E. P. Astapenko

Hydrodynamic and conformational properties of cellulose myristate molecules in solution

Cellulose myristate samples with a degree of substitution of 230–250 have been studied by the methods of molecular hydrodynamics (viscometry, analytical ultracentrifugation (flotation), and isothermal translational diffusion) in chloroform in the range M = (56–652) × 103. The experimental evidence has been interpreted within the framework of the generalized wormlike Yamakawa-Fuji model with the following parameters: the persistence length a = 115 × 10−8 cm, the chain diameter d = 45 × 10−8 cm, and the molecular mass per unit chain length M L = 270 × 108 cm−1. It has been inferred that the polymer dissolves in chloroform in the form of dimers.

Hydrodynamic and conformational properties of cellulose valerate molecules in dilute solution

Using the methods of molecular hydrodynamics, structural-conformational studies have been performed for a number of cellulose valerate and acetovalerate samples in the molecular-mass range M = (58.1–464.3) × 103 and with a mean degree of substitution of 182.4 with respect to valeric acid isomers. The conformations of valerate-substituted cellulose molecules are characterized by an increased local packing density of monomer units. The molecular conformations are quantitatively described in terms of the helix formed by the succession of vectors connecting glycoside oxygens of a chain. The molecular-hydrodynamic and conformational characteristics of cellulose valerate are compared with the corresponding characteristics of cellulose myristate.

Hydrodynamic, optical and conformational properties of molecules of aromatic polyesters containing 3,3′-biphenylene fragments in the main chains

Abstract The hydrodynamic, optical and conformational properties of molecules of fractions of two aromatic polyesters (APE) containing 3,3′-biphenylene fragments in their chains have been investigated by sedimentation-diffusion analysis and flow birefringence in dilute solutions. The experimental data on the translational mobility and dynamo-optical characteristics of molecules of these polymers are compared with those for previously investigated APE with similar structures but containing no biphenylene fragments. As a result of this analysis, the geometric parameters of the repeating chain unit were characterized, and the equilibrium rigidities of the molecule of the APE were estimated. It was shown that the flexibility of these molecules is determined by the character of intramolecular rotation about the biphenylene bond and that this rotation is virtually unhindered.

Hydrodynamic and Conformational Properties of Aromatic Polyesters Containing Flexible Polyoxyethylene Fragments

Abstract Conformational properties of molecules of the thermotropic aromatic polyesters containing mesogenic and flexible very long oxyethylene fragments are discussed on the basis of molecular hydrodynamic investigations. Changes in Conformational properties and equilibrium flexibility of molecules, caused by changes in the way of biphenylene fragments insertion into the chain are analyzed. Intramolecular orientational mobility of mesogenic fragments is characterized by a dimentionless parameter δ/A.