Aqueous Polymer Solutions Research Articles

Evidence of Many-Body Interactions in the Virial Coefficients of Polyelectrolyte Gels.

Simulation studies of aqueous polymer solutions, and heuristic arguments by De Gennes for aqueous polyethylene oxide polymer solutions, have suggested that many-body interactions can give rise to the ‘anomalous’ situation in which the second osmotic virial coefficient is positive, while the third virial coefficient is negative. This phenomenon was later confirmed in analytic calculations of the phase behavior and the osmotic pressure of complex fluids exhibiting cooperative self-assembly into extended dynamic polymeric structures by Dudowicz et al. In the present study, we experimentally confirm the occurrence of this osmotic virial sign inversion phenomenon for several highly charged model polyelectrolyte gels (poly(acrylic acid), poly(styrene sulfonate), DNA, hyaluronic acid), where the virial coefficients are deduced from osmotic pressure measurements. Our observations qualitatively accord with experimental and simulation studies indicating that polyelectrolyte materials exhibit supramolecular assembly in solution, another symptomatic property of fluids exhibiting many-body interactions. We also find that the inversion in the variation of the second (A2) and third (A2) virial coefficients upon approach to phase separation does not occur in uncharged poly(vinyl acetate) gels. Finally, we briefly discuss the estimation of the osmotic compressibility of swollen polyelectrolyte gels from neutron scattering measurements as an alternative to direct, time-consuming and meticulous osmotic pressure measurements. We conclude by summarizing some general trends and suggesting future research directions of natural and synthetic polyelectrolyte hydrogels.

A deeper insight into the dual temperature- and pH-responsiveness of poly(vinylamine)-b-poly(N-isopropylacrylamide) double hydrophilic block copolymers

Block copolymers based on poly(vinylamine) and poly(N-isopropylacrylamide), PVAmm-b-PNIPAMn, were synthetized by hydrazinolysis of poly(N-vinylphthalimide) based copolymers, PVPIm-b-PNIPAMn, obtained by RAFT polymerization. The effect of molar mass and pH on the thermoresponsive and aggregation properties of these polymers in aqueous solution was studied with UV–vis spectroscopy, differential scanning calorimetry, NMR spectrometry, light and X-ray scattering experiments. For the first time it was demonstrated that at room temperature, these copolymers are prone to self-assemble and tend to form larger aggregates upon heating. Hence core-shell nanostructures with a dense PNIPAM core and a hydrophilic PVAm shell, were notably observed above Tc when pH < pKa.

Toughening robocast chitosan/biphasic calcium phosphate composite scaffolds with silk fibroin: Tuning printable inks and scaffold structure for bone regeneration

The present work aims the production of composite bioceramic scaffolds by robocasting suppressing sintering as post printing process. To achieve this purpose, extrudable ink compositions containing a high concentration of bioceramic powders (hydroxyapatite and β-tricalcium phosphate) embedded in aqueous polymeric solutions of chitosan and silk fibroin were fine-tuned. Polymeric solutions of chitosan/silk fibroin with different ratios were tested, maintaining the total amount of bioceramic solids at 30 vol%. The inks were characterized by rheological studies in viscometry and oscillatory modes, being the printable ones selected to produce scaffolds with different macropore sizes (300 μm and 500 μm). The scaffolds were characterized by mechanical properties (dry and wet conditions) and morphological features, as well as its degradability. In vitro studies were also evaluated in the scaffolds that presented the best structural performance.The addition of 2 wt% silk fibroin to a 5 wt% chitosan matrix allows to significantly improve the mechanical performance of the printed composite scaffolds, reflected in high values for Young's modulus and maximum compressive strength. This trend was continued in wet scaffolds with a concomitant reduction of mechanical properties. Regarding degradability, the scaffolds in general presented a weight loss in the range of 14–18% after 28 days incubation in HEPES solution at two different pH values at 37 °C, with an associated release of calcium and phosphorus ions. The scaffold with 300 μm porosity comprising the both polymers in its composition presented the less rate degradation when compared to the scaffolds with similar porosity and containing only chitosan as base matrix. Moreover, the combined natural polymers gave rise to a significant increase in the metabolic activity of human osteoblasts grown on the scaffolds with both macropore' size, being in line with the full cellular filling of their surfaces, demonstrated by SEM and confocal imaging. The advances presented in this work are a promising path in the ink's development for extrusion-based additive manufacturing techniques and subsequent biomaterials, encompassing suitable physical and chemical characteristics with high potential to be used as bone substitutes.

