Molecular motion of polymers in solution

Many solid polymers are sensitive to heat stimulation and show characteristic REVERSIBLE PHASE TRANSITIONS at the GLASS TRANSITION TEMPERATURE and MELTING TEMPERATURE depending mainly on their own primary structure. This thermal sensitive property is being used in the fabrication of thermoplastic materials into any desired form in a similar means to that of fibers in the case of nylon, polyesters or films and other three dimensional products. In addition to the thermoplastic properties of polymers in the solid state, the molecular motion of polymers in solution is also achieved by thermal stimulation and has extensively been studied after pioneering works of Flory-Huggins. The effects of such thermal stimulation were detected experimantally as "sol-gel transformation", "viscosity changes", "phase separation" and so on. Egg-white and other aqueous solutions of natural proteins such as enzymes and hormones show such detectable behavior in the form of... 

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-... 

VII. Molecular Motion and Magnetic Relaxation of Polymers in Solution... 

Nuclear magnetic relaxation parameters give important information on molecular motion and have become more and more familiar to and inevitable for NMR users after the introduction of the Fourier transform (FT) method to NMR technology. The relaxation parameters are also of essential importance in adjusting data acquisition conditions in FT-NMR measurements to obtain quantitative data. Section 6 covers the reliability of spin-lattice relaxation time (7)) and the nuclear Overhauser enhancement (NOE) factor of polymers in solution and the tacticity dependence of H- and 3C-7) values of vinyl polymers in solution. 

Figures 3.9 and 3.10 show the temperature dependencies of Ti and NOE of the CH2 (rrr) of the same PMMA solution and the results (solid and broken curves) simulated by the second-order model-free treatment with p = 3 [17]. Here, the Arrhenius equation was assumed for the respective correlation times tj = tio exp(AEi/RT) and ta/ = ta,o exp(AEA,/RT). In this case the simulated results with p = 3 are also in good accord with the experimental results, indicating the validity of the model-free treatment. Similar analyses of the temperature dependencies of the Tj were successfully performed for the rubbery components of the solid polyesters with different methylene sequences [20, 21]. These results are also well analyzed by the second-order model-free treatment with p = 3. There are a large number of the publications of the temperature dependencies of Ti and NOE analyzed by different models of molecular motions for polymers in the dis-...

In most cases, the flow properties of polymers in solution or in a molten state are Newtonian, pseudoplastic, or a combination of both. In the case of liquid crystal polymer solutions, the flow behavior is more complex. The profound difference in the rheological behavior of ordinary and liquid crystalline polymers is due to the fact that, for the flrst ones, the molecular orientation is entirely determined by the flow process. The second ones are anisotropic materials already at equilibrium (Acierno and Brostow 1996). The spontaneous molecular orientation is already in existence before the flow and is switched on, varying in space, over distances of several microns or less (polydomain). If one ignores the latter, one can discuss the linear case (slow flow) as long as the rate of deformation due to flow (the magnitude of the symmetric part of the velocity gradient) is lower than the rate at which molecules rearrange their orientational spread by thermal motions. 

Liao CC, Hou SS, Wang CC, Chen CY (2010) Electrospinning fabrication of partially crystalhne bisphenol A polycarbonate nanofibers the effects of molecular motion and conformation in solutions. Eur Polym J 51 2887-2896... 

Viscoelastic and transport properties of polymers in the liquid (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, this understanding is complicated by the facts that different motional processes may occur on different 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],... 

Nakamura, K., R. Eodo, and M. Takeda. 1977. Study of molecular motion of block copolymers in solution by high-resolution proton magnetic resonanfcdPolym. Sci. Polym. Phys. EtB 2095-2101. 

In nondilute polymer solutions and melts, the polymer coils interpenetrate each other enough that the molecular motions of one chain are greatly slowed by the interfering effects of other chains. These interferences are attributed to intermolecular entanglements. 

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