School of Chemical and Environmental Engineering , Jiujiang University , Jiujiang , Jiangxi 332005 , China.
J Phys Chem B. 2019 Feb 14;123(6):1390-1399. doi: 10.1021/acs.jpcb.8b10727. Epub 2019 Jan 31.
A series of polyether based siloxane surfactants with different branched chain and alkyl groups were synthesized by thiol-ene reaction and Piers-Rubinsztajn reaction. The effect of the siloxane structures (alkyl groups and branched chains) on the adsorption and aggregation behavior in aqueous solution was investigated by surface tension, fluorescence, dynamic light scattering (DLS), freeze-fracture transmission electron microscopy (TEM), and TEM. The molecular structures of siloxane can obviously influence their surface activities and thermodynamics. Replacing the methyl of trimethylsiloxyl groups with longer alkyl groups (ethyl, propyl, and butyl) and branching trimethylsiloxyl resulted in an obvious decrease of the values of critical micelle concentration (CMC) and surface tension at CMC (γ). Dense surface films packed with CH groups result in the lower surface tensions being disordered by longer alkyl groups or branched chains of siloxane hydrophobic groups. And the minimum surface area per surfactant molecule ( A) values of Si-PG, Et-Si-PG, Pro-Si-PG, and But-Si-PG successively decrease about 3.5 Å with each increasing -CH- group. All polyether based siloxane surfactants can form nonuniform size spheroidal aggregates in aqueous solution. Concerning the driving force, the micellization process was spontaneous but less spontaneous compared with adsorption.
通过巯基-烯反应和 Piers-Rubinsztajn 反应合成了一系列具有不同支链和烷基的聚醚基硅氧烷表面活性剂。通过表面张力、荧光、动态光散射（DLS）、冷冻断裂透射电子显微镜（TEM）和 TEM 研究了硅氧烷结构（烷基和支链）对水溶液中吸附和聚集行为的影响。硅氧烷的分子结构明显影响其表面活性和热力学。用较长的烷基（乙基、丙基和丁基）和支化的三甲基硅氧基取代三甲基硅氧烷基，导致临界胶束浓度（CMC）和临界胶束浓度（CMC）时的表面张力（γ）值明显降低。由 CH 基团组成的密集表面膜由于硅氧烷疏水性基团的较长烷基或支链而变得无序，表面张力较低。Si-PG、Et-Si-PG、Pro-Si-PG 和 But-Si-PG 的每个表面活性剂分子的最小表面面积（A）值依次减少约 3.5 Å。所有聚醚基硅氧烷表面活性剂都可以在水溶液中形成非均匀尺寸的球形聚集体。就驱动力而言，胶束化过程是自发的，但与吸附相比，自发性降低。
