Local relaxation processes

Finally, it is interesting whether local relaxation processes of the glassy matrix facilitate ionic diffusion. For phosphate glasses and borate glasses, 31P and nB NMR spin-lattice relaxation studies gave evidence for some coupling of ion and matrix dynamics below Tg. Moreover, it was reported that local rearrange-... 

Anew experimental method based on the polarization-selective photochromic reactions is proposed to monitor extremely slow reorientation dynamics of molecular tracers in glassy polymer matrix. The correlations between the local relaxation processes of polymers and the reorientation dynamics of the tracers with different sizes are found from the experimental results obtained by this method. 

Reorientation dynamics of molecular tracers in polymers is not only important for the understanding of slow relaxation phenomena in glassy polymers but plays also a critical role in practical problems such as molecular design of nonlinear optical materials with long-term stability based on dyes/polymers complexes. We show here the reorientation dynamics of molecular tracers in glassy polymers obtained by the armealing-after-irradiation method described below. These experimental results are compared to the local relaxation processes of glassy polymers obtained by the already established measurement techniques such as dielectric relaxation and solid state NMR. Finally, the molecular interpretation of the relaxation of free-volume distribution in polymers will be discussed. 

The fluorescence intensity of quinoline derivatives has been found to increase dramatically with an increase in the molecular weight of the host polystyrene. " This is attributed to a decrease in the free volume in the polymer matrix restricting molecular rotation/motion of the fluorophore. Similar effects have been observed for juliodinemalononitrUe in different stereo-regular poly(methyl methacrylates), and temperature effects on the luminescence properties of indole and coumaric acid derivatives in different polymer matrices showed abrupt changes in emission intensity at temperatures which correspond to the onset of local relaxation processes in the polymer. ... 

The occurrence of several types of local relaxation processes apparent in the PL of macronwiecules with anthracene LG has been established experimentally ... 

The models that consider this approach are largely based on the assumption of effectively homogeneous local relaxation processes related to transport in each of the phases and electrical charge exchange between them. Thus, the complex problem of an uneven distribution of electrical current and potential inside the electrode can be described analytically, and impedances can be calculated. Furthermore the models may be conveniently pictured as a double-channel transmission line (Fig. 3.5). In several papers, the theory of the impedance of porous electrodes has been extended to cover those cases in which a complex frequency response arises in the transport processes [100] or at the inner surface [194,203]. 

Fig. 1 were slightly raised to improve the agreement with the experimental data. Other experimental observables such as dielectric relaxation [12] and the coherent dynamic structure factor for neutron spin echo [13] have also been calculated from simulations and used to judge the realism of the local relaxation processes in the simulations. 

The first part describes the volume of a hypothetical system without a-modes, being determined by the hard cores of the molecules, the anharmonic-ity of the vibrations and possible effects of local relaxation processes. The second term AVa accounts for the free volume produced by the a-modes. An analogous description is suggested for the enthalpy and we formulate correspondingly... 

Figure 26.7 Comparison of the normalized dielectric loss spectra for the local relaxation process of PVPh/PMMA blends at 60°C. Reprinted with permission from Ref [43].

Trancong, Q., Chikaki, S., and Kanato, H. (1994) Relationship between reori-entational motions of a photochromic dopant and local relaxation processes of a glassy polymer matrix. Polymer, 35, 4465-4469. 

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