Particle diameter, emulsions, effect

Figure 7.18 Protein-polysaccharide interactions in emulsions subjected to high pressure treatment (HPT). Influence of pH on average effective particle diameter d43 determined by static light scattering (Malvern Mastersizer) in emulsions (20 vol% soybean oil, 0.5 wt% p-lactoglobulin) prepared with untreated protein (open symbols) and high-pressure-treated (800 MPa for 30 min filled symbols) protein in the absence (O, ) and presence (A, ) of 0.5 wt% pectin. Reproduced from Dickinson and James (2000) with permission.

Equations proposed by Sherman for predicting viscosities from apparent volume fractions and particle diameters were useful in analyzing the effects of formulation and preparation variables and aging on emulsion viscosities. 

These effects can be illustrated by estimating values of < from the Sherman model [3 ] from values of relative viscosity and average particle diameter. In Table II we can see the influence of NaCl concentration on a for the two emulsions shown in Figure 6. At the NaCl concentrations of minimum viscosity, values of a also show minima. 

Bernard et al. [105] used the same strategy to decorate polyVAc latex particles with a dithiocarbonate end-functionalized dextran (dextran-RAFT), well-suited for the CRP of non-activated vinyl esters such as VAc. Dextran-RAFT was obtained by Cu(I)-catalyzed Huisgen [3+2] dipolar cycloaddition [106] between an alkyne end-functionalized dextran and an azido-containing dithiocarbonate. The low functionalization yield (30%) was apparently not an impediment for the syntheses of stable poly VAc latex particles (diameters from 80 to 150 nm) via batch emulsion polymerization. The involvement of the dithiocarbonate end-group was corroborated by the retardation effect observed when the dextran-RAFT concentration was increased. In addition, a drastic effect on particle size was observed as compared to emulsion polymerization experiments performed with native or alkyne-functionalized dextran (particle diameter above 500 nm). 

Figure 40.4 shows the SEM images of barium titanate powders synthesized at 850°C. The effect of using various barium concentration and precursor sources for titanium was studied [3] In Fig. 40.4a barium concentration is 0.3 mol/L and titanium source is Ti02 sols, in Fig. 40.4b barium concentration is 0.03 mol/L and the titanium source is the same as above, i.e., Ti02 sols in Fig. 40.4c the barium concentration is 0.3 mol/L the same as Fig. 40.4a, but the titanium source is the TiCl4 precursor. When a high concentration of barium was used (0.3 mol/L), the particles were spherical with diameters of 200-500 nm (Fig. 40.4a), whereas for a low concentration of 0.03 mol/L the particle diameter is from 100 to 200 nm (Fig. 40.4b). Therefore, the particle diameter of the barium titanate may be controlled by the metal ion concentration in the emulsion droplet. Particles in Fig. 40.4c exhibited a broader particle size distribution [3]. The diagram of Fig. 40.2 and the discussion provided later may help interpret the results observed in Figs. 40.3 and 40.4.

In aqueous emulsion polymerization, amphiphilic polymers are widely used as polymeric surfactants to stabilize the latex particles, where the hydrophobic blocks can anchor on the particle surface while the hydrophilic blocks extend into the water phase and create a hydrophilic shell [47, 49-52]. Therefore, PS-PAA-PS and HB-(PAA)47-g-(PS)48 copolymers were further used as polymeric surfactants to explore the effect of chain topology on the emulsifying efficiency. The characterization results of solid contents (t), latex particle sizes ( R)) and numbers (A p) are summarized in Table 5.2, Figs. 5.29 and 5.30, where the average particle diameters were carefully determined by DLS at pH 3.2 to ensure the full collapse... 

Araki et al. [38] studied the feasibility of applying resonant soft X-ray scattering to chemically heterogeneous soft condensed matter nanomaterials. Two structured styrene-acrylic emulsion polymer particles with average particle diameters close to 230 nm were examined. This technique can be used to obtain the effective radii corresponding to the two polymer phases within the latex particles, and it can serve as a powerful complementary tool to neutron and hard X-ray scattering techniques for the characterization of structured soft condensed matter nanomaterials. 

The emulsion polymerisation process strategy, can have a considerable effect on molecular structure and particle morphology. The intrinsic factors as well as the process conditions determine the colloidal aspects of the copolymer latex (particle diameter, surface charge density, colloidal stability etc.), the characteristics of the polymeric material in the particles and the structure of the particles (copolymer composition as a function of particle radius etc.). In turn, these factors determine the properties of the latex and the copolymer product. 

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