Stabilization and solubilization of difluprednate in aqueous cyclodextrin solution and its characterization for ophthalmic delivery

Difluprednate is a synthetic glucocorticoid used for the treatment of postoperative inflammation and pain associated with endogenous uveitis. It is very lipophilic with limited aqueous solubility and stability. The only available marketed formulation is an oil-in-water ophthalmic emulsion that has many drawbacks. Cyclodextrin (CD) molecules are widely used to increase the solubility and stability of hydrophobic drugs through the formation of drug/CD complexes. This study aims to investigate degradation kinetics, stability and solubility of difluprednate in aqueous CD solutions in an effort to develop aqueous eye drop vehicle for ophthalmic delivery. Phase-solubility and kinetics studies were performed in presence of different CDs and polymers. Characterization of the drug/CD complexes was done using techniques like NMR, DSC, and FTIR. The results show that difluprednate has maximum stability at pH 5 in aqueous CD solution. HPγCD was found to be the best solubilizer and stabilizer among all the CDs tested. The stability was further improved with the combination of HPγCD and different polymers. Characterization of the difluprednate/HPγCD complex in solid and solution state confirmed the presence of a drug/CD complex. It was possible to solubilize 0.1% difluprednate using HPγCD and stabilize the drug using combination of CD and polymer in aqueous solution.

Catalytic Reduction of Environmental Pollutants with Biopolymer Hydrogel Cross-Linked Gelatin Conjugated Tin-Doped Gadolinium Oxide Nanocomposites.

In the present study, a biopolymer nanocomposite hydrogel based on gelatin and tin-doped gadolinium oxide (Sn-Gd2O3@GH) was prepared for the efficient reduction of water pollutants. The method of Sn-Gd2O3@GH preparation consisted of two steps. A Sn-Gd2O3 nanomaterial was synthesized by a hydrothermal method and mixed with a hot aqueous solution (T > 60 °C) of gelatin polymer, followed by cross-linking. Due to the presence of abundant functional groups on the skeleton of gelatin, such as carboxylic acid (–COOH) and hydroxyl (–OH), it was easily cross-linked with formaldehyde. The structure, morphology, and composition of Sn-Gd2O3@GH were further characterized by the FESEM, XRD, EDX, and FTIR techniques. The FESEM images located the distribution of the Sn-Gd2O3 nanomaterial in a GH matrix of 30.06 nm. The XRD patterns confirmed the cubic crystalline structure of Gd2O3 in a nanocomposite hydrogel, while EDS elucidated the elemental composition of pure Sn-Gd2O3 powder and cross-linked the Sn-Gd2O3@GH samples. The synthesized Sn-Gd2O3@GH nanocomposite was used for the removal of different azo dyes and nitrophenols (NPs). It exhibited an efficient catalytic reduction of Congo red (CR) with a reaction rate of 9.15 × 10−1 min−1 with a strong NaBH4-reducing agent. Moreover, the Sn-Gd2O3@GH could be easily recovered by discharging the reduced (colourless) dye, and it could be reused for a fresh cycle.

