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Water-in-CO2 Microemulsions Stabilized by an Efficient Catanionic Surfactant.
Langmuir ( IF 3.9 ) Pub Date : 2020-06-12 , DOI: 10.1021/acs.langmuir.0c00970
Masanobu Sagisaka 1 , Tatsuya Saito 1 , Masashi Abe 1 , Atsushi Yoshizawa 1 , Marijana Blesic 2 , Sarah E Rogers 3 , Shirin Alexander 4 , Frédéric Guittard 5 , Christopher Hill 6 , Julian Eastoe 6
Affiliation  

To facilitate potential applications of water-in-supercritical CO2 microemulsions (W/CO2 μEs) efficient and environmentally responsible surfactants are required with low levels of fluorination. As well as being able to stabilize water–CO2 interfaces, these surfactants must also be economical, prevent bioaccumulation and strong adhesion, deactivation of enzymes, and be tolerant to high salt environments. Recently, an ion paired catanionic surfactant with environmentally acceptable fluorinated C6 tails was found to be very effective at stabilizing W/CO2 μEs with high water-to-surfactant molar ratios (W0) up to ∼50 (Sagisaka, M.; et al. Langmuir 2019, 35, 3445−3454). As the cationic and anionic constituent surfactants alone did not stabilize W/CO2 μEs, this was the first demonstration of surfactant synergistic effects in W/CO2 microemulsions. The aim of this new study is to understand the origin of these intriguing effects by detailed investigations of nanostructure in W/CO2 microemulsions using high-pressure small-angle neutron scattering (HP-SANS). These HP-SANS experiments have been used to determine the headgroup interfacial area and volume, aggregation number, and effective packing parameter (EPP). These SANS data suggest the effectiveness of this surfactant originates from increased EPP and decreased hydrophilic/CO2-philic balance, related to a reduced effective headgroup ionicity. This surfactant bears separate C6F13 tails and oppositely charged headgroups, and was found to have a EPP value similar to that of a double C4F9-tail anionic surfactant (4FG(EO)2), which was previously reported to be one of most efficient stabilizers for W/CO2 μEs (maximum W0 = 60–80). Catanionic surfactants based on this new design will be key for generating superefficient W/CO2 μEs with high stability and water solubilization.

中文翻译:

高效阳离子表面活性剂稳定的CO2水包水微乳液。

为了促进水-超临界CO潜在应用2微乳(W / CO 2 μEs)高效和对环境负责的表面活性剂是必需的以氟化的低的水平。这些表面活性剂不仅能够稳定水-CO 2界面,还必须经济,防止生物蓄积和强粘附力,酶失活并能耐受高盐环境。近来,离子配对负离子表面活性用环境上可接受的氟代的6尾被认为是在稳定W / CO是非常有效的2 μEs具有高的水与表面活性剂的摩尔比(w ^ 0)到〜50(Sagisaka,M .;等人的Langmuir 201935,3445-3454)。作为阳离子和阴离子表面活性剂组分单独没有稳定W / CO 2 μEs,这是在W / CO的表面活性剂的协同作用的第一个示范2微乳液。这项新研究的目的是通过使用高压小角中子散射(HP-SANS)对W / CO 2微乳液中的纳米结构进行详细研究,从而了解这些引人入胜的效应的起源。这些HP-SANS实验已用于确定头基界面面积和体积,聚集数和有效堆积参数(EPP)。这些SANS数据表明,该表面活性剂的有效性源自EPP的增加和亲水性/ CO 2的降低。-亲密平衡,与降低的有效头基离子性有关。该表面活性剂带有单独的C 6 F 13尾部和带相反电荷的头基,并且发现其EPP值类似于先前报道的双C 4 F 9尾阴离子表面活性剂(4FG(EO)2)的EPP值。为W / CO最有效的稳定剂的一个2 μEs(最大w ^ 0 = 60-80)。基于这种新的设计负离子表面活性剂将是用于产生超高效W / CO键2 μEs具有高稳定性和水溶解。
更新日期:2020-07-07
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