Flow Birefringence Method Research Articles

Hydrodynamic and dynamo-optical properties of the molecules of an aromatic polyester with p and m phenyl cycles in the main chain

The hydrodynamic and optical properties of the molecules of an aromatic polyester dissolved in dichloroacetic acid have been explored by the methods of translational diffusion, viscometry and flow birefringence (b.r.). In the chain of the polymer studied one phenyl cycle in the meta position follows every three phenyl cycles in the para position. Mark-Kuhn equations have been obtained linking the intrinsic viscosity and coefficient of translational diffusion with M; [ η] = 2·6 × 10 −3 M Dη 1.1 cm 3·g −1 and D = 5·6 × 10 −5 M Dη −0.70 . cm 2·sec −1. The results of the investigations are interpreted in terms of the theories of hydrodynamic and dynamo-optical properties of worm-like chains. The equilibrium rigidity of the polyester molecules in solution is characterized by the length of the Kuhn statistical segment 120 ± 20 A ̊ . The anisotropy per unit length of chain 5 × 10 −17 cm 2.

Hydrodynamic and dynamo-optical properties of molecules of an aromatic polyester with para- and meta-phenyl rings in the main chain

The hydrodynamic and optical properties of molecules of an aromatic polyester (PE) dissolved in dichloroacetic acid have been investigated by the methods of translational diffusion, viscometry and flow birefringence. The chain of the PE investigated contains one phenyl ring in the meta-position alternating with three phenyl rings in the para-position. The Mark-Kuhn equations relating intrinsic viscosity and the translational diffusion coefficient to molecular weight have been obtained: [ η] = 2.6 × 10 −3 M 1.1 cm 3 g −1 and D = 5.6 × 10 −5 M −0.70 cm 2 sec −1. The results are interpreted in terms of theories of hydrodynamic and dynamo-optical properties of wormlike chains. It is shown that the PE macromolecules in solution exhibit equilibrium rigidity determined by the length of the Kuhn statistical segment A = 120 ± 20 A ̊ and the anisotropy of unit chain length β = 5 × 10 −17 cm 2.

Flow birefringence and conformational properties of the molecules of para- and meta-isomers of polyhydroxyphenylbenzoxazoleterephthalamides

The flow birefringence method has been used to investigate sulphuric acid solutions of the two series of polyhydroxyphenylbenzoxazoleterephthalamides differing as to the position of the phenyl ring ( para- or meta-) in the chain. On the basis of the method, using the Tsvetkov theory of flow birefringence we obtained, as a result of quantitative evaluations, values for the optical anisotropy of the monomer unit Δa = (330 ± 30) × 10 −25 cm 3 and the Kuhn segment length A = (330 ± 30) and (115 ± 20) Å for the para- and meta-isomers respectively. An analysis of flexibility mechanisms for the chains of both monomers gives theoretical values of the rigidity parameter A that are in keeping with the experiment values, thus substantiating validity of the molecular models being used.

Flow birefringence and conformational characteristics of molecules of para-and meta-isomers of polyoxyphenyl-benzoxazoleterephthalamides

Flow birefringence (FB) has been used to study sulphuric solutions of two homologous series of polyoxyphenylbenzoxazoleterephthalamides (POPhBT) differing in the position ( para- or meta-) of phenyl ring in the chain. In the framework of the FB method alone by using the theory of flow birefringence for kinetically rigid wormlike chains, it was possible to determine quantitatively the optical anisotropy of the monomer unit Δa = (330 ± 30) 10 −25 cm −3 and the length of the Kuhn segment A = (330 ± 30) A ̊ and A = (115 ± 20) A ̊ for para- and meta-isomers, respectively. Analysis of possible mechanisms of flexibility in the chains of both polymers gives theoretical values of the rigidity parameter A in good agreement with experimental values of A. confirming the validity of the molecular models used.

Conformation and optical anisotropy of comb-like macromolecules with mesogenic side groups

The methods of flow birefringence and viscometry have been used to make a comparative study of the conformational properties of two comb-like polymers differing in the character of attachment of the mesogenic grouping. It is shown experimentally that the distancing of the mesogenic grouping from the main chain is accompanied by sharp fall in the optical anisotropy of the molecule and the intramolecular orientation order as compared with the anisotropy and degree of orderliness of the polymer molecules in which the mesogenic group is attached directly to the main chain.

