Amphoteric polystyrene latex colloids: polymerization pathway and the control of particle size and potential (original) (raw)
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Synthesis and characterization of amphoteric latex particles
2003
Amphoteric terpolymers composed of acrylamide, 2-methylacryloylxyethyl trimethyl ammonium chloride, and 2-acrylamido-2-methyl-1-propane sulfonate were prepared via free-radical polymerization in aqueous solution of ammonium sulfate (AS), using poly(2-methylacryloylxyethyl trimethyl ammonium chloride) as stabilizer to yield terpolymers with random distributions. The particle size of the synthesized amphoteric polyacrylamide (AmPAM) ranged from 1 to 8 μm and the intrinsic viscosity ranged from 5.6 to 14.2 dL/g. The influences of aqueous solution of AS concentration, stabilizer concentration, initiator concentration, monomer concentration on the conversion of monomer, the intrinsic viscosity, and the particle size were systematically investigated. The characteristic of amphoteric polymer was also be studied. Throughout the study, we found that the isoelectric point of the amphoteric polyelectrolyte we synthesized is about 7. With the increase in sodium chloride, the reduced viscosity of AmPAM increased. Among the different type of inorganic salt, the degree of influence of anionic is I > Br > Cl.
Poly(styrene-hydroxyethyl methacrylate) [P(ST-HEMA)] latex particles were prepared by surfactant-free emulsion copolymerization. As water-soluble initiator was used potassium persulfate (KPS). The influence of different reactions parameters, such as the reaction temperature, the both monomers (ST and HEMA) concentrations and the KPS concentration on the particles average diameter and particles size dispersion was investigated. Generally monodisperse spherical particles are synthesized, but we also obtained stable large three-dimensional colloidal aggregates. These are formed by the agglomeration of monodispersed spheres in certain polymerization conditions. The P(ST-HEMA) monodispersed spheres with 350 nm average diameter were assembled into colloidal crystals using dip-coating technique. Colloidal crystals with different thickness were obtained by modifying two experimental factors, the colloidal concentration and the substrate lifting speed. The morphologies of copolymer latex particles and colloidal crystals were observed using scanning electron microscopy (SEM). The optical properties of colloidal crystals films were also investigated by transmission spectroscopy.
Synthesis and Characterization of Charged Polystyrene−Acrylic Acid Latex Particles
Langmuir, 2006
Novel, monodisperse charged colloidal particles of polystyrene cross linked with divinylbenzene and surfacegrafted with acrylic acid were synthesized by emulsion polymerization and were characterized by estimating the dissociable surface charge by conductivity titration, the particle effective charge by conductivity verses particle concentration, and the particle size by dynamic light scattering and atomic force microscopy. The structural ordering and dynamics were investigated as a function of the volume fraction of the particles using static and dynamic light scattering, respectively. Furthermore, from the electrophoresis measurements, these particles are found to have a high salt tolerance due to increases in charge as a function of salt concentration.
Industrial & Engineering Chemistry Research, 2004
The synthesis of polystyrene or poly(methyl methacrylate) in the presence of carboxymethyl cellulose (CMC), a cellulose derivative, was carried out by emulsion polymerization using a cationic surfactant, cetyltrimethylammonium bromide (CTAB). First, the complex formation between CTAB and CMC was studied by surface tension measurements. The polymerization condition chosen was that corresponding to CMC chains fully saturated with CTAB and to the onset of pure surfactant micelle formation, namely, at 0.25 mmol L-1 CTAB and 1.0 g L-1 CMC. The hybrid particles were characterized by potential and light scattering measurements and scanning electron microscopy. All dispersions were stable in the ionic strength of 2.0 mol L-1 NaCl at least for 4 days. The colloidal stability was attributed to the presence of a hydrated CMC layer around the particles. The present procedure brings the advantage of synthesizing and stabilizing particles with functional groups on the surface in a one-step method using very small amounts of surfactant, a friendly condition for the environment.
