High Molecular Weight Linear Polymers Research Articles

Critical regimes of oscillatory deformation of polymeric systems above glass transition and melting temperatures

High molecular weight linear polymers and their concentrated solutions were investigated over a wide range of frequencies and amplitudes of oscillatory deformation. At definite critical deformation and stress amplitudes, the resistance to deformation drops abruptly as a result of the rupture of continuity of polymer specimens in the region of action of the highest shear stresses. The lowest critical values of deformation rate amplitudes are inversely proportional to the initial viscosity and correspond quantitatively to the critical shear rates at which the spurt occurs during the flow of polymeric systems in ducts. The spurt effect is due to the transition of the polymer systems to the forced high-elastic state, in which they behave like quasi-cured polymers whose deformability is always limited. Up to the critical values of the stress amplitudes, narrow-distribution high molecular weight linear flexible-chain polymers behave like Hookean bodies, whereas the broad-distribution polymers show a sharply defined nonlinear behavior which asymptotically passes to a spurt. The amplitude dependence of the dynamic characteristics of the high molecular weight linear polymers, as well as their non-Newtonian behavior, is due to polymolecularity. An increase in deformation amplitudes reduces the frequency at which the spurt, and hence the transition of the polymer systems to the high-elastic state, is observed. Therefore, under conditions of oscillatory deformation the physical state (fluid or high-elastic) is determined not only by the frequency but also by the value of deformation. In the high-elastic state region (estimated at low amplitude deformation), the critical deformation amplitude is frequency independent and has an unambiguous relationship with the molecular mass of the chain (Me) between the entanglements. For the bulk polymers studied, the spurt in the high-elastic state occurs at stress amplitudes of the order of 105 N/m2 irrespective of frequency, molecular mass, or polymolecularity. In concentrated polymer solutions, in the high-elastic state the critical stress amplitudes decrease with reducing polymer content, whereas the critical deformation amplitudes increase.

Flow, high‐elastic (recoverable) deformation, and rupture of uncured high molecular weight linear polymers in uniaxial extension

AbstractThe behavior of narrow molecular weight distribution polymers has been investigated under uniaxial extension at constant deformation rate and at constant stress. It has been established that up to rupture these polymers behave as linear viscoelastic bodies. A detailed investigation of the rupture phenomenon has shown that the rupture of fluid polymers is due to their transition to the rubbery state at critical deformation rates, with the result that they disintegrate like quasi‐cured rubbers. The effect of the temperature and the molecular weight on the critical conditions of rupture has been described in terms of viscoelastic relaxation.

Oxidative polymerization of diethynyl compounds

AbstractDiethynyl compounds are readily polymerized to high molecular weight linear polymers by oxidative coupling with oxygen in the presence of an amine complex of a copper salt as catalyst. Organometallic moieties can also be introduced into these polymers. Thus polymers in which silicon, arsenic, and mercury are part of the polymer backbone have been synthesized.

Drag Reduction by Additives

An examination is made of the experimental evidence for the reduction of skin friction in dilute solutions of high molecular weight linear polymers below that of the solvent alone. Inferences are drawn about the necessary properties of the polymers and their solvents, and the mechanical properties of the solutions are described. In the detailed flow measurements, those observations requiring explanation are identified. Simple dimensional considerations are applied to isolate the phenomenon in a relatively narrow region outside the viscous sublayer; these same considerations are shown to explain several of the observed anomalies. In an attempt at a deeper explanation, the influence of phenomena such as agglomeration and extension is discussed. It is shown that mechanisms of interaction which suggest themselves, while qualitatively satisfactory, are quantitatively and conceptually in disagreement with experiment, while the experimental results are in disagreement with accepted principles of fluid mechanics. ( Author )

Gradient and Time Dependence of Viscosity of Polymer Solutions in Very Viscous Solvents

Solutions of high molecular weight linear polymers in very viscous solvents exhibit two peculiar effects even at rather low concentrations. With increasing gradient the viscosity first drops to a minimum and then increases over a wide gradient range. Moreover, prolonged shearing at constant gradient induces an increase of viscosity which dependent on concentration and gradient either continues with steadily decreasing slope or after a while turns over into a gradual decrease with a finite limit not much different from the starting value. The first effect is partly due to an actual increase of intrinsic viscosity with increasing gradient and partly to the time effect. The former contribution is proportional to the concentration, the latter to the second or higher power of concentration. Both effects occur with the polymer improved lubricating oils.

Polymerization of racemic and optically active 4‐methyl‐1‐hexyne

AbstractPolymerization of racemic (I) and optically active (II) 4‐methyl‐1‐hexyne in the presence of iron‐tris(acetylacetonate)/Al (i‐C4H9)3 catalyst gives high molecular weight linear polymers with alternate double bonds in the main chain.Ozonolysis of the polymers obtained from both (I) and (II) gives 3‐methyl‐pentanoic acid (III), in 20 to 30% yield, as the sole low molecular weight product.In the ozonolysis of polymers arising from (II), (III) is formed with the same optical purity as that of the starting monomer (II).Hydrogenation of the unsaturated polymers of (I) and (II) gives substantially atactic poly [4‐methyl‐1‐hexene].