流動複屈折法を用いた単一気ほうの周りの流れの観察

Until now the flow birefringence method has been used to observe the steady state flow. We applied this method to observe the flow around a Spark-induced bubble. When a cavitation bubble collapses near a solid wall, the bubble deforms from its spherical form and a microjet arises against the solid wall. We use the birefringence method to show the appearance of this microjet.

The optical anisotropy and the rigidity equilibrium of polyamidobenzimidazole molecules in sulphuric acid

The optical anisotropy and the conformational properties of polyamidobenzimidazole (PABI) macromolecules have been studied in concentrated sulphuric acid by flow birefringence and viscometric methods. The optical anisotropy α 1– α 2 = 4300 × 10 −31 m 3 and the rigidity equilibrium have been determined for the segment. The number of monomer units present in the segment was S = 25 and the corresponding length of the Kuhn segment was 5×10 −8 m. The rigidity equilibrium, slightly less than that of other p-aromatic polyamides, is determined by an angle of about 24° between two rotation bonds adjacent to the heterocycle.

Diffusion of poly- p-phenyleneterephthalamide in concentrated sulphuric acid

The translational diffusion of poly- p-phenyleneterephthalamide molecules of different molecular weights in 96% H 2SO 4 has been investigated with the aid of a new experimental technique. The diffusion coefficients D are not concentration dependent in dilute solutions, and show marked sensitivity to the length of macromolecules. The molecular weights of the specimens M obtained from the diffusion coefficients D in the light of the theory of translational friction of persistent chains are practically equal to those calculated in terms of a Tsvetkov-Klenin hydrodynamic parameter of A 0=3·78 × 10 −10 erg/deg. A slight divergence of the M values in question from those determined by the method of flow birefringence could stem from polydispersity of the specimens and from inconstancy of A 0. In the range of M=(4·−45) × 10 3 examined in this investigation relationships have bee found between the diffusion coefficients D and the intrinsic viscosity [η] and M: D=4·0 × 10 −5 M −0.80, [ η]=2·5 × 10 −5 M 1.7 M ⩽ 10,000) and [ η]=1·7 × 10 −2 M 1.0 ( M>20,000). In the light of a joint analysis of the diffusion and viscosimetric data a conclusion is reached as to the high equilibrium rigidity of poly- p-phenyleneterephthalamide molecules and as to their hydrodynamic properties in 96% H 2SO 4 which approximate to those of another rigid chain polymer, poly- p-benzamide, in the same solvent.

Stress Analysis near a Slit Exit by Flow Birefringence Method

Measurements of birefringence and streamlines near the exit of a slit were carried out for the steady laminar flow of high density polyethylene Sholex 6008 melt. Distributions of deviatoric stress intensity and its direction were obtained by graphical method from the isochromatic and isoclinic trajectories, respectively. The results provided basic informations on the mechanical feature of the Barus effect, i. e., the enlargement phenomenon of the cross-sectional area of the extrudate than that of the nozzle. Observed directional change of the streamline suggested that large swelling was developable around the center plane in spite of small first normal stress difference there. On the other hand, near the slit wall, particularly near the slit edge, the polymer melt was highly stretched to the direction of flow and the positive normal stress was generated to the same direction. These observations were compared with the computer results obtained by Tanner et al. under Stokes' approximation for a particularly slow Newtonian liguid flow about the exit of a circular tube. Normal stresses normal to the duct wall surface was clearly generated in a short distance just before and after the exit plane. This was in contrast to the present observation where the normal stress varied over a wide range of distance from the exit plane. Thus the distribution of deviatoric normal stresses near the slit exit, suggests that the Barus effect is a kind of solid-like retarded elastic recovery phenomenon in response to the rapid release from the restriction of the sustaining duct wall.

Structure and properties of rigid chain polymer molecules in solutions

A study was made of hydrodynamic, optical and electrooptical properties of rigid chain polymer molecules in dilute solutions. Specific features were pointed out in the behaviour of rigid chain polymers in solutions, compared with conventional properties of flexible chain molecules. Special attention was given to the method of flow birefringence as one of the most effective methods used in the investigation of conformation and optical characteristics of rigid chain macromolecules. Another very effective method of investigating structural and conformation characteristics of rigid chain molecules may be the method of electrical birefringence, which is ineffective when used for flexible chain polymers. Analysis of various molecular structures using the methods indicated enables basic structural properties of polymer molecules to be shown resulting in high equilibrium and kinetic chain rigidity.

