Microwave-assisted synthesis of trisiloxane superspreader and its superspreading behavior on plant leaves surfaces
Microwave-assisted synthesis of trisiloxane superspreader and its superspreading behavior on plant leaves surfaces
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微波辅助合成三硅氧烷超级铺展剂及其在植物叶片表面的超级铺展行为
DOI：
10.1016/j.colsurfa.2016.09.079
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发表时间：
2016-12-20
影响因子：
5.2
通讯作者：
Chen, Xiaoyu
中科院分区：
文献类型：
--
作者：
Lin, Jing;Zhu, Mingning;Chen, Xiaoyu
本文介绍了一系列新型三硅氧烷表面活性剂的微波辅助合成，它们的表面和聚集特性，以及它们在植物叶片表面的超扩散行为。动力学研究表明，硅氢化反应遵循二级速率规律，与常规加热方法(109.272 kJ/m ol)相比，微波辐射下的反应活化能(84.395 kJ/m ol)显著降低。用傅里叶变换红外光谱(FTIR)和核磁共振氢谱(H-1)对三硅氧烷表面活性剂的分子结构进行了表征。用表面张力仪、透射电子显微镜和动态激光粒度仪对其表面和聚集特性进行了研究。用接触角测量、扫描电子显微镜(SEM)和原子力显微镜(AFM)研究了三硅氧烷表面活性剂水滴在水稻和芒果叶片表面的动态扩散行为。分析了各种因素对推进接触角(CA)、半径(R)、润湿面积(S)、扩散速度(dR/dt)、扩散指数(N)和临界润湿浓度(CWC)的影响。这些表面活性剂具有较低的临界聚集浓度(CMC)和表面张力(伽马(CMC))。随着乙氧基单元数的增加，CMC、γ(CMC)、每表面活性物质分子占据面积(Amin)和标准聚集自由能(Delta G(Theta)Mic)增大，而Gamma max和标准吸附自由能(Delta G Theta Ads)减小。表面活性剂的最佳HLB值约为10(S 2的最佳HLB值为10.37)，表现出最佳的超扩散行为。超扩散行为与分子结构、表面活性剂的浓度和基材的润湿性有关。提出了一个超扩散模型来描述超扩散过程。前驱体水膜和Marangoni效应的协同作用是超扩散行为的主要原因。(C)2016爱思唯尔B.V.保留所有权利。
This paper describes a facile microwave-assisted synthesis of a series of novel trisiloxane surfactants, their surface and aggregation properties, and superspreading behaviors on plant leaves surfaces. Kinetic study showed that hydrosilylation reaction followed a second-order rate law and that the activation energy was greatly reduced in case of microwave irradiation (84.395 kJ/mol) as compared to the conventional heating method (109.272 kJ/mol). The molecular structures of trisiloxane surfactants were characterized by Fourier transform infrared spectroscopy (FTIR) and H-1 nuclear magnetic resonance spectroscopy ((HNMR)-H-1). Their surface and aggregation properties were investigated by surface tensiometry, transmission electron microscopy (TEM), and dynamic laser particle size analysis (DLS). Dynamic spreading behavior of droplets of aqueous trisiloxane surfactant solutions on the surfaces of the rice and mango leaves were investigated by contact angle measurement, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Effects of various factors on the advancing contact angle (CA), radius (r), wetted area (S), velocity of spreading (dr/dt), spreading exponent (n), and critical wetting concentration (CWC) were analyzed. These surfactants were found to have low critical aggregation concentration (CMC) and surface tension (gamma(CMC)). With increase in number of ethoxy units, the values of CMC, gamma(CMC), occupied area per surfactant molecule (Amin), and standard free energy of aggregation (Delta G(theta)mic) increased, whereas Gamma max and standard free energy of adsorption (Delta G theta ads) decreased. The surfactant, with an optimal HLB value of about 10 (10.37 for S-2), showed the best superspreading behavior. The superspreading behavior was related to molecular structure, the concentration of surfactant, and substrate wettability. A super spreading model was presented to illustrate the superspreading process. Synergistic effects of precursor water film and Marangoni effect were mainly responsible for the superspreading behavior. (C) 2016 Elsevier B.V. All rights reserved.