Insights into the behavior of ethylene oxide-1,2-epoxybutane diblock copolymers in water as a function of temperature and the presence of colloidal silica

Beshah, Kebede; Campbell, Robert A.; Dan, Florin; Daugs, Edward D.; DeFelippis, James; Gu, Junsi; Wasserman, Eric; Young, Wen‐Shiue

doi:10.1016/j.jcis.2020.07.101

Cited by 2 publications

(10 citation statements)

References 31 publications

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“…It is well-known that a silica surface is negatively charged under neutral pH. As we discussed above, water molecules on a charged surface may have both χ (2) and χ (3) contributions to the detected SFG water signal. 48 If both χ (2) and χ (3) contributions exist in this study, to understand the interfacial water structure at the silica−nonionic surfactant solution interfaces, it is necessary to separate the χ (2) and χ (3) contributions.…”

Section: Methodsmentioning

confidence: 82%

“…52 Most bulk media are centrosymmetric, thus do not have SFG signal, while surfaces and interfaces lack inversion symmetry and can generate SFG signals. For a charged interface like silica−water interface, it is believed and shown that there are bulk (3) contributions from the electric double layer/diffuse layer near the silica−water interface. This can complicate the interpretation of the collected SFG water signal from the silica−water interface, which contains contributions from both the interfacial χ (2) and bulk χ (3) .…”

Section: Methodsmentioning

confidence: 99%

“…For a charged interface like silica−water interface, it is believed and shown that there are bulk (3) contributions from the electric double layer/diffuse layer near the silica−water interface. This can complicate the interpretation of the collected SFG water signal from the silica−water interface, which contains contributions from both the interfacial χ (2) and bulk χ (3) . 53,54 Thus it is important to deconvolute different contributions in order to interpret SFG data.…”

Section: Methodsmentioning

confidence: 99%

“…This change in water ordering may also result from a small increase in surfactant surface coverage even if the total amount of surfactant adsorbed increases only slightly. However, it is also the case that the χ (3) contributions from water molecules in the diffused layer (electric double layer) 47 may contribute to the SFG signals detected from a charged silica surface, which would enhance the water SFG signal as well.…”

Section: Methodsmentioning

confidence: 99%

“…Among the structures of nonionic surfactants prepared from EO and BO are the so-called “capped surfactants”, in which the terminal block of a copolymer initiated by a fatty alcohol is the BO-derived segment. How this class of structures behaves in aqueous solution and in the presence of silica has been a focus of a previous study involving NMR spectroscopy and dynamic light scattering …”

Section: Introductionmentioning

confidence: 99%

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Effect of Surfactant Concentration and Hydrophobicity on the Ordering of Water at a Silica Surface

Shi

McMillan

et al. 2021

Langmuir

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The performance of nonionic surfactants is mediated by the interfacial interactions at the solid–liquid interface. Here we applied sum frequency generation (SFG) vibrational spectroscopy to probe the molecular structure of the silica–nonionic surfactant solution interface in situ, supplemented by quartz crystal microbalance with dissipation monitoring (QCM-D) and molecular dynamics (MD) simulations. The combined studies elucidated the effects of nonionic surfactant solution concentration, surfactant composition, and rinsing on the silica–surfactant solution interfacial structure. The nonionic surfactants studied include ethylene-oxide (EO) and butylene oxide (BO) components with different ratios. It was found that the CH groups of the surfactants at the silica–surfactant solution interfaces are disordered, but the interfacial water molecules are ordered, generating strong SFG OH signals. Solutions with higher concentrations of surfactant lead to a slightly higher amount of adsorbed surfactant at the silica interface, resulting in more water molecules being ordered at the interface, or a higher ordering of water molecules at the interface, or both. MD simulation results indicated that the nonionic surface molecules preferentially adsorb onto silanol sites on silica. A surfactant with a higher EO/BO ratio leads to more water molecules being ordered and a higher degree of ordering of water molecules at the silica–surfactant solution interface, exhibiting stronger SFG OH signal, although less material is adsorbed according to the QCM-D data. A thin layer of surfactants remained on the silica surface after multiple water rinses. To the best of our knowledge, this is the first time the combined approaches of SFG, QCM-D and MD simulation techniques have been applied to study nonionic surfactants at the silica–solution interface, which enhances our understanding on the interfacial interactions between nonionic surfactants, water and silica. The knowledge obtained from this study can be helpful to design the optimal surfactant concentration and composition for future applications.

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