Building micro-capsules using water-in-water emulsion droplets as templates

The use of templates in materials chemistry is a well-established approach for producing membrane-bounded hollow spheres used for microencapsulation applications, but also in synthetic biology to assemble artificial cell-like compartments. Sacrificial solid or gel micro-particles, but also liquid-like oil-in-water or water-in-oil emulsion droplets are routinely used as templates to produce capsules. Yet, disruption of the core sacrificial material often requires harsh experimental conditions, such as organic solvents, which limits the use of such approach to encapsulate fragile solutes, including biomolecules. Recently, water-in-water emulsion droplets have emerged as promising alternative templates to produce capsules in solvent-free conditions. These water-in-water droplets result from liquid-liquid phase separation in dilute aqueous polymer or surfactants solutions. Their ease of preparation, the large palette of components they can be assembled from and the lack of harsh solvent or oil used for their production make water-in-water emulsions of practical importance in materials chemistry. Water-in-water droplets can also spontaneously sequester solutes by equilibrium partitioning, which provides a simple strategy to locally accumulate molecules of interest and encapsulate them in capsules after interfacial shell formation. Here, we review recent works that employ water-in-water emulsion droplets to prepare capsules and suggest possible additional applications in materials chemistry.

Turbulent Drag Reduction with an Ultra-High-Molecular-Weight Water-Soluble Polymer in Slick-Water Hydrofracking.

Water-soluble polymers as drag reducers have been widely utilized in slick-water for fracturing shale oil and gas reservoirs. However, the low viscosity characteristics, high operating costs, and freshwater consumption of conventional friction reducers limit their practical use in deeper oil and gas reservoirs. Therefore, a high viscosity water-soluble friction reducer (HVFR), poly-(acrylamide-co-acrylic acid-co-2-acrylamido-2-methylpropanesulphonic acid), was synthesized via free radical polymerization in aqueous solution. The molecular weight, solubility, rheological behavior, and drag reduction performance of HVFR were thoroughly investigated. The results showed that the viscosity-average molecular weight of HVFR is 23.2 × 106 g⋅mol−1. The HVFR powder could be quickly dissolved in water within 240 s under 700 rpm. The storage modulus (G′) and loss modulus (G″) as well as viscosity of the solutions increased with an increase in polymer concentration. At a concentration of 1700 mg⋅L−1, HVFR solution shows 67% viscosity retention rate after heating from 30 to 90 °C, and the viscosity retention rate of HVFR solution when increasing CNaCl to 21,000 mg⋅L−1 is 66%. HVFR exhibits significant drag reduction performance for both low viscosity and high viscosity. A maximum drag reduction of 80.2% is attained from HVFR at 400 mg⋅L−1 with 5.0 mPa⋅s, and drag reduction of HVFR is 75.1% at 1700 mg⋅L−1 with 30.2 mPa⋅s. These findings not only indicate the prospective use of HVFR in slick-water hydrofracking, but also shed light on the design of novel friction reducers utilized in the oil and gas industry.

FLOCCULATION OF DISPERSE SYSTEMS BY POLYFUNCTIONAL POLYMER-INORGANIC HYBRIDS

Development of novel high-capacity multifunctional flocculants is a promising solution to selective separation of clay suspensions. Among such flocculants, polymer-inorganic hybrids are the most attractive for their excellent performance as compared with inorganic coagulants or syn-thetic polymers. Synthesis of polymer-inorganic hybrids was carried out in two stages. At the first stage, Al(OH)3sol was obtained by condensation of aluminum chloride and ammonium carbonate in the following conditions: t = 70°C, pH = 3-4, intensive stirring. In the second stage, Al(OH)3was mixed with aqueous solutions of polymers at room temperature. By changing the melting tem-perature of hybrid samples, the presence of interactionsbetween the Al3+cation and the carboxylate groups of the analyzed acrylamide copolymers were established. This paper reports synthesis and comparative efficiency analysis of systems that contain water-soluble anionic copolymers of acryla-mide and respective polyfunctional polymer-inorganic hybrids. We performed a quantitative char-acterization of concentration and structural effects of polymer flocculants on the flocculation mechanism and sludge thickening. Sludge thickening constants were determined. Higher values of thickening constants were noted in systems with additives of hybrid samples, due to the participa-tion of their macromolecules in the formation of floccules at the first stage of the sediment process, and at the stage of thickening of sediments,their deformation and compaction were revealed while maintaining a loose structure with the formation of bulk floccules. We considered the factors al-lowing to optimize flocculation of clay dispersions by polymer-inorganic hybrids in aqueous media. These novel flocculants were shown to have a good potential for applications in filtration or flota-tion processes as well as for wastewater treatment for removal of disperse impurities.

