Studies of particle formation in styrene emulsion polymerizations using 9‐vinyl anthracene as a probe molecule

Pearson, L. T.; Louis, P.; Gilbert, Robert G.; Napper, Donald H.

doi:10.1002/pola.1991.080290408

Cited by 10 publications

(3 citation statements)

References 19 publications

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“…The main conclusion which might be drawn from our analysis is that, at least for styrene emulsion polymerization with surfactant concentrations well above CMC, early-time PSDs, when properly analyzed, are in agreement with the formation rate of latex particles being monotonically decreasing (rather than increasing) for much of the nucleation time. Recently, some new experimental data on styrene polymerization became available supporting the hypothesis that, above CMC, micellar entry can significantly contribute to particle formation mechanism (Pearson et al, 1991). Basically, these results agree with the interpretation of the PSD data given here.…”

Section: Comparison With Experimental Datasupporting

confidence: 90%

Nucleation mechanisms and particle size distributions of polymer colloids

Giannetti¹

1993

AIChE Journal

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A theoretical model is developed for the time evolution of volume particle size distributions ( PSDs) of polymer colloids during the nucleation stage. Analytic expressions for the PSD and related cumulants are presented, Negatively skewed distributions are observed only when the formation rate of mature latex particles is a monotonically decreasing function of time. When this model is tested against experimental PSD data of styrene polymerization at 5O"C, agreement between theory and experiment is found only assuming a monotonically decreasing nucleation rate. The fitting is completely missed when the production rate of mature latex particles is predicted according to the coagulative nucleation scheme. Theory and experiment can combine introducing an extended coagulative nucleation model, According to this approach, the nucleation time is much shorter than predicted by earlier theories. As a consequence, most of the mechanistic information convoluted with early-time PSDs is lost.

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Section: Comparison With Experimental Datasupporting

confidence: 90%

Nucleation mechanisms and particle size distributions of polymer colloids

Giannetti¹

1993

AIChE Journal

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“…It has been reported that a coagulation/homogeneous nucleation mechanism dominated particle formation in the batch polymerization of styrene below the CMC. 24 Water soluble oligomers were reported in the polymerization and copolymerization of styrene. 19,25 If coagulation occurred near the beginning of polymerization to produce a constant number of growing particles, this results in monodispersity.…”

Section: Mechanism Of Particle Growthmentioning

confidence: 99%

?Continuous? emulsifier-free emulsion polymerization for the synthesis of monodisperse polymeric latex particles

Salovey

2000

J. Polym. Sci. A Polym. Chem.

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“…14 The molecular weight and high hydrophobicity of STPO promote the formation of rigid surface film 35 and suppress Ostwald ripening. 15 In the former case, the transfer of hydrophobic components (initiator or its radicals) from monomer droplets to droplets or polymer particles within the droplets or particles clusters through the interface between droplets during collision is reduced and the release of primary radicals is depressed. In the latter case, the depressed monomer droplet degradation depresses the transfer of monomer and hydrophobe(STPO) to the reaction loci.…”

Section: Polymerization Ratementioning

confidence: 99%

Microemulsion Polymerization of Butyl Acrylate. Effect of Radical Scavenger and Formation of Primary Radicals

Capek

Juraničová

2000

Polym J

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:Microemulsion polymerizations of butyl acrylate initiated by dibenzoyl peroxide in the presence of a radical scavenger (RS)(stable radicals: an oil soluble RS: 4-stearoyloxy-2,2,6,6-tetramethyl piperidine-1-oxyl (STPO) and water soluble RS: 4-hydroxy-2,2,6,6-tetramethyl piperidine-1-oxyl (HTPO)}were investigated. STPO and HTPO decreased the rate of polymerization and the decrease was more pronounced with STPO. Inorganic salts and organic additives decreased the rate of polymerization. The shift of the maximum rate of polymerization to lower conversion by increasing temperature and addition of several additives was attributed to increase of particle number and decrease of monomer concentration at the reaction loci. The decrease of the particle size in the presence of RS is attributed to retardation of particle growth. A close packed structure at the droplet surface promoted by current additives acts as a barrier for entering radicals. The larger overall activation energy in runs with STPO is discussed in terms of a depressed entry ofradicals into microdroplets.KEY WORDS Microemulsion / Butyl Acrylate/ Polymerization/ Tetramethyl Piperidine-1-oxyl Radical Scavenger/ Inorganic Salts/ Rate of Polymerization/ Polymer Particles/ In the case of microemulsion polymerization initiated by the oil-soluble initiator, there are two main approaches for the production of primary radicals : 1 -3 1) in the monomer swollen micelles or polymer particles radicals desorb to the aqueous phase and 2) in the aqueous phase radicals are generated from the fraction of the oilsoluble initiator dissolved in water. -6 A partly watersoluble initiator such as a,a'-azobis(isobutyronitrile) (AIBN) forms primary radicals in both the aqueous phase and in the monomer-swollen micelles. In the case of highly hydrophobic initiator the formation of radicals from the fraction of initiator dissolved in the aqueous phase is negligible, as well as exit of hydrophobic primary radicals into the aqueous phase. Microemulsion and miniemulsion polymerizations initiated by hydrophobic initiators such as dibenzoyl peroxide (DBP) or lauroyl peroxide (LPO) are reported to be relatively fast. 1 · 2 • 7 The very low water solubility of hydrophobic initiator (DBP, LPO, etc.) and radical fragments propose a very low rate of polymerization (ca. by two orders in magnitude lower than that for peroxodisulfate initiated polymerization). The strong cage effect within the microdroplets or latex particles depresses the formation of radicals in the monomer phase. However, the rate of DBP-initiated polymerization was ca. 5 times smaller than the water-soluble peroxodisulfate initiated polymerization (polymerizations carried out under the same reaction conditions). Thus, the polymerization behavior is not properly described by two reaction approaches : 1) water-phase initiation and 2) desorption of primary (monomeric) radicals formed in the microdroplets in the aqueous phase.The non-linearity between the molecular weights of the polystyrene (much below 10 5 ) and laser r...

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Studies of particle formation in styrene emulsion polymerizations using 9‐vinyl anthracene as a probe molecule

Cited by 10 publications

References 19 publications

Nucleation mechanisms and particle size distributions of polymer colloids

Nucleation mechanisms and particle size distributions of polymer colloids

?Continuous? emulsifier-free emulsion polymerization for the synthesis of monodisperse polymeric latex particles

Microemulsion Polymerization of Butyl Acrylate. Effect of Radical Scavenger and Formation of Primary Radicals

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