Исследованы концентрационные зависимости ДЛП в потоке и вязкости растворов поли-N-винилпирролидона в воде и в бензиловом спирте. Значение собственной анизотропии сегмента макромолекулы поли-N-винилпирролидона ( 1 – 2) = –(82 ± 8) ? 10-25 см3 определено из данных ДЛП в бензиловом спирте. Для водных растворов получена сильная зависимость удельной анизотропии раствора от концентрации, что объясняется неоднородностью клубков. Предложена модель учета неоднородности, позволившая аппроксимировать концентрационную зависимость гиперболической функцией, разделить вклад анизотропии неоднородности и анизотропии микроформы в ДЛП раствора и оценить параметр асимметрии сегмента p = 3.0 ± 0.5.

Concentration dependences of flow birefringence and viscosity of poly( N -vinylpyrrolidone) solutions in water and benzyl alcohol are investigated. The intrinsic anisotropy for a poly( N -vinylpyrrolidone) macromolecular segment, (α 1 − α 2 ) = −(82 ± 8) × 10 −25 cm 3 , is determined from the results of birefringence measurements in benzyl alcohol. For aqueous solutions, a strong concentration dependence of the specific anisotropy of solution is obtained, a result that may be explained by the heterogeneity of coils. A model allowing for this heterogeneity is suggested. It makes it possible to fit the concentration dependence to a hyperbolic function, to separate contributions of heterogeneity anisotropy and form anisotropy to the birefringence of a solution, and to estimate the segment asymmetry parameter as p = 3.0 ± 0.5.

A high degree of planar orientational order of DNA molecules in thin films has been discovered by the oblique-polarized-beam method. The coefficients of surface birefringence of films with different thicknesses are measured. The thickness of optically anisotropic surface layers, which are characterized by macroscopic values higher than the diameter of DNA molecules by three orders of magnitude in terms of thickness, is determined. A difference in the main polarizabilities of the monomer unit of DNA, which is estimated for the films, is compared with the corresponding value for the solution measured by flow birefringence. The effect of temperature on the coefficient of birefringence of the films is examined. A comparison of the data on the native and denatured DNA shows that the degree of orientational order for the single-helix structure is smaller than that for the double helix.

The optical properties of four comb-shaped polymers of the methacrylic series with different optically anisotropic groups in side chains are studied by the methods of flow birefringence and viscometry. The experimental values of the optical anisotropy are compared with theoretical estimates calculated in terms of the additivity principle of polarizabilities of valence bonds. It is shown the optical properties of comb-shaped polymers significantly depend on the position (even or odd) of optically anisotropic side groups relative to the main chain.

The optical anisotropy of molecules of pyromellite-dianilic amido acid polyesters has been studied by the method of flow birefringence. Positive flow birefringence, which depends on the isomeric composition of the repeating unit, is detected. The thermodynamic rigidity of pyromellite-dianilic amido acid polyester molecules is calculated in terms of the valence-optical scheme. On passage from 100% para isomers of pyromellite-dianilic amido acid polyesters to macromolecules with a predominant content of meta isomers, optical anisotropy and equilibrium rigidity decrease by a factor of ∼2.

The orientational ordering of polystyrene molecules in surface layers is investigated by the oblique-polarized-ray method. It is shown that the experimental dependences of the birefringence coefficient on the film thickness are accurately described by an exponential model. Estimates are obtained for the orientational-order parameter of the molecular segments of polystyrene at the interphase boundary and the effective thickness of the optically anisotropic surface layer. (C) 2009 Optical Society of America.

Birefringence in thin layers of a star-shaped pentameric polyorganocyclosiloxane has been studied by the oblique polarized beam method. The coefficient of birefringence is measured in relation to temperature and thickness of the surface layer. On the basis of these data, the melting temperature of the compound concerned is determined and the orientational-order parameter is estimated as −0.27. The anisotropy of polarizabilities of pentameric polyorganocyclosiloxane molecules is theoretically estimated. A model of supramolecular structures that treats the formation of domains as stacks of pentameric polyorganocyclosiloxane molecules is advanced.

This review presents the results on studying short-range order in polymer solutions by polarization optical, electrooptical, and spectroscopic methods. The effect of short-range orientational order on dynamic birefringence, photoelasticity, electric-field-induced birefringence, IR absorption spectra, and fluorescence polarization in polymer-solvent systems has been studied. The problem concerning the account for internal field in optical and electrooptical experiments is considered. We present the results on studying the effect of characteristics of both a polymer and a solvent on the parameters characterizing short-range orientational order in polymer solutions.

The structure of the surface layers of thin films cast from water-soluble derivatives of cellulose—methyl cellulose and hydroxypropyl methylcellulose—has been studied by the methods of an oblique polarized beam and molecular hydrodynamics. It has been demonstrated that the molecular chains of the polymers under study are characterized by a high degree of order in surface film layers. The orientational order of molecular chains demonstrates a strong molecular mass dependence. This effect is associated with the concentration of terminal segments whose orientational order parameter relative to the film surface differs from the corresponding value of internal segments composing the molecular chain. The quantitative estimates of the orientational order parameter of terminal and internal segments have been performed.

The molecular structure of tolylene diurea and poly(dimethylsiloxane) copolymers has been studied by the methods of mechanical and dielectric losses, photoelasticity, and X-ray analysis. The above copolymers are found to experience microphase separation. The radius of gyration of domains formed by the hard blocks based on tolylene diurea was estimated as R ≈ 30 Å. Hard blocks connected by the hydrogen bonds in domains are shown to be perpendicular to directions of the maximum extension of domains. The proposed molecular model of a membrane based on the above copolymer includes a molecular network composed of flexible poly(dimethylsiloxane) chains connected by physical junctions; the above physical junctions are domains formed by the thermodynamically hard blocks of tolylene diurea.

