Persulfate initiated polymerization

The particle number dependency expected from the rate equation is 0.33. This is in good accord with the results of this study (Figure 8) and, significantly, corresponds well with the upper limit in the data of Ugelstad (8) for persulfate initiated polymerization. The particle number was shown to be approximately proportional to the soap concentration and independent of the initiation rate. This differs considerably from the. 6 power soap dependency and. 4 power initiator dependency found by Smith and Ewart. We suggest this difference is the result of radical de-... 

In an inverse emulsion polymerization, a hydrophilic monomer, frequently in aqueous solution, is emulsified in a continuous oil phase using a water-in-oil emulsifier and polymerized using either an oil-soluble or water-soluble initiator the products are viscous latices comprised of submicroscopic, water-swollen, hydrophilic polymer particles colloidally suspended in the continuous oil phase. The average particle sizes of these latices are as small as 0.05 microns. The technique is applicable to a wide variety of hydrophilic monomers and oil media. The inverse emulsion polymerization of sodium p-vinylbenzene sulfonate initiated by both benzoyl peroxide and potassium persulfate was compared to the persulfate-initiated polymerization in aqueous solution. Hypotheses for the mechanism and kinetics of polymerization were developed and used to calculate the various kinetic parameters of this monomer. 

Figure 10. Variation of per cent conversion with time for persulfate-initiated polymerizations at 50° C.

The other parameters for the benzoyl peroxide-initiated polymerizations were calculated in the following manner. Using the subscripts B and P to denote the benzoyl peroxide- and persulfate-initiated polymerizations respectively. Equations 2 and 3 give... 

Thus values of az can be calculated for the benzoyl peroxide-initiated polymerizations from the known values of az (persulfate-initiated polymerizations), and the ratios of average particle volumes and polymerization rates. These values of az may then be substituted in Equations 3 and 4 to give values for f/k and fk which may then be combined to give values for f and The results of these calculations are shown (Table VIII-A). The values of az are all considerably less than 2. From Figure 13 for the case where the radicals are generated in, or enter,... 

Figure 11.4 is an example for temperature profile of a FP. This figure illustrates how tricaprylmethylammonium persulfate initiated polymerization of tri(ethylene glycol)... 

By the way, it should be noted that Barlett and Nozaki included sodium pyrophosphate in their formulation to counteract the decrease in pH as a persulfate-initiated polymerization proceeds. At a low pH, the monomer is said to be susceptible to hydrolysis [18]. Work by Rinby and co-workers has indicated that the nature of the addition of free radicals such as H2N and OH is profoundly influenced by changes in the pH of the medium fix>m 1.4 to approximately 7.8 [53-55]. The radicals formed from persulfate in emulsion systems may be expected to be influenced by pH variations also. 

The results for the persulfate-initiated polymerizations were used to calculate the kinetic parameters of the benzoyl peroxide-initiated pol3mierizations. Table XIII shows that the values of z were all smaller than one, i.e., the rates of emulsion polymerization are smaller than for the corresponding persulfate-initiated solution polymerization. Moreover, the values of n were in the range 0.006-0.2, in accord with Smith-Ewart case 1 kinetics (n l). Since benzoyl peroxide is soluble in o-xylene and virtually insoluble in water, the radicals which initiate polymerization apparently arise from the decomposition of that benzoyl peroxide dissolved in the aqueous phase the presence of monomer may increase the solubility of benzoyl peroxide in the aqueous phase and the layer of Span 60 adsorbed at the particle interface may form a barrier to the diffusion of the hydrophobic radicals from the o-xylene phase to the aqueous phase. 

Potassium persulfate-initiated polymerization of acrylamide (AM) in water was chosen as a case study for chain transfer reactions monitored by ACOMP [7]. Chain transfer properties of ethanol (EtOH) and 2-propanol (PrOH) were investigated. 

Riggs JP, Rodriguez F. Persulfate-initiated polymerization of acrylamide. J Polym Sci Pol Chem 1967 5 3151-3165. 

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