丁炔二醇醚改性有机硅表面活性剂的制备及构效关系

Preparation and structure-activity relationship of ethynyl diol ether modified organosilicon surfactants

摘要:

为改善有机硅类消泡剂在水中的溶解度和消抑泡能力，以八甲基环四硅氧烷（D4）和四甲基环四硅氧烷（D4H）为缩聚单体，六甲基二硅氧烷（MM）为封端剂，在酸性条件下经缩聚反应制得不同链长（m+n）和硅氧烷链节与含氢硅氧烷链节比（m/n）的含氢聚硅氧烷（LPMHS），再以丁炔二醇二乙氧基醚（BEO）对其进行氢化硅烷化反应，通过在LPMHS链上接枝BEO分子，制备得到一系列具有消抑泡效果的丁炔二醇醚改性有机硅（PSi-EO）表面活性剂。采用FTIR和1HNMR表征PSi-EO的结构，采用鼓泡、水接触角以及动态光散射等测试Psi-EO的消抑泡性能、表面活性和润湿铺展性等，探究其结构与性能之间的构效关系。结果表明，当m/n=4时，随着m+n 的增加（4+1~24+6），PSi-EO消泡能力持续降低，抑泡能力在m+n=16+4时最高（抑泡时间16.53 min），但之后出现降低趋势，而其水溶液的临界胶束浓度（CMC）不断减小、最低表面张力不断提高，PSi-EO水溶液的最低表面张力由硅氧烷链长 （m+n）决定；当m+n=20时，随着m/n的减小（18/2~14/6），PSi-EO的消泡能力增加，抑泡能力随之降低，m/n＝17/3时的PSi-EO具有较优的消抑泡能力（消泡时间71.28 s；抑泡时间19.34 min）；随着m+n的增加和m/n的降低，PSi-EO分子链延长且亲水基接枝量增加，其接触角也随之增大，润湿能力降低；PSi-EO在水溶液中均能形成球形胶束，较小的聚集体可自组装形成大而复杂的聚集体，平均粒径为100~300 nm，其聚集体形态与其硅氧烷链长和链长比无关；PSi-EO的标准吸附自由能（ΔG0 ads）的绝对值均高于标准胶束自由能（ΔG0 mic）的绝对值，表明PSi-EO分子更倾向吸附于气液界面，因而可以迅速降低分子附近泡膜的表面张力，从而促使气泡破灭。

Abstract:

In order to improve the solubility and defoaming/foam inhibition ability of silicone antifoam agents in water, a series of hydrogen-containing polysiloxanes (LPMHS) with different chain lengths (m+n) and ratios of siloxane links to hydrogen-containing siloxane links (m/n) were prepared by polycondensation under acidic condition, using octamethylcyclotetrasiloxane (D4) and tetramethylcyclotetrasiloxane (D4H) as condensate monomers, and hexamethyldisiloxane (MM) as a terminating agent. A series of butynediol ether modified organosilicone (PSi-EO) surfactants with anti-foaming effect were prepared by grafting butynediol diethoxylate (BEO) molecules on the LPMHS chain, and then hydrogenated with BEO. The structures of PSi-EO were characterized by FTIR and 1HNMR, and the defoaming performance, surface activity and wetting and spreading properties of PSi-EO were tested by bulging, water contact angle and dynamic light scattering to investigate the conformational relationship between structure and performance. The results showed that when m/n=4, the defoaming ability of PSi-EO continued to decrease with the increase of m+n (4+1~24+6), and the foam inhibition ability was highest at m+n=16+4 (foam inhibition time of 16.53 min), but after that there was a tendency to decrease, whereas the critical micelle concentration (CMC) of its aqueous solution continued to decrease, the minimum surface tension continued to increase. The minimum surface tension of PSi-EO aqueous solution was determined by the siloxane chain length (m+n). When m+n=20, with the decrease of m/n (18/2~14/6), the defoaming ability of PSi-EO increases and the foam inhibition ability decreases, and the PSi-EO with m/n=17/3 has an excellent defoaming and foam inhibition ability (defoaming time of 71.28 s; foam inhibition time of 19.34 min). With the increase of m+n and the decrease of m/n, the molecular chain of PSi-EO was extended and the amount of hydrophilic group grafting was increased, and its contact angle was also increased, and the wetting ability was reduced. PSi-EO can form spherical micelles in aqueous solution, and the smaller aggregates can self-assemble to form large and complex aggregates with an average particle size of 100~300 nm, and its aggregate morphology is independent of its siloxane chain length and chain-length ratio. The absolute values of the standard adsorption free energies (ΔG0 ads) of PSi-EO were higher than those of the standard micellar free energies (ΔG0 mic), indicating that PSi-EO molecules were more inclined to adsorb at the gas-liquid interface, and thus the surface tension of the vesicle film in the vicinity of the molecules can be rapidly reduced, which can lead to the bubble bursting.