Seeded emulsion polymerization styrene

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... 

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... 

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. 

ASA structural latexes have been synthesized in a two stage seeded emulsion polymerization. In the first stage, partially crosslinked poly(n-butyl acrylate) and poly( -butyl acrylate-sfaf-2-ethylhexyl acrylate) rubber cores are synthesized. In the second stage, a hard styrene acrylonitrile copolymer (SAN) shell is grafted onto the rubber seeds (16). 

S. Tolue, M.R. Moghbeli, and S.M. Ghafelebashi, Preparation of ASA (acrylonitrile-styrene-acrylate) structural latexes via seeded emulsion polymerization, Enr. Polym. ]., 45(3) 714-720, March 2009. 

We now report on some experiments using seeded emulsion polymerization of styrene in which conditions were carefully chosen to ensure that Smith-Ewart Case 2 kinetics (6) would obtain throughout, in the absence of chain transfer/radical desorption effects. Various hydrocarbons were investigated for their effects on kinetics of polymerization and equilibrium swelling of the latex particles. 

Effect of Additives on the Rate of Seeded Emulsion Polymerization of Styrene... 

Figure 1 gives the conversion-time curves for the seeded emulsion polymerization of styrene in the absence and presence of various low molecular weight additives. Table I summarizes the results given in Figure 1. The rates of polymerization were determined from the straight line portion of the conversion-time curves (below 40% conversion) by least squares analysis of the experimental points. Table I also gives the calculated rates assuming a mere dilution of the monomer in the seed by the additive. It is clear that in every case the rate of polymerization is retarded much more than that due to dilution alone.

Figure 1. Effect of addition of low molecular weight hydrocarbons as additives upon the progress of the seeded emulsion polymerization of styrene at 50°C.

Kinetics of the Seeded Emulsion Polymerization of Styrene in the Presence of Ethylbenzene, at 30°C... 

When water-insoluble compounds are mixed with the monomer in styrene seeded emulsion polymerizations, the rate of polymerization is lowered below a simple dilution effect. Since the additive is not transported through the water, it remains in the droplets of monomer,... 

Bartholme t al. (22) found for styrene with persulfate initiation and a sodium alkyl benzene sulfonate emulsifier that there was a discrepancy between their measured value of E (21.7 kJ mol- ) and that calculated (on the assumption that Att = 0) from the expression EN = /5(E - E ). However their value of E (which was derived from measuremlnts of the rate of seeded emulsion polymerization experiments in which N was the same at all temperatures) now seems to be too high probably because the average number of radicals per particle, n < 0.5 at the lower temperatures taking E =32.5 kJ mol-1 as the best estimate, AHg can be calculated rom AHg = /2(E (exp) - E (calc))... 

In the seeded emulsion polymerization of some monomers —e.g., styrene—it is possible to obtain final latexes with uniform, large particles by adjusting, during polymerization, the quantity of added emulsifier the formation of new particles is prevented by the limited amount of emulsifier. For vinyl chloride, limited emulsifier is not sufficient to prevent the formation of new particles in fact, to obtain a monodispersed latex, the surface of the particles seeded in a given water volume must be controlled. It is assumed that the growth of new nuclei is related either to the rate of formation of primary useful radicals or to the rate that these are taken by the surface of sized particles. 

Recently, core-shell type microgels, which contain a hydrophobic core and a hydrophilic thermosensitive shell, have become attractive for scientists because such systems can combine the properties characteristic of both the core and the shell [53], We have prepared core-shell microgel particles consisting of a poly(styrene) core onto which a shell of polyCA-isopropylacrylamide) (PS-PNIPA) has been affixed in a seeded emulsion polymerization [54-56], In this case, the ends of the crosslinked PNIPA chains are fixed to a solid core, which defines a solid boundary of the network. In this respect, these core-shell latex particles present crosslinked polymer brushes on defined spherical surfaces. The solvent quality can be changed from good solvent conditions at room temperature to poor solvent conditions at a temperature... 

