Comparative Study of the Adsorption of Nonionic Surfactants:  Triton X-100 and C₁₂E₇ on Polystyrene Latex Particles Using Dynamic Light Scattering and Adsorption Isotherm Measurements

Abstract

The adsorption of the nonionic surfactants Triton X-100 and C12E7 on predominantly hydrophobic polystyrene latex particles has been examined as a function of surfactant concentration by measuring the hydrodynamic radius by dynamic light scattering and adsorption isotherms by a surface tension technique. The adsorption behavior of these materials differs significantly and is related to the structures of the surfactant “tails”. Adsorption of TX-100 most probably occurs in an approximately perpendicular geometry with contact between its methyl end groups and the partially extended polymer chains at the latex surface and is accompanied by association between the aromatic nuclei of the adsorbed surfactant molecules. The latter leads to cooperative adsorption and an S-type isotherm. The perpendicular adsorption mode leads to expansion of the polymer chains for steric reasons, giving a pronounced increase in the hydrodynamic radius in the initial adsorption stage. There is a larger adsorbed amount of TX-100 compared with the C12E7. C12E7 has a straight dodecyl chain and an extended molecular conformation. This favors bridging of neighboring polymer chains through interactions both between the alkyl tails and the polymer chains and between the POE chain and the terminal sulfate groups. Bridging leads to aggregation of the polymer chains and reflects the strong interaction between C12E7 and the polymer chain which gives an L-type adsorption isotherm. The adsorption isotherm is two-stepped in TX-100/latex solutions but is single-stepped for C12E7/latex suspensions, except in 100 mM added NaBr and at 35 °C. The characteristic types of adsorption isotherms observed with the two surfactants remain unchanged on altering other parameters, for example, the ionic strength or the temperature. NaBr augments C12E7 adsorption partly owing to salting-out of water from the hydration shell of the POE chain. On the other hand, TX-100 adsorption in 100 mM NaBr is complicated by competition between adsorption and micellization in aqueous solution since there is a pronounced tendency for TX-100 to aggregate in bulk solution at higher ionic strengths. Enhanced adsorption of both surfactants occurs on increasing the temperature, owing to a decrease in surfactant solubility in aqueous solution deriving from a combination of changes in the POE chain conformation and a reduction in the amount of structured water around the surfactant head group.

Fabrication of large scale two-dimensional colloidal crystal of polystyrene particles by an interfacial self-ordering process

“…Therefore, one could conclude that the contact point between PS particles should locate below the water surface. It has been reported that the adsorption of TX 100 occurred in an approximately perpendicular geometry and the surface of the PS particles was surrounded by poly (oxyethylene) chains [51]. Thereby it was reasonable to consider that the extended poly (oxyethylene) chains of TX 100 reduced the hydrophobic interaction force between PS particles.…”

“…Previous investigations of the adsorption of TX 100 on particles, such as hydrophobic PS nanoparticles [51] and alkyl-grafted silica nanoparticles [52], indicated that TX 100 molecules were adsorbed on particle surfaces through the interaction between the hydrocarbon tail of the surfactant and the polymer chains, resulting in the conversion from the hydrophobicity to the hydrophilicity of particle surface state. To evaluate the effect of TX 100, an UV-vis absorption method was used to determine the amount of TX 100 adsorbed on PS particles surface.…”

Determination of the Adsorption Isotherm of the Nonionic Surfactant Triton X-405 on Polystyrene Latex Particles Using1H NMR

“…Another method of analyzing the data consists of a more extended surfactant layer around the particles. Evidence for this type of behavior has been suggested in the literature (8). The sharp peak determining the number of ethylene oxide groups initially present in the solution.…”

Adsorption of Ionic Surfactants on Solid Particles Determined by Zeta-Potential Measurements: Competitive Binding of Counterions

“…Various techniques have been applied to measure the depletion effect: colorimetric titration methods (1)(2)(3)(4), static (5)(6)(7) and dynamic (8) surface-tension experiments, UV spectroscopy (9)(10)(11), fluorescence (12), and high-pressure liquid chromatography (13) [see also studies cited in Ref. (2)].…”

“…Consequently, to determine the surfactant adsorption one has also to measure the area of the solid-liquid interface per unit mass of the particles; the latter can be achieved by means of the BET-N 2 desorption method (9,11), dynamic light scattering (6,7), or electron microscopy (13).…”