arXiv subjects

Andrei N. Yakunin

Publications and source records attributed to Andrei N. Yakunin.

6 recordsLinked to original sources

arXiv2012

Self-organising Dissipative Polymer Structures

In frameworks of the scaling theory of phase transitions and critical phenomena the quantitative dependence of macroscopic properties on nanostructural parameters in a polymeric material is revealed. The draw ratios at neck and at break are referred to the macroscopic properties. The structure is characterized by an average thickness of amorphous layers in isotropic melt-crystallized linear high density polyethylene which is chosen as an example. The square of the neck draw ratio is equal to the product of the square of the draw ratio at break and the chain ends collision probability. This probability in its turn is proportional to the average thickness of amorphous layers in the isotropic material. The neck draw ratio is a parameter of order. Polymers with flexible chains are solutions in solid state as well as in melt, the interacting ends of a marked chain serving as a solvent. At critical polymerization degree all the phases are identical. This research is an important contribution to the molecular theory of polymer liquids. It has been found that the melt viscosity vs the molecular weight of linear flexible-chain polymer follows the power law with the 3.4-exponent within the reptation model near the critical point. This is different from the value 3 expected for the melt of ring macromolecules. The rotation vibration precession motion of chain ends about the polymer melt flow direction were taken into account to find better agreement with the experiment.

cond-mat.soft↗

arXiv2005

Rotation Diffusion as an Additional Mechanism of Energy Dissipation in Polymer Melts

The research is important for a molecular theory of liquid and has a wide interest as an example solving the problem when dynamic parameters of systems can be indirectly connected with their equilibrium properties. In frameworks of the reptation model the power law with the 3.4-exponent for the melt viscosity relation to the molecular weight of linear flexible-chain polymer is predicted as distinct from the value 3 expected for a melt of ring macromolecules. To find the exponent close to experimental values it should be taken into account the rotation vibration precession motion of chain ends about the polymer melt flow direction.

cond-mat.dis-nn↗

arXiv2003

A bicontinuous structure in some systems with cubic mesophases

A cubic structure of polymer colloid complexes is studied. The technique of the research includes i) an analysis of well-known literature SAXS data; on this base, at some assumptions, ii) constructing a simple model to estimate geometric structure parameters and to receive a simulated scattering curve, iii) calculations of energetic parameters by help of the analytical fluctuation theory of the phase transitions; iv) comparing the model with the real structure obtained from the SAXS data by the electron density distribution reconstruction method. In the presence of an effective field the 2-nd order phase transition transforms to the 1-st order one in the vicinity of the Lifshitz point. As a result, a bicontinuous structure in cubic mesophases is formed.

cond-mat.stat-mech↗

arXiv2003

Gauge fields in dissipation processes

An technique is extended to estimate some critical exponents without using the expansion over the coupling constant. The data obtained is in a agreement with those found by help of the 2D Onsager method or with recent 3D results. In the second case the exponent of the correlation radius can be expressed in terms of the fine structure constant. The polymer plastic deformation process is regarded as the energy dissipation one due to the spontaneous symmetry breaking controlled by gauge fields. A comparison of the theory with other ones and different experimental data is carried out.

cond-mat.stat-mech↗

arXiv2002

Nematic Ordering Problem As Polymer Excluded Volume One

The new method of the mean-field approximation is extended. An approach which enables to estimate some parameters of the transition from the isotropic state of hard sticks to the nematic ordering phase is suggested. An technique of the investigation of the model jointed to the so-called polymer excluded volume problem is proposed. The critical exponents are estimated. The transition of a swelling polymer coil to ideal is revealed as the polymerization degree of the chain increases. The entanglement concentration obtained is in accordance with experimental data for polymers with flexible chains. The number of monomers between neighbor entanglements assumes to be the ratio of the stick length to its diameter. The comparison of the theory with experimental data is made.

cond-mat.stat-mech↗

arXiv2002

Polymer Melt Viscosity

The research is important for a molecular theory of liquid and has a wide interest as an example solving the problem when dynamic parameters of systems can be indirectly connected with their equilibrium properties. In frameworks of the reptation model the power law with the 3.5-exponent for the melt viscosity relation to the molecular weight of flexible-chain polymer is obtained. In order to find the exponent close to experimental values it should be taken into account the rotation vibration precession motion of chain ends with respect to the polymer melt flow direction.

cond-mat.stat-mech↗