Electrosteric Stabilization of Polymer Colloids

Abstract

Four electrostatic surfactants, CmH2m+iO(CH2CH20)nS03Na, with m averaging between 12 and 15 and n, the ethylene oxide chain length, being 3,7,9, or 15, were used to investigate the steric chain length effect in the stabilization of model latices and in emulsion polymerization of styrene. It was found that during polymerization, the number of particles stabilized and the rate of reaction decreased with increasing ethylene oxide chain length in the surfactant. The addition of an electrolyte to the polymerization system caused a decrease in the rate of polymerization. This electrolyte effect decreased with increasing ethylene oxide chain length. Coagulation tests of latices stabilized by these four surfactants indicated a switch in stabilization mechanism from primarily electrostatic to steric stabilization between 9 and 15 ethylene oxide units.

Colloidal Stability of Polymer Colloids with Different Interfacial Properties: Mechanisms

“…First, we again estimated A and C d by fitting the modified stability factor (W ) proposed by Spielman (Eq. [8]) to our experimental data that appear in Fig. 4.…”

“…It was found that the stability curve, 0d log W/d log C e , is related to the radius particle, of polymer colloids with polyelectrolytes or ionic surfactants to the diffuse potential associated with the charged polymer adsorbed on the particle surface is also affected by electrosurface, c d , and to the electrolyte valence, z, by the expresstatic and steric effects. The combined effect of these two sion mechanisms is known as electrosteric stabilization (7,8). Colymerization of hydrophobic and hydrophilic monomers 0d log W/d log C e Å 2.15 1 10 9 ag 2 /z 2 , [2] leads to a final dispersion stabilized by the electrostatic effect and by the existence of hydrophilic oligomers at the particle where g Å tanh(zec d /4kT ).…”

Sequential Adsorption of Triton X-100 and Sodium Dodecyl Sulfate onto Positively and Negatively Charged Polystyrene Latexes

“…To fit the theoretical expression of W to the experimental values there are three more parameters, that is, the FloryHuggins solvency parameter (χ), the average thickness of surfactant chains covering the external surface of a particle (δ), and the effective volume fraction of segments in the external layer (ϕ 2 ). In this work, we have decided to keep constant the Flory-Huggins solvency parameter, χ = 0.45 (32), and δ = 20 A estimated from electrokinetic measurements (33 On PS[+] the stability of the dispersion is mainly due to the amount of SDS that is on the latex surface. It should be noted that this effect is independent of which surfactant is adsorbed first (Figs.…”

“…stabilization of the system. Non-ionic surfactants adsorbed onto colloidal particles can act as steric stabilizers (2)(3)(4), and polyelectrolytes or ionic surfactants adsorbed cause electrostatic and steric effects, i.e., electrosteric stabilization (5,6).…”

Miniemulsion Polymerization of Styrene Initiated by Tween-surfinit

“…The formation of monodisperse polymer particles formed in the emulsion stabilized by non-ionic emulsifier was connected with the diffusion controlled regime [10,11]. The low weight ratio of monomer to polymer (ca.…”