Interfacial Rearrangements of Block Copolymer Micelles Toward Gelled Liquid–Liquid Interfaces with Adjustable Viscoelasticity

Abstract

modified by several types of additives such as low molecular weight surfactants and proteins, [3][4][5] particles, [6][7][8][9] or polymers. [10][11][12][13][14][15][16] Hereby, the adsorption of surface-active entities can occur by adsorption of unimers to form eventually more or less homogeneous monolayers. However, amphiphiles are often present in colloidal form as micelles. Since other colloidal particles, e.g., nanoparticles and microgels, can adsorb to interfaces in a pickeringlike fashion, intact micelles might also be prone to adsorb to the interface. [10,17,18] However, little is known on the fate of such interfacially attached micelles. In most cases, the kinetics of the rearrangements toward a monolayer are hard to capture.Generally, the interfacial tension is regarded as a primary indicator of adsorption processes, often deemed sufficient to trace changes at liquid interfaces. However, the involvement of certain substances or combinations can lead to complex interfaces with additional rheological properties, completely different to the ones of the pure interface. [1,19,20] Examples could involve, e.g., interfacial polymerization [21] (including classical nylon thread fabrication) or even interfacial crosslinking (bubble tea preparation). In some of these cases, the interfacial film is rather thick. However, also monolayers of amphiphiles can exhibit viscoelastic properties being essential for the properties of the whole system. Hence, Though amphiphiles are ubiquitously used for altering interfaces, interfacial reorganization processes are in many cases obscure. For example, adsorption of micelles to liquid-liquid interfaces is often accompanied by rapid reorganizations toward monolayers. Then, the involved time scales are too short to be followed accurately. A block copolymer system, which comprises poly(ethylene oxide) 110 -b-poly{[2-(methacryloyloxy)ethyl]diisopropylmethylammonium chloride} 170 (i.e., PEO 110 -b-qPDPAEMA 170 with quaternized poly(diisopropylaminoethyl methacrylate)) is presented. Its reorganization kinetics at the water/n-decane interface is slowed down by electrostatic interactions with ferricyanide ([Fe(CN) 6 ] 3-). This deceleration allows an observation of the restructuring of the adsorbed micelles not only by tracing the interfacial pressure, but also by analyzing the interfacial rheology and structure with help of atomic force microscopy. The observed micellar flattening and subsequent merging toward a physically interconnected monolayer lead to a viscoelastic interface well detectable by interfacial shear rheology (ISR). Furthermore, the "gelled" interface is redox-active, enabling a return to purely viscous interfaces and hence a manipulation of the rheological properties by redox reactions. Additionally, interfacial Prussian blue formation stiffens the interface. Such manipulation and in-depth knowledge of the rheology of complex interfaces can be beneficial for the development of emulsion formulations in industry or medicine, where colloidal stability or adapted permeabil...

Supramolecular Polymeric Material Based on Twisted Cucurbit[14]uril: Sensitive Detection and Removal of Potential Cyanide from Water

“…However, the use of potassium ferricyanide cannot be avoided, as it is an important chemical in various industrial processes, including pharmaceuticals, metallurgy, and pigments. Accidental release of cyanide into the water can lead to serious environmental problems and life-threatening health issues. − The World Health Organization (WHO) requires that the maximum concentration of cyanide in drinking water does not exceed 1.9 μM, which makes potassium ferricyanide in the water a potential threat. Given this, the detection of potassium ferricyanide is a particularly important project.…”

“…In particular, the construction of supramolecular polymers with AIE properties based on macrocyclic compounds has received much attention in numerous fields, including biology, 29 fluorescent sensors, and the field of stimuli-responsive materials. 30−32 Twisted cucurbit [14]uril (tQ [14]) 33−36 is a rare macrocyclic compound of the Q [n]s family and possesses good water solubility. 37−44 Due to the two cavities of tQ [14] can simultaneously bind two homologs or heterologous compounds, they can be further assembled to construct supramolecular polymers with different topologies.…”

“…30−32 Twisted cucurbit [14]uril (tQ [14]) 33−36 is a rare macrocyclic compound of the Q [n]s family and possesses good water solubility. 37−44 Due to the two cavities of tQ [14] can simultaneously bind two homologs or heterologous compounds, they can be further assembled to construct supramolecular polymers with different topologies.…”

“…Schematic Illustration of the AIE Supramolecular Polymer Formation Process and Anion Removal Figure 1. Illustration of the formation of TPAP-Mb@tQ [14] (top), and the 1 H NMR titration (D 2 O, pD = 6.75, 298 K) of TPAP-Mb at different concentrations of tQ [14] from 0 (i), 1.0 (ii), and 2.0 (iii). The specific chemical shift data are shown in Table S1.…”

“…The specific chemical shift data are shown in Table S1. [14], and its alkyl chain and methylpyridine fraction can easily interact with tQ [14] through host-guest interactions, thereby inducing the restriction of the intramolecular rotation (RIR) effect of TPAP-Mb, and finally constructing the AIE fluorescent supramolecular polymer (TPAP-Mb@tQ [14]). TPAP-Mb@tQ [14] can detect Fe-(CN) 6 3− in an aqueous solution with an ultra-sensitive limit of detection (LOD) of up to 1.64 × 10 −7 M. More importantly, TPAP-Mb@tQ[14] also can effectively remove K 3 Fe(CN) 6 from aqueous solutions, and the tQ [14] can be cleaned and utilized from the organic phase.…”