Advances in Polymer Science: Vol 134 Neutron Spin Echo Spectroscopy/Viscoelasticity/Rheology (Advances in Polymer Science Vol 134)
By: T Shiga (contributor), D Richter (contributor), M Mours (contributor), H H Winter (contributor), B Ewen (contributor)Hardback
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Viscoelasticandtransportpropertiesofpolymersintheliquid(solution, melt)or liquid-like (rubber) state determine their processing and application to a large extent and are of basic physical interest [1 3]. An understanding of these dynamic properties at a molecular level, therefore, is of great importance. However, thisunderstandingiscomplicatedbythefactsthatdi?erentmotional processes may occur on di?erent length scales and that the dynamics are governed by universal chain properties as well as by the special chemical structure of the monomer units [4,5]. The earliest and simplest approach in this direction starts from Langevin equations with solutions comprising a spectrum of relaxation modes [1 4]. Special features are the incorporation of entropic forces (Rouse model, ) which relax uctuations of reduced entropy, and of hydrodynamic interactions (Zimm model, ) which couple segmental motions via long-range back ow elds in polymer solutions, and the inclusion of topological constraints or entanglements (reptation or tube model, [8 10]) which are mutually imposed within a dense ensemble of chains. Another approach, neglecting the details of the chemical structure and concentratingontheuniversalelementsofchainrelaxation, isbasedondynamic scalingconsiderations[4,11].Inparticularinpolymersolutions, thisapproach o?ers an elegant tool to specify the general trends of polymer dynamics, although it su?ers from the lack of a molecular interpretation. A real test of these theoretical approaches requires microscopic methods, which simultaneously give direct access to the space and time evolution of the segmental di?usion. Here, quasi-elastic scattering methods play a crucial role sincetheyallowthemeasurementofthecorrespondingcorrelationfunctions.In particular, thehigh-resolutionneutronspinecho(NSE)spectroscopy[12 15]is very suitable for such investigations since this method covers an appropriate range in time (0.005)t/ns)40) and space (r/nm [15). Furthermore, the possibilityoflabellingbyhydrogen-deuteriumexchangeallowstheobservation of single-chain behavior even in the melt."
B. Ewen, D. Richter: Neutron Spin Echo Investigations on the Segmental Dynamics of Polymers in Melts, Networks and Solutions.T. Shiga: Deformation and Viscoelastic Behavior of Polymer Gels in Electric Fields.H.H. Winter, M. Mours: Rheology of Polymers Near Liquid-Solid Transitions.
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- ID: 9783540627135
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