N.V. Pogodina

The flow birefringence and rigidity equilibrium of p- and m-aromatic copolyamide molecules☆

The flow birefringence of the sulphuric acid solutions of poly-p-phenylene terephthalamide and poly-m-phenylene isophthalamide, and of 13 of their copolymers with differing molar contents of the components have been examined. The experimental optical shear coefficients Δn/Δτ have been used to determine the number of monomer units S of the Kuhn segments in all the samples. The molecular models of the homo- and copolymers have been examined. A formula has been arrived at for the chain flexibility 1/S as a function of the copolymer composition Z on the basis of the suggested models. The good correlation of the experimental with the theoretical 1/S-Z function confirms the additivities of the structural and deformation mechanisms of the polymer chain flexibilities.

Molecular characteristics of highly-substituted cellulose nitrate in solutions from forward diffusion, flow birefringence and viscometry☆

Abstract Flow birefringence, diffusion and characteristic viscosity in solutions of 14 fractions of highly substituted cellulose nitrate with a percentage content of nitrogen of 13·2% have been studied. The experimental dependence of reduced birefringence [n]/[η] and the characteristic angles of orientation [χ/g] on the molecular mass of cellulose nitrate found is interpreted in the light of the Noda-Hearst theory for kinetically flexible chains taking into account polydispersity in molecular masses. The dynamo-optical and hydrodynamic data obtained are used to determine the equilibrium and kinetic rigidity, anisotropy of the monomer unit and polydispersity of the fractions of cellulose nitrate. The effect of the microform in study of flow birefringence is shown in five solvents differing in refractive indices.

The hydrodynamic and dynamo-optical properties of cellulose dinitrate solutions

Abstract The flow birefrigence, diffusion, sedimentation and the intrinsic viscosity have been studied of 28 fractions of cellulose dinitrate (CDN) solutions with a 12·1% nitrogen content. The comparison of the results with the molecular characteristics of cellulose nitrate samples having a differing N-content has shown that an increase of the nitro-groups increases the rigidity equilibrium and the absolute optical anistropy of the monomer chain unit present in cellulose nitrates.

The Kerr effect as a method of investigating the structure and conformation of polymer molecules in solutions

Abstract A description is given of theoretical and experimental results concerning electrical birefringence in solutions of flexible chain (unchanged and charged) rigid chain and comb-like crystalline polymers, in order to establish the significance of this method of obtaining information about the structure and morphology of macromolecules.

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

Abstract 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) A 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.

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 × 10−3M0·8, D = 3·3 × 10−4M−0·6, and S0 = 8·1 × 10−15M0·4. The optical anisotropy of the segment has been experimentally determined as α1 − α2 = −440 × 10−25 cm3, that of the monomer chain unit as a‖ − a⊥ = −18 × 10−25 cm3, 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).

Flow birefringence and rigidity of molecules of aromatic copolyamides of para-structure☆

The authors have studied the flow birefringence and characteristic viscosities in sulphuric acid solution of a number of samples of copolyamides containing poly-p-phenylene terephthalamide and poly-p-benzamide units. From the experimental dependence of the reduced bierfringence [n]/[n] on the length of the chain using the Tsvetkov theory of flow birefringence for kinetically rigid vermiform chains, they determine the length of the Kuhn segment A = (520±60) × 10−10 m and the optical anisotropy of the monomer unit Δa=80 × 10−31m3 of the copolymers. The value of A obtained reasonably matches the theoretical for the structural model with weak hindrance of rotation.

Electrical and flow birefringence of ladder polychlorophenylsilsesquioxane solutions

A study was made of the flow birefringence (FBR) and electrical birefringence (EBR) of dilute solutions of a number of cyclolinear (ladder) polychlorophenylsilsesquioxane (CLCPS) fractions. The FBR and EBR are negative in sign, and their characteristic values increase with molecular mass in line with behaviour characteristic of polymers featuring equilibrium rigidity. The Kerr effect dispersion appearing in sinusoidal fields is characteristic of kinetically rigid chains, and its dependence on molecular mass is quantitatively in agreement with the theory of the relaxation and rotational friction of rigid molecules. The validity of a CLCPS molecular model in the form of a double chain ladder cis-structure is borne out by experimental results, and yields quantitative information concerning important molecular parameters such as the mode of rotation of side phenyl rings, the size of bond angles in the chains and oxygen bridges and the dipole moments of the monomer unit of the molecular chain and the SiO bond.

Intramolecular liquid crystalline structure in polynonyloxybenzamide styrene solutions

Abstract Dynamo- and electro-optical properties of polynonyloxybenzamide stryrene solutions in benzene were studied. It was shown that in this polymer lateral chain groups form an intramolecular liquid crystalline structure. As a consequence, macro-molecules are characterized by the presence of an oriented polar short range order in the mutual arrangement of side radicals.

The electrical birefringence of cellulose carbanilate solutions as a function of molecular weight

The electron, dynamo-optical and hydrodynamic properties of a series of solutions of fractions of cellulose carbanilate (CC) were studied in dioxane and in ethyl acetate. There was a strong Kerr dispersion effect in an alternating electrical field which indicated a dipole oriented mechanism for electrical birefringence and its relaxation. Comparison of the relaxation periods of these fractions with their molecular weights (mol.wt) and the intrinsic viscosities has led to the conclusion that the mechanism responsible for the Kerr effect is a molecular rotation of the entire molecule in the electrical field (a kinetically rigid molecule). The relaxation period as a function of mol.wt. M has shown that an increase of the latter causes the CC molecular conformations to change from a slightly bent rod to a rigid Gaussian coil. The same conclusion was also reached in the study of the Kerr equilibrium constant K as a function of M. The Kerr effect depends in the Gaussian range (larger M) on the parallel component (relative to the chain) of the dipole moment formed by the CO bond present in the glucoside ring. A considerable part is played in birefringence at small M by the transverse component of monomeric dipoles.