Poly latex particles, swelling

Polyelectrolytes provide excellent stabilisation of colloidal dispersions when attached to particle surfaces as there is both a steric and electrostatic contribution, i.e. the particles are electrosterically stabilised. In addition the origin of the electrostatic interactions is displaced away from the particle surface and the origin of the van der Waals attraction, reinforcing the stability. Kaolinite stabilised by poly(acrylic acid) is a combination that would be typical of a paper-coating clay system. Acrylic acid or methacrylic acid is often copolymerised into the latex particles used in cement sytems giving particles which swell considerably in water. Figure 3.23 illustrates a viscosity curve for a copoly(styrene-... 

A. Loxley and B. Vincent, Equilibrium and kinetic aspects of the pH swelling of poly(vinylpyridine) latex particles, Colloid Polymer Sci. 275, 1108-1114 (1997). 

In the presence of poly(styrene sulphonate) at 40 C the particles flocculate as a consequence of depletion forces operative in the system. It is believed that the polymer does not adsorb onto the particles from water at neutral pH as both species have negative charges. Other hard sphere colloids have been reported to undergo similar depletion flocculation processes with poly(styrene sulphonate) (2,6) under similar conditions but at a fixed temperature. The flocculated latex on cooling down to 25 C redisperses, as a consequence of the particles swelling with solvent and then undergoing conformational rearrangments. The soft nature of the particles at 25 C... 

Another technique of precipitating poly(vinyl chloride) from a latex consists of adding approximately 10% on a dry solids basis of xylene or toluene to the latex along with more than an equal volume of water. After vigorous agitation to permit the solvent to swell the polymer particles, a 10% aqueous solution of aluminum sulfate is added with agitation, and steam is led into the mixture to drive off the solvent [148]. 

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