Dual-responsive polyacrylonitrile-based electrospun membrane for controllable oil-water separation.

Membrane separation based on smart materials with responsive wettability has attracted great attention due to the excellent performance of controllable oil-water separation. Herein, responsive copolymer originated from N-isopropylacrylamide and 2-(dimethylamino) ethyl methacrylate was synthesized and electrospun with polyacrylonitrile to fabricate smart composite membrane. The introduction of the responsive copolymer endowed the membrane with stimuli-responsive wettability to pH and temperature. Specifically, at the initial state, water was selectively blocked while oil passed through the membrane. After treatment with acidic water or CO2, the reverse separation was realized due to the protonation of the tertiary amine group in the copolymer. Water was selectively passed through the membrane after heat treatment because of the structural change of membrane upon temperature. The developed membrane was able to separate different types of oil-water mixtures and surfactant-stabled emulsions with high efficiency. Additionally, two membranes controlled by temperature and pH were designed to construct a logic AND gate for oil-water separation, and the results demonstrated that only the temperature and acidity of the solution were simultaneously satisfied, the water could flow through the valve combination, and such capability made this smart membrane great potential for remotely controlling the oil-water separation process.

Preparation of Poly(acrylic acid-acrylamide/starch) Composite and Its Adsorption Properties for Mercury (II).

The poly(acrylic acid-acrylamide/starch) composite was synthesized by solution polymerization, aiming to adsorb mercury (II) in water. The resulted copolymer was characterized by particle size exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), scanning electron microscopy (SEM) and dynamic light scattering particle size analyzer (DLS). It turned out that starch was successfully incorporated with the macromolecular polymer matrix and played a key role for improving the performance of the composites. These characterization results showed that the graft copolymer exhibited narrow molecular weight distribution, rough but uniform morphology, good thermal stability and narrow particle size distribution. The graft copolymer was used to remove Hg(II) ions from aqueous solution. The effects of contact time, pH value, initial mercury (II) concentration and temperature on the adsorption capacity of Hg(II) ions were researched. It was found that after 120 min of interaction, poly(acrylic acid-acrylamide/starch) composite achieved the maximum adsorption capacity of 19.23 mg·g-1 to Hg(II) ions with initial concentration of 15 mg·L-1, pH of 5.5 at 45 °C. Compared with other studies with the same purpose, the composites synthesized in this study present high adsorption properties for Hg(II) ion in dilute solution. The adsorption kinetics of Hg(II) on the poly(acrylic acid-acrylamide/starch) composite fits well with the pseudo second order model.

Photo-regulated supramolecular star with a pillar[6]arene-coated metal-organic polyhedron (MOP) core.

We herein report a 12-armed photo-responsive supramolecular star centered by a pillar[6]arene-coated M6L12 metal-organic polyhedron (MOP) via a core-first approach.

Preparation and Modification of Biomass-Based Functional Rubbers for Removing Mercury(II) from Aqueous Solution.

Biomass-based functional rubber adsorbents were designed and prepared via inverse vulcanization and post-modification. The plant rubber was synthesized with sulfur and renewable cottonseed oil as well as various micromolecular modifiers with nitrogen-containing functional groups. Results showed that types of nitrogen-containing functional groups and dosages of modifiers had a significant impact on the adsorption capacities of the resulting polymers for Hg2+. Notably, when the mass ratio of 2-aminoethyl methacrylate (AEMA) to sulfur was 0.05, the resulting polymer polysulfide-co-cottonseed oil modified by AEMA (SCOA2) showed the highest adsorption capacity (343.3 mg g-1) among all the prepared samples. Furthermore, the Hg2+ removal efficiency of SCOA2 remained over 80% of its original value after five adsorption-desorption cycles. It demonstrated a promising case for utilizing cheap industrial by-products (sulfur) and renewable materials (cottonseed oil). The prepared functional rubber provides alternative approach for mercury removal in waste utilization and sustainable chemistry.

Improved Ozonation Efficiency for Polymerization Mother Liquid from Polyvinyl Chloride Production Using Tandem Reactors.

