Particle Nucleation during Microemulsion Polymerization of Methyl Methacrylate (original) (raw)
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Journal of Research Updates in Polymer Science, 2016
Miniemulsion polymerization is widely used to produce polymer nanoparticles. In many applications, it is important to ensure the narrow particle size distribution of the final product, which means that secondary micellar and homogeneous nucleation must be avoided during the reaction course. The present study proposes the use of hydrophilic comonomers to inhibit the occurrence of secondary particle nucleation in miniemulsion polymerizations of methyl methacrylate. Acrylic acid, metacrylic acid, 2-hydroxy ethyl methacrylate and methacrylamide were used as hydrophilic comonomers. It was observed that the use of small amounts of hydrophilic comonomers in miniemulsion polymerizations promoted by oil-soluble initiators could prevent secondary particle nucleation and lead to products with more homogeneous particle size distributions.
Macromolecules, 2003
The effect of surfactant concentration on particle nucleation in emulsion polymerization of n-butyl methacrylate has been studied using sodium dodecyl sulfate as the surfactant and potassium persulfate as the initiator. The rates of reaction as a function of time were determined for surfactant concentrations above and below critical micelle concentration of the surfactant. The order of dependence of the particle number on the surfactant concentration was found to be different in different ranges of surfactant concentration. This has been explained on the basis of the predominant phenomenon that affects particle nucleation in each range of surfactant concentration. In the range where the end of particle nucleation is determined by a critical surfactant coverage necessary for colloidal stability, the particle number is expected to increase in proportion to the third power of the surfactant concentration. It has been shown how a size-dependent volumetric growth-rate of particles can result in different exponents in the Smith-Ewart equation relating the particle number to surfactant concentration. A constant volumetric growth rate of particles is assumed in the Smith-Ewart theory of particle nucleation.
Polymerization of methacrylate in a W/O microemulsion stabilized by a methacrylate surfactant
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1999
A water-in-toluene microemulsion stabilized by the polymerizable surfactant didecyldimethylammonium methacrylate has been used to form polyelectrolyte particles. The microemulsion was photopolymerized using AIBN as the initiator, resulting in aggregates having hydrodynamic diameters of 11 nm, starting with 5 -6 nm initial nanodroplets with and without added sodium methacrylate (NaMA). The dried latexes have a diameter of 6 nm up to a [NaMA]/[surfactant] mole ratio (R) of 0.5, but 12 nm for R= 1.0. For R =0 -0.5, the maximum degree of polymerization was 50%, but it was 83% for R= 1.0. The polydispersity decreases with increasing R, while the film-forming tendency of the latexes increases.
Journal of Colloid and Interface Science, 2006
The polymerization of n-hexyl methacrylate (n-HMA) in three-component microemulsion stabilized with dodecyltrimethylammonium bromide (DTAB) is reported as a function of monomer and initiator concentrations and temperature. The obtained latices were bluish, transparent, and translucent. Particle sizes and molar masses were on the order of 20 nm and 3 × 10 6 g/mol, respectively. In all cases, high reaction rates and final conversions of 98% were obtained. Polymerization temperature has a strong effect on reaction rate and conversion.
Macromolecules, 2001
We investigate the polymerization kinetics of microemulsions prepared with the cationic surfactant dodecyltrimethylammonium bromide and the hydrophobic monomers n-butyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, and styrene. Our previous model for microemulsion polymerization kinetics cannot account for the kinetics of these systems. Using the results of smallangle neutron scattering monomer partitioning studies and an extended kinetic model to analyze the data, the failure of the original kinetic model is shown to be due to a combination of nonlinear monomer partitioning, nonnegligible bimolecular termination, and, in some cases, diffusion limitations to propagation.
Synthesis and characterization of poly(n-hexyl methacrylate) in three-component microemulsions
European Polymer Journal, 2001
The polymerization of n-hexyl methacrylate in three-component microemulsions stabilized with dodecyltrimethylammonium bromide is examined here as a function of the concentration of a water-soluble (V-50) and an oil-soluble (2, 2-azobisisobutyronitrile) initiators, of monomer concentration in the parent microemulsions and temperature. At high temperatures and high initiator concentrations, only two reaction rate intervals are observed; however, at low temperatures and low
2011
Here, we present the oil/water (O/W) microemulsion polymerization in three-component microemulsions of n-butyl acrylate, ethyl acrylate, and methyl acrylate, monomers with similar chemical structures but different water solubilities using the cationic surfactant dodecyl trimethyl ammonium bromide. The effects of monomer water solubility, initiator type and initial monomer concentration on the polymerization kinetics were studied. Reaction rates were high with final conversions between 70 and 98% depending on the monomer and reaction conditions. The final latexes were bluish, with a particle size ranging between 20 and 50 nm and polymer with molar masses in the order of 10 6 g mol À1 . Increasing monomer water solubility resulted in a slower reaction rate, larger particles and a lower number density of particles. A higher reaction rate, larger average particle size and higher particle number density were obtained by increasing the monomer concentration.
Journal of Polymer Science Part A: Polymer Chemistry, 2004
Nanoscale poly(methyl methacrylate) (PMMA) particles were prepared by modified microemulsion polymerization. Different from particles made by traditional microemulsion polymerization, the particles prepared by modified microemulsion polymerization were multichain systems. PMMA samples, whether prepared by the traditional procedure or the modified procedure, had glass-transition temperatures (T g 's) greater than 120°C and were rich in syndiotactic content (55-61% rr). After the samples were dissolved in CHCl 3 , there were decreases in the T g values for the polymers prepared by the traditional procedure and those prepared by the modified process. However, a more evident T g decrease was observed in the former than in the latter; still, for both, T g was greater than 120°C. Polarizing optical microscopy and wide-angle X-ray diffraction indicated that some ordered regions formed in the particles prepared by modified microemulsion polymerization. The addition of a chain-transfer agent resulted in a decrease in both the syndiotacticity and T g through decreasing polymer molecular weight.