Polymer latices monodisperse

An important step in tire progress of colloid science was tire development of monodisperse polymer latex suspensions in tire 1950s. These are prepared by emulsion polymerization, which is nowadays also carried out industrially on a large scale for many different polymers. Perhaps tire best-studied colloidal model system is tliat of polystyrene (PS) latex [9]. This is prepared with a hydrophilic group (such as sulphate) at tire end of each molecule. In water tliis produces well defined spheres witli a number of end groups at tire surface, which (partly) ionize to... 

Hansen, F.K. Matijevic, F. (1980) Heterocoagulation. Part 5. Adsorption of carboxylated polymer latex on monodispersed metal hydrated oxides. J. Chem. Soc. Faraday Trans. I. 76 1240-1262... 

A similar seeding technique can be used to prepare monodispersed polymer latex dispersions by emulsion polymerisation (see page 17). 

An edditional complication arises with relatively monodisperse samples in that slight changes in the focus of the electron microscope introduce random errors in the exact magnification of the final print. These problems of focus adjustment can be corrected for by the use of an internal standard (frequently another polymer latex with a significantly larger average particle size). It is usually mandatory for the PSD of the internal standard to be completely separate from the PSD of the sample. 

Likewise, the polymer latex data of Figure 3.34 have a much higher slope (mass transfer coefficient) than would be expected from the latex particle dif-fusivity. Monodisperse polystyrene latexes have both suspension viscosities and... 

Colloidal Crystalline Arrays Colloidal spheres of silica and of polymers can be made relatively monodisperse, with standard deviations of 4% of the mean diameter for silica and 1% for polymer latexes. The spheres pack as shown in Figure 11.22a from fluid dispersions into fee (sometimes hep or bcc) colloidal crystals (CC) by gravity, by membrane filtration, or by capillary forces at the surface of an evaporating dispersion (80-82). The crystalline order of the materials is strictly at the length scale of the packed colloidal particles the packing of the atoms and molecules within the silica and polymer particles is totally amorphous. The CCs diffract... 

Furusawa and Anzai investigated the heterocoagulation of a highly monodisperse amphoteric polymer latex (particle diameter 250 nm, lEP ca. pH 6.8 in 5.0 mM KCl background electrolyte, positively charged at low pH) onto various silica spheres (diameters 240, 460, 960, and 1590nm lEP ca. pH 3.0) dispersed in pure water or upon addition of various hydroxypropyl celluloses (HPCs) [17, 18]. Stable dispersions for both individual particles under the condition that they had opposite... 

Semiconductor particles can also be used advantageously in coating applications to provide specific optical response to the material. As an example, Kumacheva et al. recently described the synthesis of monodisperse nanocomposite particles with inorganic CdS nanocrystals sandwiched between a PMMA core and a P(MMA-co-BA) outer copolymer shell layer. The particles are prepared by emulsion polymerization in three steps (Fig. 4.21) [144]. In a first step, polymer latexes are used as host matrices for CdS nanocrystals formation [145,146]. To do so, monodisperse poly(methyl methacrylate-co-methacrylic acid) (PMMA-PMAA) latex particles were ion-exchanged with a Cd(Cl04)2 solution. The Cd + ions thus introduced into the electrical double layer were further reduced into CdS nanoclusters by addition of a Na2S solution. The CdS-loaded nanocomposite particles were subsequently recov-... 

J. Lee, M. Senna, Preparation of monodispersed polystyrene microspheres uniformly coated by magnetite via heterogeneous polymerization. Colloid Polym. Sci. 1995,273, 76-82 (c) F. Camso, A.S. Susha, M. Giersig, H. Moh-wald. Magnetic core-shell particles preparation of magnetite multilayers on polymer latex microspheres, Adv. Mater. 1999, 11,950-953. 

Iridescence due to Bragg diffraction of visible light is exhibited by electrolyte-free monodisperse polymer latexes, and also by redispersions of the polymer spheres in certain polar organic media. The center-to-center particle separation D, the particle diameter D, and the volume fraction ( ) are related by < >(D/D =... 

Emulsion polymerization produces latexes whose particles are almost perfectly spherical polymer latexes of highly uniform particle size have been knovm since their accidental discovery in 19 7 l y scientists at the Dow Chemical Company. Concentrated monodisperse latexes are frequently iridescent, whereas heterodisperse latexes are white. The iridescence was correctly attributed by Luck, Wesslau and Klier (l) to Bragg reflection of visible light from ordered arrays of particles. Because of the approximate equivalence of their measured Bragg spacing to that expected for a packed array at the same particle diameter (and also beca ase the... 

Emulsion polymerization has been extensively studied in order to prepare quasi monodisperse polymer latex particles. Ding and coworkers employed Cj MelmCl as a surfactant in the emulsion polymerization of PS [24]. Monodisperse PS latex particles with average diameter of 126nm and extremely low polydispersity (index of 0.002) were obtained by using this process. When the concentration of Cj MelmCl... 

