Birefringence Of Solutions Research Articles

Electrical birefringence in solutions of cellulose esters

Electro-optical properties of solutions of several cellulose esters in dioxan have been investigated. It was shown that macromolecules of the esters display high equilibrium and kinetic chain rigidity. The coincidence of the Kerr and Maxwell effects in solutions of the samples reveals general relationships exhibited by all rigid chain polymers for which the longitudinal geometric axis of the molecule (direction of the greatest geometric length) is also the symmetry axis of its polar and optical properties.

Flow birefringence of graft copolymer solutions

An homologous series of methyl methacrylate-styrene graft copolymers with a wide range of contour lengths has been obtained by grafting on to a backbone polymer made polydisperse by artificial means. As the length of the molecules is increased the reduced birefringence at first increases linearly (with a change in sign), in agreement with the requirements of the theory of flow birefringence in solutions of shortchain molecules of finite thickness, and then it reaches a limiting value. Estimations of the ratio of the persistent length of the molecule to its thickness, from the results of optical and hydrodynamic measurements, are in good agreement.

Electric Birefringence in Solutions of High Molecular Weight Ribonucleic Acid

The electric birefringence of low ionic strength solutions of high molecular weight ribonucleic acids from various sources was studied. RNA preparations with a high helical content were found to have negative electric birefringence as a result of the segment anisotropy of the helical portions of the RNA molecule. For completely unfolded molecules of RNA, the electric birefringence is positive and results from the orientation of the macromolecular coil. In intermediate cases, the observed electric birefringence is the sum of negative and positive birefringence. The negative birefringence is caused by the segment orientation of helical sections, and the positive birefringence is caused by the orientation of the macromolecular coil as a whole. Different relaxation times for the positive and negative birefringence permit the pulsed electric birefringence method to analyze these separate phenomena.

Dynamic birefringence of solutions of polydimethylsilmethylene

Dynamic birefringence of solutions of polydimethylsilmethylene

Time dependence of viscosity and streaming birefringence of solutions of high molecular weight polymethylmethacrylate in Aroclor

I t was previously reported that solutions of linear polymers of very high molecular weight in extremely viscous solvents show an increase in viscosity with increasing shear gradient (1, 2). The effect was observed with polymethylmcthacrylate (Mw = 4.2 X 106) in Aroclor, polystyrene (My ~-~ 7 X 106) in Aroclor, and polyisobutene (My ~ 6 X 106) in polybutene oligomers (3). The solutions were dilute (0.125 2.0 • .3 g/ec) and the solvents were extremely viscous (~2 = 1 to l0 S P). The purpose of this note is to report that in experiments, so far confined to polymethylmethacrylate in Aroclor, changes in viscosity may be observed by prolonged shearing at a constant gradient. Moreover, related time dependent effects are also observed in streaming birefringence experiments. Polymethylmethacrylate, polymerized by conventional free radical initiation, of molecular weight Mw = 4.2 • 106, was dissolved in chloroform and the solution mixed with Aroclor 1248 (a chlorinated diphenyl). The chloroform was subsequently pumped off completely at about 70 ~ in vacuo with occasional gentle stirring, to yield a solution containing 1.0 • 10 -~ g/cc of polymer. t~igs. 1 a und 1 b show plots of extinction angle, Z, and streaming birefringence, An, against velocity gradient. The behaviour of the solvent is normal and also changes of Z and An for a first run of the solution are, qualitatively, typical of results obtained with long flexible macromolecules. However, in two consecutive runs at 25 ~ unusual changes were observed for the solution in that there was a trend towards lower values of Z accompanied by higher values of An. Immediately before a fourth run the solution was sheared for some minutes at 60 see -1 with the result tha t the upward displacement of the curve for An versus gradient became even more pronounced. Similar behaviour also was observed with a portion of the solution which had been passed through a "medium" glass filter. Further experiments were run at a lower temperature of 15.5~ and, consequently, at a higher viscosity (for Aroclor 1248~/ = 1.97P at 15~ 7.93P at 15.5~ At gradients of less than 10 see -i the solution behaved normally. By contrast, its behaviour at a gradient of 20 see -i was found to be influenced in a striking and complex manner by the time of shearing. An increased

Flow birefringence in solutions of deoxyribonucleic acid—III. Dependence of the optical anisotropy of deoxyribonucleic acid molecules on the molecular weight

Flow birefringence in solutions of deoxyribonucleic acid—III. Dependence of the optical anisotropy of deoxyribonucleic acid molecules on the molecular weight

The flow birefringence of solutions of polystyrene in bromoform

THE MOST important source of information on the shape of macromolecules is the s tudy of the birefringence and orientation angles in flowing streams of polymer solutions. The theory that regards the action of flow at very low rate gradients, 9, as the orientation of non-spherical particles leads to the following relationship between the intrinsic value of the orientation angle, [q/g], the molecular weight of the polymer, M, its intrinsic viscosity, [t/J0, and the viscosity of the solvent, t/o f ~ ] =KMtl°[rl]°RT (1)