A Study of Viscoelastic Fluid Flow : 3rd Report, Turbulent Flow in a Circular Pipe

Dilute solutions of high molecular weight linear polymers with viscoelastic properties display significant reduction of frictional resistance in the turbulent pipe flow. This anomalous phenomenon is analytically treated with the concept that the turbulence intensity is partially surpressed by the elasticity of fluid. Combination of Weissenberg assumption and the power law for non-Newtonian viscosity is adopted as the flow model. The expression of the friction factor λ derived as the function of rheological constant n and two dimensionless numbers R6 and N6 includes Karman-Prandtl's formula for Newtonian fluids and Dodge-Metzner's formula for non-elastic, non-Newtonian fluids as special cases.

The fractionation of protein mixtures by linear polymers of high molecular weight

The protein fractionating properties of the high molecular weight linear polymers, polyethylene glycol, dextran, nonylphenol-ethoxylate, polyvinyl alcohol and polyvinyl pyrrolidone have been investigated. All were protein precipitants, but varied in selectivity. Polyethylene glycol (mol. wt. 6000) appears to be the most suitable protein precipitants in this group because its solutions are less viscous and cause virtually no denaturation at room temperature. The efficiency of protein fractionation increases with the molecular weight, and therefore chain length, of the polymer. Rapid simple methods for the preparation of γ-globulin and fibrinogen with the aid of polyethylene glycol are described. The products were homogeneous on electrophoresis and centrifugation and retained satisfactory biological properties.

Rheological Properties of Fermentation Broths

Publisher Summary This chapter presents the rheological properties of fermentation broths and an appraisal of the use of these properties in engineering and analytical correlations employed in fermentation practice. From theoretical considerations, only fermentation broths containing microorganisms of simple shape and in dilute solution should be expected to behave as Newtonian fluids. Rheological properties reported for streptomycin broth and penicillin indicate that these fluids approximate plastic behavior. The pseudoplastic and plastic behaviors of some broths are clearly evident at certain times during the course of the fermentations. Little is known about the quantitative relationship between rheological properties and cellular concentration in broths in which there are mycelia structures. The pseudoplastic behavior commonly associated with unidimensional particles, such as high molecular weight linear polymers, can be expected in bacterial fermentation broths in which the bacteria are encapsulated or form unusually long cellular chains.

Rheological Properties of Fermentation Broths

Publisher Summary This chapter presents the rheological properties of fermentation broths and an appraisal of the use of these properties in engineering and analytical correlations employed in fermentation practice. From theoretical considerations, only fermentation broths containing microorganisms of simple shape and in dilute solution should be expected to behave as Newtonian fluids. Rheological properties reported for streptomycin broth and penicillin indicate that these fluids approximate plastic behavior. The pseudoplastic and plastic behaviors of some broths are clearly evident at certain times during the course of the fermentations. Little is known about the quantitative relationship between rheological properties and cellular concentration in broths in which there are mycelia structures. The pseudoplastic behavior commonly associated with unidimensional particles, such as high molecular weight linear polymers, can be expected in bacterial fermentation broths in which the bacteria are encapsulated or form unusually long cellular chains.

Condensation polymers from diisocyanates and dioximes

AbstractDiisocyanates condense readily with the two active hydrogen atoms in dioximes to give high molecular weight linear condensation polymers. In several cases these polymers, such as the one from cyclohexanedione dioxime and 4,4′‐biphenylene diisocyanate, magnified image may be converted to tough films or fibers. Thermal, hydrolytic, and light stability of these polymers were in general poor.

The Formation of High Polymers by Condensation between Metallic Polysulfides and Dihalogenated Hydrocarbons and Ethers

Abstract The general theory of formation of high molecular weight linear polymers by condensation between bifunctional compounds of low molecular weight to form products of large molecular mass has been so thoroughly reported in the literature that no extensive citation is believed to be advisable here. A very thorough study of this type of reaction has been made by Carothers and his co-workers on the formation of polyesters, the reaction being of the general type: One can, without taxing the imagination, conceive of the polymerization of isoprene or butadiene as belonging to the same general type of phenomenon, differing only in the fact that the reacting molecules are alike instead of different and that the “condensate” is one double bond per molecule. Therefore, no attempt will be made in this paper to distinguish between condensation and polymerization. When organic dihalides having CH2X terminals, in which “X” denotes a halogen, are caused to react with metallic polysulfides, MSxM, there usually results a linear polymer of high molecular weight.

The formation of high polymers by condensation between metallic poly-sulphides and dihalogenated hydrocarbons and ethers

Abstract The general theory of formation of high molecular weight linear polymers by condensation between bifunctional compounds of low molecular weight to form products of large molecular mass has been so thoroughly reported in the literature that no extensive citation is believed to be advisable here. A very thorough study of this type of reaction has been made by Carothers and his co-workers on the formation of polyesters, the reaction being of the general type: One can, without taxing the imagination, conceive of the polymerization of isoprene or butadiene as belonging to the same general type of phenomenon, differing only in the fact that the reacting molecules are alike instead of different and that the “condensate” is one double bond per molecule. Therefore, no attempt will be made in this paper to distinguish between condensation and polymerization. When organic dihalides having CH2X terminals, in which “X” denotes a halogen, are caused to react with metallic polysulfides, MSxM, there usually resu...