Emulsion light scattering

Water is extensively used to produce emulsion polymers with a sodium stearate emulsifrer. The emulsion concentration should allow micelles of large surface areas to form. The micelles absorb the monomer molecules activated by an initiator (such as a sulfate ion radical 80 4 ). X-ray and light scattering techniques show that the micelles start to increase in size by absorbing the macromolecules. For example, in the free radical polymerization of styrene, the micelles increased to 250 times their original size. 

Seligson s group (95) has published a similar turbidimetric procedure but used nephelometry to measure continuously the effect of lipase on the light scattering of an olive oil emulsion. The instrumentation and approach is the same as that described above for the nephelometric determination of amylase. The method according to the authors is fast and precise with good specificity and sensitivity. The short time required for analysis makes it suitable for emergency use. The technical simplicity permits this method to be easily automated, and it appears to be the lipase method of choice. 

J.-B. Salmon, L. Becu, S. Marmeville, A. Colin 2003, (Towards local rheology of emulsions under Couette flow using dynamic light scattering), Eur. Phys. J. E 10, 209. 

Figure 3.12. Light-scattering intensity as a function of the wave vector for an emulsion with 4> = 4% at a series of times. The inset shows that, except at the earliest times, the data can be scaled onto a single curve. (Adapted from [27].)...

Polystyrene can be prepared as follows A mixture of styrene, detergent (Na-dodecanoate), and water is agitated ultrasonically to produce a fine emulsion. On the addition of hydrogen peroxide (initiator), PS is obtained as a polymer, which can be extracted after filtration. The polymer molecular weight is determined by various methods (such as light scattering and osmotic pressure). 

Dickinson, E., Semenova, M.G., Belyakova, L.E., Antipova, A.S., Il in, M.M., Tsapkina, E.N., Ritzoulis, C. (2001). Analysis of light scattering data on the calcium ion sensitivity of caseinate solution thermodynamics relationship to emulsion flocculation. Journal of Colloid and Interface Science, 239, 87-97. 

Figure 3.5 Demonstration of correlation between the stickiness of protein-coated droplet pair encounters in shear flow (left ordinate axis) and viscoelasticity of concentrated emulsions (right ordinate axis) with the strength of protein-protein attraction as indicated by the second virial coefficient A2 determined from static light scattering , percentage capture efficiency (0%) A, complex shear modulus (G ) for emulsions stabilized by asl-casein or (3-casein (pH = 5.5, ionic strength in the range 0.01-0.2 M).

Figure 6.11 Effect of ionic strength on (a) weight-average molar weight, Mw ( ), and second virial coefficient, A2 ( ), of p-casein in solution at pH = 5.5 and 22 °C, as determined by static light scattering and (b) average droplet diameter, c/43 (A.), and extent of gravity creaming ( ) of p-casein-stabilized emulsion (11 vol% oil, 0.6 wt% protein, pH = 5.5, 22 °C).

Hence, from the previously described light-scattering study of caseinate self-assembly in solution, we can postulate that heating/cooling not only alters the nature and strength of the physical (hydrophobic) interactions between emulsion droplets covered by caseinate. It most likely also transforms the nanoscale structural characteristics of the protein network in the bulk and at the interface, thereby affecting the viscoelastic and microstructural properties of the emulsions. 

Light scattering study of sodium caseinate + dextran sulfate in aqueous solution relationship to emulsion stability. FoodHydrocolloids, 23, 629-639. 

Figure 7.17 Influence of i-carrageenan on the state of flocculation of BSA-stabilized emulsions (20 vol% oil, 1.7 vt% protein. pH = 6, ionic strength = 0.005 M) stored at 25 °C for 40 hours. The average droplet size measured by static light scattering (Malvern Mastersizer), d32, is plotted against the polysaccharide concentration ch added to the freshly made emulsion. Reproduced from Dickinson and Pawlowsky (1997) with permission.

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