Polymerization mother liquid (PML) is one of the main sources of wastewater in the chlor-alkali industry. The effective degradation of the PML produced in PVC polymerization using three or five ozone reactors in tandem was designed with a focus on improving the ozonation efficiency. The ozonation efficiency of the tandem reactors for the degradation of PML, along with the effect of ozone concentration, the number of reactors utilized in series, and the reaction time on the chemical oxygen demand (COD) removal were investigated in detail. The results showed that the COD removal increased as the ozone concentration was increased from 10.6 to 60 mg·L-1, achieving 66.4% COD removal at ozone concentration of 80.6 mg·L-1. However, when the ozone concentration was increased from 60 mg·L-1 to 80 mg·L-1, the COD removal only increased very little. The COD decreased with increasing ozone concentration. During the initial degradation period, the degradation rate was the highest at both low and high ozone concentrations. The degradation rate decreased with reaction time. The rate at a low ozone concentration decreased more significantly than at high ozone concentration. Although high ozone concentration is desirable for COD removal and degradation rate, the utilization efficiency of ozone decreased with increasing ozone concentration. The ozone utilization efficiency of the five-reactor device was three times higher than that of three tandem reactors, demonstrating that ozonation utilization efficiency can be improved by increasing the number of tandem reactors. Ozonation in tandem reactors is a promising approach for PML treatment.

Investigating Stability and Tautomerization of Gossypol-A Spectroscopy Study.

The stability of gossypol was investigated by the spectroscopic method. Gossypol was dissolved in three different solvents (CHCl3, DMSO, and CH3OH) under different storage conditions (dark and with nitrogen protection, natural light and with nitrogen protection, ambient air conditions) for different time intervals (0 days, 3 days, 5 days, 7 days, 15 days, 30 days, and 45 days) at room temperature. Then, the stability of gossypol was investigated by ¹H NMR, UV-vis, and HPLC-QTOF-MS spectrometry. Results showed that gossypol existed in aldehyde-aldehyde form in chloroform within five days. Then, both aldehyde-aldehyde and lactol-lactol tautomeric forms existed and maintained a stable solution for 45 days. Gossypol dissolved in methanol mainly existed in aldehyde-aldehyde form. Only a tiny amount of lactol-lactol was found in freshly prepared methanol solution. Gossypol was found to only exist in lactol-lactol form between 30-45 days. Gossypol existed in aldehyde-aldehyde, lactol-lactol, and ketol-ketol forms in dimethyl sulfoxide, and there was a competitive relationship between aldehyde-aldehyde and lactol-lactol form during the 45 days. Among all the solvents and conditions studied, gossypol was found to be highly stable in chloroform. Under the tested conditions, the natural light and atmospheric oxygen had little effect on its stability. Although the spectroscopy data seemed to be changed over time in the three different solvents, it was actually due to the tautomeric transformation rather than molecular decomposition.

Molecularly Imprinted Polymers for Gossypol via Sol⁻Gel, Bulk, and Surface Layer Imprinting-A Comparative Study.

Three gossypol molecularly imprinted polymers (MIPs) were prepared by bulk polymerization (MIP1), surface layer imprinting using silica gel as the support (MIP2), and the sol-gel process (MIP3). The as-prepared MIPs were characterized by SEM and nitrogen adsorption-desorption techniques to study the morphology structure. The adsorption experiments exhibited that MIP1 had adsorption capacity as high as 564 mg·g-1. The MIP2 showed faster adsorption kinetics than MIP1 and MIP3. The adsorption equilibrium could be reached for gossypol in 40 min. A selectivity study showed that the adsorption capacity of MIPs for gossypol was about 1.9 times higher than that of the structurally-similar analogs ellagic acid and 6.6 times higher than that of the quercetin. It was found that the pseudo-second-order kinetic model and the Freundlich isotherm model were more applicable for the adsorption kinetics and adsorption isotherm of gossypol binding onto the MIP1 and MIP2, respectively. Results suggested that among those three, the MIP2 was a desirable sorbent for rapid adsorption and MIP1 was suitable for selective recognition of gossypol.

Preparation and Applications of Salt-Resistant Superabsorbent Poly (Acrylic Acid-Acrylamide/Fly Ash) Composite.

