Motion of polymers

In addition to giving conformational information, solid state NMR relaxation experiments can be used to probe the thermal motion of polymers in the hydrated cell wall (5). The motion of the polymers can give us clues as to the environment of the polymer. When there are both rigid and mobile polymers within a composite material, NMR spin-diffusion experiments can be used to find out how far apart they are. 

This article gives a comprehensive review of NSE investigations performed on the large-scale motion of polymers of various architectures in melts, networks... 

When the VFT equation was applied every system gave a linear fit (Fig. 9). This implies that ion transport was assisted by segmental motion of polymer chains in a... 

Summary The utility of the NMR parameters longitudinal relaxation time (Tj) and nuclear Overhauser effect (NOE) for a deeper insight into the molecular structure and motion of polymer siloxanes was tested. A few characteristic examples of siloxanes investigated were presented to show problems and results. 

The aim of this work was to find out how to get more information about stereochemistry and molecular motion of polymer methyl- and methyl-phenyl-siloxanes by measuring longitudinal relaxation times, Tj, and nuclear Overhauser effects, NOE, of the individual building blocks. 

Figure 5.5 Effect of scre A/-particle adhesion on the motion of polymer pellets. The zero pressure solids conveying device at Clarkson w/as used for these experiments...

The spectrum of scattered light contains dynamical information related to translational and internal motions of polymer chains. In the self-beating mode, the intensity-intensity time correlation function can be expressed (ID) as... 

Hikichi.K. Molecular motions of polymers having helical conformation. II. J. Phys. Soc. Japan 19,2169 (1964). 

After this paper was completed, a number of studies were carried out which analyzed the structure of the family of steady solutions and the conditions of ignition in spherical and cylindrical vessels. Regarding these studies, see the monograph by Ya.B. et al.2 In this same monograph one may find literature on various applications of the concept of thermal explosion in other problems of physics, in particular, in the physics of polymers where, as was first shown by A. G. Merzhanov and his colleagues, as a result of viscous heating, steady flow of the polymer becomes impossible in the motion of polymer melts. 

TABLE 18.1. Molecular Motions of Polymers with Increasing Thermal Energy... 

Higgins JS, Roots JE (1985) Effect of entanglement on the single-chain motion of polymer molecules in melt samples observed by neutron scattering. J Chem Soc Faraday Trans II 81 757-767... 

Motion of Polymer Chains in Polymer Solutions and Swollen Networks... 

Modern developments in bifurcation and stability theory, which lead on to chaos or turbulence in dynamical systems, only serve to show why it is worth embedding as much complexity as possible within the constitutive description of material properties. There is a sound intellectual case for trying to subsume fine-scale motions of polymer melt molecules within an Oldroyd... 

The motion of polymers in concentrated solution and bulk is of major theoretical and practical concern. For example, the strong dependence of zero-shear viscosity on molecular weight (approximately the 3.4 power) and the marked decrease of viscosity 1) with shear rate y not only bespeak some of the unusual properties of long-chain molecules but also are of essential importance in virtually every processing operation. Yet the reasons for these unusual behaviors have become clear only recently. The reptation con-... 

The absorption of vapor by the surface layer of a polymer film will necessitate some rearrangement of the polymer molecules, and it is reasonable to consider that the more active the segmental motion of polymer chains becomes, the more rapidly the surface layer takes up penetrant to the equilibrium concentration. This implies that the surface concentration gradually approaches an equilibrium value at a finite rate which may depend upon the rate of relaxation motions of the polymer molecules. Crank and Park (1951) expressed this situation by the equation ... 

Examination of the Long-Richman solution to Eq. (1) indicates that the quantity defined previously, i. e., the time for the inflection point on the sigmoid second stage portion, is very nearly equal to 1/2/8, provided D/L2 is not too small compared with /8. If, as has been discussed in section 3.3, it is plausible to interpret / as being related to the rate of relaxation motions of polymer molecules, then the second stage portion should shift to the short time region as the initial concentration of the experiment becomes higher, since as the solid contains more diluent it is more plasticized and thus the chain relaxation becomes more rapid [Fujita and Kishimoto (1958)]. This expectation is borne out by the data shown in Fig. 9. 

At the segment level, the cooperative motions of polymer segments that allow chain movement are the key determinant of the dynamic behavior of a polymer under mechanical stress. The concept of glass transition rests on these segmental motions, which refiect the steric inhibition of backbone conformational relaxation. The impact of backbone conformation on electronic and optical properties is becoming better understood. 

The still faster ( nsec) dynamics of local motions of polymer molecules in dilute solutions have been investigated by Ediger and coworkers (Zhu and Ediger 1995, 1997). They find that the rates of these local motions of a few bonds are not proportional to the solvent viscosity, unless the solvent reorientation rate is fast compared to the polymer local motion. Thus, for local motions (such as bond reorientations) of polymer molecules, Stokes law of drag does not always hold. 

The theoretical aspects of the micro-Brownian motion of polymer chains in solution in connection with problems of the PL are dealt with in Sect. 5. They include the problems of the shape and width of relaxation spectra and the most probable relaxati6n times manifested in the motion of a given labelled chain element, active in the PL, and the problems of the superposition of various types of motions and the anisotropy of local relaxation properties etc. 

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