Stabilization of Latex Dispersions Using a Graft Copolymer of Inulin Based Surfactants

Abstract

Polystyrene (PS) latex dispersions were prepared by surfactant-free emulsion polymerization. Poly-(methyl methacrylate) (PMMA) latex dispersions were prepared using the same procedure except by adding INUTEC SP1 as emulsifier. The two latex dispersions were characterized by photon correlation spectroscopy (PCS) to obtain the average particle size and the polydispersity index. The stability of these latex dispersions was measured by determination of the critical coagulation concentration (CCC) of three electrolytes, namely, NaCl, CaCl2, and Al2(SO4)3. The CCC was 0.375 mol‚dm -3 for NaCl, 0.007 mol‚dm -3 for CaCl2, and 0.0004 mol‚dm -3 for Al2(SO4)3. A polymeric surfactant, namely, a graft copolymer of polyfructose on which alkyl groups were grafted to the backbone, were added to latex dispersions and their stability was investigated. On addition of this polymeric surfactant, the stability of the latex dispersions was significantly increased and the CCC became very high above a critical polymer concentration. For the PS latex, the CCC of CaCl 2 was higher than 4.3 mol‚dm -3 when the polymeric surfactant concentration was 0.25 wt %. The results could be rationalized in terms of the enhanced steric repulsion resulting from the adsorption of the graft copolymer. It was assumed that the molecule produces large "loops" of polyfructose between the adsorbed alkyl groups, forming a hydrated layer thickness of approximately 4 nm. In addition, these polyfructose chains were still hydrated even in the presence of high electrolyte concentrations.

Interaction forces between particles stabilized by a hydrophobically modified inulin surfactant

“…It is higher than the approximate value (4 nm) obtained before, by measuring the small increase in the hydrodynamic radius of latex particles, determined from diffusion coefficients obtained by PCS, as a function of surfactant concentration [12]. The PCS measurements are less accurate since δ is obtained from the difference between the hydrodynamic radius of the polymer coated particles and the bare particles.…”

“…The molecule was previously studied for his stabilization properties of O/W emulsions [11] and colloidal dispersions such as latex particles [12][13].…”

“…Preliminary investigations by dynamic light scattering (PCS) using polystyrene latex particles, indicated an adsorbed polymer layer thickness of 4 nm [12]. It proved to be very effective as a steric stabilizer [12,13] and indeed more efficient in comparison to classical surfactants, based on poly(ethylene oxide) [12][13][14][15].…”

“…It proved to be very effective as a steric stabilizer [12,13] and indeed more efficient in comparison to classical surfactants, based on poly(ethylene oxide) [12][13][14][15].…”

Emulsion polymerization of styrene using mixtures of hydrophobically modified inulin (polyfructose) polymeric surfactant and nonionic surfactants

“…1,2 One of the most interesting findings of this previous work was the low [INUTEC SP1]/[Monomer] ratio that was sufficient to produce stable aqueous latexes up to 50 wt % PS. 2 This ratio was 0.0033.…”