L. N. Andreeva

Diffusion and flow birefringence of alkylene-aromatic thermotropic polyesters

Abstract Hydrodynamic and optical properties of dilute solutions of polydecamethylene-terephthaloyl-di- p -oxybenzoate (P-10-TOB), polypentamethylene-terephthaloyl-di- p -oxybenzoate (P-5-TOB) and polytetramethylene-terephthaloyl-di- p -oxybenzoate (P-4-TOB) in dichloroacetic and trifluoroacetic acids were investigated by translational diffusion, velocity sedimentation, viscometry and flow birefringence. The results of hydrodynamic investigations are interpreted from the standpoint of theories taking account of the draining effect in macromolecules. It is shown, on the basis of hydrodynamic and optical data, that the equilibrium rigidity of molecules (the Kuhn statistical segment) is several times higher for P-10-TOB, P-5-TOB and P-4-TOB than for polyethyleneterephthalate.

Hydrodynamic and dynamo-optical properties and conformation of cyanoethyl cellulose molecules in solution

Translational diffusion, velocity sedimentation and viscosity in acetone as well as flow birefringence (FB) and viscosity in cyclohexanone have been investigated for cyanoethyl cellulose (CEC) with degree of substitution 2.6 in the range of M = (24.5−317) × 103. The dependences of [ν], So and Do on M were obtained. The value of the hydrodynamic constant is A0 = 3.27 × 10−10erg deg−1mol−13. According to hydrodynamic data, the equilibrium rigidity of CEC molecules is characterized by the length of the Kuhn segment A = 240 − 350 A and the coefficient of hindrance to intramolecular motion σ = 4.5-5.4. The hydrodynamic diameter of the chain is 8–14 A. According to the FB data, the value of A is 260 A. This value is in agreement with hydrodynamic data. The high value of optical anisotropy of the monomer unit, a| - a⊥ = 17.8 × 10−25 cm3, is in agreement with the structure and anisotropy of the substituting groups, and the investigation of orientation angles of FB leads to the conclusion that, apart from high equilibrium rigidity, CEC in solution is characterized by considerable kinetic chain flexibility. The data for CEC are compared with the characteristics of other cellulose esters and ethers.

Kerr effect in solutions of a thermotropically mesogenic alkylene-aromatic polyester

Abstract Electric birefringence (EB, Kerr effect) has been investigated for solutions of fractions of thermotropically liquid-crystalline alkylene-aromatic polyester (PE-10) and of its monomer. A very specific dependence of EB on the molecular weight (M) of the polymer was found: for low molecular weight substances the Kerr constant is negative, changes its sign with increasing M and, in the range of positive values, increases with M. These data are in quantitative agreement with the dependence of K on M predicted by the EB theory for kinetically rigid worm-like chains in which the longitudinal components of dipole moments of monomer units are “accumulated” with increasing chain length. The detected relationships show that in PE-10 solutions the Kerr effect is due to the large-scale chain motion in which the behaviour of a dipole molecule is similar to the motion of a kinetically rigid particle rotating as a whole by the action of the field.

Synthesis, hydrodynamic, and conformational properties of poly(N-acryloyl-11-aminoundecanoic acid) in solutions

Poly(N-acryloyl-11-aminoundecanoic acid) samples are synthesized in monomer solutions occurring in both micellar and nonmicellar states. It is shown that polymeric ionogenic surfactants of various molecular masses can be prepared through variation in the concentration of a polymerizable surfactant or in the ionic strength of a solution. The polymer of interest is investigated in detail via the methods of molecular hydrodynamics (viscometry, isothermal diffusion, and velocity sedimentation), dynamic light scattering, GPC, and scanning probe microscopy. The solubility of the polymer in various solvents is examined in detail, and the tendency of this polymer toward association in DMF solutions is discovered. The equilibrium rigidity of macromolecules, which is characterized by the Kuhn segment length A = 100 × 10−8 cm, and the effective hydrodynamic radius are determined in a dioxane-cyclohexanol mixed solvent.

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

Abstract 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 M1.1 cm3 g−1 and D = 5.6 × 10−5 M−0.70 cm2 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 cm2.

