Aqueous solutions of tetrahydrofuran, ethanol, urea, and R-cyclodextrin were studied by a combination of static and dynamic laser light scattering (LLS). In textbooks, these small organic molecules are soluble in water so that there should be no observable large structures or density fluctuation in either static or dynamic LLS. However, a slow mode has been consistently observed in these aqueous solutions in dynamic LLS. Such a slow mode was previously attributed to some large complexes or supramolecular structures formed between water and these small organic molecules. Our current study reveals that it is actually due to the existence of small bubbles (∼100 nm in diameter) formed inside these solutions. Our direct evidence comes from the fact that it can be removed by repeated filtration and regenerated by air injection. Our results also indicate that the formation of such nanobubbles in small organic molecule aqueous solutions is a universal phenomenon. Such formed nanobubbles are rather stable. The measurement of isothermal compressibility confirms the existence of a low density microphase, presumably nanobubbles, in these aqueous solutions. Using a proposed structural model, that is, each bubble is stabilized by small organic molecules adsorbed at the gas/water interface, we have, for the first time, estimated the pressure inside these nanobubbles.

A new diblock copolymer, poly [3-(triisopropyloxysilyl)propyl methacrylate]-block-poly [2-(perfluorooctyl)ethyl methacrylate] (P1 or PIPS-MA-b-PFOEMA), that bore a fluorinated PFOEMA block and a solÀgel forming PIPSMA block was synthesized by sequential anionic polymerization and was characterized. P1 was then used to coat silica particles. Factors affecting the amount of P1 grafted onto the silica particles by the solÀgel reactions of the PIPSMA block were investigated, and the coating conditions were optimized. At sufficiently high P1-to-silica mass feed ratios, P1 chemically grafted onto silica surfaces to yield a monolayer. While monolayer formation was supported by results of thermogravimetric analyses, dynamic light scattering, atomic force microscopy, and transmission electron microscopy, our X-ray photoelectron spectroscopy study suggested that the monolayer was topped by the PFOEMA block. Depositing these particles onto microscope slides and printing paper yielded rugged silica films. These films were superamphiphobic, and both water and oil droplets (cooking oil, diodomethane, and hexadecane) possessed large contact angles. The films composed of P1-coated silica particles had substantial resistance to etching by aqueous NaOH solution.

Evidences were gathered to support mesogen-driven formation of cylindrical micelles from BCF and ACF triblock copolymers. Here A, B, C, and F denote poly(acrylic acid), poly(tert-butyl acrylate), poly(2-cinnamoyloxylethyl methacrylate), and the liquid crystalline poly(perfluorooctylethyl methacrylate) block, respectively. At room temperature (21 °C) in all tested solvents that were selective for the A or B blocks, three of the four copolymers with various compositions formed exclusively cylindrical micelles possessing an F core, a C shell, and an A or B corona. Our further analyses indicated that the F core chains were almost fully stretched, and the C shell chains were compressed relative to their unperturbed dimensions. These abnormal chain packing motifs suggest that the need to form a liquid crystalline F phase in the cores dictated micelle formation and prevailed over the needs of the shell chains to achieve their normal stretched conformations. A subsequent wide-angle X-ray scattering study of the dried cylindrical micelles confirmed smectic A phase formation for the F blocks at room temperature. The smectic A to isotropic phase transition upon raising temperature was detected by a differential scanning calorimeter for the dry cylindrical micelles and by 19F NMR for the solvated micelles. This smectic A to isotropic phase transition was accompanied by a morphological transformation from cylindrical micelles at room temperature to other morphologies at 70 °C. More interestingly, this cylinder to vesicle conversion could be cycled repeatedly by temperature cycling for one ACF sample.

Multiple emulsions are complex polydispersed systems in which both oil-in-water (O/W) and water-in-oil (W/O) emulsion exists simultaneously. They are often prepared accroding to a two-step process and commonly stabilized using a combination of hydrophilic and hydrophobic surfactants. Recently, some reports have shown that multiple emulsions can also be produced through one-step method with simultaneous occurrence of catastrophic and transitional phase inversions. However, these reported multiple emulsions need surfactant blends and are usually described as transitory or temporary systems. Herein, we report a one-step phase inversion process to produce water-in-oil-in-water (W/O/W) multiple emulsions stabilized solely by a synthetic diblock copolymer. Unlike the use of small molecule surfactant combinations, block copolymer stabilized multiple emulsions are remarkably stable and show the ability to separately encapsulate both polar and nonpolar cargos. The importance of the conformation of the copolymer surfactant at the interfaces with regards to the stability of the multiple emulsions using the one-step method is discussed.