Well-defined polyacrylamides with AIE properties via rapid Cu-mediated living radical polymerization in aqueous solution: thermoresponsive nanoparticles for bioimaging

There is a requirement for the development of methods for the preparation of well-controlled polymers with aggregation-induced emission (AIE) properties.

Extremely large electro-optic effect of TPPS J-aggregates in the PVA or PVP polymer matrix and aqueous solution.

The molecules of tetra-phenyl porphyrin tetra-sulfonic acid (TPPS) form a J-aggregate via self-organization in aqueous solution. The J-aggregates formed in an aqueous solution with added hydrochloric acid were dispersed in PVP polymer and subjected to electric field modulation spectroscopy. The observed difference in the static polarizability Δαp between the excited and ground states in the TPPS J-aggregates reached a value 2.66 × 104 times and 1.22 × 105 times larger than in the monomer molecules in PVA and PVP polymer matrices, respectively. This large enhancement factor of the electro-optic effect (EOE) may be induced by the higher-order structure of the J-aggregate. The different enhancement factor for each polymer matrix may be introduced by the structural differences between the polymer matrices. Electric field modulation spectroscopy of the J-aggregate in aqueous solution showed an absorbance change of 25% of the magnitude of absorbance peak.

E-Beam Cross-Linking of Complex Hydrogels Formulation: The Influence of Poly(Ethylene Oxide) Concentration on the Hydrogel Properties.

In the present study, we report on the complex hydrogels formulations based on collagen-poly(vinyl pyrrolidone) (PVP)-poly(ethylene oxide) (PEO) cross-linked by e-beam irradiation in an aqueous polymeric solution, aiming to investigate the influence of different PEO concentrations on the hydrogel properties. The hydrogel networks’ structure and their composition were investigated using equilibrium swelling degree, complex rheological analysis, and FT-IR spectroscopy. Rheological analysis was performed to determine the elastic (G′) and viscous (G″) moduli, the average molecular weight between cross-linking points (Mc), cross-link density (Ve), and the mesh size (ξ). The effect of the PEO concentration on the properties of the hydrogel was investigated as well. Depending on the PEO concentration added in their composition, the hydrogels swelling degree depends on the absorbed dose, being lower at low PEO concentrations. All hydrogel formulations showed higher G′ values (9.8 kPa) compared to G″ values (0.2 kPa), which shows that the hydrogels have a predominantly elastic behavior. They presented stability greater than 72 h in physiological pH buffers and reached equilibrium after 25 h. The Mc parameter is strongly dependent on the PEO concentration and the absorbed dose for all hydrogel compositions. The cross-linking density increased with the absorbed dose.

Synthesis and characterization of novel thermo- and salt-sensitive amphoteric terpolymers based on acrylamide derivatives

