V.S. Skazka

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.

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].

Structural changes in polyethylene induced by small deformations

Abstract Anisotrophy in thermal conductivity and small-angle light scattering have been measured with films made of high-density polyethylene. Polyethylene deformation obeys different mechanisms in the regions of small ( 1·2) elongations. Deformation of polyethylene is of a complex, orientational-deformational character with participation of different molecular and supermolecular structures. Measurement of anisotropy in thermal conductivity in dependence on degree of elongation has been developed as a new method for determining the orientation function of macromolecular chains in deformed polymer films.

Study of the structure and molecular mobility of crystalline polyethylene by the methods of photo-elasticity and torsion pendulum☆

The authors have studied the temperature dependence of birefringence and the phase difference between stress and birefringence of PE films in a sinusoidal mechanical field. PE films with different degrees of crosslinkage and different degrees of extension were studied. It was found that the phase difference ϕ between stress σ and birefringence δn changes sign from positive to negative in the temperature region 40–70°C. The results are interpreted in terms of the biphasic PE model containing an amorphous phase with positive optical anisotropy and the crystalline phase with negative anisotropy.

Hydrodynamic and optical properties of polyvinylstearate molecules in solution

Abstract The viscosity, light-scattering, diffusion, sedimentation and flow birefringence of polyvinylstearate (PVS) solutions were investigated. The optical anistropy and thermodynamic rigidity of the molecular chains of PVS have been determined. A regular rise in the equilibrium rigidity of the main chain accompanying lengthening of the side radical has been confirmed by comparing the properties of PVS with those of other vinyl polymers.

Physical properties of the system poly(ethylene oxide)-resorcinol☆

Abstract Physical properties of the system poly(ethylene oxide)-resorcinol have been investigated by X-ray diffraction, small-angle light scattering, polarization microscopy with crossed Nicols, and differential scanning calorimetry. Formation of a molecular complex is accompanied by changes in the crystalline and supermolecular spherulitic structure. Temperatures and heats of phase transformations have been determined.

A study of the photoelastic properties of segmented polyurethanes

The photoelastic effect of oligo-oxyethylene blocks in films of segmented polyurethanes of various MMs has been studied. Complicated time dependences of birefringence, when the load was applied and then removed, were found. It was shown that this is connected with the 2-phase morphology of these polymers. Comparison of the experimental values of their optical anisotropy with those calculated from a valency-optical scheme permitted an estimate of the thermodynamic rigidity of the chain.

A study of the mechanical and optical properties of the tri-block copolymer of styrene with butadiene☆

Abstract Temperature dependences of the mechanical loss tangent, photoelastic coefficient e and birefringence, Δn , of isometric samples of butadiene-styrene block components with 45% polystyrene (PS) were studied. At 120°, melting of the superlattice of the block copolymer, accompanied by a substantial decrease in the e and Δn values, was found to occur. The differences between the process of melting for superlattice copolymers, containing 45 and 27% of PS phase are discussed.

Structure and properties of epoxide-amine molecular networks☆

Mechanical testing and photo-elasticity have been used to study the epoxideamine molecular networks representing the product of the interaction of the diglicidyl ether of resorcinol with metaphenylenediamine and aniline. The temperatures of the α transitions have been determined as a function of the average network molecular weight Mc. It is shown that the networks studied represent the superposing of structures with both positive and negative values of differences in their main polarizibilities. The thermodynamic rigidity of the molecular chains of the branches of the network is evaluated. It is shown that fall in the half-with of the α-process with rise in Mc is apparently associated with decline in the relative role of the small scale relaxation mechanisms.

The study of relaxational properties of molecular networks of polyoctafluoroamyl methacrylate by photoelasticity and torsion pendulum methods

Abstract The time dependencies of photoelasticity and the temperature dependencies of the mechanical properties of films of copolymers of octafluoroamyl methacrylate with ethylene glycol dimethacrylate have been studied. Three regions of mechanical loss were found. The transition at 170° is related to local processes in side groups. The main α-maximum of relaxation is due to segmental mobility; the λ-maximum at 120–150° is determined by cooperating processes of segmental mobility: the α-process is satisfactorily described by a bimodal distribution of relaxation times. The dimensions of kinetic units and the activation energies of fast and slow α-relaxation processes have been determined. The mean size of the kinetic units of the α-process is increased with increasing concentration ν of ethylene glycol dimethacrylate, affecting the degree of crosslinking of the copolymer network.