Polymerization of styrene miniemulsions

Choi, Yongtaek; El‐Aasser, M. S.; Sudol, E. David; Vanderhoff, J. W.

doi:10.1002/pol.1985.170231206

Cited by 162 publications

(107 citation statements)

References 9 publications

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“…21 The (co)emulsifier properties of STPO propose that STPO penetrates the interface layer and forms a complex with the emulsifier. 22 This interaction increases the residence time of STPO in microdroplets. The STPO/SDS complex produces a barrier for exiting and entering radicals.…”

Section: Polymerization Ratementioning

confidence: 99%

“…27 -30 The rigid surface film depresses interactive collisions between droplets, the transfer of radicals between droplets (by hoping) and radical entry events. 22 Additives (inorganic salt and organic component) alone or their mixtures with RS influence Rp,max in a complex way (Table I ). The redox system DBP/FeC1 2 accelerates the decomposition ofDBP and so increase in RP should appear.…”

Section: Polymerization Ratementioning

confidence: 99%

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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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Section: Polymerization Ratementioning

confidence: 99%

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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“…A large number of fine emulsified monomer droplets (ca. 10 21 per dm 3 ) promotes the continuous nucleation of polymer particles up to high (final) conversion. The concentration of monomer decreases throughout the polymerization, 1 · 15 and that monomer droplets exist throughout the polymerization.…”

Section: Kinetic Parametersmentioning

confidence: 99%

Microemulsion Polymerization of Alkyl (Meth)acrylates Initiated by UV Light

Capek

1999

Polym J

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ABSTRACT:Radical polymerizations of polar unsaturated monomers ethyl acrylate, methyl methacrylate and nonyl methacrylate in an o/w microemulsion photoinitiated by a UV light were investigated. Polymerizations were conducted at low temperature to follow the effects of a varied solubility of monomer (coemulsifier) and/or diffusional degradation of monomer droplets on the kinetic and colloidal parameters. The rate versus conversion curve showed four regions with two rate maxima ca. at 5% to 20% and 50 to 70% conversion. The first rate maximum results from abrupt decrease of the monomer concentration at microemulsion loci and the second one from the increased accumulation of radicals in the latex particles. The higher polymerization rate of ethyl acrylate compared to that for methyl methacrylate or nonyl methacrylate was attributed to higher monomer concentration at reaction loci and propagation rate constant and lower quenching rate. The rate of polymerization was found to increase with incident light intensity and was most pronounced with nonyl methacrylate. The reaction order (the dependence of the rate of polymerization or the number of particles on the incident light intensity) was taken as a measure of particle nucleation efficiency. Particle size distribution was observed to be very narrow at low conversion and increased with increasing conversion.KEY WORDS Microemulsion j Polymerization I Alkyl (Meth)acrylates I Kinetics I Particle I Nucleation/ Microemulsion and miniemulsion polymerizations offer convenient access to well-defined microlatex particles being typically one order of magnitude smaller than polymer particles obtained by conventional emulsion polymerization. The fine monomer emulsion exhibits a large interface between monomer droplets and the aqueous phase. Under such conditions, continuous nucleation up to (very) high conversion is operative. There is no apparent constant rate period in the o/w microemulsion or miniemulsion polymerization. 1 -3 Ugelstadt et a/. 4 clearly demonstrated that monomer droplets could effectively compete with monomer-swollen micelles for capture of free radicals generated in the aqueous phase when the total surface area of the droplets became large enough. In conventional emulsion polymerization, the principle locus of particle nucleation is the aqueous phase or the monomer swollen micelles depending on the degree of water solubility of the monomers, an initiator and amount of emulsifier. Monomer droplets are considered only as monomer reservoir supplying monomer to the growing polymer particles. However, the small size of the monomer droplets (micro-or minidroplets) enables them to become the principle locus of particle nucleation ..The principle behind the formation ofmicroemulsions (droplet size I 0-50 nm) is penetration of coemulsifier into the water/oil interface, thereby decreasing surface tension and increasing interface area. Coemulsifier also decreases the rigidity of interface film due to increasing the molecular disorder. Coemulsifier promotes the formatio...

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“…As the molecular weight decreases, crosslink density increases and the Tg increases for polymers having similar chemical structures. This can be seen with polyurethane acrylate1, 2, 3 (10.6˚C, 6.66˚C, −8.78˚C respectively), that are very similar in backbone, but vary in molecular weight (PEG 6000, 12,000 and 20,000 g/mol respectively) [13]. It is also clear that Tg of PUA 4 (36.4˚C) is higher than those of later mentioned polyurethane acrylate, this may be attributed to the chain length and structure configuration (stuff CH 3 group) which results in the difficulty of mobility of polymer chains and also the chain rigidity is increased.…”

Section: Effect Of Structure Of Polyurethane Acrylate Polymers On It'mentioning

confidence: 94%

“…The number average molecular weight is a way of determining the molecular weight of a polymer [13]. Moreover, it considers a property, which is only sensitive to the number of molecules present-a property that is not influenced by the size of any particle in the mixture.…”

Section: Effect Of Structure Of Polyurethane Acrylate On the Moleculamentioning

confidence: 99%

Part 1: Synthesis and Evaluation of Novel Nano Scale Powdered Polyurethane Acrylate Binders

El‐Molla¹,

Haggag²,

El-Shall³

et al. 2012

ACES

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Some new an aqueous polyurethane acrylate (waterborne binder) based on polyethylene glycol with different M. wt. mixed with polyol were carried out. Seven different polyurethane acrylate co-polymers were prepared aiming at substituting the two hydroxyl groups of polyethylene glycol (6000, 12,000 and 20,000 g/mol) and two primary hydroxyl groups of polyol through their reaction with corresponding calculated amounts of either isophorone diisoyanate or toluene diisocyanate and caped the remaining isocyanate group with either hydroxy ethyl acrylate or hydroxy propyl methacrylate to get on the polyurethane acrylate polymers [PUA]. From DSC measurement the result of Tg of synthesized PUA are in range from −8.78˚C to 36.4˚C. So they can classify as soft binders. The infrared spectra, rheological properties, viscosity measurement, the weight average molecular weight, of the synthesize binders were investigated.

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Polymerization of styrene miniemulsions

Cited by 162 publications

References 9 publications

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

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

Microemulsion Polymerization of Alkyl (Meth)acrylates Initiated by UV Light

Part 1: Synthesis and Evaluation of Novel Nano Scale Powdered Polyurethane Acrylate Binders

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