Mobility of macromolecule

To maintain a high polymerization rate at high conversions, reduce the residual amount of the monomer, and eliminate the adverse process of polyacrylamide structurization, polymerization is carried out in the adiabatic mode. An increase in temperature in the reaction mixture due to the heat evolved in the process of polymerization is conductive to a reduction of the system viscosity even though the polymer concentration in it rises. In this case, the increase in flexibility and mobility of macromolecules shifts the start of the oncoming gel effect into the range of deep transformation or eliminates it completely. 

The rate of polymerization, as well as the mobility of macromolecules at the contact zone, is affected by the presence of the filler near the matrix. This results in a reduction of the number of possible conformations of molecules in the boundary layer developed, causing the formation of a denser material in the boundary layer than in the bulk. 

In description of effects observed in extension of molten polymers, the determinant is the phenomenon of anisotropy of the mobility of macromolecules. In the Doi-Ed-vards reptation theory the anisotropy of the mobility of macromolecules is taken into account topologically by means of placing a macromolecule into a certain hypothetical tube. In this case large-scale movements are allowed only along the macromolecule and are totally inhibited in the lateral direction. This, indeed, is a limiting case of mobility anisotropy. 

It has been demonstrated 54) that the dependency of viscosity upon elongation velocity varies significantly in its character with alteration of the lateral (transverse) mobility of macromolecules. In case there is no lateral mobility of macromolecules, the longitudinal viscosity strictly decreases under tension (see Fig. 11) which corresponds to prognostications proceeding from the Doi-Edvards theory. In case there is a lateral mobility of macromolecules, an insignificant maximum or monotonous increase in longitudinal viscosity of the medium with increase in extension velocity is observed. 

Fig. 11. Longitudinal viscosity at different values of the parameter of lateral mobility of macromolecules b...

There were different generalisations of the reptation-tube model, aimed to soften the borders of the tube and to take into account the underlying stochastic dynamics. It seems that the correct expansion of the Doi-Edwards model, including the underlying stochastic motion and specific movement of the chain along its contour - the reptation mobility as a particular mode of motion, is presented by equations (3.37), (3.39) and (3.41). In any case, the introduction of local anisotropy of mobility of a particle of chain, as described by these equations, allows one to get the same effects on the relaxation times and mobility of macromolecule, which are determined by the Doi-Edwards model. 

The mobility of a macromolecule, constrained by other macromolecules, can be also calculated as (5.1). In the linear approximation, the zeroth normal co-ordinates of the macromolecule (equation (4.1), at z/jj = 0) define diffusive mobility of macromolecule. The one-sided Fourier transform velocity correlation function is determined by expression (4.15), so that we can write down the Fourier transform... 

Thus, in dependence on the way of macromolecule conformation change, ratio of life times of salt bonds and correlation time of macromolecule segment rotation, change of local macromolecule units density, under formation of complex polyelectrolyte-SAS segment mobility of macromolecule may be increased, decreased or remains constant. 

The interpretation of the diffuse scattering from macromolecular crystals will provide increasing information on the mobility of macromolecules. 

The viscoelastic properties of the vulcanizates in the function of temperature were examined by means of the method of resonance-free, forced vibrations, using Rheovibron apparatus DDV-II-C at frequency of 110 Hz. The mobility of macromolecules and their fragments was examined by means of the nuclear magnetic resonance (NMR) method. 

T able 12 Connection between temperature and mobility of macromolecules regarding the course of mechanical damping in the main softening range [4]... 

Both stmcture and macromolecular d5mamics render the significant influence on its stability, i.e., chemical nature of the solvent (plasticizer), its basicity, specific and non-specific solvation, degree of PVC in a solution (solubility), segmental mobility of macromolecules, thermodynamic properties of the solvent (plasticizer), formation of associates, aggregates, etc. 

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