbed Polystyrene Surface, Alexander D. Schwab, Ali Dhinojwala
College of Polymer Science and Polymer Engineering
The relaxation dynamics of a rubbed polystyrene (PS) surface have been characterized using infrared-visible sum frequency generation spectroscopy (SFG). The SFG results were compared with previous relaxation of retardation measurements, and the results show that the rubbed PS surface has the same T(g) as the bulk where T(g) is defined as tau(T(g))=5 s, however, the surface has a lower activation energy (DeltaE) and a larger stretching exponent (beta(KWW)) than bulk PS. This indicates that the surface region relaxes more quickly than the bulk. The thickness of this region of lower DeltaE and larger beta(KWW) is estimated to be roughly 12 …