A novel linear amphoteric terpolymers based on neutral monomer — N-isopropylacrylamide (NIPAM), ani- onic monomer — 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (AMPS), and cationic mono- mer — (3-acrylamidopropyl) trimethylammonium chloride (APTAC) were synthesized by free-radical polymerization in aqueous solution and characterized by methods of 1H NMR and FTIR spectroscopy, TGA, GPC, Dynamic light scattering (DLS) and zeta-potential. The thermal and salt sensitivity of amphoteric ternary polymers of various compositions, particularly, [NIPAM]:[AMPS]:[APTAC] = 90:2.5:7.5; 90:5:5; 90:7.5:2.5 mol.% were studied in aqueous and aqueous-salt solutions in the temperature range from 25 to 60 C and at the NaCl ionic strength  interval from 10–3 to 1M. It was found that due to hydrophobic/hydrophilic balance, the temperature dependent conformational and phase change of macromolecular chains becomes sensitive to salt addition and allows the fine-tuning of the phase transition. In aqueous and aqueous-salt solutions, the average hydrodynamic size of amphoteric terpolymers is varied from 8 to 300 nm exhibiting bimodal distribution at room temperature. The number average (Mn) and weight average (Mw) molecular weights, polydispersity index (PDI), and zeta-potentials of amphoteric terpolymers in aqueous solu- tions were determined

Higher-order structure of DNA determines its positioning in cell-size droplets under crowded conditions

BackgroundIt is becoming clearer that living cells use water/water (w/w) phase separation to form membraneless organelles that exhibit various important biological functions. Currently, it is believed that the specific localization of biomacromolecules, including DNA, RNA and proteins in w/w microdroplets is closely related to their bio-activity. Despite the importance of this possible role of micro segregation, our understanding of the underlying physico-chemical mechanism is still unrefined. Further research to unveil the underlying mechanism of the localization of macromolecules in relation to their steric conformation in w/w microdroplets is needed.Principal findingsSingle-DNA observation of genome-size DNA (T4 GT7 bacteriophage DNA; 166kbp) by fluorescence microscopy revealed that DNAs are spontaneously incorporated into w/w microdroplets generated in a binary aqueous polymer solution with polyethylene glycol (PEG) and dextran (DEX). Interestingly, DNAs with elongated coil and shrunken conformations exhibit Brownian fluctuation inside the droplet. On the other hand, tightly packed compact globules, as well as assemblies of multiple condensed DNAs, tend to be located near the interface in the droplet.Conclusion and significanceThe specific localization of DNA molecules depending on their higher-order structure occurs in w/w microdroplet phase-separation solution under a binary aqueous polymer solution. Such an aqueous solution with polymers mimics the crowded conditions in living cells, where aqueous macromolecules exist at a level of 30–40 weight %. The specific positioning of DNA depending on its higher-order structure in w/w microdroplets is expected to provide novel insights into the mechanism and function of membraneless organelles and micro-segregated particles in living cells.

Radiation synthesis of poly(acrylic acid) nanogels for drug delivery applications – post-synthesis product colloidal stability

Abstract Synthesis of polymer nanogels (NGs) for biomedical applications is considered to be a very promising application in radiation engineering. Under high-dose pulse irradiation of dilute aqueous polymer solution, reactive species generated by water radiolysis can create multiple radicals on each macromolecule and consequently induce intramolecular cross-linking of polymer chains, resulting in NG formation. The obtained products are free from harmful monomers, initiators, and cross-linking agents, which makes them potentially applicable for drug delivery applications. One of the biggest challenges in handling and use of nanoparticles, however, is the colloidal stability, when aqueous suspensions are stored for prolonged periods. Therefore, development of the best protocols for the particular nanocarrier storage is key. To address this need, we have performed the prospective study in which we systematically assessed the influence of various processing and storage scenarios feasible in our lab, on the colloidal stability of the radiation-synthesized poly(acrylic acid) (PAA) NG particles in suspension. This allowed us to choose the optimal way of handling the product after its synthesis. We confirmed that none of the strategies we used and tested are substantially detrimental to our product. Filtration with 0.2-μm filters was proven sufficient for sample purification and prolonged storage in aqueous suspension did not exert a negative effect on the colloidal stability of particles suspension. We have also demonstrated that lyoprotectant-free lyophilization was suitable for our polymer nanoparticles. This is an important fact for further application of particles as nanocarriers for biologically active compounds such as targeting ligands or therapeutic moieties.

