Polycondensation kinetics

In actual fact a considerable amount of intramolecular reaction occurs in many polycondensation systems. This has the effect of reducing a, in that some of the reactive chain ends are used up. Because of this complication and because of the unequal reactivity of active groups, the present theories discussed above do not fit experimental data exactly. Nevertheless, the primary argument that the general scheme of polycondensation kinetics is largely in line with the kinetic mechanisms of the same reactions leading to low-molecular-weight compounds has been adequately demonstrated from experimental results on a number of chemical systems. 

As it follows from the Eq. (29), the value is defined through reaction kinetic characteristics and, as consequence, is the parameter, controlling polycondensation kinetics [44, 45]. 

Within the frameworks of fractal analysis the polycondensation kinetics is described by the general Eq. (27). If the indicated relationship describes polycondensation kinetics correctly, then the dependence Q(t) in double logarithmic coordinates should give a straight line, from the slope of which the value Dp changing within the limits of 1 < Dj,< 3 [4], is determined. The determined by the indicated mode Df values are also adduced in Table 2. 

Thus, the stated above results have shown, thatpolyarylates series high-temperature polycondensation kinetics, characterized by the reaction rate constant pi, at different temperatures and solvents is controlled by three main factors process thermal activation (T), diphenol reactiveness (Z r) and macromolecular coil stmc-ture (Dj.). The obtained generalized dependence Ig allows to perform... 

THE DESCRIPTION OE POLYCONDENSATION KINETICS WITHIN THE FRAMEWORKS OF IRREVERSIBLE AGGREGATION MODELS... 

In paper [67] it has been shown, that high-temperature polycondensation kinetics of polyaiylates and polysnlfones series, characterized by reaction rate constant kr (determined on the first initial part of the kinetic curve Q,) at different temperatures and reactive medinms is described by three main factors. These factors are Process thermal activation, bisphenols reactive ability and macromo-lecular coil structure. The indicated factors can be characterized quantitatively... 

Kozlov, G. V Burya, A. I. Temiraev, K. B. Mikitaev, A. K. Chigvintseva, O. P. The description of low-temperature polycondensation kinetics within the frameworks of irreversible aggregation models and fractal analysis. Problems of Chemistry and Chemical Technology, 1998, (3), 26-29. 

In modeling the polycondensation kinetics, there is also a question of how we define the reaction rate constants. In the above reaction represented by a functional-group modeling framework, the forward rate constant k is the reaction rate constant for reaction of a methyl ester group with a hydroxyl group, not the reaction rate constant for DMT and ethylene glycol molecules. For example, the above reaction can be represented as follows ... 

In order to evaluate the effect of the glycol type and temperature on the polycondensation kinetics, the variation of the intrinsic viscosity with time was measured in [45] and presented in Figure 4.14a-c. As was expected, a great increase of... 

Esterification and polycondensation kinetics of PPSu synthesis can be well described on the basis of rather simple simulation models, taking into account the reaction kinetics and the functional group modeling approach. The latter is a very beneficial technique which includes aspects of the reaction mechanism although with the minimum computational effort. 

This reaction would provide completely unique polycondensation kinetics and explain perhaps the peculiarities of several phase transfer catalyzed poly-etherifications. One of these peculiarities observed also in the present case refers to the formation of polyethers at low conversion (Table 1). 

Harshe, Y. M., Storti, G., Morbidelli, M., Gelosa, S. Moscatelli, D. 2007. Polycondensation kinetics of lactic acid. Macromolecular Reaction Engineering, 1, 611-621. 

Rankin S.E., Macosko C.W., McCormick A.V. Sol-gel polycondensation kinetic modeling Methylethoxysilanes. AIChE J. 1998 44(5) 1141-1156 Ramakrishnan S., Zukoski C.F. Characterizing nanoparticle interactions Linking models to expai-ments. J. Chem. Phys. 2000 113(3) 1237-1248 Ramakrishnan S., Fuchs M., Schweizer K.S., Zukoski C.F. Entropy driven phase transitions in colloid-pol3mer suspensions Tests of depletion theories. J. Chem. Phys. 2002a 116(5) 2201-2212... 

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