A gemini-type superspreader: Synthesis, spreading behavior and superspreading mechanism

Abstract

Please cite this article as: A gemini-type superspreader: synthesis, spreading behavior and superspreading mechanism, Chemical Engineering Journal (2016), doi: http://dx.doi.org/10. 1016/j.cej.2016.12.132 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ABSTRACTThis paper describes the facile microwave-assisted synthesis of a series of trisiloxane gemini superspreaders, as well as their surface and aggregation properties and superspreading behavior on plant leaf surfaces. The molecular structures of the trisiloxane gemini surfactants were characterized by Fourier transform infrared spectroscopy (FTIR) and 1 H nuclear magnetic resonance spectroscopy ( 1 H NMR). The obtained thermodynamic parameters showed that an increase in the spacer group (CH 2 ) resulted in decreases in the critical aggregation concentration (CAC), corresponding surface tension (γ CAC ), and surface excess concentration (Γ max ) but increases in the occupied area per surfactant molecule (A CAC ) and absolute values of the standard free energies of aggregation (△G θ mic ) and adsorption (△G θ ads ). An increase in ethoxy units (CH 2 -CH 2 -O-) resulted in increases in the CAC, γ CAC , and A CAC but decreases in Г max and the absolute values of △G θ mic and △G θ ads . The transmission electron microscopy and dynamic light scattering results showed that the average sizes of the aggregates of superspreader solutions increased with an increasing number of spacer units (CH 2 ) but decreased with an increasing number of ethoxy units (CH 2 -CH 2 -O-). The dynamic spreading behavior results demonstrated that the average spreading velocity increased with increasing spacer chain length, and the dependence of the maximum spreading velocity on the ethoxy chain length was nonmonotonous with a maximum at n(EO) = 8.68. The optimal HLB value was essential to obtaining good superspreading behavior, and the substrate wettability (hydrophobic rice plant and hydrophilic mango plant surfaces) greatly influenced the superspreading. The synergistic effects from the precursor film and Marangoni effect existed in the proposed superspreading model.

Controlling high‐speed droplet splashing and superspreading behavior on anisotropic superhydrophobic leaf surfaces by ecofriendly Pseudogemini surfactants

“…Spreading and wetting also play an important role in pesticide delivery after droplet impact and deposit onto hydrophobic leaf surfaces, and can be evaluated by the change in dynamic contact angles of droplets on the leaf surface. 31 As shown in Fig. 4(a),(b), it was found that the contact angle of the pure water droplet on the leaf surface of barnyard grass is 152.7°, and this almost did not change with time, suggesting that it is difficult for pure water droplets to spread on and wet the leaf surface of barnyard grass, and is easy for them to roll off from the leaf surface.…”

“…5(a),(b),(d)), which is a self-assembly behavior of some gemini surfactants with special structures. 31,38 In our work, since the hexamethylenediamine molecule contains two cationic hydrophilic groups at both ends, when one cationic amino group participates in the assembly of one micelle, the other amino group can also participate in the other micelle, and the micelles are connected to each other through carbon chains (Fig. S4), thus forming an aggregated spherical micelle with a network structure (Fig.…”

“…38,39 Moreover, other physicochemical parameters related to surface activity are shown in Table S1. It was found that LAL has the largest Γ max and the smallest A min , suggesting that it has the largest adsorption quantity at the interface and is more closely packed, 31 which can significantly reduce the surface tension. Excellent surface activity is one of the factors that inhibits droplet splashing and leads to superspreading behavior.…”

Deposition and Spread of Aqueous Pesticide Droplets on Hydrophobic/Superhydrophobic Surfaces by Fast Aggregation of Surfactants

“…Ruckenstein and Karapetsas et al proposed that the “caterpillar-like” motion of the liquid can reduce hydrodynamic resistance at the leading edge of spreading and provide lower energy dissipation. The trisiloxane surfactants have a unique “hammer-like” molecular structure with a hydrophobic part and long hydrophilic tail, , and the specific T-shape is a preferential configuration to propagate TPCL and promote the “caterpillar-like” motion. , Meanwhile, the trisiloxane surfactants form vesicles in bulk solution, and the bilayer structure of vesicles is inclined to adsorb at the leading edge of spreading and induces water suction in their hydrophilic interior. , Then, the surfactants may be continuously dissociated by “unzippering” of the dangling bilayers on the surface of the droplets, enabling these molecules to directly transfer to the liquid/air and solid/liquid interface (decreasing σ SL and σ LV ) and reduce viscous dissipation in the vicinity of TPCL …”

Morpholine-Based Gemini Surfactant: Synthesis and Its Application for Reverse Froth Flotation of Carnallite Ore in Potassium Fertilizer Production

“…Gemini molecules are a new type of surfactants that consist of two traditional monomeric amphiphiles that are covalently connected by a spacer unit. , In contrast to conventional monomeric surfactants, Gemini molecules possess superior properties, such as lower critical micelle concentration, lower Krafft point, higher solubilization power, higher surface activity, improved wetting, and foaming properties. , Therefore, Gemini surfactants are widely applied in different fields such as phase transfer catalysts, drug entrapment/release, body care products, biomedical processes including gene transfection, preparation of high-porosity materials, synthesis of nanomaterials, food industry, oil recovery, polymerizations, antibacterial, and antifungal preparations, etc. − …”