A gemini-type superspreader: Synthesis, spreading behavior and superspreading mechanism
A gemini-type superspreader: Synthesis, spreading behavior and superspreading mechanism
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DOI：
10.1016/j.cej.2016.12.132
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发表时间：
2017-05
影响因子：
15.1
通讯作者：
Jing Lin;Wei Wang;Bai Wenli;Mingning Zhu;C. Zheng;Zi-li Liu;X. Cai;Dongdong Lu;Zhiwei Qiao-Zhiwei
中科院分区：
文献类型：
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作者：
Jing Lin;Wei Wang;Bai Wenli;Mingning Zhu;C. Zheng;Zi-li Liu;X. Cai;Dongdong Lu;Zhiwei Qiao-Zhiwei
本文介绍了一系列三硅氧烷Gemini超铺展剂的微波辅助合成，以及它们的表面和聚集特性和在植物叶片表面的超铺展行为。用傅里叶变换红外光谱（FTIR）和核磁共振氢谱（1H NMR）对三硅氧烷双子表面活性剂的分子结构进行了表征。热力学参数表明，随着连接基团（CH 2）的增加，临界聚集浓度（CAC）、表面张力（γCAC）和表面过剩浓度（Γmax）均减小，而表面活性剂分子占有面积（ACAC）、标准聚集自由能（ΔGθmic）和标准吸附自由能（ΔGθads）均增大.乙氧基结构（CH 2-CH 2-O-）的增加导致CAC、γCAC和ACAC的增加，而ΔGθ mic和ΔGθads的最大值和绝对值则减小。透射电子显微镜和动态光散射结果表明，超分散剂溶液聚集体的平均尺寸随间隔单元（CH 2）数目的增加而增大，但随乙氧基单元（CH 2-CH 2-O-）数目的增加而减小。动态扩展行为的结果表明，平均扩展速度增加的间隔链长度的增加，和最大扩展速度的乙氧基链长度的依赖关系是非单调的，在n（EO）= 8.68的最大值。最佳HLB值是获得良好超铺展行为的必要条件，基底润湿性（疏水性水稻植物和亲水性芒果植物表面）对超铺展有很大影响。超铺展模型中存在前驱膜和Marangoni效应的协同效应。
This 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) and1H nuclear magnetic resonance spectroscopy (1H NMR). The obtained thermodynamic parameters showed that an increase in the spacer group (CH2) resulted in decreases in the critical aggregation concentration (CAC), corresponding surface tension (γCAC), and surface excess concentration (Γmax) but increases in the occupied area per surfactant molecule (ACAC) and absolute values of the standard free energies of aggregation (ΔGθmic) and adsorption (ΔGθads). An increase in ethoxy units (CH2-CH2-O-) resulted in increases in the CAC,γCAC, andACACbut decreases inГmaxand the absolute values of ΔGθmicand ΔGθads. 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 (CH2) but decreased with an increasing number of ethoxy units (CH2-CH2-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.