S.Ya. Lyubina

Flow birefringence and viscosity of chitosan solutions in acetic acid of various ionic strengths

Chitosan solutions of different ionic strength I were studied, using viscometry and double flow birefringence. The MWs of the samples used were in the range 1 × 104–5 × 105. A linear dependence of intrinsic viscosity on chitosan concentration in a 100 fold range of I was observed in iso-ionic solutions. The characteristic viscosity is a linear function of I−0.5. Folding of the molecular chain during polyelectrolyte swelling causes 2–3 fold increase in the optical anisotropy of the segment, which is explained by an increase in the length of the Kuhn segment. In the solutions studied, the chitosan macromolecules have a swollen coil conformation, the dimensions and rigidity of which are determined by the magnitude of I.

Hydrodynamic and optical characteristics of cellulose macromolecules in cadoxene

Abstract The sedimentation S , translational diffusion D , intrinsic viscosity [η] and flow birefringence of solutions of cellulose linters in cadoxene have been studied over the range of molecular weights M = 2 × 10 3 −7 × 10 5 . The relationships obtained are [ η ] = 4·5 × 10 4 M 0.74 , D = 7·2 × 10 −5 M −0.58 and S = 1.8 sx 10 −15 M 0.42 . The length of the Kuhn segment in a 1 : 1 mixture of cadoxene and water is A = 100 A , which indicates the high rigidity of the cellulose molecule. In cadoxene cellulose has positive anistropy, ( α 1 − α 2 ) = 180 × 10 −25 cm 3 , due mainly to the contribution of anisotropy of molecular shape. Replacement of cadoxene by a cadoxene-water mixture (1 : 1·9) brings about an increase in [η] and ( α 1 − α 2 ) as a result of increase in the rigidity of the polymer molecule. It is shown that the optical anisotropy of the cellulose molecule is the same, regardless of the nature of the cellulose (bacterial, cellulose hydrate, mercerized or linters).

Molecular characteristics of cellulose tributyrate according to results of light scattering and hydrodynamic properties of solutions

Abstract It was shown by light scattering that cellulose tributyrate (CTB) molecules have increased rigidity. The size of the Kuhn segment reaches 200 A in methylethyl ketone and 140 A in bromoform. The conformation of CTB molecules in solution in the range of molecular weights studied corresponds to the conformation of a Gaussian sphere, which is characterized by the flow effect caused by a considerable equilibrium rigidity of the macromolecular chain of CTB. Molecular chain diameters of CTB calculated from experimental results are correlated with values obtained previously from hydrodynamic results.

Graft polymerization of 2-methyl-5-vinylpyridine on cellulose, catalysed by Co (III) salts. The kinetics of the reaction and investigation of the structure of the copolymers☆

Abstract A study has been made of the kinetics of graft polymerization of 2-methyl-5-vinylpyridine (MVP) on cellulose by means of Co (III) salts. The ratio of the rate constants of propagation and termination of the grafted chains, the grafting initiation rate constants and the rate constants of oxidation of cellulose radicals by Co (III) were determined. The investigation of the reaction kinetics and study of the viscosity, sedimentation, diffusion and birefringence of solutions of copolymers of cellulose tributyrate with PVMP has enabled the grafting reaction to be described mathematically and the structure of the copolymers to be defined quantitatively (3–5 grafted chains of molecular weight 5 × 10 3 –10 5 per molecules of cellulose tributyrate). Differences in the grafting process and in the properties of the graft copolymers depending on the monomer being grafted, are discussed.

Structural study of cellulose-acrylamide copolymers☆

Abstract The sedimentation S , progressive diffusion D , intrinsic viscosity [η], and the flow birefringence [n] in Cadoxene solutions of cellulose (C) and its copolymers with acrylamide (AA) were investigated. The copolymers produced by grafting AA on to C in the presence of cobalt salts are graft copolymers containing 8–13 grafts of poly-AA molecules having M = 4 × 10 4 −5 × 10 5 . The molecular weights of the grafts depend on the ratio of Co (III) ions to monomer concentration over a wide range of copolymer compositions. The molecular weight of the fundamental material in the copolymer remains fairly large ( M ∼ 2 × 10 5 ) despite the strong oxidizing effect of the cobalt. The following correlations were found for the copolymers: [ η ] = 1·5 × 10 −3 M 0·5 , S 0 = 1·5 × 10 −16 M 0·5 , D 0 = 3·5 × 10 −5 M −0·5 . The C-AA copolymers have a narrow MWD and small compositional heterogeneity of macromolecular structure of the native cellulose.

Hydrodynamic and optical properties of poly-4-vinylpyridine molecules in solution☆

The present paper reports work on a study of the optical anisotropy, viscosity, sedimentation and diffusion of solutions of poly-4-vinylpyridine (PVP) with the aim of comparing the optical and hydrodynamic properties of PVP molecules with the properties of poly-2-methyl-5-vinylpyridine (PMVP) studied previously [1].

Synthesis and study of macromolecules of bent rod structure using molecular optics

Abstract Poly- γ -benzyl- L -glutamate samples containing one of the following fragments in the molecular chain were synthesized: o -diglycylamino-diphenyl-disulphide, azo-bis-isobutyryl-hydrazide, decamethylenediamine. The synthesized molecules were considered to be rods with a single bend. Solutions of the polymers were studied at 25°C in DMFA by light scattering, flow birefringence, and viscometric methods. Equations showing the relation between the intrinsic viscosity and the MM were derived for all structures studied. The mean square dimensions of the macromolecules, the second virial coefficients, and the optical shear coefficients were determined. The persistence length was calculated for all the structures from the intrinsic viscosity and the birefringence. The decamethylene fragment introduced into the poly- γ - L -glutamate chain was the only fragment which decreased the equilibrium rigidity, and this by 25–30%.

Synthesis of the triblock copolymers poly-γ-benzyl-l-glutamate-PMMA-poly-γ-benzyl-l-glutamate and study of their conformation in solution☆

Using the polymeric initiator PMMA with terminal amino groups the authors have synthesized samples of the triblock copolymer of the ABA type, where A is poly-γ-benzyl-l-glutamate (PBG), B is PMMA. The synthesized polymer constitutes a coil of a flexible polymer to the ends of which are attached the helical sequences of PBG. The MM and the fraction of each component in the copolymer vary. Light scattering, flow birefringence and viscometry have been used to investigate solutions of the synthesized samples in DMFA at 25°C. The composition, MMs, intrinsic viscosities, the radii of inertia, the second varial coefficients and optical anisotropy of the copolymers and their components have been determined. A comparative analysis is made of the dependence of the intrinsic viscosity and optical anisotropy on the molecular mass for the copolymers and PBG homopolymer studied. It is shown that the introduction of a flexible long PMMA spacer into the rigid PBG macromolecule does not change its equilibrium rigidity. A model of the structure of the PBG-PMMA-PBG triblock copolymer is proposed helping to explain the body of experimental data.

Optical anisotropy and conformation of the molecules of soluble (transport) ribonucleic acid (S-RNA)☆

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Separation by dynamic light scattering of internal motion in polymer coils from brownian motion

The coefficient of translational diffusion of a narrow-distribution polymer—poly(α-methylstyrene), M = 3.3 × 106—calculated from the low-frequency component of dynamically scattered light has been shown to coincide with the value determined by the classical method of macroscopic diffusion. The correctness has been shown of a method for decomposing the correlation function into a low- and a high-frequency component, based on a program which makes use of a regularization algorithm. The method has been used to separate the large-scale motion in polymer chains from the motion of the macromolecule as a whole.