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On the basis of a model of the structure of amorphous polymers the ahutors make a thermodynamic analysis of nucleation on crystallization of oriented polymer melts with reference to the generalized influence of such types of defects as loops and through chains at the end surface of the nuclei formed. Equations are derived determining the various parameters characterizing the process of orientation crystallization. It is found that the loops or folds which may remain at the surface of the nucleus even for high degrees of orientation lead to rise in the potential barrier of nucleation and fall in the melting point on orientation.

Calculation of the distribution of scattering intensity of polarized light by large anisotropic particles in polymers is purely a “model” calculation and is based on the appropriate selection of parameters of the scattering element immersed in an isotropic matrix and subsequent analysis of interaction with electromagnetic radiation. This analysis normally enables ratios to be derived which relate the dimensions and form of element with the pattern of scattering. However, the approach itself and the approximation used (Rayleigh-Hans) require an experimental verification of these ratios. This verification was made precisely for two main ratios which relate parameters of spherulitic supermolecular organization of polymers with the pattern of small angle polarized light scattering. It was shown that these ratios are valid for systems containing spherulites with dimensions of one to ten microns.

The dependence of the time and heat of additional isothermal crystallization on the temperature of the main process of isothermal crystallization has been established during the annealing of polychloroprene. Crystallization during annealing leads to a redistribution of the intensities and temperatures of mechanical loss peaks. According to the proposed model crystallization results in additional crystallite formation on the main crystallite surface within intercrystallite layer limits. The redistribution of various types of mobility of portions of macromolecules of the intercrystallite layer is regarded as being a liquid-liquid type phase transition which accompanies crystallization and annealing of amorphous-crystalline elastomers.

The free energy of melting of polymer crystals has been examined and the effect of the conformational entropy of non-crystalline chain segments taken into consideration; this gave the correlations allowing determination of the melting range of the polymers. Polyethylene (PE) is being used in the experimental confirmation of the established correlation.

Calculation of the free energy of nucleus formation of platelet crystals, taking into account the change in conformational entropy, has provided an explanation of the limited thickness of such crystals. Expressions are derived for the crystallization temperature, which is dependent on the magnitude of the hetero-phase fluctuations in the melt, and for the melting point of the platelet crystals, which is determined by their dimensions and the “defectiveness” of the amorphous region. The results of the analysis are extended to the case of formation of secondary, monolayer nuclei.

Analysis of the statistical properties of a three-dimensioonal system of ordered chains at quite high values of the order parameter has been carried out using a method employed to calculate the fluctuations in the orientation of particles in low-molecular weight nematic single crystals. The degree of order, the mean-square projection of the chain-length vector h in the direction of the axis of order, z , (√〈 h ∥ 2 〉) and on the x , y plane normal to the axis (√〈 h ⊥ 2 〉) have been calculated as functions of the ratio of the energy of thermal motion to the energy constants characterizing the chain rigidity in bending and the interchain orientational interaction. Unfolding of the chain in the direction of the axis of order appears as an increase in 〈 h ∥ 2 〉 and a decrease in 〈 h ⊥ 2 〉 as the degree of order rises. The effective coefficient of translational diffusion of the chain as a whole in the direction of the axis of order increases, and its ability to diffuse transverse to this direction decreases, as the degree of order of the chains increases.

The conformational and dynamic properties of two- (d2) and three- (d3) dimensional “network” systems consisting of polymeric chains orientationally ordered at the level of Gaussian sub-chains have been considered. If the sub-chains have comparatively weak orientation-strain interaction and the flexural regidity of the chain is low, a long chain included in the ordered matrix remains Gaussian. As the constant for the interchain interaction increases, the mean-square dimensions of the sub-chains and chains increase. In both models there is a “critical” point at which the system of Gaussian sub-chains loses its stability. At this point, the mean-square dimensions of the Gaussian sub-chains either become infinitely large (in the d2 model) or remain finite (in the d3 model). On passing through the “critical point”, it is necessary to take account of the finite extensibility of the sub-chains and to go on to a theoretical description based on chains made up of rigid segments.

On introducing into dilute ([η]McM⩽0·6) solution of the M-mer large amounts of the P-mer (M >P) in presence of a network of a “thickening agent” it is possible to study the properties of the M-mer macromolecules in moderately concentrated solutions. The dimensions of the M-mer macromolecules decrease with rise in [η]PcP and the retraction effect for large M is more strongly marked. Change in P does not alter the degree of retraction of the M-mer coils with no change in the nature of the dynamics of the M-mer as compared with the behaviour in the low molecular weight solvent at least up to [η]PcP≈4. In all cases the invariance of the relaxation time relative to [η], η0 and M in the intervals studied of variation in these parameters persists.

The thermodynamic properties of polydecamethylene-terephthaloyl-bis-(4-oxybenzoate) samples differing in their intrinsic viscosity have been investigated by differential scanning calorimetry and by polarization-optical microscopy methods. The type of mesophase has been determined for a number of the samples. The influence of annealing on the behaviour of the samples during melting processes has been studied.

