Polystyrene seed emulsion

Sheu and coworkers [111] produced polysty-rene-polydivinylbenzene latex interpenetrating polymer networks by the seeded emulsion polymerization of styrene-divinylbenzene in the crosslinked uniform polystyrene particles. In this study, a series of uniform polystyrene latexes with different sizes between 0.6 and 8.1... 

The soapless seeded emulsion copolymerization method was used for producing uniform microspheres prepared by the copolymerization of styrene with polar, functional monomers [115-117]. In this series, polysty-rene-polymethacrylic acid (PS/PMAAc), poly sty rene-polymethylmethacrylate-polymethacrylic acid (PS/ PMMA/PMAAc), polystyrene-polyhydroxyethylmeth-acrylate (PS/PHEMA), and polystyrene-polyacrylic acid (PS/PAAc) uniform copolymer microspheres were synthesized by applying a multistage soapless emulsion polymerization process. The composition and the average size of the uniform copolymer latices prepared by multistage soapless emulsion copolymerization are given in Table 11. 

In another study, uniform composite polymethyl-methacrylate/polystyrene (PMMA/PS) composite particles in the size range of 1-10 fim were prepared by the seeded emulsion polymerization of styrene [121]. The PMMA seed particles were initially prepared by the dispersion polymerization of MMA by using AIBN as the initiator. In this polymerization, poly(7V-vinyl pyrolli-done) and methyl tricaprylyl ammonium chloride were used as the stabilizer and the costabilizer, respectively, in the methanol medium. Seed particles were swollen with styrene monomer in a medium comprised of seed particles, styrene, water, poly(7V-vinyl pyrollidone), Polywet KX-3 and aeorosol MA emulsifiers, sodium bicarbonate, hydroquinone inhibitor, and azobis(2-methylbu-... 

A research group in Lehigh University has extensively studied the synthesis and characterization of uniform macroporous styrene-divinylbenzene copolymer particles [125,126]. In their studies, uniform porous polymer particles were prepared via seeded emulsion polymerization in which linear polymer (polystyrene seed) or a mixture of linear polymer and solvent were used as inert diluents [125]. The average pore diameter was on the order of 1000 A with pore volumes up to... 

Hollow and porous polymer capsules of micrometer size have been fabricated by using emulsion polymerization or through interfacial polymerization strategies [79,83-84, 88-90], Micron-size, hollow cross-linked polymer capsules were prepared by suspension polymerization of emulsion droplets with polystyrene dissolved in an aqueous solution of poly(vinyl alcohol) [88], while latex capsules with a multihollow structure were processed by seeded emulsion polymerization [89], Ceramic hollow capsules have also been prepared by emulsion/phase-separation procedures [14,91-96] For example, hollow silica capsules with diameters of 1-100 micrometers were obtained by interfacial reactions conducted in oil/water emulsions [91],... 

Adsorption behavior and the effect on colloid stability of water soluble polymers with a lower critical solution temperature(LCST) have been studied using polystyrene latices plus hydroxy propyl cellulose(HPC). Saturated adsorption(As) of HPC depended significantly on the adsorption temperature and the As obtained at the LCST was 1.5 times as large as the value at room temperature. The high As value obtained at the LCST remained for a long time at room temperature, and the dense adsorption layer formed on the latex particles showed strong protective action against salt and temperature. Furthermore, the dense adsorption layer of HPC on silica particles was very effective in the encapsulation process with polystyrene via emulsion polymerization in which the HPC-coated silica particles were used as seed. 

It was apparent that the dense adsorption layer of HPC which was formed on the silica particles at the LCST plays a part in the preparation of new composite polymer latices, i.e. polystyrene latices with silica particles in the core. Figures 10 and 11 show the electron micrographs of the final silica-polystyrene composite which resulted from seeded emulsion polymerization using as seed bare silica particles, and HPC-coated silica particles,respectively. As may be seen from Fig.10, when the bare particles of silica were used in the seeded emulsion polymerization, there was no tendency for encapsulation of silica particles, and indeed new polymer particles were formed in the aqueous phase. On the other hand, encapsulation of the seed particles proceeded preferentially when the HPC-coated silica particles were used as the seed and fairly monodisperse composite latices including silica particles were generated. This indicated that the dense adsorption layer of HPC formed at the LCST plays a role as a binder between the silica surface and the styrene molecules. 