Polystyrene latex particles bearing primary amine groups via soap‐free emulsion polymerization
Polymer International, 2020
Polystyrene latexes were prepared in the presence of an amino-containing functional comonomer, i.e. N-(3-aminopropyl) methacrylamide hydrochloride (APMH), via soap-free batch emulsion polymerization initiated by the cationic initiator 2,2'-azobis (2-amidino propane) di-hydrochloride (V50). These latexes were characterized through studying the influence of ionic comonomers on the polymerization kinetics, particle size, surface charge density and colloidal properties. The synthesized latexes were monodisperse with a final size between 100 and 600 nm depending on the APMH concentration. The initial polymerization rate and the particles number increased in accordance with the Smith-Ewart theory for soapfree styrene emulsion polymerization with a hydrophilic functional comonomer. The final functionalization rate of the particles has been particularly studied with the intention of fitting the prepared latexes to be utilized in the immobilization of biological molecules for biological sample preparation and diagnostic applications.
Journal of Applied Polymer Science, 2006
The evolution of the main colloidal parameters in the seeded starved-feed semi-continuous emulsion polymerization of butyl methacrylate (BMA) was investigated, with the main purpose of assessing the effectiveness of the semi-empirical relationship S ¼ K Á S S Á DA/A S as a tool to define the surfactant/monomer feed ratio (! K) best suited to achieve a target particle size. In particular, the effect of the type and amount of surfactant [i.e., anionic, sodium dodecyl sulfate (SDS), or nonionic, Brij 58P] added during the semi-continuous stage was considered. Coagulum formation was never observed under the adopted experimental conditions. To detect the occurrence of secondary nucleation or particle aggregation, or both, the particle size and number of particles, the surface tension and the particle surface cov-erage ratio were correlated. The best results were obtained with SDS and 0.8 K 3. In fact, under the selected experimental conditions, only with SDS did the number of particles remain nearly constant throughout the polymerization at the value defined by the seed latex; the particle size distribution was highly monodisperse, and the final particle diameter closely matched the calculated one ($ 120 nm). The above semi-empirical relationship based on the adjustable parameter K was validated by running test polymerizations aimed at lattices with well-defined particle size.
Journal of Applied Polymer Science, 2009
Monodisperse styrene/methyl methacrylate/acrylic acid (St/MMA/AA) copolymer microspheres have been prepared with surfactant-free emulsion polymerization in air. The presence of oxygen in the system not only caused an induction period but also decreased the average particle size (D p ). However increasing AA concentration ([AA]) gave a reduction in the induction period. The FTIR and NMR analysis of the latex copolymer confirmed that the correlation of the copolymer compositions with the feed compositions was much better at the lower [AA] than at the higher levels. The AA contents of the copolymers obtained in air were much lower than those of the copolymers obtained under N 2 protection.
The role of acid-base equilibrium in emulsifier-free styrene polymerization with a carboxyl-containing initiator, namely, 4,4'-azobis(4-cyanovaieric acid) (CVA), was investigated at the pH of the starting emulsion from 8.3 to 11.5. It was found that the polymerization kinetics, the particle diameter, and the degree of polydispersity of the latexes synthesized at different CVA concentrations and styrene/water ratios depend substantially on both the initial pH of the reaction mixture and the pattern of the changes in pH during the synthesis. Both minima and maxima are observed in the kinetic dependences of pH in different periods of synthesis. The deviations of pH from the starting values were as large as two pH units. The influence of the buffer salt (NaJB'O,) concentration on the polymerization process and the parameters of the latexes synthesized was also studied. It was shown that the establishment of the acid-base equilibrium in the system depends also on the formation of the surface-active oligomers and their distribution between the emulsion phases. The results obtained indicate that the surface charge formed upon ionization of the end carboxyl groups of polymer chains is the main factor of stabilization of growing polymer particles in the system studied.