Solvents polymer solutions

Harrington, MG Lee, KH Bailey, JE Hood, LE, Sponge-Like Electrophoresis Media Mechanically Strong Materials Compatible with Organic Solvents, Polymer Solutions and Two-Dimensional Electrophoresis, Electrophoresis 15, 187, 1994. 

Diffusivity, 15 671-675 effective, 15 729-730 in gases and vapors, 15 673-675 in solvents, polymer solutions, and gels, 15 672-673... 

As discussed above, we believe adsorption becomes less important and absorption (swelling) becomes more important as the size of the added alkyl group increases. Since the x parameter describes the "goodness" of the solvent-polymer solution, and has nothing to do with surface interactions, the more reliable x parameter will be obtained for the O-octylated extract-benzene system. Even so, the ground O-octylated extract possesses considerable surface area and any adsorption of benzene onto surfaces will lead to errors in x-Sorption experiments were therefore conducted on the unground extract, which possessed only 11 w /g surface area, x was determined to be 0.65, which was independent of pressure. 

In a recent study, as the first trial case, a liquid injection technique was applied to a dry blending system (25). This introductory application concerns the study of the interaction of particles with injected liquid (solvent, polymer solution, colloidal solution, etc.) and will be reported elsewhere. 

Keywords Gas solubility Mixed solvents Polymer solutions... 

M = 110 000 g mol fall in the crossover between the two limiting cases of Eq. (8.40) and do not obey the scaling of either clean limit. Unfortunately, the molar mass range of 20000 < M<200OOOgmoP is the important range for commercial polymers, and it corresponds to the crossover for most good solvent/polymer solutions. 

G. Raos and G. Allegra, Chain collapse and phase separation in poor-solvent polymer solutions a unifiedmoleculardescription,J. C/tew. P/tys. 104 1626(1996). 

INO Inomata, H., Honma, Y., Imahori, M., and Aral, K., Fundamental study of de-solventing polymer solutions with supercritical CO2, Fluid Phase Equil, 158-160, 857,1999. 

In addition to values for Dq and [ n ] accurate values for the hydrodynamic coefficients and P are required to use equation (22), The individual values of and P vary unpredictably for solvent-polymer solution combinations. However several investigators have... 

The latter part of the equation is valid for a binary solvent-polymer solution and vr is the infinite dilution activity coefficient of the solvent. 

The FH model for the activity coefficient, proposed in the early 1940s by Flory and Huggins, is a famous Gibbs free energy expression for polymer solutions. For binary solvent-polymer solutions and assuming that the parameter of the model, the so-called FH interaction parameter x,2, is constant, the activity coefficient is given by the equation ... 

K. J. Zhang, M. E. Briggs, R. W. Gammon, and J. V. Sengers. Thermal and mass diffusion in a semidilute good solvent-polymer solution. J. Chem. Phys., Ill (1999), 2270-2282. 

This book is divided into nine chapters. Chapter 1 describes the composition of polymer compounds and the chemical nature and physical properties of ingredients. Chapters 2 through 5 describe binary compounds of polymers with solid particles (Chapter 2), solvents (polymer solutions) (Chapter 3), additives such as stabilizers and curatives (Chapter 4), and a second polymer (blends) (Chapter 5). We turn to ternary compounds in Chapters 6 and 7. Chapter 6 discusses polymers with two low molecular weight liquids, two polymers with one low molecular weight substance, and three polymers including compatibilized polymer... 

Dissimilarity in the physical and chemical forces has the most pronounced effect, followed by dissimilarity in free volumes. The latter becomes dominant in solvent-polymer solutions. 

In polymer solutions and blends, it becomes of interest to understand how the surface tension depends on the molecular weight (or number of repeat units, IV) of the macromolecule and on the polymer-solvent interactions through the interaction parameter, x- In terms of a Hory lattice model, x is given by the polymer and solvent interactions through... 

Two of the most important functions in the application of neutron scattering are the use of deuterium labelling for the study of molecular confomiation in the bulk state and the use of deuterium solvent in polymer solutions. In the following, we will consider several different applications of die general fomuda to deuteration. 

In dilute polymer solutions, hydrodynamic interactions lead to a concerted motion of tire whole polymer chain and tire surrounding solvent. The folded chains can essentially be considered as impenneable objects whose hydrodynamic radius is / / is tire gyration radius defined as... 

Anotlier simple way to obtain the molecular weight consists of measuring tire viscosity of a dilute polymer solution. The intrinsic viscosity [q] is defined as tire excess viscosity of tire solution compared to tliat of tire pure solvent at tire vanishing weight concentration of tire polymer [40] ... 

