Synthesis of low surface energy thin film of polyepichlorohydrin-triazole-ols

Cotton fabrics modified with tannic acid/1-eicosanamine grafting layer for oil/water separation

The wettability of the surface of hydrophilic cotton fabrics was modified using a one-step protocol with tannic acid (TA) to provide its excess catechol groups to be grafted with 1-eicosanamine at pH 8.5 and room temperature with catalysts CuSO4/H2O2. The modification over the synthesis conditions revised the contact angles of water and diiodomethane droplets from 132.68 ± 0.49° to 143.95 ± 0.80° and from 100.08°±1.42° to 82.96 ± 1.38°, respectively. The corresponding dispersive of the so-yielded cotton surface ranged from 8.6 to 16.0 mJ/m2, and the polar components ranged from 0.08 to 2.7 mJ/m2, much lower than polytetrafluoroethylene. The modified cotton fabrics are omniphobic and can repel water and commercial oil products. The absorption tests revealed that the modified cotton fabrics absorbed 1.10 g hexane/g cotton by contacting hexane (top)-water (bottom) layers and absorbed 1.26 g hexane/g cotton by contacting water first for 30 s, then hexane for another 30 s. The modified fabrics reveal good absorption reusability as hexane absorbent is even pre-saturated with water. This conclusion is also valid for commercial unleaded gasoline #95 and diesel. A parametric study revealed that the added catalysts and prolonged reaction time would enhance the hydrophobicity of the surface. These modified cotton fabrics can absorb oil from water and oil spills. Mechanisms corresponding to this observation are discussed.

Hydrophobic cotton fabric with 3-mercaptopropyltriethoxysilane/polyhedral oligomeric silsesquioxane/1-octadecanethiol modification for oil/water separation

A protocol to produce a silsesquioxane (POSS) with a long alkyl chain coating on natural cotton (CT) fabric is applied. The surface hydroxyl groups of cotton fabric are converted with 3-mercaptopropyltriethoxysilane (MPTES) to thiol groups. Then the POSS links to the thiol groups by thiol-ene click reactions triggered by UV irradiation to produce POSS-CT or grafted with 1-octadecanethiol (ODT) using one-pot or two-pot modification protocols to generate the ODT-POSS-CT fabrics. The POSS-CT is highly hydrophobic, could absorb 0.96 g hexane/g fabrics when competing with invaded water, and reach 1.12 hexane g/g fabrics when water was absorbed separately. The one-pot modification protocol yielded surfaces with almost constant water contact angle (144o) and perfect wetting by diiodomethane (0o), producing constant dispersive component (50.8 mJ/m2) and polar component (13.6 mJ/m2). The ODT-POSS-CT via two-pot modification leads to water contact angles >143o and diiodomethane contact angle of about 46o, with corresponding dispersive and polar components being 36.1 mJ/m2 and 9.4 mJ/m2, respectively. The complete grafting of ODT onto POSS yields a compact hydrophobic layer with reduced effective surface area for dispersive components, transferring the surface from hydrophobic to omniphobic for both water and diiodomethane.

Dynamic electrostatic assembly of polyelectrolytes and perfluorosurfactants into environmentally Adaptable, freestanding membranes with ultralow surface energy and surface adhesion

HYPOTHESIS

Integration of ultralow surface energy and surface functionality on one surface coatings is highly desirable in chemical and biomedical applications. However, it is a fundamental challenge to reduce surface energy without cost of surface functionality and vice versa. To address this challenge, the present work made use of the rapid and reversible change of surface orientation conformations of weak polyelectrolyte multilayers to create ionic, perfluorinated surfaces.

EXPERIMENTS

Poly(allylamine hydrochloride) (PAH) chains and the micelles of sodium perfluorooctanoate (SPFO) were layer-by-layer (LbL) assembled into (SPFO/PAH)_n multilayer films, which readily exfoliated to freestanding membranes. The static and dynamic surface wetting behaviors of the resulting membranes were studied by sessile drop technique and their surface charge behaviors in water by electrokinetic analysis.

FINDINGS

As-prepared (SPFO/PAH)_n membranes exhibited ultralow surface energy in air; the lowest surface energy is 2.6 ± 0.5 mJ/m² for PAH-capped surfaces and 7.0 ± 0.9 mJ/m² for SPFO-capped surfaces. They readily became positively charged in water, which allowed not only effective adsorption of ionic species for further functionalization with subtle change in surface energy, but effective adhesion onto various solid substrates such as glass, stainless steel, and polytetrafluoroethylene to endorse the wide applicability of (SPFO/PAH)_n membranes.

Green preparation of carbon dots with different surface states simultaneously at room temperature and their sensing applications

It is a considerable challenge to develop environmental friendly, low-cost methodology for green preparation of carbon dots (CDs). Herein, CDs with different surface states are prepared using o-phenylenediamine (o-PD) and hydroquinone (HQ) as precursors via oxidation/polymerization and Schiff base reaction at room temperature without additional oxidizing agents. Two CDs products (YCDs and GCDs) are obtained after separation with silica gel column chromatography based on their polarity differences. The different surface states endow these two CDs with different properties. The rich NO₂ and OH groups on the surface of YCDs contribute to a narrow band gap, resulting in the red-shifted photoluminescence (PL) emission of this CDs product, making it a sensitive probe for the detection of toxic pollutant p-nitrophenol (p-NP) attributed to the inner filter effect, along with a detection limit of 0.08 μmol/L. GCDs are characterized with abundant surficial NH₂ groups, and can be used as a potential probe to detect H₂O content in D₂O, giving a detection limit of 0.17 vol%.

Building N-Heterocyclic Carbene into Triazine-Linked Polymer for Multiple CO2 Utilization

The development of new CO₂ detection technologies and CO₂ "capture-conversion" materials is of great significance due to the growing environmental crisis. Here, multifunctional triazine-linked polymers with built-in N-heterocyclic carbene (NHC) sites (designated as NHC-triazine@polymer) are presented for simultaneous CO₂ detection, capture, activation, and catalytic conversion. NHC-triazine@polymer were readily obtained through polymerization of cyanophenyl-substituted NHC. The obtained film-like polymers exhibited interesting CO₂ -triggered fluorescence "turn-on" response and CO₂ -sensitive reversible color change. Both NHC and triazine sites could act as efficient binding sites for CO₂ , and the CO₂ uptake of NHC and triazine reached 1.52 and 1.36 mmol g^-1 , respectively. Notably, after being captured by NHC, CO₂ was activated into a zwitterionic adduct NHC-CO₂ that could be easily transformed into cyclic carbonate in the presence of epoxides. Moreover, NHC-triazine@polymer were stable and active catalysts for the conversion of low-concentration CO₂ in a gas mixture (7 vol %) into cyclic carbonates as well as for hydrosilylation of CO₂ to formamides.