Orientation Birefringence of Macromolecular Solutions in Shear Flow and Electric Field

The orientation distribution function of polar rigid macromolecules in dielectric media is obtained by solving the rotary diffusion equation in the steady state, when the solution flows with a constant velocity gradient and is acted upon by an electrostatic field perpendicular to the stream line. The optical properties, such as birefringence of the solution, are calculated by averaging the optical anisotropy of each macromolecule over all molecular orientations, which are weighted according to the orientation distribution function. The extinction angle and the amount of birefringence are expressed as functions of the velocity gradient and the electric field strength. The behavior of these properties is specifically dependent on the shape and the electric parameters of macromolecule. This method can provide new information about the macromolecular structure.

Flow birefringence in solutions of deoxiribonucleic acids DNA—I. The optical anisotropy of native and aggregated denaturated DNA : E. V. Frisman, V. I. Vorobev, L. V. Shchagina and N. K. Yanovskaya, Vysokomol. soedin. 4: No. 5, 762–768, 1962.

Flow birefringence in solutions of deoxiribonucleic acids DNA—I. The optical anisotropy of native and aggregated denaturated DNA : E. V. Frisman, V. I. Vorobev, L. V. Shchagina and N. K. Yanovskaya, Vysokomol. soedin. 4: No. 5, 762–768, 1962.

Electric Properties of Macromolecules. IV. Determination of Electric and Optical Parameters from Saturation of Electric Birefringence in Solutions

Electric Properties of Macromolecules. IV. Determination of Electric and Optical Parameters from Saturation of Electric Birefringence in Solutions

A remark on the theory of flow birefringence of solutions of chain molecules

A remark on the theory of flow birefringence of solutions of chain molecules

A remark on the theory of flow birefringence of solutions of chain molecules

A remark on the theory of flow birefringence of solutions of chain molecules

Flow birefringence in solutions of macromolecules: Effect of fluctuations of the shape of the molecule

AbstractA treatment is given for the Brownian deformation of an elastic sphere which permits extension of the theory of the Maxwell effect of solutions of elastic spheres to arbitrary values of the ratio of the time of establishment θ′, of a preferential orientation to the deformation relaxation time θ of the sphere. For large values of η0/ηi the (ratio of solvent viscosity to internal viscosity) the effect reduces to the simple deformation effect described in previous papers. For decreasing values of η0/ηi the deformation effect is gradually replaced by the orientation effect (orientation of elongated configurations). The influence of the intensity of the fluctuations as measured by the mean square value δ02 of the deformation coefficient is discussed. Values of δ0 are given for a series of polystyrene samples of increasing molecular weight. The theory is in qualitative agreement with experimental results on solutions of chain molecules and leads in particular to a new interpretation of the data for thymonucleic acid. The incompatibility of the Kuhn and Kuhn dumbbell theory with experimental results is discussed in more detail than in previous papers.

Flow Birefringence in Solutions of Macromolecules.

Flow Birefringence in Solutions of Macromolecules.

LV.Magnetic birefringence in solutions of organic substances

LV.<i>Magnetic birefringence in solutions of organic substances</i>

Magnetic birefringence in solutions of organic substances, Part I

A number of aromatic hydrocarbons containing two or more benzene rings have been studied for their magnetic birefringence in solution in suitable solvents. For diphenyl and most of its simple derivatives the molecular magnetic birefringence is nearly 4 times, form-diphenylbenzene containing 3 benzene rings, it is 9 times, and for triphenyl benzene nearly 14 (∼42) times, that of benzene, suggesting that the benzene rings in these molecules are, to a first approximation, either coplaner or parallel to one another.

LXVI.Magnetic birefringence in solutions of paramagnetic salts of rare earths

LXVI.<i>Magnetic birefringence in solutions of paramagnetic salts of rare earths</i>

Hydrolysis of esters in weak acid.—Neutral salt solutions

The flow and electrical birefringence in solution of a number of fractions of para-aromatic polyester are studied, using dioxane and dichloracetic acid as solvents. In passing from a non-polar (dioxane) solvent to a polar solvent the optical and hydrodynamic properties of the molecular chain remain unchanged, whereas the electro-optical characteristics undergo sharp changes. The hydrodynamic and dynamo-optical characteristics of the polymer under study in dioxane correspond to the properties of a typical rigid chain polymer, whereas the electro-optical properties are typical of a flexible chain. This unique combination of properties can be explained by the specific dipole structure of the monomer unit and the significant difference in the longitudinal and lateral dipole rigidity of the polymer chain of the polyester under study.