Deionized water (720 g), sodium lauryl sulfate (4.3 g), dioctanoyl peroxide (40 g), and acetone (133 g) were emulsified using an ultrasonic probe for 10 minutes. The step 1 polystyrene seed (48.0 g seed, 578 g latex) was added to the emulsion together with lauryl sulfate (0.8 g) and acetone (29.6 g). The mixture was transferred to a flask and left to agitate at approximately 25°C for 48 hours. Acetone was then removed and the solution added to a 5-liter double-walled glass reactor. The temperature was increased to 40°C while styrene (336 g) and divinyl benzene (0.88 g) were added drop-wise over approximately 60 minutes. After 4 hours the mixture was treated with deionized water (1200 g), potassium iodide (1.28 g), and polyvinyl pyrrolidone (18.48 g) with the temperature increased to 70°C. The polymerization continued for 6 hours at 70°C and 1 hour at 90°C. Styrene-based oligomer particles with a diameter of 1.7 pm and with a narrow size distribution were obtained. 

Core-shell nanoparticles can also be fabricated using microemulsions. This was performed using a two-stage microemulsion polymerization beginning with a polystyrene seed [62]. Butyl acrylate was then added in a second step to yield a core-shell PS/PBA morphology. The small microlatex led to better mechanical properties than those of similar products produced by emulsion polymerization. Hollow polystyrene particles have also been produced by microemulsion polymerization of MMA in the core with crosslinking of styrene on the shell. After the synthesis of core-shell particles with crosslinked PS shells, the PMMA core was dissolved with methylene chloride [63]. The direct cross-... 

The potential of SAXS for a precise analysis of the radial structure of latexes can be discussed best when considering model particles consisting of a well-defined core and a closed shell of a second polymer. The particles analyzed by SAXS [45-49] have been prepared recently [45] by a seeded emulsion polymerization [97] of PMMA onto a polystyrene core having a narrow size distribution. The alteration effected by seeded emulsion polymerization can be seen directly in the analysis of the size distribution by ultracentrifugation [87], the resulting distributions are shown in Fig. 17. Besides the increase in radius when going from the... 

It must be noted that the process of seeded emulsion polymerization does not lead to an equilibrium structure. Hence, the sharp interface between PS and PMMA observed in the above core-shell particles cannot be explained by thermodynamic arguments. A possible mechanism maybe sought in the adsorption of oligo(methylmethacrylate) radicals from the water phase onto the PS-seed particles [45]. The temperature of the seeded emulsion polymerization (80 °C [45]) is well below the glass transition temperature of polystyrene and the adsorbed chains bear a sulfate endgroup. The adsorbed oligomers will therefore remain at the surface of the core particles and in consequence there is no extended interface between PS and PMMA in these. particles. 

Yang et al. [27], using small-angle neutron scattering (SANS), reported the formation of supermolecular structures in polystyrene latex particles prepared by the seeded emulsion polymerization of styrene onto deuterated polystyrene particles. The recorded scattering intensities, which were much higher than those expected on the basis of the Debye random coil model, indicate the presence... 

An example of emulsion polystyrene-seeded spectroscopic results are shown in Figure 10. The left figure shows a typical comparison between the measured and the calculated spectra. The right plot shows the evolution of the particle size as function of time (approximately at 20, 60 and 120 Minutes). 

Acrylonitrile is also commonly found in impact modifiers, such as the acrylonitrile-butadiene-styrene (ABS) type, produced by emulsion polymerisation. Polybutadiene seed latex particles are grafted onto styrene and acrylonitrile in a seeded emulsion polymerisation process. As the styrene-acrylonitrile copolymer shell forms, polybutadiene domains are spontaneously separated within. The resulting impact modifier particles are subsequently compounded with polystyrene to product high impact polystyrene (HIPS). The impact modification properties of the latex particles may be optimised through varying the butadiene content, the particle size and structure, and the shell molecular weight. A basic formulation for an ABS impact modifier is given in Table 6. 

Okubo et al. examined the penetration/release behavior of various solvents in-to/from the interior of micron-sized monodisperse cross-linked polystyrene/poly-divinylbenzene composite particles [63]. The hollow particles were produced by the seeded polymerization utilizing the dynamic swelling method [64], Itou et al. prepared crosslinked hollow polymer particles of submicron size by means of a seeded emulsion polymerization [65]. The morphology of the particles depends on the composition of divinylbenzene and methyl methacrylate. 

CuCl/CuCl2/bpy as the catalyst. The ATRP initiator layer on the surface of polystyrene particles was prepared by seed emulsion polymerization of 2-(2-bromoisobutyryloxy) ethyl methacrylate (BIEM) using polystyrene (PS) latex as seeds. 

Okubo (16) used a similar approach to follow the growth of seeded emulsion polymerizations. When polystyrene was used as the seed particles, followed by the addition of methyl methacrylate, overcoating of the seed particles with a layer of poly(methyl methacrylati was observed. In the reverse situation, however, a distinctly different morphology was produced as indicated by the surfactant adsorption variations with monomer conversion. Instead of overcoating the PMMA seed particles with a uniform layer, the PSTY tended to separate into spherical domains eventually producing a... 

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