Solution polymerization synthesized alt-resistant superabsorbent poly (acrylic acid-acrylamide/fly ash) composites. The mass ratio of acrylic acid (AA) to acrylamide (AM), the concentration of crosslinker, the neutralization degree (ND) of AA, and the polymerization temperature were investigated by single-factor method. Optimized conditions for the synthesis of poly (acrylic acid-acrylamide/fly ash) (PAA-AM/FA) are, as following: m (AA)/m (AM) is 1.5, the content of crosslinker N, N-methylenebisacrylamide. (MBA) is 0.7%, neutralization degree of AA is 70%, polymerization temperature is 70 °C, and fly ash (FA) content is 50%. The prepared PAA-AM/FA demonstrated superior water absorption performance. The absorption capacities of PAA-AM/FA for pure water and 0.9% NaCl solution were found to be 976 g·g-1 and 81 g·g-1, respectively. Furthermore, PAA-AM/FA was found to have excellent adsorption capacity (148 mg·g-1) for Rhodamine B in water. Fourier Transform-Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM) characterized the prepared materials. Results showed that fly ash was incorporated into the macromolecular polymer matrix and played a key role in improving the performance of the polymer composites.

Design and synthesis of supramolecular functional monomers bearing urea and norbornene motifs.

Three sets of functional monomers namely urea-based, 2-ureido-4[1H]-primidone (UPy)-based and norbornene based functional monomers were designed and synthesized. These functional monomers (FM) were obtained in decent yields using amine and isocyanate/norbornene as starting materials. Methacrylate and styrene isocyanate with 1,4-diaminobutane/tris(2-aminoethyl)amine were chosen for the synthesis of symmetrical, asymmetrical and three-branched urea-functional monomers, respectively. UPy-based FMs were synthesized with isocyanate and 2-amino-4-hydroxy-6-methylpyrimidine. The synthesis of these monomers feature short reaction times, mild reaction conditions and no need for column chromatographic purification. Furthermore, the norbornene based FM was used for preparing molecularly imprinted polymers (MIPs) by Ring-Opening Metathesis Polymerization (ROMP). Results showed that these synthetic routes represent a convenient and useful approach for synthesis of novel functional monomers.

Influence of Size and Shape of Silica Supports on the Sol⁻Gel Surface Molecularly Imprinted Polymers for Selective Adsorption of Gossypol.

The influence of various silica gel supports with different shapes and sizes on the recognition properties of surface molecular imprinted polymers (MIPs) was investigated. MIPs for selective recognition and adsorption of gossypol were synthesized via the sol⁻gel process with a surface imprinting technique on silica gel substrates. 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) were chosen as the functional monomer and the cross-linker. The morphology and structure of the gossypol-MIPs were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and a standard Brunauer⁻Emett⁻Teller (BET) analysis. Results indicated that the surface imprinted polymer layer facilitated the removal and rebinding of the template, and thus, achieved fast binding kinetics. Compared with the MIPs prepared on irregularly shaped silica with a broad particle size distribution, the MIPs using regularly-shaped silica of uniform size showed higher imprinting factor (IF), and the MIP made with a relatively larger sized (60 μm) spherical silica, demonstrated higher adsorption capacity compared to the MIPs made with smaller sized, spherical silica. The MIP prepared with 60 μm spherically shaped silica, featured a fast adsorption kinetic of 10 min, and a saturated adsorption capacity of 204 mg·g−1. The gossypol-MIP had higher selectivity (IF = 2.20) for gossypol over its structurally-similar analogs ellagic acid (IF = 1.13) and quercetin (IF = 1.20). The adsorption data of the MIP correlated well with the pseudo-second-order kinetic model and the Freundlich isotherm model, which implied that chemical adsorption dominated, and that multilayer adsorption occurred. Furthermore, the MIP exhibited an excellent regeneration performance, and the adsorption capacity of the MIP for gossypol only decreased by 6% after six reused cycles, indicating good application potential for selective adsorption of gossypol.

Bioresource derived porous carbon from cottonseed hull for removal of triclosan and electrochemical application.

