Reactivity ratios and monomer partitioning in the microemulsion copolymerization of vinyl acetate and butyl acrylate (original) (raw)
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Colloid and Polymer Science, 2009
Vinyl acetate and butyl acrylate were copolymerized in microemulsion under monomer-starved conditions by a semicontinuous process using different monomer addition rates (R a). A mixture of sodium dodecyl sulfate and polyethylene glycol dodecyl ether (Brij®35) were used as surfactants. Potassium persulfate was the initiator. High copolymer content latexes (around 40 wt.%), average particle diameters (D p)<50 nm and polymer-to-surfactant ratios (12 to 14, weight/weight) were obtained with weight average molar masses (M w) between 180,000 and 760,000. D p and M w of the copolymers decrease as R a is decreased. As R a increases, a shoulder in the molar mass distribution was observed at high values of M w , which was ascribed to chain transfer to polymer. Homogeneous copolymer compositions were observed throughout the reaction, which cannot be obtained by the usual batch process.
Polymer Bulletin, 2011
Monomer mixtures of vinyl acetate (VAc)/butyl acrylate (BuA) were polymerized in batch reactions at 60°C with potassium persulfate as the initiator in microemulsions consisting of VAc:BuA (85:15 wt/wt)/water/sodium dodecyl sulfate (SDS)/polyoxyethylene (23) dodecyl ether (3:1 wt/wt). The effect of the concentration of the monomer mixture on the kinetics was studied. It was found that, as the total monomers concentration ([M] 0) increases, the polymerization rate increases also, and that the maximum polymerization rate is proportional to [M] 0 1.26. Particle size increases with total monomers concentration. In all cases, final average particle diameter was less than 50 nm. Particle number density is independent of total monomers concentration. A mathematical model that takes into account the partition of monomers between the different phases during polymerization using a minimum of adjustable parameters was applied to simulate the experimental data. A correlation for the radical desorption coefficient, which is a function of the rate of
Copolymerization of vinyl acetate with acrylic monomers in microemulsion
European Polymer Journal, 2001
Composition domains corresponding to``one phase microemulsions'' have been studied for the monomer mixtures consisting in vinyl acetate (VAc)±2-ethyl-hexyl acrylate (EHA) and VAc±ethyl acrylate (EtA). Maleic monoester with nonyl phenol ethoxylated with 25 mol ethylene oxide has been used as surfactant; n-propanol (n-PrOH), t-butanol (t-BuOH) and 2-ethyl-hexanol have been employed as cosurfactants. The number of microemulsions formed in the frame of the existing systems (as shown in ternary diagrams) is higher for polar monomers and cosurfactants: EtA > EHA; n-PrOH > t-BuOH. Refractometric and conductometric studies have proved the reality of three types of microemulsions: O=W , bicontinuous and W =O respectively. The homogeneous domains lessen after radical copolymerization. However, for the zone with a bicontinuous microstructure the conversion for the comonomer mixture reaches a minimum; a degradative chain transfer of the growing radicals with the cosurfactant might explain this phenomenon. It has been proved by GPC, that the concentration of unreacted surfactant increases when the concentration of the acrylic monomer increases as well. Ó
Semicontinuous heterophase copolymerization of vinyl acetate and butyl acrylate
Journal of Applied Polymer Science, 2013
Vinyl acetate (VAc) and butyl acrylate (BuA) were copolymerized in heterophase by a semicontinuous process (unseeded) and compared with the seeded semicontinuous microemulsion polymerization of the same monomers. A mixture of sodium dodecyl sulfate (SDS) and poly(ethylene oxide) dodecyl ether (Brij-35 V R) were used as surfactants. The effects of monomer addition rate (R a) and surfactants concentrations (4 or 1 wt % with respect to the initial mixture of reaction) on polymer and latex properties were studied. High copolymer content latexes (24-36 wt %) with average particle diameters (D p) from 38 to 55 nm and relatively narrow particle size distributions, high polymerization rates, weight ratios of polymer to surfactant (P/S) from 13.3 to 32.8 were obtained. The number-average molecular weights (M n) were between 96,000 and 188,000 g/mol. Homogeneous copolymer compositions were obtained throughout the reaction for both, seeded and unseeded processes, which is not possible by the usual batch microemulsion process. V
Macromolecular Symposia, 2006
This work investigates the influence of carboxylic monomers such as acrylic acid (AA) and methacrylic acid (MAA) on the reaction rate and the colloidal stability during semicontinuous vinyl acetate (VA) and butyl acrylate (BA) emulsion copolymerizations. A number of copolymerization runs was carried out under different reaction temperatures and concentrations of AA and MAA. Samples were collected for off-line analysis of particle size and conversion, allowing calculations of particle number values giving an indication of the particle stability. Additionally, partitioning analysis using conductometric and potentiometric titrations were performed in order to assess the distribution of carboxylic monomers among the main phases of the latex. Results showed that for both carboxylic monomers the increasing of the reaction temperature produces an increase in the coalescence rate and that the increasing of the concentration of these monomers leads to the increase in the amount of adsorbed COOH groups on the particle surface, which enhances latex stability. Nevertheless, when the concentration of methacrylic acid was increased a strong reduction of the polymerization rate was observed with a greater incorporation of acid groups buried in the particles.