Preparation and polymerization analysis of poly-(alkenyl-based di-ionic ionic liquid)

In this study, bis-imidazole-containing ionic liquids (VDILs) featuring halide counteranions and substituted with different numbers of alkenyl groups were designed and synthesized. The VDILs were further subjected to a one-pot free radical polymerization in aqueous solution, forming hydrophobic PVDILs. GPC, FT-IR, XPS, and XRD were performed to determine the influence of the number and position of the alkenyl groups in the VDIL monomers on the molecular weight, molecular weight distribution, and polymeric structure of the PVDILs. The GPC results showed that the position of the alkenyl groups had a significant influence on the molecular weight of the PVDILs. The linker alkenyl group in the VDIL monomer was easier to polymerize than the alkenyl group connected to the N(1) atom of the imidazole ring of the VDIL due to the steric bulk of the counteranions, which mitigated cross-polymerization of the vinyl groups. As the interconnected polymeric network was being formed, the steric bulk of the anions hindered chain growth, resulting in a lower-than-expected molecular weight of PVDIL-3. XPS and FT-IR results indicated that there were still a certain number of alkenyl groups that remained in the PVDIL-1 and PVDIL-3 structures after polymerization, with the PVDIL-3 sample containing 3% more alkenyl groups than PVDIL-2. This study demonstrates a new method for the polymerization of alkenyl-based DILs and provides a foundation for the application of PDILs.

Synthesis, Characterization and Demulsification Performance of Polymethylamyldiallylammonium Chloride

The lipophilic modification of dimethyldiallylammonium chloride monomer (DMDAAC) with resulting excellent lipophilic performance can provide an effective way to improve the application performance of the resulting monomers and copolymers. In this paper, polymethylamyldiallylammonium chloride (PMADAAC) homopolymer was prepared by using methylamyldiallylammonium chloride (MADAAC) as the monomeric unit, 2,2’-Azobis(2-methylpropionamide) dihydrochloride (V50) as the initiator and ethylenediaminetetraacetic acid tetrasodium (Na4EDTA) as a metal ion complexing agent via an aqueous solution polymerization method. Using the intrinsic viscosity of the product as the inspection index, the polymerization reaction conditions were optimized by the response surface optimization method, and the optimum conditions obtained were: w(MADAAC)=70.2%, m(V50):m(MADAAC)=2.05%, m(Na4EDTA):m(MADAAC) =0.0141%, T 1=55.0 °C, T 2=60.0 °C and T 3=80.1 °C, with the reaction lasting 9 h (see below). The average value of the intrinsic viscosity ([η]) of the obtained product was 0.84 dL/g, and the monomer conversion degree (Conv.) was 72.77%. The molecular weight characterizations of PMADAAC showed that the highest M w of PMADAAC was 2.380 × 105 and its polydispersity index d(M w/M n) was 1.952 for optimum properties. The results indicated that the introduction of the amyl group could increase the lipophilicity of the diallyl quaternary ammonium salts based on its good water solubility. For the demulsification performance of simulated crude oil O/W emulsions, the demulsification degrees were 88.9% for PMADAAC, 83.6% for polymethylpropyldiallylammonium chloride (PMPDAAC) and 45.5% for polydimethyldiallylammonium chloride (PDMDAAC), all at the same intrinsic viscosity.

Instantaneous Degelling Thermoresponsive Hydrogel.