Conformational and dynamic characteristics of copolymers of N,N-dimethylaminoethyl methacrylate and 2-deoxy-2-methacrylamido-D-glucose

The conformational and relaxation properties of N,N-dimethylaminoethyl methacrylate and 2-deoxy-2-methacrylamido-D-glucose copolymers in solutions are studied by the methods of molecular hydrodynamics (sedimentation, diffusion, viscometry), polarized luminescence, and flow birefringence. Kuhn-Mark-Houwink equations are obtained, and Kuhn statistical segment lengths at various degrees of protonation of amino groups are estimated. It is found that there is a correlation between the Kuhn statistical segment length and the intramolecular mobility of the copolymers.

Side chain functionalized liquid crystalline polymers and blends, 1. Reentrant nematic phase formation in hydrogen‐bonded blends of liquid crystalline functionalized copolymers with a low molecular weight non‐mesogeic dopant

Hydrogen-bonded blends based on smectic comb-shaped functionalized LC copolymers containing alkyloxy-4-hydroxybenzoic acid fragments (proton donor) and the low molecular weight dopant 4-(4-pyridyloyl)cyanobenzoate (proton acceptor) were obtained. It was observed that blends containing 10–25 mol-% of low molecular weight dopants form a reentrant nematic phase (SmA-RN-SmA-I). The blend behavior in the magnetic field was studied, and the orientational elastic constants of the RN phase were determined.

Electric birefringence in solutions of rigid-chain aromatic polyamides

Abstract Electric birefringence (EB) in solutions of a number of fractions and samples of polyamide benzimidazole (PABI) in dimethylacetamide (DMAA) and polyamide hydrazide (PAH) in dimethylsulphoxide (DMSO) has been investigated by using rectangular pulsed and sinusoidal pulsed fields. Study of EB dispersion in sinusoidal fields and the kinetics of rise and decay of EB in rectangular pulse fields indicates that the main mechanism responsible for the measured EB for both polymers is the large-scale motion of their polar molecules caused by the orienting effect of the field on rigid permanent dipoles of their chains. Relaxation times τ are determined from the dispersion of EB. The Kuhn segment lengths are estimated from the dependence of τ on molecular weight. The values of these length for PABI and PAH chains virtually coincide at (25 ± 10) nm. Study of the value of the Kerr constant and its dependence on molecular weight shows that strongly polar and electroconducting solvents, DMAA and DMSO, used in this work play an important part in the formation of macromolecular dipoles.

Molecular, conformational, and optical characteristics of poly(dodecylammonium-2-acrylamido-2-methylpropanesulfonate) in organic solvents

A number of samples of poly(dodecylammonium-2-acrylamido-2-methylpropanesulfonate)—a comb-like polymer with ionically bound side chains—are obtained by the polymerization of dodecylammonium-2-acrylamido-2-methylpropanesulfonate in an aqueous medium. The samples are obtained in a wide molecular-mass range. Molecular, hydrodynamic, and optical characteristics of the samples are determined by the methods of sedimentation-diffusion analysis, viscometry, and flow birefringence in dilute polymer solutions in chloroform and dimethyl sulfoxide containing small amounts of 0.1 M LiCl. It is shown that conformational and optical characteristics based on hydrodynamic and dynamo-optic investigations agree with the data available for acrylic and methacrylic polymers with the same lengths of side groups. In other words, the character of attachment (covalent or ionic) of long side chains to the backbone has no effect on the conformational and optical characteristics of macromolecules.

Optical, dynamic, and electro-optical properties of poly(N-acryloyl-11-aminoundecanoic acid) in solutions

The optical, electro-optical, and dynamic characteristics of poly(N-acryloyl-11-aminoundecanoic acid) in organic solvents and of the sodium salt of its monomer in water were studied via the methods of flow birefringence, equilibrium and nonequilibrium electric birefringence, and dynamic light scattering. It is shown that, in aqueous solutions, the monomer forms coarse particles of both symmetric and asymmetric shapes. The linear dimensions of these particles are estimated from the data of translational and rotational diffusion. Polymer macromolecules in organic solvents feature negative anisotropy of optical polarizability. Contributions of optical microform and macroform effects to the observed flow birefringence are analyzed in detail. The intrinsic optical anisotropy of the monomer unit of the polymer, which correlates well with the corresponding values for comb-shaped polymers of a similar structure, is estimated. It is shown that polymer molecules lack marked intrinsic permanent macromolecular dipoles and that electric birefringence in their solutions is associated with macroscopic induced dipole moments that appear during orientation of the dipole moments of polar groups in side chains of the polymer under application of an electric field.