Surface Chemistry Aspects of Emulsion Polymerization

Roe, Charles P.

doi:10.1021/ie50705a006

Cited by 204 publications

(81 citation statements)

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“…According to the hypothesis of the formation mechanism of PMP for homogeneous nucleation [27,[35][36][37][38][39][40][41][42], the formation of particles or macromolecules derived from the radicals who have reached the critical length (j ), where they lose solubility and precipitate in the aqueous phase. Further growth of the polymer particles dropped in the water is treated differently.…”

Section: The Mechanism Of Homogeneous Nucleationmentioning

confidence: 99%

“…Later on, these ideas found their development in the investigations of Priest [35], Roe [36], Fitch and Tsai [39,40], Yeliseyeva [37,38], Christiansen [44], Ugelstad [27], Pepard [45] Wilkinson [46][47][48], Oganesyan [49][50][51], Tauer [52][53][54][55][56][57], etc.…”

Section: The Mechanism Of Homogeneous Nucleationmentioning

confidence: 99%

“…According to the representations of micellar [1][2][3][4][5][6][7] and homogeneous [27,[35][36][37][38][39][40] theories of particles nucleation, the monomer droplets play the role of a reservoir from which the monomer in the polymerization process goes into growing PMP by the diffusion through the aqueous phase. Subsequent studies performed by Pravednikov, Gritskova, Taubman where σ12 is interfacial tension, dwp is the density of the dispersion medium, and E is the energy expended to move a unit mass of the medium [80].…”

Section: Mechanism Of Particle Formation From Microdroplets Of Monomermentioning

confidence: 99%

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An Advanced Approach on the Study of Emulsion Polymerization: Effect of the Initial Dispersion State of the System on the Reaction Mechanism, Polymerization Rate, and Size Distribution of Polymer-Monomer Particles

Khaddazh¹,

Литвиненко²

2012

Polymerization

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According to these ideas, in the presence of surfactants, the initial emulsion consists of two kinds of particles of different sizes: the monomer droplets with diameters of 5-20 microns and colloidal degree of dispersion and monomer-swollen surfactant micelles (5-10 nm).The mechanism of Harkins-Yurzhenko lied in the base of Smith and Ewart quantitative theory [5][6][7], with further refinements in the works of other authors . The main aspect of this theory is that radicals formed in the aqueous phase are trapped by the monomer swollen surfactant micelles and turn to PMP. It is assumed that only one out of every 100-1000 micelles captures a radical and becomes PMP, and the rest of the micelles are spent to stabilize the growing PMPs. Polymer-monomer particles formation ends with the disappearance of micelles of the emulsifier in the aqueous phase, after which the number of particles remains constant.Initial system contains monomer droplets with a diameter of 5-15 microns, their concentration being 10 12 -10 14 droplets/l, the monomer-swollen micelles with diameters of 5-10 nm and the number of micelles 10 18 -10 21 l -1 , and a water-soluble initiator (usually potassium persulfate) at a concentration of 1% per monomer [8]. Only a small fraction of the molecules of the monomer is located in the interior of the micelles (1-2%) and is dissolved in the aqueous phase (0.03% for styrene). In the aqueous phase, 10 14 -10 16 PMP / l are formed with a diameter in the range of 20-200 nm. Monomer droplets due to their relatively small surface area hardly compete with micelles in capturing radicals.In the polymerization process PMPs increase their size due to the diffusion of the monomer from droplets and monomer-swollen micelles which contains no radicals [1-3, 5, 9-15].Three limiting cases were considered:1. The number of free radicals in the particles is small compared with the total number of radicals, thus the average number of radicals per particle is much less that unity. 2. The average number of radicals per particle is equal to 0.5. This case is realized under following conditions: the activity of the radical in the particle persists as long as the second radical enter the particle, and the time of chain-breaking is small as compared with the average time interval of successive absorption of radicals by the particle. The authors believe that case 2 corresponds to the emulsion polymerization of styrene in the presence of potassium persulfate [5]. The rate of formation of primary radicals is equal to 10 13 radicals• ml -1 s -1 . The average number of polymer particles is of the order of 10 14 -10 16 in 1 ml of the system. If all the radicals formed by the decay of the initiator enter the polymer particles, the average frequency at which a radical enters a particle is once per 10 -100 sec. At any time, the particle contains either one radical or does not contain radicals at all, since it is assumed that chain termination occurs immediately in contact with the second radical in the particle. The particle is inactive unt...

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Section: The Mechanism Of Homogeneous Nucleationmentioning

confidence: 99%

Section: The Mechanism Of Homogeneous Nucleationmentioning

confidence: 99%

Section: Mechanism Of Particle Formation From Microdroplets Of Monomermentioning

confidence: 99%

See 1 more Smart Citation

An Advanced Approach on the Study of Emulsion Polymerization: Effect of the Initial Dispersion State of the System on the Reaction Mechanism, Polymerization Rate, and Size Distribution of Polymer-Monomer Particles

Khaddazh¹,

Литвиненко²

2012

Polymerization

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“…His conceptual picture has remained essentially unchanged to the present day, although there has Been some evidence presented to support the theory that particle nucleation occurs in the water phase while polymer particles are merely stabilized by soap molecules (28). Flory (6) presents an excellent discussion of emulsion polymerization in his book.…”

Section: States In the Late 1930's (3)mentioning

confidence: 99%

“…Funderburk (7) showed that the Smith-Ewart model could be modified to account for particle size variation. Whereas Funderburk proceeded to average the recursion relation in a manner similar to Stockmayer's technique, the procedure here will be to use this relation directly in Equation 28. The rate of formation of the N^-type particle can be written as :…”

Section: Emulsion Polymerization Rate Expressionmentioning

confidence: 99%