Phase Behaviors of Giant Surfactants with Different Numbers of Fluorinated Polyhedral Oligomeric Silsesquioxane “Heads” and One Poly(ethylene oxide) “Tail” at the Air–Water Interface

Abstract

Giant surfactants with different numbers of aryl-trifluorovinyl ether-functionalized polyhedral oligomeric silsesquioxane (FVPOSS) heads and one poly­(ethylene oxide) (PEO) tail, (FVPOSS) n –PEO227, are precisely synthesized. The phase behaviors of (FVPOSS) n –PEO227 at the air–water interface were investigated through surface pressure measurements (isotherm and hysteresis experiments) and the Brewster angle microscopy. Upon increasing the number of FVPOSS heads, the interfacial behaviors of these giant surfactants greatly change. More phase transitions occur during the compression as the number of FVPOSS heads increased from one to two and three. The evolution of morphologies of Langmuir films and compression–expansion hysteresis curves further illustrate phase transitions at the air–water interface. Furthermore, molecular mechanisms to describe phase transitions of (FVPOSS) n –PEO227 at the interface are put forward. This study deepens the understanding of interfacial phase behaviors of special giant surfactants and provides knowledge of nanostructure design and construction at the interface.

Interfacial Behaviors of Giant Amphiphilic Molecules Composed of Hydrophobic Isobutyl POSS and Hydrophilic POSS Bearing Carboxylic Acid Groups at the Air–Water Interface

“…Additionally, giant surfactants with multi­hydrophobic POSS heads but one hydrophilic PEO chain exhibit different hysteresis behaviors, as we previously repoted . The isotherms of giant surfactants show a larger hysteresis loop when the monolayer is collapsed, which is similar to that of giant molecules.…”

“…The molecular topology and the volume fraction of the hydrophobic block of molecules can influence the shape of isotherms. Usually, the increased hydrophobic block volume fraction of molecules would improve the limiting area and collapse surface pressure. , By changing the topology structure of molecules of the hydrophilic and hydrophobic blocks, the shape of the π – A isotherm also changes accordingly . Duran et al studied in detail the surface behavior of different topological molecules of polystyrene (PS) and poly­(ethylene oxide) (PEO) star block copolymers .…”

“…In our previous studies, we synthesized “one-head, one-tail” (POSS-PEO), “bola-form” (POSS-PEO-POSS), and “multiheaded” ((POSS) n -PEO) giant surfactants by linking POSS derivative at one or both ends of a poly­(ethylene oxide) (PEO) chain. ,, When dispersing these giant surfactants on the water surface and compressing the air–water interface, POSS-PEO and POSS-PEO-POSS giant surfactants show the monolayer phase transition of the gas–liquid–solid phase . By transferring the monolayer onto the silicon wafer surface, the thin monolayer shows a fractal growth pattern endowed by the crystallization of the PEO chain within the limited two-dimension plane of the silicon wafer. ,, In addition, we found that a giant amphiphilic molecule containing a hydrophobic and a hydrophilic POSS and linked by 4,4′-azodianiline undergoes a phase transition from gas to liquid expanded to liquid condensed to solid during the compression on the water surface .…”

Interfacial Behavior of Giant Amphiphiles Composed of Azobenzene and Polyhedral Oligomeric Silsesquioxane

“…Compression–expansion hysteresis of the π– A isotherm can reveal phase states and phase transitions of amphiphilic molecules at the water surface. , If the compression and expansion cycle is limited in one phase, then generally, there will be no hysteresis. If compression and expansion cross phases or a collapse happens, then hysteresis will be present.…”

One-Step Interfacial Integration of Graphene Oxide and Organic Chromophores into Multicomponent Nanohybrids with Photoelectric Properties

“…Self-assembly at interfaces is a powerful tool for integrating organic and inorganic compounds into hybrid nanostructures for a number of potentially useful applications, such as sensing membranes, photoactive surface coatings, charge transferring layers, diffraction patterns, and some others. − The interface itself provides a convenient platform for ordering components with a desirable molecular orientation into ultrathin layers. − The opportunity to manipulate molecular packing is especially important for light-absorbing nanofilms, for example, those in organic solar cells using potent aromatic chromophores, which exhibit strong dependence of the absorption efficiency on their orientation with respect to incident light. , Because the interfacial self-assembly exploits interactions between components at the nanoscale, this kind of structuring is also useful for inducing effective energy/charge transfer in the ultrathin hybrids. , Another important aspect of the self-assembly at interfaces is that it allows combinations of components with different solubilities, and therefore, it expands the variety of properties exhibited by resulting hybrids. Inorganic components can improve the mechanical stability of the hybrid films, whereas fine-tuning of a range of light absorption or that of the ratio of energy levels can be performed by varying the chemistry and structure of organic components .…”