Guoyong Wang

Surface Activity and Aggregation Behavior of Siloxane-Based Ionic Liquids in Aqueous Solution.

Six novel siloxane-based surface-active ionic liquids (SAILs)--siloxane ammonium carboxylate [Si(n)N(2)-CA(1), (n = 3, 4)]--were designed and synthesized. Their melting points, surface activities, and self-aggregation behavior in aqueous solution were studied. The results showed that because of the bulky hydrophobic siloxane chains at the end of the tail, all six siloxane-based SAILs are room-temperature ionic liquids (RT-SAILs). The introduction of the siloxane group can reduce the melting point of ionic liquids to below room temperature and can promote the micellization and aggregation behavior more efficiently. These siloxane-based SAILs can greatly reduce the surface tension of water, as shown by the critical aggregation concentration (γCAC) values of 20 mN·m(-1); all six siloxane RT-SAILs can form a vesicle spontaneously in aqueous solution, indicating potential uses as model systems for biomembranes and vehicles for drug delivery.

Aggregation Behavior of Trisiloxane-Tailed Surface Active Ionic Liquids in Aqueous Solution: Coarse-Grained Molecular Dynamics Study

The aggregation behaviors of two trisiloxane-tailed surface active ionic liquids in water have been investigated by coarse-grained (CG) molecular dynamics simulation on the basis of MARTINI force field. The new CG model is developed from the optimized molecule computed by using density functional theory. Direct comparison of angles and bonds obtained from all-atom (AA) simulations with those calculated from the CG model has been conducted to validate the latter model. Excellent agreement between AA and CG demonstrates that the potential of the new CG model can represent the complex system well. The long time CG simulation has been performed to understand the formation process of micelles when dissolving ionic liquids in water. Vesicles were observed at the final stage of the simulation and their partially truncated views and density profiles were obtained to describe the structure in detail.

Synthesis, Surface Activities, and Aggregation Behaviors of Butynediol-ethoxylate Modified Polysiloxanes.

Five different butynediol-ethoxylate modified polysiloxanes (PSi-EO) were designed and synthesized via two-step reactions: the preparation of low-hydrogen containing silicone oil (LPMHS) by acid-catalyzed polymerization and the following hydrosilylation reaction with 1,4-bis(2-hydroxyethoxy)-2-butyne. The chemical composition of each product was confirmed by FT-IR, (1)H NMR, and (29)Si NMR. The surface activities and aggregation behaviors of PSi-EO surfactants in aqueous solution were studied systematically using surface tension, dynamic light scattering (DLS), transmission electron microscopy (TEM), and contact-angle methodologies. Relatively low critical aggregation concentration (15-34 mg·L(-1)) and surface tension (∼25 mN·m(-1)) were measured for PSi-EO aqueous solution. The rate of surface tension reduction increased both with increasing PSi-EO concentration and with increases in the proportion of hydrophilic moieties within the synthesized compounds. Furthermore, DLS and TEM studies revealed that PSi-EO self-assembled in aqueous solution to form spherical aggregates. Contact-angle measurements conducted upon low-energy paraffin film surfaces demonstrated that PSi-EO exhibited efficient spreading at concentrations above the critical aggregation concentration.

One-step strategy for synthesis of yolk–shell silica spheres using trisiloxane-tailed ionic liquids as a template

Yolk–shell silica spheres consisting of a core and an outer shell were prepared by a one-step method using a new class of eco-friendly templates, trisiloxane-tailed surface active ionic liquids. The effects of pH, calcination, and template concentration were investigated in detail. Our results showed that yolk–shell silica spheres could be obtained only in alkaline conditions when using trisiloxane-tailed ionic liquids as templates. The particle diameter, core diameter, dimension of void space, and shell thickness, which we measured by transmission electron microscopy and nitrogen adsorption–desorption techniques, could be tuned by precisely varying the template concentration. The organosilicon component of the ionic liquid template contributes to the reaction during the formation of yolk–shell nanostructures, which leads to a firm silica sphere skeleton resulting in essentially identical morphology and void structure before and after calcination. This investigation provides a convenient approach to fabricate yolk–shell silica spheres, which may expand the application of organosilicon ionic liquids in the field of nanomaterials and could be expected to generate tailor-made yolk–shell silica with functionality in both the core and shell.

Thermostable mesoporous silica nanospheres produced through the use of a trisiloxane-tailed ionic liquid as a template

Mesoporous silica nanospheres can be prepared by a facile route using a new class of eco-friendly template: trisiloxane-tailed ionic liquids. The organosilicone component of the ionic liquids template contributes to the reaction during the formation of mesoporous material, which leads to a firm skeleton of pores resulting in excellent thermal stability.

Properties of Glucosamide-Based Tetrasiloxane Surfactants

The interfacial properties of new glucosamide-based tetrasiloxane surfactants were studied. Members of the glucosamide-based tetrasiloxane surfactants reduce the surface tension of water to approximately 21 mN · m−1 at concentration levels of 10−5 mol · L−1. The wetting and spreading behavior of the glucosamide-based tetrasiloxane surfactants on Teflon and Paraffin were investigated and compared with that of trisiloxane. A new glucosamide-based tetrasiloxane β shows the best spreading ability both on Teflon and Paraffin, which is similar with that of trisiloxane. It is suggested that a lower surface tension is a necessary but not sufficient condition for enhanced spreading. The spreading performance was affected by the hydrophilic-lipophilic balance (HLB) significantly. Furthermore, the molecular structure of the surfactant and the hydrophobic substrate also play important roles for showing spreading behavior.

Properties of ABA and BA polysiloxane amphiphiles modified by polyether

ABSTRACT To investigate the effect of content of polyether (F400) grafted on the properties of polysiloxane amphiphiles, polyether was grafted on the polysiloxane by hydrosilylation reaction with H2PtCl6 catalyst. The modified polysiloxanes were divided into two types; moreover, the ratio of polyether and polysiloxane was 1:1 or 1:2. The first one was similar to the conventional surfactant structure that is BA polysiloxane amphiphile, which own one hydrophobic chain and one hydrophilic group. Another one was ABA polysiloxane amphiphile, which possess one hydrophobic chain and two hydrophilic groups at the terminal. In our work, we compared the property of modified polysiloxanes with various contents of polyether in aqueous solution at room temperature to analyze the impact of polyether content on siloxane surfactants. The conclusion was that siloxane amphiphiles possess good solubility, high surface activity, and excellent spreading property. GRAPHICAL ABSTRACT