Nomura et al. [285] and Lichti et al. [286] studied the effects of transfer agents on the kinetics of ab initio and seeded emulsion polymerization of styrene, respectively. Nomura et al. found that the polymerization rate per particle decreased with increasing amounts of carbon tetrachloride, carbon tetrabromide and primary mercaptans, and that the effects were stronger when... 

Fig. 11. Conversion versus time curves for seeded emulsion polymerizations of styrene with hexadecane present in the monomer phase. T — 333 K.

Figure 5.14 The slope of the straight-line region of the instantaneous number MMD for 44 and 130 nm radii seeded emulsion polymerizations of styrene at 30 °C (one example of which is shown in Figure 5.12) rec culated from data in [57], The slope is plotted as A = —AfodlnP(A/)/

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... 

Muller and coworkers prepared disc-like polymer Janus particles from assembled films of the triblock copolymer SBM and, after hydrolysis of the ester groups into methacrylic acid units, used these as Pickering stabilizer in the soap-free emulsion polymerization of styrene and butyl acrylate [111]. Armes and coworkers described the synthesis of PMMA/siUca nanocomposite particles in aqueous alcoholic media using silica nanoparticles as stabilizer [112], extending this method to operate in water with a glycerol-modified silica sol [113, 114]. Sacanna showed that methacryloxypropyltrimethoxysilane [115] in the presence of nanosized silica led to spontaneous emulsification in water, which upon a two-step polymerization procedure afforded armored particles with an outer shell of PMMA [116]. Bon and coworkers demonstrated the preparation of armored hybrid polymer latex particles via emulsion polymerization of methyl methacrylate and ethyl methacrylate stabilized by unmodified silica nanoparticles (Ludox TM O) [117]. Performance of an additional conventional seeded emulsion polymerization step provided a straightforward route to more complex multilayered nanocomposite polymer colloids (see Fig. 14). 

A few years later, Charleux s team developed a similar strategy using SGl-based macroalkoxyamine, after having thoroughly smdied the use of water-soluble molecular alkoxyamines based on SGI in both miniemulsion and seeded emulsion polymerizations [127-131]. First, the conditions for control of the polymerization of acrylic acid in solution with SGI were determined and allowed the preparation of well-defined SGl-capped polyAA [132, 133]. After purification, a polyAAjj-SGl (PDI = 1.17) was used to initiate the polymerization of styrene or BA in basic water at 120°C and 3 bar pressure, and with a typical solids content of 20 wt% [134] (Fig. 13). 

Figure 24, Initial and final reflectance spectra obtained with probe 4, measured from a seeded emulsion polymerization reaction of styrene, concentration is approximately 30 %...

Molecular weight distributions of the seed poly(BuA) latex (Mn,sEc = 5 900g- moP ) prepared by RITPand of the block copolymer latex poly(butyl acrylate)-bock-poly(styrene-co-butyl acrylate) (M sec = 53 400 g-moP ) prepared by seeded emulsion polymerization at 85 °C ( ) refractive index detector (seed latex), (O) UV detector at 254 nm (copolymer latex), (A) refractive index detector (copolymer latex). Seed [ACPA]/[IJ = i.6, [SDS] = 0.15 X CMC, targeted Mn = 2500 g mol, conversion =40%, particle diameter = i27 nm Block copolymer second monomer = styrene Monomerpee[Pg.165]

S. W. Prescott, M. J. Ballard, E. Rizzardo, R. G. Gilbert, Successful use of RAFT techniques in seeded emulsion polymerization of styrene living character, RAFT agent transport and rate of polymerization. Macromolecules 2002, 35, 5417-5425. 

No.26,18th Dec. 2001, p.8907-12 EFFECT OF A REACTIVE SURFACTANT AND ITS POLYMERIC COUNTERPART ON THE KINETICS OF SEEDED EMULSION POLYMERIZATION OF STYRENE Wang X Boya B Sudol E D El-Aasser M S Lehigh University... 

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