The results of examining the low-density polyethylene (LDPE) under conditions of creep and stress relaxation in isothermal, isobaric and isochoric regimes are described. The results have shown that pressure, temperature and volume are parameters which are present in the equation of state as independent variables; stress relaxation is therefore a function of all 3 parameters. The effect of the volume on the relaxation time can be accounted for by the addition of a fourth item in the exponent of the Aleksandrov-Lazurkin-Gurevich equation τ = τ0exp [U0−γ1σi+γ2σm+γ2θRT]. The effective activation energies and activation volumes of the polymer were determined by processing the experimental results.

Volume deformation in shear of a number of polymers was measured. The volume variation of polymers in shear, elongation and compression is described by a “hereditary” type equation of visco-elasticity. Using PTFE it was established that the rate of shearing creep depends to a considerable extent on volume deformation. The addition to the nucleus of a “hereditary” equation of creep of the first invariant of the deformation tensor enables us to link with one equation stress and tensile strain, compression and shear.

Statistical and relaxation properties have been studied on dynamic models of a two-dimensional system consisting of oriented chains with kinetic units formed by rigid segments smaller in size than the statistical chain segment. Depending on the ratio between the energy of thermal motion and the geometric mean of energies that characterize the chain rigidity with respect to bending and the orientational interaction between chains, the dependence of the mean-square dimension of a long but finite section of chain embedded in the ordered matrix on the number of segments can assume several forms. The relaxation times in various modes of motion in the entire system of chains are proportional to the mean-square fluctuation corresponding to the given normal mode.

Features of the design of a capillary viscosimeter and dilatometer for measuring the viscosity and specific volume of fluid polymer systems under hydrostatic pressure (up to 500 MPa, temperatures of 280–380 K) are described. Viscosity and specific volume measurements have been carried out for polyorganosiloxane rubbers of differing molecular weights. The volume reduction under hydrostatic compression obeys the Tate equation. The viscosity at various temperatures and pressures is an exponential function of the specific volume.

It was shown that thermo-mechanical spectrometry can only be used in thermo-mechanical studies if temperature shows a linear variation over a period of time. A principle was proposed and a description given of the structural features of a linear temperature programmer. A study was made of the thermo-mechanical behaviour of twelve polymer fibres of different chemical structures. It was found possible to examine the energetics of corresponding processes as a result of the displacement of the transition temperature of relaxation due to a variation of the rate of heating and the sample used in thermo-mechanical tests.

Two dimensional and three dimensional nucleus formation in crystallization of polymers is discussed, account being taken of change in the conformational entropy of segments of the macromolecules that have not crystallized. It is shown that crystal growth in polymers with flexible chains is substantially dependent on the degree of crystallinity attained at the given moment. Analysis of the magnitudes of the energy barriers in secondary nucleus formation showed that because of entropic hindrance to crystallization of entangled chains, crystal growth is restricted in the direction of the polymer chains. An expression is obtained for determining the rate of growth and the final degree of crystallinity in isothermal crystallization, relating these parameters to the thermal prehistory of the sample.

An experimental study has been made of volume strains for some polymers under uniaxial drawing, compression and hydrostatic pressure. The volume compliance in the case of a positive average stress is shown to be higher by almost one order than the corresponding value under compression from all sides. The fracture process depends solely on the rupture of main chains, and takes place as soon as the volume increase attains some definite value. The volume deformation is the main factor responsible for the physical nonlinearity of the creep process and by introducing it into hereditary equations of viscoelasticity it is possible to describe nonstationary regimes of deformation (loading) in the complex stressed state.

FOR interpretation of the diagrams of low-angle scattering of polarized light by films and solutions of polymers in terms of the supermolecular structure of the polymers, it is necessary to establish the correlation between the azimuthal intensity distribution and the dimensions and orientation of the scattering elements. In a study with a previously described polarizing dlffractometer [1], of the detailed kinetics of supermolecular ordering in solutions of helical poly-~benzyl-L-glutamate (PBG) [2], we distinguished four types of diffraction diagram (Fig. 1). The first (Fig. la) corresponds to scattering from spherulites, and is easily interpreted on the basis of the theory that regards spherulites as optically anisotropic spheres [3, 4]. The second (Fig. lb) is characteristic of a supersaturated system of spherulites, which leads to collapse of the primary spherulitic structures. The next stage of structure formation is characterized by a rhomboidal diffraction diagram (Fig. lc) denoting the onset of orientational order in the system. Complete orientational order produces the fourth type of diagram (Fig. ld), which is completely analogous to X-ray patterns from orientated polymers and is interpreted in exactly the same way as X-radiograms. We have also obtained rhomboidal diagrams from orientated films of polyethylene (PE), a polyamide (PA) and polymethylmethacrylate (PMMA)t (Fig. 2). The last example (Fig. 2c) is of special interest because the experiments were made with an ordinary (atactic) specimen, i.e. with a polymer known not to crystallize. Rhomboidal diagrams have also been obtained by Stein and Rhodes [4], who measured the scattering from the periphery of isolated spherulites. For an understanding of the nature of the structural processes leading to spontaneous occurrence of orientational order in polymer solutions, or occuring during the "forced" orientation of fibres or films, the correct interpretation of the rhomboidal diffraction diagrams of the type of Figure lc and Figure 2 is of particular importance.

A study was made of the possible use of dark-field optical microscopy of the analysis of polymer specimens with complex supermolecular organization.