Interactions between a Series of Pyrene End-Labeled Poly(ethylene oxide)s and Sodium Dodecyl Sulfate in Aqueous Solution Probed by Fluorescence

The interactions between a series of poly­(ethylene oxide)­s covalently labeled at both ends with pyrene pendants (PEO­(<i>X</i>)-Py₂, where <i>X</i> represents the number-average molecular weight of the PEO chains and equals 2K, 5K, 10K, and 16.5K) and an ionic surfactant, namely, sodium dodecyl sulfate (SDS), in water were investigated at a fixed pyrene concentration of 2.5 μM corresponding to polymer concentrations smaller than 21 mg/L and with an SDS concentration range between 5 × 10^–6 and 0.02 M, thus encompassing the 8 mM critical micelle concentration (CMC) of SDS in water. The steady-state fluorescence spectra showed that the <i>I</i>₁/<i>I</i>₃ ratio decreased from 1.73 ± 0.06 for SDS concentration smaller than 2 mM where pyrene was exposed to water to 1.43 ± 0.03 for SDS concentration greater than 6 mM where pyrene was incorporated inside SDS micelles. The ratio of excimer-to-monomer emission intensities (the <i>I</i>_E/<i>I</i>_M ratio) of all PEO­(<i>X</i>)-Py₂ samples remained constant at low SDS concentrations, then increased, passed through a maximum at the same SDS concentration of 4 mM before decreasing to a plateau value that is close to zero for PEO­(10K)-Py₂ and PEO­(16.5K)-Py₂ but nonzero for PEO­(2K)-Py₂ and PEO­(5K)-Py₂. The pyrene end groups of these two latter samples could not bridge two different micelles due to the short PEO chain, and excimer was formed by intramolecular diffusion inside the same SDS micelle. Time-resolved fluorescence decays of the pyrene monomer and excimer of the PEO­(<i>X</i>)-Py₂ samples were acquired at various SDS concentrations and globally fitted according to the “Model Free” analysis over the entire range of SDS concentration. The molar fractions of various excited pyrene species and the rate constant of pyrene excimer formation retrieved from the analysis of fluorescence decays were obtained as a function of SDS concentration. Interactions between SDS and PEO could not be detected by isothermal titration calorimetry, potentiometry with a surfactant selective electrode, and conductance measurements

Self-Assembly Behavior of Thermoresponsive Oligo(ethylene glycol) Methacrylates Random Copolymer

A well-defined random copolymer containing 2-(2-methoxyethoxy) ethyl methacrylate (MEO₂MA, <i>M</i>_n = 188 g/mol) and poly­(ethylene glycol) methyl ether methacrylate (PEGMA, <i>M</i>_n = 2080 g/mol) (poly­(MEO₂MA-<i>co</i>-PEGMA₂₀₈₀)), <i>M</i>_n = 17300 g/mol) was synthesized using the atom transfer radical polymerization (ATRP) process, and its thermoresponsive behaviors in aqueous solution were investigated. In comparison to other temperature-sensitive random copolymers based on oligo­(ethylene glycol) methacrylates, this copolymer exhibited an unusual thermally induced two-stage aggregation process. The copolymer chains associate at the first thermal transition followed by a rearrangement process at the second thermal transition to produce a stable core–shell micellar structure. The morphology of the micelle comprises of a methacrylate core stabilized by the longer ethylene glycol segments (<i>M</i>_n = 2080 g/mol) shell

Cellulose-Based Irreversible Hydrogels Used for CO₂ Sequestration

CO2-switchable hydrogels have been well documented during the past decade; however, the reversible response makes them unable to sequestrate CO2 owing to the gas release and viscosity reduction under high temperatures, weakening their capacity to absorb CO2. To address this issue, a series of copolymers based on grafting poly(dimethylaminopropyl methacrylamide) onto the backbone of sodium carboxymethyl cellulose (NaCMC) were prepared, characterized, and examined rheologically. In the semidilute entangled regime, the copolymer aqueous solutions can be gelled in the presence of CO2, but they cannot revert to the solution phase after bubbling N2 at 60 °C. With such irreversibility, 1 wt % aqueous solution of the copolymer with 24.88 mol % DMAPMAm can absorb CO2 up to 12.1 mg·g–1, whereas only 18.2% of the absorbed CO2 is released after heating at 60 °C. This work paves a new way to develop irreversible hydrogels for CO2 sequestration

Highly Biocompatible, Underwater Superhydrophilic and Multifunctional Biopolymer Membrane for Efficient Oil–Water Separation and Aqueous Pollutant Removal

Conventional wastewater treatment systems generally require multiple steps and complex procedures to remove aqueous pollutants and oil contaminants from polluted water. Herein, we fabricate an underwater superoleophobic membrane by cross-linking konjac glucomannan on pristine fabrics, demonstrating that the concept of oil–water separation and the principle of aqueous pollutant removal can be integrated. Such biopolymer-modified fabric not only separates oil–water mixtures with high efficiency (up to 99.9%), but also exhibits the intriguing characteristic of removing water-soluble pollutants (including polyaromatic dyes and heavy metal ions). As a proof of concept, the synthetic wastewater purified with biopolymer membranes was used to cultivate and irrigate pinto beans, causing no observable deleterious effect on seed germination and growth. These results further confirm the biocompatibility and effectiveness of biopolymer membranes, offering an encouraging solution to challenges including wastewater treatment and cleanup of oil spills

Hierarchical, Self-Healing and Superhydrophobic Zirconium Phosphate Hybrid Membrane Based on the Interfacial Crystal Growth of Lyotropic Two-Dimensional Nanoplatelets

We demonstrate a facile route to in situ growth of lyotropic zirconium phosphate (ZrP) nanoplates on textiles via an interfacial crystal growing process. The as-prepared hybrid membrane shows a hierarchical architecture of textile fibers (porous platform for fluid transport), ZrP nanoplatelets (layered scaffolds for chemical barriers), and octadecylamine (organic species for superhydrophobic functionalization). Interestingly, such a hybrid membrane is able to separate the oily wastewater with a high separation efficiency of 99.9%, even at in harsh environments. After being chemically etched, the hybrid membrane is able to restore its hydrophobicity autonomously and repeatedly, owing to the hierarchical structure that enables facile loading of healing agent. We anticipate that the concept of implanting superhydrophobic self-healing features in anisotropic structure of lyotropic nanoparticles will open up new opportunities for developing advanced multifunctional materials for wastewater treatment, fuel purification, and oil spill mitigation