We concluded the last section with the observation that a polymer solution is expected to be nonideal on the grounds of entropy considerations alone. A nonzero value for AH would exacerbate the situation even further. We therefore begin our discussion of this problem by assuming a polymer-solvent system which shows athermal mixing. In the next section we shall extend the theory to include systems for which AH 9 0. The theory we shall examine in the next few sections was developed independently by Flory and Huggins and is known as the Flory-Huggins theory. 

We consider this system in an osmotic pressure experiment based on a membrane which is permeable to all components except the polymeric ion P that is, solvent molecules, M" , and X can pass through the membrane freely to establish the osmotic equilibrium, and only the polymer is restrained. It does not matter whether pure solvent or a salt solution is introduced across the membrane from the polymer solution or whether the latter initially contains salt or not. At equilibrium both sides of the osmometer contain solvent, M , and X in such proportions as to satisfy the constaints imposed by electroneutrality and equilibrium conditions. 

In addition to an array of experimental methods, we also consider a more diverse assortment of polymeric systems than has been true in other chapters. Besides synthetic polymer solutions, we also consider aqueous protein solutions. The former polymers are well represented by the random coil model the latter are approximated by rigid ellipsoids or spheres. For random coils changes in the goodness of the solvent affects coil dimensions. For aqueous proteins the solvent-solute interaction results in various degrees of hydration, which also changes the size of the molecules. Hence the methods we discuss are all potential sources of information about these interactions between polymers and their solvent environments. 

The viscosity of a polymer solution is one of its most distinctive properties. Only a minimum amount of research is needed to establish the fact that [77] increases with M for those polymers which interact with the solvent to form a random coil in solution. In the next section we shall consider the theoretical foundations for the molecular weight dependence of [77], but for now we approach this topic from a purely empirical point of view. 

A detailed examination of the correlation between Vj and M is discussed in references on analytical chemistry such as Ref. 6. We shall only outline the problem, with particular emphasis on those aspects which overlap other topics in this book. To consider the origin of the calibration curve, we begin by picturing a narrow band of polymer solution being introduced at the top of a solvent-filled column. The volume of this solvent can be subdivided into two categories the stagnant solvent in the pores (subscript i for internal) and the interstitial liquid in the voids (subscript v) between the packing particles ... 

Next let us consider the light scattered by liquids of low molecular weight compounds. We are actually not directly interested in this quantity per se, but in scattering by solutions-polymer solutions eventually, but for now solutions of small solute molecules. The solvent in such a solution does scatter, but, in practice, the intensity of light scattered by pure solvent is measured and subtracted as a blank correction from the scattering by the solution. 

Polymer solution viscosity is dependent on the concentration of the solvent, the molecular weight of the polymer, the polymer composition, the solvent composition, and the temperature. More extensive information on the properties of polymer solutions may be found ia refereaces 9 and 54—56. 

Chain transfer is an important consideration in solution polymerizations. Chain transfer to solvent may reduce the rate of polymerization as well as the molecular weight of the polymer. Other chain-transfer reactions may iatroduce dye sites, branching, chromophoric groups, and stmctural defects which reduce thermal stabiUty. Many of the solvents used for acrylonitrile polymerization are very active in chain transfer. DMAC and DME have chain-transfer constants of 4.95-5.1 x lO " and 2.7-2.8 x lO " respectively, very high when compared to a value of only 0.05 x lO " for acrylonitrile itself DMSO (0.1-0.8 X lO " ) and aqueous zinc chloride (0.006 x lO " ), in contrast, have relatively low transfer constants hence, the relative desirabiUty of these two solvents over the former. DME, however, is used by several acryhc fiber producers as a solvent for solution polymerization. 

Extrusion Processes. Polymer solutions are converted into fibers by extmsion. The dry-extmsion process, also called dry spinning, is primarily used for acetate and triacetate. In this operation, a solution of polymer in a volatile solvent is forced through a number of parallel orifices (spinneret) into a cabinet of warm air the fibers are formed by evaporation of the solvent. In wet extmsion, a polymer solution is forced through a spinneret into a Hquid that coagulates the filaments and removes the solvent. In melt extmsion, molten polymer is forced through a multihole die (pack) into air, which cools the strands into filaments. 

The heated polymer solution emerges as filaments from the spinneret into a column of warm air. Instantaneous loss of solvent from the surface of the filament causes a soHd skin to form over the stiU-Hquid interior. As the filament is heated by the warm air, more solvent evaporates. More than 80% of the solvent can be removed during a brief residence time of less than 1 s in the hot air column. The air column or cabinet height is 2—8 m, depending on the extent of drying required and the extmsion speed. The air flow may be concurrent or countercurrent to the direction of fiber movement. The fiber properties are contingent on the solvent-removal rate, and precise air flow and temperature control are necessary. 

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