Biomass-derived porous carbon materials have drawn considerable attention due to their natural abundance and low cost. In this work, nitrogen enriched porous carbons (NRPCs) with large surface areas were designed and prepared from cottonseed hull via simultaneous carbonization and activation with a facile one-pot approach. The NRPCs were tunable in terms of pore structure, nitrogen content and morphology by adjusting the ratio of the carbon precursor (cottonseed hull), nitrogen source (urea), and activation agent (KOH). The as-synthesized NRPCs exhibited three-dimensional oriented and interlinked porous structure, high specific surface area (1160-2573 m2 g-1) and a high level of nitrogen-doping (6.02-10.7%). In a three electrode system, NRPCs prepared at 800 °C with the ratio (cottonseed hull : KOH : urea) of 1 : 1 : 2 (NRPC-112) showed a high specific capacitance of 340 F g-1 at a current density of 0.5 A g-1 and good rate capability (∼80% retention at a current density of 10 A g-1) with 6 M KOH as electrolyte. In a two electrode cell, NRPC-112 demonstrated a high specific capacitance of 304 F g-1 at 0.5 A g-1 and an excellent rate capacity (∼71% retention at current density of 10 A g-1) as well as excellent cycling stability (∼91% retention at 5 A g-1) after 5000 cycles. Furthermore, the NRPCs exhibited an extraordinary adsorption capacity up to 205 mg g-1 for emerging pollutant triclosan. The work provided a sustainable approach to prepare functional carbon materials from biomass-based resource for environment remediation and electrochemical applications.

Probing the single pair rupture force of supramolecular quadruply hydrogen bonding modules by nano-adhesion measurement.

Studying quadruply hydrogen bonding (QHB) module interactions in materials matrices presents a significant challenge because a wide variety of non-covalent interactions may be relevant. Here we introduce a method of surface modification with DeUG (7-deazaguanine urea), DAN (2,7-diamido-1,8-naphthyridine) and UPy (2-ureido-4[1H]-pyrimidone) modules to form self-assembled monolayers (SAMs) on a glass surface. The QHB interactions under mechanical stress were investigated by measuring adhesion force using PS-DAN (DAN modified polystyrene), PBMA-DeUG (DeUG modified poly butyl methacrylate) and PBA-UPy (UPy modified poly butyl acrylate) as adhesion promoters. A mechanical lap-shear test was used to evaluate the fracture resistance of QHB heterocomplexes. The maximum load at fail showed that QHB interaction contributed significantly (72%) to overall adhesion. For the QHB modified glass surface, using a polymer modified with its complementary QHB partner greatly facilitated their pairing efficiency, up to 40% for DAN-DeUG. A general method from which single pair ruptures force of QHB modules could be obtained using thermodynamic data obtained from solution chemistry was proposed. Using this method, the single pair rupture force for UPy-UPy was measured as 160 pN, and the single pair rupture force for DAN-DeUG was obtained as 193 pN.

Facile synthesis of bio-based nitrogen- and oxygen-doped porous carbon derived from cotton for supercapacitors.

Biomass-derived O- and N-doped porous carbon has become the most competitive supercapacitor electrode material because of its renewability and sustainability. We herein presented a facile approach to prepare O/N-doped porous carbon with cotton as the starting material. Absorbent cotton immersed in diammonium hydrogen phosphate (DAP) was activated at 800 °C (CDAP800s) and then was oxidized in a temperature range of 300-400 °C. The electrochemical capacitance of the impregnated cotton was significantly improved by doping with O and N, and the yield was improved from 13% to 38%. The sample oxidation at 350 °C (CDAP800-350) demonstrated superior electrical properties. CDAP800-350 showed the highest BET surface area (1022 m2 g-1) and a relatively high pore volume (0.53 cm3 g-1). In a three-electrode system, the CDAP800-350 electrodes had high specific capacitances of 292 F g-1 in 6 M KOH electrolyte at a current density of 0.5 A g-1. In the two-electrode system, CDAP800-350 electrode displayed a specific capacitance of 270 F g-1 at 0.5 A g-1 and 212 F g-1 at 10 A in KOH electrolyte. In addition, the CDAP800-350-based symmetric supercapacitor achieved a high stability with 87% of capacitance retained after 5000 cycles at 5 A g-1, as well as a high volumetric energy density (18 W h kg-1 at 250 W kg-1).

A mechanically robust hydrogel with thermally induced plasticity and a shape memory effect.

A new class of smart structural hydrogels is prepared by introducing dual cross-linkers into a single-network system. The present hydrogel, on the one hand, exhibits excellent mechanical properties; on the other hand, it exhibits thermally induced plasticity and a shape memory effect without any overlap.

Tough polypseudorotaxane supramolecular hydrogels with dual-responsive shape memory properties.