Responsive polymeric hydrogels have found wide application in the clinic as injectable, biocompatible, and biodegradable materials capable of controlled release of therapeutics. In this article, we introduce a thermoresponsive polymer hydrogel bearing covalent disulfide bonds. The cold aqueous polymer solution forms a hydrogel upon heating to physiological temperatures and undergoes slow degradation by hydrolytic cleavage of ester bonds. The disulfide functionality allows for immediate reductive cleavage of the redox-sensitive bond embedded within the polymer structure, affording the option of instantaneous hydrogel collapse. Poly(ethylene glycol)-b-poly(lactic acid)-S-S-poly(lactic acid)-b-poly(ethylene glycol) (PEG-PLA-SS-PLA-PEG) copolymer was synthesized by grafting PEG to PLA-SS-PLA via urethane linkages. The aqueous solution of the resultant copolymer was a free-flowing solution at ambient temperatures and formed a hydrogel above 32 °C. The immediate collapsibility of the hydrogel was displayed via reaction with NaBH4 as a relatively strong reducing agent, yet stability was displayed even in glutathione solution, in which the polymer degraded slowly by hydrolytic degradation. The polymeric hydrogel is capable of either long-term or immediate degradation and thus represents an attractive candidate as a biocompatible material for the controlled release of drugs.

Light-Induced In Situ Chain Extension and Critical Gelation of Benzophenone End-Functionalized Telechelic Associative Polymers in Aqueous Solution

Light-Induced In Situ Chain Extension and Critical Gelation of Benzophenone End-Functionalized Telechelic Associative Polymers in Aqueous Solution

Application of an Acrylic Polymer and Epoxy Emulsion to Red Clay and Sand.

The use of nontraditional soil stabilizers increases. Various new soil binding agents are under study to augment renewability and sustainability of an earth structure. However, despite increasing interest involved in red clay, there is minimal research investigating the stabilizing red clay with polymer. This paper presents the findings obtained by applying the acrylic polymer and epoxy emulsion as binding agent for red clay and that for sand. The epoxy–hardener ratio, amount of epoxy emulsion, and amount of polymer aqueous solution were manipulated to quantify their effects on red clay and sand, respectively. After compacting a pair of cylindrical samples of which diameter and height are 5 cm and 10 cm, respectively, it is cured for 3 and 7 days in a controlled condition. Each pair is produced to represent the engineering performance at each data point in the solution space. An optimal composition of the binding agents for red clay and that for sand mixture are identified by experimenting every data point. In addition, given lime into each sample, the maximum unconfined compressive strength (UCS) endured by red clay sample and that by sand sample are 2243 and 1493 kPa, respectively. The UCS obtained by the sample mixed with clay and sand reaches 2671 kPa after seven days of curing. It confirms that the addition of lime remarkably improves the UCS. When the clay–sand mixture, of which the ratio is 70:30, includes 5% lime, the UCS of the mixture outperforms. Indeed, these findings, i.e., the optimal proportion of components, may contribute to the increase of initial and long-term strength of an earth structure, hence improving the renewability and sustainability of the earth construction method.

Mussel-inspired superhydrophilic membrane constructed on a hydrophilic polymer network for highly efficient oil/water separation

HypothesisSuperhydrophilic/underwater superoleophobic membrane constructed by hydrophilic polymers possesses great advantage in the separation of oily waste water, due to its intrinsic oil-repellent property. The formation of hydration layer to repel and block oil is considered as the mechanism of underwater superoleophobicity and subsequent oil/water separation. Constructing a stable hydrophilic polymer network on the substrate surface would significantly improve the robustness of hydration layer. ExperimentsIn this work, a feasible and universal mussel-inspired dip-coating method was developed for constructing stable hydrophilic polymer network onto target substrate surface, via successively immersing substrate membranes into aqueous solutions of polydopamine (PDA) and catechol-functionalized hydrophilic polymer (CFHP). After pre-wetting with water, the polymer network would swell with water to form a thin and stable water film layer, serving as a barrier against oil penetration. FindingsThe as-prepared CFHP/PDA modified membranes exhibit outstanding performance in separating various oil/water mixtures and oil-in-water emulsions stabilized by surfactants, with separation flux up to 5641.1 L·m−2·h−1 and separation efficiency achieving 99.98%. The surface modification method developed in this work can be easily extended to various materials and membrane systems, for achieving a variety of practical applications such as industrial wastewater treatment.