Polymerization rate, dependence

The overall polymerization rate depends on the number of forming particles within the emulsion medium. 

Niwa et al. [297] prepared a mixed SAM from dithiols on gold which partly bears a dithiocarbamate group. The RAFT-SIP of methacrylic acid was monitored by in situ quartz crystal microbalance. The polymerization rate depended strongly on the composition of the SAM. 

Consider the activation energy for various radical chain polymerizations. For a polymerization initiated by the thermal decomposition of an initiator, the polymerization rate depends on the ratio of three rate constants kp (kj/k,) 2 in accordance with Eq. 3-32. The temperature dependence of this ratio, obtained by combining three separate Arrhenius-type equations, is given by... 

The polymerization rate depends on both the reactivity of monomers and the nature of the counter anion of the initiator salt. In the fastest case (3-vinylcyclohexene oxide), a quantitative conversion was attained at 25 °C within 1.5 minutes whereas in the slowest case (e-caprolactone), irradiation at 60 °C for 60 min was required. 

In zirconocene-catalyzed olefin polymerizations similar processes are involved. Here polymerization rates depend at least linearly on olefin concentrations an... 

The effect of pulsed discharge on plasma polymerization may be viewed as the analogue of the rotating sector in photoinitiated polymerization. The ratio r of off time 2 to on time ti, r = l2lti, is expected to influence the polymerization rate depending on the relative time scale of t2 to the lifetime of free radicals in free radical addition polymerization of a monomer. This technique was used to estimate the average lifetime of free radicals in the polymerization. 

The polymerization rate depends on the nature of the 7r-allylic grouping attached to the initial catalyst and there does not appear to be an acceleration stage corresponding to a slow initiation step followed by a faster propagation reaction [248], which would have been expected. Values for fep (1 mole sec at 30°C) and activation energies (kcal mole ) for ir-allyl, ir-methallyl and ir-crotyl nickel trifluoroacetates are 1.2 X 10 3 and 12.2, 1.66 x 10 and 10.7 and 4.3 x 10 and 10.2, respectively. 

Polymerization Rate Dependence on Residual Polymerization Heat Lauryl Acrylate Photopolymerization... 

As Eq. (6.26) shows, polymerization rates depend on the monomer and initiator concentrations. Since these concentrations are known most accurately at zero time, it is useful to work with initial rates of polymerization, as given by... 

The polymerization rate depends on both the monomer reactivity and the nucleophilicity of the counteranion of the Initiator salt. The order of reactivity in photoinduced polymerization correlates well with the known relative nucleophilicities of the anions, that is, SbF > AsFg > PFg > BF. ... 

The polymerization rate depends upon the concentration of the amine and the monomer. The degree of polymerization is often, but not always, equal to the ratio of the monomer to the amine. ft means that the reaction may be similar to, but not identical to, a living-type polymerization. In addition, the molecular weight distribution curve may be broadened or bimodal. This may be due to some chemical termination reactions. These can be intramolecular reactions of the terminal amine group with some functional group in the side chain and lead to formation of hydantoic acid end groups. It may also be due to physical termination from precipitation of the product. 

The rates of plasma polymerizations depend on the chemical nature of the monomer, the electrode gap, the frequency and the power of discharges, the reactor configuration, the pressure, and the flow rate. Reactive species are abundant at low flow rates and the polymerization rate is limited by the monomer supply. At high flow rates, monomer is overabundant and the polymerization rate depends on the residence time. The polymerization rate thus goes through a maximum with increasing flow rate. 

The polymerization rate depends upon the concentration of the amine and the monomer. The degree of polymerization is often but not always equal to the ratio of the monomer to the amine... 

The polymerization rate depends very much on the proportion of free macroanions present. In the anionic polymerization of styrene with sodium as gegenion in THF, kinetic measurements (see below) gave the rate constants for polymerization via free macroanions as /C(-> = 65000 dm mol s" and fc(+) = 80 dm mol s for the polymerization via ion pairs (Table 18-2). According to the relation Vp = kp[P ] [M], the rate of the propagation reaction depends on the active species concentration [P ] as well as on the rate constant kp. But in this system, the dissociation equilibrium constant Kjy for ion pairs into free ions is only 10" mol/dm. If the polymerization is carried out in a solution with 10 mol/dm, then the proportion of free ions is consequently only (10 10 ) = 0.01, that is, 1 %, with 99% of the active species being ion pairs. Thus, despite a much lower rate constant, the polymerization rate is also determined to a considerable extent by the ion pairs. 

This equation show that the polymerization rate depends on the square root of the initiation rate. If we make an arrangement on this equation by using Equation 2.9, we can say that the pol rmerization rate depends on the square root of the initiator concentration ... 

According to observations of the authors [9] the polymerization rate depends on the state of conversion corresponding to the beginning of the dark period of the process. The same dependence is observed also in another study [10] after the UV-illumination is... 

The objective of kinetic modeling is to build a description of how polymer architecture and polymerization rate depend on reaction conditions (temperature, pressure) and species concentrations from a defined set of kinetic mechanisms a dynamic model is required to examine how properties change as a function of time. The mechanisms to be included in a model depend upon its end-use. For simple... 

Since it is a chain breaking process, chain transfer leads to lower molecular weights. However, its effect on the polymerization rate depends on the values of the rate coefficients. In the case where the rate limiting step is a radical transfer to the CTA (T), there is a decrease in M but no effect on monomer conversion rate. If the radical transfer from T to monomer is much slower than the transfer to T, then inhibition can occur, which slows down the reaction and leads to formation of longer chains. 

The emulsion polymerization of vinyl acetate (to homopolymers and copolymers) is industrially most important for the production of latex paints, adhesives, paper coatings, and textile finishes. It has been known that the emulsion polymerization kinetics of vinyl acetate differs from those of styrene or other less water-soluble monomers largely due to the greater water solubility of vinyl acetate (2.85% at 60°C versus 0.054% for styrene). For example, the emulsion polymerization of vinyl acetate does not follow the well-known Smith-Ewart kinetics and the polymerization exhibits a constant reaction rate even after the separate monomer phase disappears. The following observations have been reported for vinyl acetate emulsion polymerization [78] (a) The polymerization rate is approximately zero order with respect to monomer concentration at least from 20% to 85% Conversion (b) the polymerization rate depends on the particle concentration to about 0.2 power (c) the polymerization rate depends on the emulsifier concentration with a maximum of 0.25 power (d) the molecular weights are independent of all variables and mainly depend on the chain transfer to the monomer (e) in unseeded polymerization, the number of polymer particles is roughly independent of conversion after 30% conversion. 

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