Cyclization of PEG and Pluronic Surfactants and the Effects of the Topology on Their Interfacial Activity

Abstract

A series of cyclic surfactants were synthesized from a poly(ethylene glycol) (PEG) homopolymer and Pluronic surfactants L35, L64, P123, F68, 10R5, and 17R4, and their interfacial activity depending on the topology, chain ends, and block sequence was investigated. The cyclization was performed in a single step through etherification of the PEG homopolymer and the hydrophilic−hydrophobic−hydrophilic (ABA type) poly(ethylene glycol)−poly(propylene glycol)−poly(ethylene glycol) (PEG−PPG−PEG), while the hydrophobic−hydrophilic−hydrophobic (BAB type) PPG−PEG−PPG was cyclized via acetalization. The cyclized surfactants were rigorously characterized by nuclear magnetic resonance spectroscopy and size exclusion chromatography. Cyclization of the surfactants induced a significant decrease in the hydrodynamic volume, which was more pronounced than that of the PEG homopolymer. Surface tension (γ) measurements indicated that the interfacial activity of the cyclized surfactants is stronger than their corresponding linear precursors, due to the increase in the surfactant density at the air−water interface as a consequence of the decreased molecular occupational area (A) upon cyclization. In the case of the PEG homopolymer, A considerably decreased from 410 Å 2 for the linear PEG prepolymer to 100 Å 2 for the cyclized PEG product. While the effects of chain-end groups were found to be limited to surfactants of relatively small molecular weights, the influence of cyclization depended strongly on the hydrophilic/ hydrophobic ratio; the higher the PEG composition the surfactants had, the larger the decrease in γ and A; in other words, stronger enhancement in the interfacial activity was observed.

Stabilizing Zn Anodes by Molecular Interface Engineering with Amphiphilic Triblock Copolymer

“…Focusing on the Zn/electrolyte interface, the amphiphilic property of Pluronic additives featuring both hydrophobic and hydrophilic segments at the molecular level is beneficial for regulating interfacial reactions via construction of a functional hydrodynamic layer. As shown in Figure b, the hydrophobic PPO center of normal Pluronic can adsorb quasi-irreversibly to the hydrophobic Zn metal surfaces, and the two side PEO segments are spread in the aqueous electrolyte. , The adsorbed PPO segments on the Zn surface can create a localized water-poor interphase to limit direct contact of water with Zn metal. Such a water-shielding environment not only suppresses water-induced Zn corrosion and hydrogen evolution but also fosters the desolvation of Zn 2+ from hydrated water .…”

“…As shown in Figure 2b, the hydrophobic PPO center of normal Pluronic can adsorb quasi-irreversibly to the hydrophobic Zn metal surfaces, and the two side PEO segments are spread in the aqueous electrolyte. 28,29 The adsorbed PPO segments on the Zn surface can create a localized water-poor interphase to limit direct contact of water with Zn metal. Such a water-shielding environment not only suppresses water-induced Zn corrosion and hydrogen evolution but also fosters the desolvation of Zn 2+ from hydrated water.…”

Size Control and Enhanced Stability of Silver Nanoparticles by Cyclic Poly(ethylene glycol)

“…[ 25 ]. Among all topologies, cyclic polymers without end groups exhibit unique physical/chemical properties such as higher glass transition temperature [ 26 ], reduced hydrodynamic volume [ 27 ], higher density [ 28 ], lower viscosity [ 29 ], higher resistance of their micelles towards salt [ 30 ] and temperature [ 31 ], and higher interfacial activity [ 32 ] compared with their respective linear counterparts. In particular, we reported that dispersion stability of AuNPs [ 33 ] and AgNPs [ 34 ] was drastically enhanced by the physisorption of cyclic PEG.…”

Passerini Multicomponent Reactions Enabling Self-Reporting Photosensitive Tetrazole Polymers

“…However, the challenging removal of the unreacted mPEG-Mal (e.g., extraction and precipitation, as is also reported in the literature) , resulted in a lower M n than expected. Therefore, peak deconvolution of the SEC trace was conducted, , giving the actual M n of P4 (Figure S6 in the SI). On the other hand, 3,4,5-trifluoroaniline (TFA) was employed, evidencing the photochemical postmodification of P2 via 1 H and 19 F NMR spectroscopy (Figures S7–S8 in the SI), affording the respective polymer P5 (refer to Scheme ).…”