Polymer relaxation process

The designations Y and N in the scheme refer to the observation of tracking between specific experimental quantities. These researchers use the term tracking to signify that a plot of one experimental quantity versus another is independent of the scan rate and scan direction. They also note that tracking merely signifies that a pseudoequilibrium exists on the selected time scale of the experiment. Slower polymer relaxation processes may not be detected electrochemically. 

We end this section with a discussion of the interrelationship between mobile species transport and polymer relaxational processes in permselective electroactive polymer films when the latter undergo redox switching. This discussion is based to a large extent on a paper recently presented by Hillman and Bruckenstein. " ... 

Structure. Polymer relaxation processes (such as those involving extended segmental motion and chain (dis)entanglement) are manifest only on the longest time scales. Local segmental motion occurs much more rapidly, and may be a prerequisite for ion and neutral species transport. We conclude that redox switching is therefore quite a complex process. 

Star polymer relaxation process. Individual arms cannot reptate rather, they relax by retracting from the tubes created by entanglements with surrounding polymers. 

Fig. 2. Plot of peak intensity versus temperature for the polymer chain CH2 asymmetric stretching mode (2924 cm" ) and the phenyl ring C-H out-of-plane bending mode (699 cm" absorption peaks from 20°C to 2S0 C. Slope changes in both profiles indicate the presence of polymer relaxation processes. After Boyer, refs. 6 and 13. 

In tire limit of a small defonnation, a polymer system can be considered as a superjDosition of a two-state system witli different relaxation times. Phenomenologically, tire different relaxation processes are designated by Greek... 

However, the relaxation process is rather slow whereas thermoplast processing calls for almost instantaneous cooling of the melt after molding and due to this fact the chain structure is not restored. From this it follows that in molding a conducting polymer composite the cooling of the melt should have a speed comparable to the speed of restoration of the filler secondary structure, otherwise the conductivity of the polymer composite will be reduced. 

Holzmiiller, W. Molecular Mobility, Deformation and Relaxation Processes in Polymers. Vol. 26, pp. 1 —62. 

Williams, G. Molecular Aspects of Multiple Dielectric Relaxation Processes in Solid Polymers. Vol. 33, pp. 59—92. 

Wilkes, G. L. The Measurement of Molecular Orientation in Polymeric Solids. Vol. 8, pp. 91-136. Williams, G. Molecular Aspects of Multiple Dielectric Relaxation Processes in Solid Polymers. Vol. 33, pp. 59-92. 

In order to obtain the current consumed during the nucleated relaxation process under a constant potential, we assume that a stationary density of charge (<, ) will be stored in the polymer at the polarization potential E. The storage of these charges is controlled by both conformational relaxation (3r) and diffusion ( processes, so... 

The rate and type of release can be analyzed by the expression Mt/Moo=ktn (76). In the case of pure Fickian diffusion n = 0.5, whereas n > 0.5 indicates anomalous transport, i.e., in addition to diffusion another process (or processes) also occurs. If n = 1 (zero order release), transport is controlled by polymer relaxation ("Case II transport") (76). The ln(Mt/Mco) versus In t plots, shown in Figure 4, give n = 0.47 and 0.67 for samples A-9.5-49 and A-4-56, respectively. Evidently theophylline release is controlled by Fickian diffusion in the former network whereas the release is... 

When a penetrant diffuses into a polymer, the perturbation will cause the polymer molecules to rearrange to a new conformational state. The rate at which this conformational adaptation occurs depends on the mobility of the polymer chains. At temperatures well above the glass transition, this occurs quite rapidly and the diffusive process resembles that in the liquid state. At temperatures near or below the glass transition, the conformational change does not take place instantaneously. Instead, there is a finite rate of polymer relaxation induced by the... 

Although many different processes can control the observed swelling kinetics, in most cases the rate at which the network expands in response to the penetration of the solvent is rate-controlling. This response can be dominated by either diffu-sional or relaxational processes. The random Brownian motion of solvent molecules and polymer chains down their chemical potential gradients causes diffusion of the solvent into the polymer and simultaneous migration of the polymer chains into the solvent. This is a mutual diffusion process, involving motion of both the polymer chains and solvent. Thus the observed mutual diffusion coefficient for this process is a property of both the polymer and the solvent. The relaxational processes are related to the response of the polymer to the stresses imposed upon it by the invading solvent molecules. This relaxation rate can be related to the viscoelastic properties of the dry polymer and the plasticization efficiency of the solvent [128,129],... 

This averaging process somewhat obscurses the relationship between Pf and S(Q,t). For many relaxation processes, however, where the quasi-elastic width varies with power laws in Q, the smearing of (12) is of no practical importance. For example, for internal relaxation of polymers in dilute solution, we have S(Q, t) = S(Q2t2/3) [34]. Since Q varies with /X and t with 3, the wavelength dependence drops out completely. For illustration, Fig. 3 shows a technical... 

We have speculated that when the melt is kept above the melting temperature, ve gradually increases with an increase of At and approaches the equilibrium ve (ve = 1). It was shown that the melt relaxation process takes a long time, i.e., it takes several hours or a few days depending on the annealing temperature (Tmax) and Mn. However, this experimental fact was indirect evidence of the role of entanglement in the nucleation of polymers. 

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