Investigation of the optical anisotrophy of solutions of stereospecific polymethylmethacrylate synthesized under different conditions

Using methods of flow birefringence and viscometry a study has been made of the optical anisotropy of solutions of stereospecific PMMA synthesized under different conditions: in presence of BuLi, PhMgBr, PMMA of stereoblock structure prepared in presence of BuLi, as well as PMMA synthesized on BuLi in presence of syndiotactic PMMA. The optical anistropy values of solutions of the PMMA samples examined. and variations in these values with temperature, show that different conditions of stereospecific polymerization of methyl methacrylate lead to the formation of polymers having different intramolecular and supermolecular structures.

The equilibrium and kinetic flexibility of the poly-(cetyl p-methacrylylhydroxybenzoate)

Diffusion, sedimentation, viscometric and flow birefringence methods in an electric field were used to investigate poly-(cetyl p-methacrylylhydroxybenzoate) (PMHC). Equations have been compiled in which the intrinsic viscosity, the diffusion coefficient and that of sedimentation were found as dependences of the molecular weight M, namely [ η] = 3·3 × 10 −3 M 0·8, D = 3·3 × 10 −4 M −0·6, and S 0 = 8·1 × 10 −15 M 0·4. The optical anisotropy of the segment has been experimentally determined as α 1 − α 2 = −440 × 10 −25 cm 3, that of the monomer chain unit as a ‖ − a ⊥ = −18 × 10 −25 cm 3, and the dipole moment of the segment as μ = 7·5 Debye. The PMHC molecule was found to behave in an electric field as a flexible kinetic chain, but the value of the kinetic chain segment was much superior to the size of the monomer unit, which obviously is the consequence of an orientational reaction between the branches (secondary groups).

Effect of temperature and solvent on hydrodynamic and optical properties of cellulose carbanilate molecules

Two high molecular weight cellulose carbanilate (CPC) samples with degrees of substitution of 2·5 and 3·0 were examined at temperatures of 2·5 to 75° by methods of progressive diffusion, rapid sedimentation (in ethylacetate), viscometry and flow birefringence (in dioxane and other solvents). The coefficient of progressive friction of CPC molecules and dynamic flow birefringence, the same way as the intrinsic viscosity of CPC solutions, decrease with an increase of temperature. This reduction may be due to the variation of equilibrium rigidity of CPC molecules. The statistical Kuhn segment calculated from diffusion and sedimentation in ethylacetate considering the flow properties of CPC molecules approximately doubles (from 200–250 to 500 Å) with a reduction of temperature from 50 to 2·5°. Results of dynamic birefringence and viscometry confirm this conclusion and indicate that the variation of temperature or solvent may be accompanied by a variation of optical anisotropy of the CPC monomer unit. The considerable increase in equilibrium rigidity of CPC molecules with a reduction of temperature may be caused by the formation of intramolecular hydrogen bonds or a redistribution in the number of stereo-isomers of the cellulose chain.

The helix content of tropomyosin and the interaction between tropomyosin and F-actin under various conditions

The interaction between tropomyosin and F-actin was studied by means of flow birefringence and optical rotatory dispersion methods. An analysis of the results suggests that the conformation of tropomyosin plays an important role in its binding to F-actin, i.e. there exists a threshold value for the helix content of tropomyosin necessary for binding. Investigations of the binding under various conditions also showed that (1) the lowering of pH and the addition of ethanol induced, as a primary effect, the stabilization of the helical structure of tropomyosin, while (2) the addition of small amounts of divalent cations made the polymer structure of F-actin more rigid. Both conditions made the binding of tropomyosin to F-actin stronger. Urea affected both F-actin and tropomyosin, making their structures more flexible or looser, thus causing a weakening of the binding. The effects of pH, ethanol, urea and divalent cations on structure of the proteins and on their interactions are discussed from the point of view of the conformational change of protein structure. Finally, the effect of salt (KCl) on this interaction is also discussed.

