Propagation rate constants, polymer

Ionic polymers may exist as undissociated, unsolvated ion pairs undissociated ion pairs solvated to some extent solvated ions dissociated to some extent or some combination of these. The propagation rate constant kp and the dissociation equilibrium constant K of the lithium salt of anionic... 

Here Ceq is the ethylene concentration equilibrium to the concentration in a gaseous phase, Kp the propagation rate constant, N the concentration of the propagation centers on the catalyst surface, Dpe the diffusion coefficient of ethylene through the polymer film, G the yield of polymer weight unit per unit of the catalyst and y0at, ype are the specific gravity of the catalyst and polyethylene. 

By quenching the polymerization with C1402 or Cl40 the determination of the number of propagation rate constants was found to be also possible for the two-component catalytic system TiCl2 + AlEt2Cl 158, 159). In contrast to alcohols, carbon dioxide and carbon monoxide under polymerization conditions react only with titanium-carbon active bonds and do not react with inactive aluminum-polymer bonds. 

Development of a relationship which gives the decrease in the propagation rate constant as a function of temperature and polymer molecular weight and concentration. 

Largest polymer chain length in polymer distribution Smallest polymer chain length in seed distribution and reactor effluent Initiation rate constant Propagation rate constant... 

The effect of media viscosity on polymerization rates and polymer properties is well known. Analysis of kinetic rate data generally is constrained to propagation rate constant invarient of media viscosity. The current research developes an experimental design that allows for the evaluation of viscosity dependence on uncoupled rate constants including initiation, propagation and macromolecular association. The system styrene, toluene n-butyllithium is utilized. 

As the polymerization reaction proceeds, scosity of the system increases, retarding the translational and/ or segmental diffusion of propagating polymer radicals. Bimolecular termination reactions subsequently become diffusion controlled. A reduction in termination results in an increase in free radical population, thus providing more sites for monomer incorporation. The gel effect is assumed not to affect the propagation rate constant since a macroradical can continue to react with the smaller, more mobile monomer molecule. Thus, an increase in the overall rate of polymerization and average degree of polymerization results. 

Propagation constants, 20 219 Propagation plant, brewer s yeasts, 3 581 Propagation rate constants (kp), in VDC polymer degradation, 25 715-716, 717t Propagation reactions, 14 274... 

P. H. Plesch, S. H. Shamlian, The Propagation Rate-Constants of the Cationic Polymerisation of Alkenes Part III. Indene, two Vinyl Ethers, and General Discussion, Europ. Polym. J., 1990, 26, 1113. 

A similar technique was used almost simultaneously by Penczek [18, 19] for the polymerisation of bis-chloromethyl oxetan (BCMO) by (i-Bu)3A/-H20 in chlorobenzene. In this system, too, there is termination by reaction of growing centres with polymer, but initiation is slow and the equations are correspondingly more complicated. The authors believe that their value of the propagation rate-constant refers to ion-pairs and is thus k"v, and we see no reason to disagree with their view they also determined k and kt. 

The Propagation Rate-Constants in Cationic Polymerisations, P.H. Plesch, Advances in Polymer Science, 1971, 8, 137-154. 

The Propagation Rate-Constants of the Cationic Polymerisation of some Alkenes in Nitrobenzene - Part IV. Not the Real kp, (Developments in the Theory of Cationic Polymerisation, Part XII), P.H. Plesch, European Polymer Journal, 1993, 29, 121-124. 

Auguste S, Edwards HGM, Johnson AF et al. (1996) Anionic polymerization of styrene and butadiene initiated by n-butyllithium in ethylbenzene determination of the propagation rate constants using Raman spectroscopy and gel permeation chromatography. Polymer 37 3665-3673... 

The results obtained by liquid-phase oxidation or co-oxidation of various hydrocarbons are reviewed, and new results are reported for new kinds of compounds such as alkyl-aromatics, alcohols, and ethers, which were also systematically studied by co-oxidation. Gathering all kinetic data and discussing them in connection with data on absolute termination constants, obtained by other groups through physical measurements, enables us to estimate the termination and propagation rate constants for about 40 compounds and to present characteristic values for some new classes of compounds. Examples demonstrate that co-oxidation studies make it possible to explain the behavior of complex compounds reacting by different kinds of bonds, and more particularly the behavior of polymers oxidized in solution. 

Moreover, the size of the polyacrolein blocks depends on the ratio of the propagation rate constant kpr to the transfer rate constant hm (kpr/hm). This ratio may depend on the nature but also on the complexatlon of the living ends. Indeed, an evolution of the complexatlon state exists for the (1,4) living end and may involve a variation of (kpr/hm) (1,4) during the propagation. The previous mechanism can explain the bimodal weight distributions obtained for both homopolyacrolelns and block polymers. 

The information available up to 1965 on the polymerization kinetics of vinyl acetate has been reviewed by Lindemann 184% who collected data on the transfer coefficients with monomer and polymer, which may be denoted as Clm and Clp respectively. These are the ratios of rate constants for attack on monomer or polymer (per monomer unit) to the propagation rate constant they are the... 

Fig. II. Dependence of apparent propagation rate constant on living end concentration styrene-n-butyllithium-benzene-dimethoxyethane, 25° C, DME contents (vol.-%) from the top 50, 45, 40, 30 and 10%. A 5 KV/cm, 3 KV/cm, o 0 KV/cm. Reproduced, with permission, from Ise, Hirohara, Makino, Takaya, and Nakayama presented at the 17th Discussion Meeting of High Polymers, October, 1968, Matsuyama, Preprint p. 261...

Table 2. The propagation rate constants for the polymerisation of NCA s of n,L-leucine and n,L-phenyl alanine initiated by the pre-formed polymer Rate = k [NCA] [growing ends]...

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