Light scattering emulsion polymer particles

Light Scattering Studies of the Internal Structure of Emulsion Polymer Particles... 

The rotor of the ultracentrifuge is spun at speeds of up to 60 000 rpm in a vacuum to minimize air drag [75-77]. It may be used, therefore, to measure the size distribution of ver> fine particles. McCormick [78], for example, describes its use for determining the size distribution of polystyrene (0.088 < d < 0.511) pm and Brodnyan [79] uses it for determining emulsion particle size. It has also been used in combination with light scattering for polymer size distribution determination [80]. 

Bartsch S. Kulicke WM, Fresen I, Moritz HU. Seeded emulsion polymerization of styrene determination of the particle size by flow field-flow fractionation coupled with multi-angle laser light scattering. Acta Polym 1999 50 373-380. 

The preservation of particle character and size throughout polymerization itself is very hard to determine. The size of the final polymer particles is easily determined by light scattering or microscopic methods since the dispersions can be diluted without changing the particle size. Measurements of the emulsion droplets in concentrated media on the other hand are a very difficult task and have already been discussed above. 

Experimental investigations that deal in detail with particle formation in emulsion copolymerization are scarce. Nomura et al. [78] studied the kinetics of particle formation and growth in the emulsion copolymerization of VDC and MMA using NaLS as the emulsifier and KPS as the initiator. The number of polymer particles produced was determined using particle diameters measured by both electron microscopy (TEM) and dynamic light scattering (DLS) for comparison. They found that where Sq and Iq are the initial... 

The emulsion polymerization in the third step is carried out in the presence of a water soluble monomer, such as acrylic acid. The radicals formed by the photolysis of HMEM (Fig. 6.18b) on the surface start radical chain polymerization by a grafting-from technique (see Section 6.13.3) thus generating chains of poly(acrylic acid). The polymer chains remain bound to the surface by an ester bond which can be cleaved by hydrolysis to obtain the polymer for analysis. Thus the molecular weight of the bound polymer chains can be determined which gives their contour length Lc. The thiclcness L of the brush (Fig. 6.17) attached to the surface of the particles can be deduced from the hydrodynamic radius as measured by dynamic light scattering. 

Dynamic light scattering measurements of the miniemulsion lattices prove the successful incorporation of the inorganic cores into the miniemulsion droplet. All silica based polymer composites show particle sizes between 120 nm and 150 nm with a low PDI, whereas the silica precursor itself showed an average particle size of 79 nm. Hence, all silica nanoparticles have been incorporated into the emulsion droplet and each droplet contains only one silica particle. This can be proved by the SEM image of the composite. 

Several techniques are commonly used to measure the size distributions of metal colloid particles. Electron microscopy. X-ray diffi ction, and small angle X-ray scattering are the most commonly used, although dassical methods such as sedimentation rates are sometimes reported. The techniques whidi have been extensively applied to the sizing of polymer colloids and emulsions, [183] such as light scattering and neutron scattering, have been only rarely applied to the characterization of metal sols. [103, 151, 153, 184]... 

Process Monitoring Regarding the use of spectroscopic data in anulsion polymerizations for monitoring and control purposes, few smdies are found in the open literature. This is probably due to the complexity of emulsion polymerization systans, which involve different phases (aqueous phase, monomer droplets, and polymer particles), several compounds (water, monomer, polymer, initiator, stabilizer, and buffers) providing spectra of difficult interpretation. Moreover, polymer particles and monomer can scatter light to such an extent that the use of spectra for quantitative purposes may require the application of special mathonatical... 

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