Conformation and rigidity of ladder polymer molecules

Two new samples of cyclo-linear polyphenyl-siloxane (CLPhS) and a sample of cyclo-linear poly-3-methyl-butene-1 silsesquioxane (CLMBS) have been investigated by viscometry, diffusion, sedimentation and flow birefringence methods. The size of the Kuhn statistical segment ( A), characterizing the rigidity of macromolecules, was determined from hydrodynamic models using the theory of a persistent model. The values of A greatly exceed the corresponding values for flexible (coil-shaped macromolecules) and for linear siloxanes. This confirms the ladder structure of the double main chain of the polymers under investigation. The values of segmental anisotropy, anisotropy of the monomer unit and the unit length of the macromolecules in the CLPhS samples were determined from dynamooptical properties. A comparison of the rigidity for the three CLPhS samples investigated (one of them studied previously) shows that it is different for different samples. This fact suggests that the flexibility mechanism of polymers of this type is affected by the defectiveness of structure, i.e. by the occurrence of single bonds in the main chain. It is shown that the study of hydrodynamic and optical properties of the molecules of such polymers may serve as a sensitive method for detection and quantitative investigation of defectiveness of structure.

Development of a New Aqueous Solution Highly Sensitive to Flow Birefringence

An aqueous solution, highly sensitive to flow birefringence and showing Newtonian viscosity is developed from the standpoint of material design to make the flow measurement easier using the flow birefringence method. The highly sensitive solution to flow birefringence is obtained by dissolving Congo Red (CR), which has a large optical anisotropy, into the aqueous solution of polyvinyl alcohol (PVA) of the average degree of polymerization 500 and of the average degree of saponification 98.8%, which can be easily oriented under the action of shear rate. The birefringence and viscosity of PVA–CR aqueous solutions are measured for a range of shear rate from 0 to 2000 s-1. The dispersion of flow birefringence with various wavelengths is also determined. The sensitivity of flow birefringence for shear rate is higher by one or two orders of magnitude than that in aqueous solutions employed by previous investigators. The relation between viscosity and shear rate in the solution is Newtonian.

Normal stress measurements

A review of the methods for obtaining the normal stress differences in simple shear flow from force measurements on the walls of apparatus in which curvilinear shear flows are generated is given. Indirect methods, for example the flow birefringence method, are considered. Some new work on normal stress measurement using cone and plate, parallel plate pressure distribution and total thrust measurements in conjunction with flow birefringence methods are reviewed. The difficulties found in obtaining consistant results are discussed.

Influence of the structure of unsaturated imides on their polymerizability and on the polymer properties

AbstractOn the basis of the comparison between the polymerization rates, intrinsic viscosities and molecular weights of the polymers of N‐substituted maleimides and citraconimides a conclusion is drawn that the methyl group in citraconimide causes a decrease in the reactivity of its double bond. Fractions of poly‐N‐isobutylmaleimide (P‐N‐IBMI) were investigated by the methods of translational diffusion, sedimentation, and flow birefringence. In the range of molecular weights from 0.19 × 106 to 3.6 × 106 relationships are obtained between the molecular weight M of the fractions investigated, their intrinsic viscosity [η], diffusion coefficient D, and sedimentation coefficient S. The hydrodynamic data obtained indicate that macromolecules of P‐N‐IBMI exhibit high rigidity due to the presence of cycles in their main chain. A marked optical anisotropy of the P‐N‐IBMI molecules is positive and indicates that molecular chains of P‐N‐IBMI in solution have a trans conformation.

Organization of DNA in bacteriophage T4

A quantitative evaluation of the degree of preferred orientation of the DNA in bacteriophage T4 has been carried out, principally by the method of flow birefringence. The results indicate that the degree of preferred orientation is small, with about 9% of the DNA aligned preferentially along the long axis of the phage.

A flow birefringence method for the determination of deoxyribonuclease activity

A quantitative method for the study of deoxyribonuclease activity by means of a photocell-flow birefringence apparatus is described. The amount of elliptically polarized light transmitted by DNA or DNP solutions varried directly as the velocity gradient and the concentration of the DNA or DNP solutions. Salts decreased the flow birefringence. The decrease in flow birefringence due to the action of DNase is comparable to the data obtained by viscosimetry.