Dilute Solution Viscous Properties

The intrinsic viscosity [q] provides a sensitive measure of polymer size and architecture in dilute solution. Equation 7.38 can be used to determine the intrinsic viscosity of a polymer solution from measurements of the solution viscosity q and the solvent viscosity q  

Equations 7.39 and 7.40 are applicable only in dilute solutions where q, is less than about 2. 

In analogy to the treatment of osmotic pressure, results obtained at higher solution concentrations can be linearized using an equation of the form [45]  

Staudinger proposed on empirical grounds that [q] is proportional to the molecular weight of a given polymer-solvent combination [46]. A more general expression 

On dimensional grounds, we would expect the intrinsic viscosity of a polymer in dilute solution to be proportional to the ratio of its hydrodynamic volume to its molecular weight  

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Taking into account the relevance of the range of semi-dilute solutions (in which intermolecular interactions and entanglements are of increasing importance) for industrial applications, a more detailed picture of the interrelationships between the solution structure and the rheological properties of these solutions was needed. The nature of entanglements at concentrations above the critical value c leads to the viscoelastic properties observable in shear flow experiments. The viscous part of the flow behaviour of a polymer in solution is usually represented by the zero-shear viscosity, rj0, which depends on the con-... 

The observed anomaly in the viscous properties of dilute organotin copolymer solutions seems to be attributable to the existence of both intra- and intermolecular associates,due to coordination interactions between SnR3 and C=0 fragments of side groups. 

The overlaps between SPs in semidilute concentrations can be thought of in very similar terms to the entanglements defined above. Supramolecular interactions create large stmctures that physically interact to determine the mechanical response (in this case, viscous flow). The primary relaxation is the diffusion of an SP that is effectively intact on the timescale of the diffusion process. Thus, at a fixed concentration, the SP properties in dilute solution are therefore quite similar to those of covalent polymers of the same molecular weight and molecular weight distribution. 

Abstract Macromolecular coils are deformed in flow, while optically anisotropic parts (and segments) of the macromolecules are oriented by flow, so that polymers and their solutions become optically anisotropic. This is true for a macromolecule whether it is in a viscous liquid or is surrounded by other chains. The optical anisotropy of a system appears to be directly connected with the mean orientation of segments and, thus, it provides the most direct observation of the relaxation of the segments, both in dilute and in concentrated solutions of polymers. The results of the theory for dilute solutions provide an instrument for the investigation of the structure and properties of a macromolecule. In application to very concentrated solutions, the optical anisotropy provides the important means for the investigation of slow relaxation processes. The evidence can be decisive for understanding the mechanism of the relaxation. 

Generally, gels are somewhat intermediate between a solid and a liquid. Under deformation this shows elasticity, but it keeps a permanent memory of its form. Water and dilute solutions do not show any elasticity, they flow under pressure and are purely viscous (Newtonian liquids). In between both viscous-elastic fluids are located. These solutions have the property of a viscous solution and of a solid, depending on the forces applied and on the time scale. Under fast deformation they are elastic, keep a memory of their shape, but under slow deformation they behave like viscous solutions. 

In practice, very dilute solutions are used in AAS, so that the physical properties of the sample solutions are close to those of the pure solvent (water). Physical properties will be changed if the sample solution contains large amounts of acids, salts, or organic compounds. Concentrated solutions are viscous which may cause problems with the sample intake and nebulization. The absorption signal decreases with increasing viscosity. Viscosity... 

The morphology of the spun structures is influenced by the properties of the polymer solution, namely viscosity, surface tension and density. As the stability of the jet depends of the viscous and viscoelastic properties of the polymer solution, the choice of solvent is a critical factor. Therefore, the solvent should be chosen according to its ability to dissolve the polymer in sufficient amounts to make a viscous solution. When a solid polymer is dissolved in a solvent, the viscosity of the solution is proportional to the polymer concentration. Thus, higher polymer concentration produces larger fibre diameter, whereas a diluted solution leads to breakage of the polymer fibre into droplets due to the effects of surface tension [84]. 

Papkov, S. P. Estimation of Kuhn segment value of rigid-chain polymers by viscous properties of diluted solutions. High-Molecular Compounds, B, 1982, 24(11), 869-873. 

In a simple infinitely diluted solution, the parameters for charge transport can be linked to some of the solvent s properties. In fact, the movement of a solvated ion in the solution can be viewed as similar to the displacement of a rigid sphere in a viscous medium. 

The polymer molecules are isolated from each other in solution. They take on the statistically most likely conformation and form a coil. The dimension of this coil in dilute solution is what affects the viscous properties of a polymer solution. Despite of the regional isolation between the coils, as shown in Fig. 4.1, there are interactions that take effect during the flow process. These interactions are only prevented when the state of the so-called ideal dilute solution is reached. In this case, the polymer concentration c O and the single polymer molecule only interacts with the solvent. The following description for the determination of the intrinsic viscosity is based on this idealized state of solution. 

This chapter is about semidilute solutions, c > c. We learn both thermodynamics and dynamics. The properties of semidilute solutions are drastically different from those of dilute solutions. With a mere tenfold increase in the concentration, the osmotic pressure can easily increase by a factor of several hundred. In the ideal solution, in contrast, the osmotic pressure is proportional to c. Furthermore, the overall chain motion is slow in semidilute solutions because the chains are entangled semidilute solutions of a high-molecular-weight polymer can barely flow. The solutions are highly viscous and may even behave like elastic rubber. 

In studying the viscous properties of dilute solutions of rigid-chain polymers [10-16], it was shown that the Martin equation [9] applies to them, as to solutions of flexible-chain polymers, for low concentrations c ... 

Processes such as diffusion, sedimentation and viscous flow involve the motion of individual molecules. When a polymer molecule moves through a dilute solution it undergoes frictional interactions with solvent molecules. The nature and effects of these frictional interactions depend upon the size and shape of the polymer molecule as modified by its thermodynamic interactions with solvent molecules. Thus the chain dimensions can be evaluated from measurements of the frictional properties of a polymer molecule. 

Ellis AT, Ting RY, Napolink RH (1970) Some effects of storage and shear history on the friction reducing properties of dilute polymer solutions Prog Astronaut Aeronaut 70 Viscous flow flow drag reduction (AIAA) 532... 

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