The effects of spontaneous ordering of molecular chains of poly(siloxane imide) block copolymers in the surface layers of thin films on glass and gold supports have been studied by the oblique polarized beam and photoelasticity methods. The effective thermodynamic rigidity of molecular chains of the block copolymers (the statistical segment length) has been found to be A = 10.4 × 10 −7 cm. The orientational ordering of molecular chains in poly(siloxane imide) surface layers is characterized by small values of the orientational order parameter ( S 0 ∼ 0.007). This finding is explained by the microphase separation of the block copolymers. The evaporated gold layer contributes to the effect of surface birefringence owing to formation of the ordered system composed of islets—clusters of gold atoms.

Optical properties of poly-1-trimethylsilyl-1-propyne (PTMSP) stereoisomers in solutions have been studied by means of flow birefringence method. Stereoisomers were chosen with various trans- and cis-configurations abundances of double CC bonds in monomeric units. The differences of main polarizabilities (α1−α2) or statistical segments have been determined. Significant growth of (α1−α2) values with increasing of the trans-isomer contents in chain molecule has been found. Optical anisotropy of monomeric segments, having cis- and trans-configurations, has been theoretically evaluated. It has been shown that observed significant increase of experimentally measured (α1−α2) values cannot be sufficiently explained by only specific chain polarizability growth due to higher trans-isomers contents. It has been demonstrated that high (α1−α2) value and it’s growth with increase of abundance of monomeric segments in trans-configuration has been caused by thermodynamical rigidity increase, i.e., higher number of monomeric units included into PTMSP statistical segment.

The optical properties of poly(1-trimethylsilyl-1-propyne) solutions in solvents possessing optical anisotropy have been studied with dynamic birefringence measurements. In solvents characterized by refractive indexes different from the refractive index of a dry polymer, the optical form effect has been discovered. This effect is determined by the shape asymmetry of a macromolecular segment and its rigidity. Estimates showed that the length of the statistical segment, which characterizes the thermodynamic rigidity of the macromolecular chains under study, is 82 × 10−8 cm. The shear optical coefficient for solutions of the test polymer in an anisotropic solvent is markedly higher than the corresponding value in an isotropic solvent. This difference is related to the orientation of anisotropic solvent molecules along the main chain of a macromolecule by their highest polarizability axis. Under the assumption that the orientational order of solvent molecules relative to chain macromolecules is independent of the thermodynamic rigidity of chain molecules, the size of the statistical segment of the macromolecules in question has been independently estimated as 98 × 10−8 cm.

Surface birefringence in polysaccharide films prepared by evaporation of aqueous solutions was studied by the polarized-beam technique at oblique incidence. The correlation between the value of birefringence and the structure of a repeating unit of a polymer was established. The effects of structural and orientational factors determining the surface birefringence in the films of polymer-analogous entities were analyzed. It was shown that the degree of orientational order of fragments of chain molecules in the surface layers of polysaccharide films is determined by the length of a statistical segment of polymer chain.

Problems related to the dependence of the orientational order parameter S-o = (1)/(2) (3 < cos2 theta >-1) of fragments of chain molecules at interfacial boundaries on the geometric asymmetry p = L/d of the statistical segment of a polymer chain (theta is the angle between the direction of the segment and normal to the interfacial boundary, and d is the diameter of polymer chain) are revised. According to the assumption that the orientational ordering of segments at interfacial boundaries is provided by purely steric causes, the theoretical variations of S-0 with p are obtained for two models of segments (a cylinder and a spherocylinder). Parameter S-0 is shown to be controlled noticeably by the thermodynamic rigidity of a polymer chain. Theoretical and experimental dependences of S-0 on p are compared, and their satisfactory agreement is revealed. In the case of flexible-chain polymers, the absolute values of S-0 are rather low. As the thermodynamic rigidity of a chain molecule is increased, the absolute values of S-0 tend to increase and achieve saturation (So = -0.5) for rigid-chain polymers (p > 10).

This paper uses the oblique-polarized-ray method to investigate birefringence in thin films of disklike heptameric polycyclosiloxane (HPCS). The surface birefringcnce B is determined at various temperatures. It is determined that B is independent of T in the region from room temperature to 40degreesC, while B decreases to zero in absolute magnitude when the samples are heated further. A theoretical estimate is made of the polarizability anisotropy of HPCS molecules as Delta gamma = -450X10(-25) cm(3). The orientational-ordering parameter of the HPCS molecules relative to the interphase boundaries is determined as = -0.25. It is shown that the sixth-order symmetry axes of the HPCS molecules are oriented predominantly perpendicularly relative to the normal to the surface of the layer. A model is proposed for supermolecular structures, associated with the formation of domains in the form of stack's of predominantly parallel disklike HPCS molecules. (C) 2005 Optical Society of America.

The optical anisotropy and thermodynamic rigidity of poly [(1-trimethylsilyl)-1-propyne] molecules in relation to the ratio of cis and trans configurations of C=C bonds in the backbone were studied by the flow birefringence technique. The optical anisotropy of the stereoisomers of interest was estimated in terms of the concept of bond polarizability tensor additivity. It was demonstrated that a significant discrepancy in the experimental values of optical anisotropy of polymers is associated with different thermodynamic rigidities of their macromolecules. The values of thermodynamic rigidity evaluated by comparing the experimentally measured optical anisotropy of stereoisomers and the calculation data are consistent with the analogous estimates based on hydrodynamic measurements. It was inferred that the macromolecules under examination, which were prepared using different catalysts, are two-component systems whose thermodynamic properties differ appreciably.