Journal of Polymer Science Part A: Polymer Chemistry, 1989
The role of the cosurfactant (hexadecane) in the miniemulsion copolymerization of 50 : 50 molar ratio vinyl acetate-butyl acrylate monomer mixture is analyzed from an experimental point of view. The main factor responsible for the different kinetic behavior between the miniemulsion and conventional emulsion copolymerization processes was found to be the different particle nucleation mechanism operating in each process. Experimental evidence is presented indicating that in the miniemulsion copolymerization particle nucleation takes place in the preformed stable submicron monomer droplets.
Polymer International, 2007
The inverse microemulsion copolymerization of acrylamide and butyl acrylate initiated by ammonium peroxodisulphate, a water-soluble initiator, and stabilized by anionic emulsifiers sodium bis-2ethylhexylsulfosuccinate and sodium dodecylsulphate (SDS) has been studied. An increase of SDS concentration was observed to increase both the rate of polymerization and the particle size. The average number of radicals per particle (n) is much below 0.5, which indicates desorption of monomeric radicals from polymer particles. The exit (desorption) rate constants k des (cm 2 s −1 ) and k des (s −1 ) were evaluated as a function of SDS concentration (or the particle size) according to the Ugelstad/O'Toole (I), Nomura (II) and Gilbert (III) models. The value of k des (s −1 ) decreases with increasing particle size (or SDS concentration) for all three (I, II and III) models. A complex trend appears for k des (cm 2 s −1 ): the Ugelstad/O'Toole model estimates a decrease, the Nomura model finds no variation and the Gilbert model estimates even a slight increase in k des with increasing SDS concentration.
Colloid and Polymer Science, 2014
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Microemulsion and conventional emulsion copolymerizations of methyl methacrylate with acrylonitrile
Journal of Applied Polymer Science, 2002
The microemulsion (ME) and conventional emulsion (CE) copolymerizations of methyl methacrylate (MMA) with acrylonitrile (AN) are carried out at 70°C by employing sodium lauryl sulphate (SLS) and n-octanol (OA) as surfactant and cosurfactant, respectively, and potassium persulphate (KPS) as initiator. The copolymerization reactions are arrested at lower conversions, and the copolymers prepared are characterized by FTIR, NMR, TG/DTA, and GPC techniques. The reactivity ratios for microemulsion and conventional emulsion copolymerizations are evaluated by Fineman-Ross (F-R), Kelen-Tüdös (K-T), and Mayo-Lewis (M-L) graphical methods. The K-T method yields the reactivity ratios of MMA (rMMA) and AN (rAN) as 2.03 ± 0.02 and 0.10 ± 0.02, and 1.97 ± 0.02 and 0.13 ± 0.02, respectively, for ME and CE copolymerization methods. The results are compared with the literature. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1503–1510, 2002
Miniemulsion and macroemulsion copolymerization of vinyl acetate with vinyl versatate
Journal of Applied Polymer Science, 2002
The miniemulsion and macroemulsion polymerization of vinyl acetate with vinyl versatate in batch and semibatch systems was investigated. Vinyl versatate was added either as an emulsion with the vinyl acetate, or as a neat liquid stream. In the batch runs, there is a poor dispersion of vinyl versatate during the nucleation period for the runs in which the vinyl versatate was added neat at the beginning of the polymerization. This led to smaller particles, lower polymerization rate, and different polymer composition evolution when compared with runs in which the vinyl versatate was emulsified with the vinyl acetate. In seeded semibatch runs, residual surfactant in the seed latex, along with the propensity for homogeneous nucleation in vinyl acetate emulsions, resulted in continuing nucleation during the entire semibatch interval. The polymerization rate was primarily affected by monomer feed rate rather than the feeding mode. The effect of monomer feeding mode on copolymer composition was weak when the semibatch feed rate was low, indicating some level of vinyl versatate mass transfer resistance. In all runs, only one glass transition temperature was observed, indicating effective copolymerization.