Cyclodextrin-polypseudorotaxane hydrogels have attracted extensive attention for their potential application in biomedical fields. Herein, we develop a facile strategy for the in situ formation of mechanically tough polypseudorotaxane hydrogels through photoinitiated copolymerization of poly(ethylene glycol) methyl ether methacrylate, acrylamide and sodium acrylate in α-CD solution at 60 °C. For the first time, we manage to screen the host-guest interaction between α-CD and PEG before copolymerization in the presence of a temporary hydrogen bonding weakening monomer (acrylamide) at a suitable temperature (60 °C). This shielding effect weakens gradually during polymerization, thus leading to the formation of polypseudorotaxane aggregations and a tough physical hydrogel. The hydrogel can bear a large compressive strain (80%) without rupture, and exhibits excellent antifatigue properties. Furthermore, this hydrogel could be endowed with thermal/ascorbic acid activated shape memory performance after being treated with FeCl3 solution. This simple method will contribute to the design and application of smart supramolecular hydrogels.

Dual-responsive shape memory hydrogels with novel thermoplasticity based on a hydrophobically modified polyampholyte.

Shape memory hydrogels offer the ability to recover their permanent shape from temporarily trapped shapes without application of external forces. Here, we report a novel dual-responsive shape memory hydrogel with characteristic thermoplasticity. The water-insoluble hydrogel is prepared by simple ternary copolymerization of acrylamide (AM) and acrylic acid (AA) with low amounts of a cationic surfmer, in the absence of organic crosslinkers. Through either ionic/complex binding of carboxyl groups via trivalent cations or salt-dependent hydrophobic association, the hydrogel can memorize a temporary shape successfully, which recovers its permanent form in the presence of a reducing agent or deionized water. Besides, the unique thermoplasticity of the hydrophobic polyampholyte hydrogel allows the change of its permanent shape upon heating and the fixation after cooling, which is in strong contrast to the conventional chemically cross-linked shape memory hydrogels. This fascinating feature undoubtedly enriches the shape memory hydrogel systems. Thus, we believe that the facile strategy could provide new opportunities with regard to the design and practical application of stimulus-responsive hydrogel systems.

Shape Memory Hydrogel based on a Hydrophobically-Modified Polyacrylamide (HMPAM)/α-CD Mixture via a Host-Guest Approach.

A novel thermally sensitive shape memory (SM) hydrogel is prepared by block copoly-merization of a cationic surfactant monomer, dimethylhexadecyl[2-(dimethylamino)ethylmethacrylate]ammoniumbromide (C(16)DMAEMA), and acrylamide (AM) in the presence of α-cyclodextrin (α-CD) using N,N'-methylenebisacrylamide (MBA) as a crosslinker. XRD, solid state (13)C NMR, and DSC measurements show that the crystalline domains, induced by the hydrogen bonds between α-CDs threaded on the hydrophobic units of the polymer chains through the host-guest approach, can reversibly melt and crystallize at different temperatures. Rheological measurements show that both the elastic modulus G' and viscous modulus G'' drastically change due to the formation and dissolution of the crystalline domains. These thermo-sensitive crystalline domains serve as reversible physical crosslinks, endowing the hydrogel with excellent SM properties. Cyclic experiments show that the hydrogel can recover to almost 100% of the deformation in each cycle and can be reused several times.

A shape memory hydrogel induced by the interactions between metal ions and phosphate.

A novel ferric-phosphate induced shape memory (SM) hydrogel is prepared by the one-step copolymerization of isopropenyl phosphonic acid (IPPA) and acrylamide (AM) in the presence of a crosslinker polyethylene glycol diacrylate (PEGDA). Different from the traditional SM hydrogels, our SM hydrogel can be processed into various shapes as needed and recovers to its original form in 'multiconditions' such as in the presence of a reducing agent or in the presence of a competitive complexing agent. This unique feature is attributed to the fact that the oxidized ferric ions show a high complexation ability with phosphate groups of IPPA, which acts as a physical crosslinker to form the secondary networks within the hydrogels to induce the shape memory effect. The memory behavior was totally reversible, owing to Fe3+ that can be reduced to Fe2+ and extracted by the complexing agent. Particularly, the SM hydrogels exhibit controllable and good mechanical characteristics by introduction of the ferric ions, i.e., the elastic modulus can increase from 2 kPa to 70 kPa dramatically. Learning from biological systems, phosphate-metal ion based hydrogels could become an attractive candidate for various biomedical and environmental applications.