The prospects are alluring. Colloidal polymer patterning is similar to very well-established painting and coating processes, so that existing equipment could be adapted for the production of coatings and materials with new properties. The polymer latex formulations that form the basis of the process are well-known in industry, and the step to monodispersed particles and controlled deposition seems viable. For applications where molding methods are inapplicable, particle-based polymer patterns could form the basis of industrial processes. 

In the second chapter (Preparation of polymer-based nanomaterials), we summarize and discuss the literature data concerning of polymer and polymer particle preparations. This includes the description of mechanism of the radical polymerization of unsaturated monomers by which polymer (latexes) dispersions are generated. The mechanism of polymer particles (latexes) formation is both a science and an art. A science is expressed by the kinetic processes of the free radical-initiated polymerization of unsaturated monomers in the multiphase systems. It is an art in that way that the recipes containing monomer, water, emulsifier, initiator and additives give rise to the polymer particles with the different shapes, sizes and composition. The spherical shape of polymer particles and the uniformity of their size distribution are reviewed. The reaction mechanisms of polymer particle preparation in the micellar systems such as emulsion, miniemulsion and microemulsion polymerizations are described. The short section on radical polymerization mechanism is included. Furthermore, the formation of larger sized monodisperse polymer particles by the dispersion polymerization is reviewed as well as the assembling phenomena of polymer nanoparticles. 

A new process, from Norway, has filled the size gap between emulsion and suspension polymerization techniques [7,8]. This novel polymerization method, the so-called swollen emulsion polymerization has been developed by Ugelstad for producing uniform polymeric particles in the size range of 2-100 /nm. This process comprises successive swelling steps and repolymerizations for increasing the particle size of seed polymer particles by keeping the monodispersity of the seed latex. 

In the same year, Fulda and Tieke [75] reported on Langmuir films of monodisperse, 0.5-pm spherical polymer particles with hydrophobic polystyrene cores and hydrophilic shells containing polyacrylic acid or polyacrylamide. Measurement of ir-A curves and scanning electron microscopy (SEM) were used to determine the structure of the monolayers. In subsequent work, Fulda et al. [76] studied a variety of particles with different hydrophilic shells for their ability to form Langmuir films. Fulda and Tieke [77] investigated the influence of subphase conditions (pH, ionic strength) on monolayer formation of cationic and anionic particles as well as the structure of films made from bidisperse mixtures of anionic latex particles. 

Ali, S. A. Sengupta, M. J., Preparation and characterization of monodisperse polystyrene latexes of varying particle sizes without the use of surfactants, Polym. Mater. Sci. Eng. 1991, 8, 243 250... 

Polystyrene latexes were similarly prepared by Ruckenstein and Kim [157]. Highly concentrated emulsions of styrene in aqueous solutions of sodium dodecylsulphate, on polymerisation, yielded uncrosslinked polystyrene particles, polyhedral in shape and of relative size monodispersity. Interestingly, Ruckenstein and coworker found that both conversions and molecular weights were higher compared to bulk polymerisation. This was attributed to a gel effect, where the mobility of the growing polymer chains inside the droplets is reduced, due to increased viscosity. Therefore, the termination rate decreases. 

Monodisperse Polystyrene Latexes Surface Charge and Number of Sulfate Endgroups/Polymer Molecule (3,5,9)... 

The foregoing methods developed for the preparation and characterization of monodisperse polystyrene latexes to be used as model colloids can also be applied to the characterization of industrial latexes. The recipes used for the preparation of these industrial latexes are complex, and most contain a small amount of a functional monomer, e.g., acrylic acid, 2-sulfoethyl methacrylate, or N-methylolacrylamide. These functional monomers are often predominantly water-soluble, so that their use may have several results (i) the monomer may polymerize in the aqueous phase to form a water-soluble polymer that remains in the serum ... 

The polystyrene seed latex was monodispersed. Even after several grow-ups (polymerizations) the final 1650 A latex was monodispersed. Hydrodynamic chromatography on the 1650 A latex gave a mean diameter of 1660 a with a size variance as small as for normal polystyrene latex standards (typical standard of 1760 8 with a standard deviation of 23 a). The final latex particle size could be accurately predicted from the initial particle size and the total amounts of monomer and polymer used. 

Seed Characterization. A monodisperse seed latex of known initial diameter is required if continued seed growth by second stage polymers is to be unambiguously measured by particle size analysis. The seed recipes selected were known to give uniform sized particles (14,15). All five of the latexes were monodisperse as measured by JLDC (Table II) and exhibited a character-... 

Ha et al. [93,94] prepared monodisperse polymer microspheres from 1 to 40 pm in diameter for medical diagnostic tests, as chromatography column packing and as calibration standards. The work deals with the synthesis of large and uniform poly (butadiene-styrene) latex. The ceramic SPG membrane, with a pore diameter of 1.6 pm, was employed. The uniform particle sizes were in the diameter range of 4-6 pm. 

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