Aqueous heterophase polymerization of styrene—a study by means of multi-angle laser light scattering

Kozempel, Steffen; Tauer, Klaus; Rother, G.

doi:10.1016/j.polymer.2004.11.060

Cited by 30 publications

(30 citation statements)

References 31 publications

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“…This was observed for the first time by multi-angle laser light scattering during a surfactant-free styrene emulsion polymerization. [95] Subsequently, it was proven by means of light microscopy that at the quiescent interface of immiscible liquids, that is, in the absence of any mechanical shear forces, droplet formation takes place on either side. [96] Association and formation of clusters of various sizes in water has also been detected for hydrophilic solutes such as acetic acid, D-glucose, urea, dimethyl sulfoxide, or ethanol.…”

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confidence: 99%

Molecular Aspects of Radical Polymerizations—The Propagation Frequency

Tauer

Hernández

2010

Macromol. Rapid Commun.

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The product of the propagation rate constant and monomer concentration is a central issue of radical polymerization. Both quantities are strongly interrelated as the determination of a reliable value of the propagation rate constant requires exact knowledge of the monomer concentration. Even for homogeneous polymerization conditions, exact knowledge of the monomer concentration at the reaction site from the molecular perspective is not trivial. For emulsion polymerizations the situation is additionally complicated by mass transfer events and colloid-chemical effects. Molecular modeling appears as an attractive alternative or complement to the deterministic kinetic description of radical polymerizations.

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confidence: 99%

Molecular Aspects of Radical Polymerizations—The Propagation Frequency

Tauer

Hernández

2010

Macromol. Rapid Commun.

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“…With multi angle laser light scattering in glass cuvettes the development of a strong scattering signal in the aqueous phase was observed over a period of some hours after styrene was quiescently place on top of the water. [15] These data indicate the formation of styrene droplets via spontaneous emulsification. Additional proofs for the existence of styrene droplets in a quiescent surfactant-free styrene in water system come from electron microscopy and light microscopy.…”

Section: Monomer Concentration and Particle Morphologymentioning

confidence: 84%

Adaption of the Mechanism of Emulsion Polymerization to New Experimental Results

Tauer¹,

Hernández²,

Kozempel³

et al. 2007

Macromolecular Symposia

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Summary: New experimental investigations of the 'classical' batch ab-initio emulsion polymerization of styrene reveal the important role of monomer droplets for the whole process. Monomer droplets with a size between a few and some hundreds of nanometers, which are formed by spontaneous emulsification as soon as styrene and water are brought into contact, have a strong influence on the particle nucleation, the particle morphology, and the swelling of the particles. Experimental results confirm that micelles of low molecular weight surfactants are not a major locus of particle nucleation. Brownian dynamics simulations show that the capture of matter by the particles (monomer or radicals) strongly depends on the polymer volume fraction and the size of the captured species (primary free radicals, oligomers, single monomer molecules, or clusters).

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“…A further development of the mechanism of nucleation of aggregate particles is reflected in the publications of Tauer, Kuhn et al [52][53][54][55][56][57]66]. This theory is indeed a combination of ideas proposed by Fitch et al [39][40][41] and Oganesyan [51] with the difference that the authors consider the surface energy of the particles as an adjustable parameter of the model.…”

Section: Aggregative Nucleation Mechanismmentioning

confidence: 97%

“…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%

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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Aqueous heterophase polymerization of styrene—a study by means of multi-angle laser light scattering

Cited by 30 publications

References 31 publications

Molecular Aspects of Radical Polymerizations—The Propagation Frequency

Molecular Aspects of Radical Polymerizations—The Propagation Frequency

Adaption of the Mechanism of Emulsion Polymerization to New Experimental Results

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

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