Synthesis, Properties, and Aggregation Behavior of Tetrasiloxane-Based Anionic Surfactants

Research Progress in Structure Synthesis, Properties, and Applications of Small-Molecule Silicone Surfactants

Silicone surfactants have garnered significant research attention owing to their superior properties, such as wettability, ductility, and permeability. Small-molecular silicone surfactants with simple molecular structures outperform polymeric silicone surfactants in terms of surface activity, emulsification, wetting, foaming, and other areas. Moreover, silicone surfactants with small molecules exhibit a diverse and rich molecular structure. This review discusses various synthetic routes for the synthesis of different classes of surfactants, including single-chain, "umbrella" structure, double chain, bolaform, Gemini, and stimulus-responsive surfactants. The fundamental surface/interface properties of the synthesized surfactants are also highlighted. Additionally, these surfactants have demonstrated enormous potential in agricultural synergism, drug delivery, mineral flotation, enhanced oil recovery, separation, and extraction, and foam fire-fighting.

Syntheses, Properties, and Aggregation Behavior of Novel Carboxylate-Based Silicone Surfactants

Two new anionic silicone surfactants were synthesized for the first time from dichloromethylvinylsilane or trichlorovinylsilane through hydrolysis-condensation and then thiol-ene reactions. Their structures were characterized by FT-IR, ¹ H NMR and ESI-MS. The surface tension (γ), critical aggregate concentration (CAC), surface pressure at CAC ( Π C A C ${\Pi _{C{\rm{A}}C} }$ ) and minimum surface area per surfactant molecule ( A min ${{A}_{\min } }$ ) were studied by surface tension and electrical conductivity, demonstrating their high surface activity at the gas/liquid interface. Transmission electron microscopy measurements showed that uniform spherical aggregates former in aqueous solution for both surfactants. Moreover, the size of the aggregates was determined to be in the range from 50 to 300 nm by dynamic light scattering.

Silicone polyether surfactant enhances bacterial cellulose synthesis and water holding capacity

The versatility and unique properties of bacterial cellulose (BC) motivate research into enhancing its synthesis. Here a silicone polyether surfactant (SPS) was synthesized and tested as a non-nutritional additive to the cultivation media of Komagataeibacter xylinus. The addition of SPS to the Hestrin-Schramm (HS) medium resulted in a concentration-dependent decrease in surface tension from 59.57 ± 0.37 mN/m to 30.05 ± 0.41 mN/m (for 0.1% addition) that was correlated with an increased yield of BC, up to 37% wet mass for surfactant concentration close to its critical micelle concentration (0.008%). Physicochemical characterization of bacterial cellulose obtained in presence of SPS, showed that surfactant is not incorporated into BC structure and has a moderate effect on its crystallinity, thermal stability. Moreover, the water holding capacity was enhanced by over 40%. Importantly, obtained BC did not affect L929 murine fibroblast cell viability. We conclude that SPS provides an eco-friendly approach to increasing BC yield in static culture, enabling more widespread industrial and biomedical applications.

Synthesis and Solution Behavior of Sulfonate-Based Silicone Surfactants with Specific, Atomically Defined Hydrophobic Tails

A series of sulfonate-based silicone surfactants with different hydrophobic groups were synthesized. Two synthetic strategies are introduced to permit exquisite control over the hydrophobic moieties. Solution behavior of these surfactants was investigated by surface tensiometry, electrical conductivity, transmission electron microscopy, and dynamic light scattering. The results indicate that the aqueous behavior of the surfactants was distinctly influenced by the hydrophobic groups. Subtle distinctions in surfactant-related properties, which can be attributed to the three-dimensional molecular structures of the surfactants, can be seen for compounds with different hydrophobic moieties. Contact angle results of these surfactants indicate that they have super dispersal ability with the potential value in agriculture.

Aggregation Behavior of "Linear" Trisiloxane Surfactant with Different Terminal Groups (CH3-, ClCH2-, and CF3-) in Aqueous Solution

Novel "linear" trisiloxane surfactants with different terminal groups (CH₃-, ClCH₂-, CF₃-) and two polyether hydrophilic groups were successfully synthesized and confirmed using ¹H NMR, ¹³C NMR, ²⁹Si NMR, and FT-IR spectroscopy. The aggregation and adsorption behavior of the "linear" trisiloxane surfactants in aqueous solution was studied by surface tension, dynamic light scattering (DLS), transmission electron microscopy (FF-TEM), and TEM. Owing to the introduction of two polyether hydrophilic groups in the terminal positions of the trisiloxane hydrophobic part, "linear" trisiloxane surfactants (Me-Si₃-EO₈, Cl-Si₃-EO₈, and F-Si₃-EO₈) tend to lie flat in the air/water interface and result in an increasing the surface tension at the CMC ( γ_CMC) and single trisiloxane surfactant molecule at the air/water interface ( A _min) values. Following the difference in the intermolecular forces and molecular volumes (CH₃- < ClCH₂- < CF₃-), the γ_CMC values decrease following the order Me-Si₃-EO₈ > Cl-Si₃-EO₈ > F-Si₃-EO₈, and the adsorption efficiency ( p C₂₀), surface pressure at the CMC ( π_CMC), CMC/ C₂₀ , and A _min values increase following the order Me-Si₃-EO₈ < Cl-Si₃-EO₈ < F-Si₃-EO₈. As comparison, fluorinated trisiloxane surfactant (F-Si₃-EO₈) has greater surface activity attributed to the terminal CF₃- group. The TEM and FF-TEM results illustrated that all the investigated "linear" trisiloxane surfactants can form nonuniform size spherical aggregates.