Dynamic Light Scattering and Viscosity Studies on the Association Behavior of Silicone Surfactants in Aqueous Solutions

Abstract

The micellar structure of three nonionic amphiphilic silicone surfactants based on polyether-modified poly-(dimethylsiloxane) has been investigated by dynamic light scattering (DLS) and viscosity measurements. Out of these three, two surfactants have a comblike structure, and one has a trisiloxane-type structure with a linear poly(dimethylsiloxane) backbone chain and a grid containing block oligomers of oxyethylene and/or oxypropylene attached to one of the units as grafts. The dilute-solution phase diagram of the trisiloxane surfactant has been constructed and explained. The hydrodynamic radius, R h , and the size distribution in terms of the translational diffusion coefficient of the micelles were obtained from the analysis of the time correlation function of the scattering intensity measured at a fixed scattering angle of 90°and for different concentrations and temperatures (30, 45, and 60°C). The micellar systems under study were found to have a less polydisperse size distribution. The analysis of DLS data revealed the presence of oblate ellipsoidal micelles that showed continuous growth along the semimajor axis, b, with the rise in temperature. The values of the mass average association number, the hydrodynamic expansion factor, and the intrinsic viscosity of the micelles exhibited a similar temperature dependence, but the dominant repulsive solute (hydrophobic part)-solvent interactions noticed at 30°C were found to get weaker. The combination of small-angle neutron scattering (SANS), DLS data, and intrinsic viscosities of micellar solutions were used to estimate the hydration of the micelles. The observed unusual temperature dependence of the micellar hydration has been explained.

Synthesis and Self‐Assembly Behavior of Comb‐Like Surfactant Polymethyl Methacrylate‐g‐Methoxy Polyethylene Glycol

“…Dynamic light scattering (DLS) was used to determine the hydrodynamic diameters and the intensity weighted size distributions of the micelles [37]. At 25°C, the apparent hydrodynamic diameters (R h,app ) distribution of the micelles in aqueous solution of different PMMA-g-MPEG concentrations are shown in Fig.…”

Synthesis, characterization and properties of amphiphilic block copolymers of 2-hydroxyethyl methacrylate and polydimethylsiloxane prepared by atom transfer radical polymerization

“…The conversion yield of carbinol-terminated PDMS to the PDMS macroinitiator was almost 99 wt%. The chemical structure of the macroinitiator was confirmed by nuclear magnetic resonance (NMR) analysis: 1 …”

“…Several architectures can be prepared using amphiphilic block copolymers for applications such as coatings, inks, paints, textile, agriculture, cosmetics and biomaterials. [1][2][3][4][5] The physical and chemical properties of amphiphilic copolymers, for example, the modulus 3 and surface tension, 6 can be adjusted by varying the block length, composition and architecture of the copolymer. These properties affect the morphology and critical micelle concentration (CMC).…”

Silicone emulsions

“…Silicone polymers comprising a non-ionic hydrophilic group and a hydrophobic poly(dimethyl siloxane) chain (also known as silicone copolyols) have been studied for their emulsifying properties in some detail [3,10,13]. The molecular architecture of these polymers can be tailored to suit specific applications.…”

“…In most cases, the hydrophilic moiety of choice has been poly (oxyethylene) (EO groups) because of its good water solubility and ease of synthesis with a wide range of molecular weights. The hydrophilicity/hydrophobicity of these polymers can be controlled by varying the chain length of EO groups, partial or complete substitution of EO with poly(oxypropylene) (PO groups), or by varying the degree of modification in the case of grafted polymers [13]. Silicone copolyols can also be modified with various alkyl chains in order to make them compatible with hydrocarbon oils, thereby making them good stabilizers for emulsions of hydrocarbon oil and water.…”