A method for the formation of monodisperse polystyrene (PS) and polymethylmethacrylate (PMMA) spheres, in the micron diameter range, was developed. The polymerisation reaction was carried out in a series of alcohols, using homo‐ and co‐polymers as steric stabilisers in combination with a quaternary ammonium salt which probably acts as an electrostatic co‐stabiliser. Monodisperse PS spheres were formed in the particle size range of 1–6 μm, by a single step process. The size range could be extended by further addition of monomer to the reaction mixture during the polymerisation. The solubility parameter of the alcohol used and the nature of the surfactant determine the diameter of the resulting spheres. However, the concentration of surfactant did not seem to affect strongly the size of the spheres but only the dispersity.

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Forces between polystyrene layers absorbed on mica and immersed in cyclohexane have been measured. The measurements were made on two different molecular weights (6 X 10s and 9 X 10s) in two different laboratories and therefore support the quantitative reliability of the results. We have reproduced previous results of this type of measurement below the temperature and extended the force measurement to (a) adsorbed layers at lower surface coverage and (b) temperatures above the bulk polystyrene-cyclohexane temperature. At a coverage of about 1.1 mg/m2 of polystyrene, which is on the order of 20-30% of saturation, we found strongly attractive forces below Te, detectable at separations of about 300 Á between the bare mica surfaces. The forces can be measured very accurately and precisely in this situation. The force reaches a minimum at 46 ± 2 Á and becomes strongly repulsive closer in. The long-range attractive portion of the force curve is very nearly exactly exponential, with a decay length of 45 ± 2 A. For saturated surfaces with about 4.5 ± 1 mg/m2 the force is detectably attractive at larger distances (600-1200 Á) both below (23 and 26 °C) and above (37 ± 2 °C) the temperature (34.5 °C). For each molecular weight the positions of the minimum in the F(D) curve and of the short-range repulsive barrier are at smaller separations at T > TB. The magnitudes of the minima are smaller at T > Te as well. Both of these new results suggest strongly that the forces, especially the attractive components, between the polymer surfaces are influenced by effects in addition to the usual segment-segment interactions which determine bulk thermodynamic properties.

The influence of poly(vinyl alcohol) (PVA), a steric stabilizer, and sodium dodecyl sulfate (SDS), an electrostatic stabilizer, on the stability of styrene dispersion polymerized systems was studied. It was shown that in stabilization by PVA there was pronounced bridging of the submicron emulsion particles to 10‐μ dispersion particles and that the emulsion particles could not be washed off. In SDS stabilization, on the other hand, the emulsion formed was easily washed off because bridging with SDS does not occur. The surface tension of the aqueous phase measured during polymerization showed different characteristics for stable and unstable systems.

The conditions for obtaining stable dispersions of 10‐μ droplets of monomer in an aqueous phase using steric and electrostatic stabilizers, were studied. The nature and concentration of the surfactant in the aqueous phase has an important effect on the size of the droplets and the stability of the dispersion during the polymerization reaction. The amount of polyvinylalcohol adsorbed on the interface was measured and the rate of desorption was shown to be very slow. It was also shown that sodium dodecyl sulfate, on the other hand, is more readily desorbed. These findings have an effect on the amount of the submicron emulsion particles formed during the polymerization process.