Polymer dynamic heterogeneity

The onset of glass formation in a polymer melt is associated with the development of orientational correlations that arise from chain stiffness. At the temperature Ta, there is a balance between the energetic cost of chain bending and the increased chain entropy, and below this temperature orientational correlations are appreciable while the melt still remains a fluid. Such a compensation temperature has been anticipated based on a field theoretic description of semiflexible polymers by Bascle et al. [120]. The temperature 7a is important for describing liquid dynamics since the orientational correlations (and dynamic fluid heterogeneities associated with these correlations) should alter the polymer dynamics for T < Ta from the behavior at higher... 

It should be kept in mind that do and Do are really mean values, recognizing the fact that glassy polymers are heterogeneous and contain a distribution of structural and dynamic states (28). As such, these parameters are dependent on the nature of the penetrant and of the polymer (13), as well as the distribution of properties in the polymer. 

In proton T2 experiments conducted by Litvinov [18] a strong dynamic heterogeneity in the fraction of EPDM bound to carbon black could also be detected an immobilised EPDM layer covering the carbon black surfaces and a mobile EPDM part outside of this interfacial layer. In dynamic-mechanical experiments by Haidar [19], it was found that the polymer layer on the filler surface had glass-like mechanical properties. 

Books. M. W. Roberts, Chemistry of the Metal-Gas Interface , Oxford University Press, Oxford, 1978 F. C. Tompkins, Chemisorption of Gases on Metals , Academic Press, London, 1978 Experimental Methods in Catalysis Research , ed. R. B. Anderson and P. T. Dawson, Academic Press, London, 1976 Chemistry and Physics of Solid Surfaces , ed. R. Vanselow and S. Y. Yong, CRC Press, Cleveland, Ohio, 1977 Advances in Characterisation of Metal and Polymer Surfaces , ed. L. H. Lee, Academic Press, New York, 1976 K. Tamaru, Dynamic Heterogeneous Catalysis , Academic Press, London, 1978 The Solid-Vacuum Interface , ed. A. van Oostrom and M. J. Sparnay, Surface Sci., 1977, 64 Electron Spectroscopy , ed. C. R. Brundle and A. D. Baker, Academic Press, New York, 1977, Vol. 1 Auger Electron Spectroscopy (Bibliography 1925—1975) , compiled by D. T. Hawkins, Plenum, New York, 1977. 

A H-NMR study of the dynamics of the phenyl ring of a side-chain liquid crystal polymer has been carried out. The rotation of the phenyl ring about its paru-axis has been attributed to the relaxation process and a Gaussian distribution of the activation energy points to a dynamic heterogeneity of the... 

From the early 1980s, it was well accepted that the desired performance of a polymer-based heterogeneous material would pass through a well-optimized interaction level across the interphases between the components (4). The interphase is defined as the dynamic and finite spatial region placed between the border of each of the two different phases where momentum, mass, and energy transport phenomena may occur. 

There could be two possible reasons for this apparently contradictory situation,. First, in the above discussion, we adopted a diffusion constant that was evaluated from the diffusion constant of polymer chains at the interface between two bulk polymeric layers [72]. Recent measurements have revealed the existence of heterogeneous dynamics in confined geometries such as thin films and nanopores [73,74]. For stacked thin films of polymers, the dynamics vary with an essential dependence on the distance of the layer of interest from the free surface or from the substrate [75]. If such dynamical heterogeneity is taken into account, the diffusion of polymer chains could be restricted by the existence of an immobile region. 

Keywords Dynamic heterogeneity Inelastic and quasielastic neutron scattering Polymer thin film... 

In this review, we investigate the dynamic heterogeneity or anomalous dynamics of polymer thin films at temperatures from far below bulk Tg to above bulk Tg by neutron scattering. We also discuss the effect of dynamic heterogeneity on the resulting glassy and molten dynamics of polymer thin films. 

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