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Dynamic covalent bonds, particularly the ones exhibiting bond-breaking and bond-regeneration under ambient conditions, are attractive for the design and application of smart materials. This study demonstrates that the Meldrum's acid-based ketene chemistry is an effective approach to build up dynamic N-hindered amide bonds effectively workable at ambient conditions and under sunlight. The corresponding polyamides have been applied for sunlight-driven and self-repairing polymeric materials, and anticorrosion coatings. In addition to exhibiting sunlight-driven and self-repairing features on scratched surfaces, a high anticorrosion recovery of about 97% has been recorded. A smart anticorrosion coating requiring less maintenance is demonstrated.

This work reports a study on employing lignin in the formation of a selective layer of thin-film composite (TFC) membranes for pervaporation desalination. The TFC membranes with lignin-based separation layers are fabricated using a solution-casting method. With a reduction of the separation layer thickness to about 0.47 μm, a water permeation flux of 18.5 kg h−1 m−2 and a salt rejection of above 99.95% have been recorded on the lignin based TFC membrane with a feeding solution of 3.5 wt% NaCl(aq) at 45 °C. The membrane also exhibits high stability in long-term operation tests and can be applied for operations on high salinity water (up to 15 wt% NaCl(aq)). While being applied to seawater desalination, the membrane exhibits a water permeation flux of about 20.4 kg h−1 m−2 and a salt rejection of above 99.95% at 45 °C. A membrane separation process, which uses sustainable materials for salty wastewater treatments and water resource generation, has been demonstrated.

Electrospun nanofibers of polybenzoxazines (PBzs) were fabricated using an electrospinning process and crosslinked by a sequential thermal treatment. Functionalization by the direct sulfonation process followed after the post-electrospinning modification treatment. The first stage of experiment determined the effects of varying the concentration of sulfuric acid as the sulfonating agent in the sulfonation reaction under ordinary conditions. The second stage examined the mechanism and kinetics of the sulfonation reaction using only concentrated H2SO4 at different reaction time periods of 3 h, 6 h, and 24 h. The mechanism of the sulfonation reaction with PBz nanofibers was proposed with only one sulfonic acid (–SO3H) group attached to each of the repeating units since only first type substitution in the aromatic structure occurs under this condition. The kinetics of the reaction exhibited a logarithmic correlation where the rate of change in the ion exchange capacity (IEC) with the reaction time increased rapidly and then reached a plateau at the reaction time between 18 h and 24 h. Effective sulfonation was confirmed by electron spectroscopy with a characteristic peak associated with the C–S bond owing to the sulfonate group introduced onto the surface of the nanofibers. ATR-FTIR spectroscopy also confirmed these results for varying reaction times. The SEM images showed that sulfonation has no drastic effects on the morphology and microstructure of the nanofibers but a rougher surface was evident due to the wetted fibers with sulfonate groups attached to the surface. EDX spectra exhibited sulfur peaks where the concentration of sulfonate groups present in the nanofibers is directly proportional to the reaction time. From surface wettability studies, it was found that the nanofibers retained the hydrophobicity after sulfonation but the inherent surface property of PBz nanofibers was observed by changing the pH level of water to basic, which switches its surface properties to hydrophilic. The thermal stability of the sulfonated nanofibers showed almost the same behavior compared to non-sulfonated nanofibers except for the 24 h sulfonation case, which has slightly lower onset temperature of degradation.

Objective To investigate the relationship of TSH levels and TPOAb status before 20 weeks gestation with adverse pregnancy outcomes. Methods A total of 2885 pregnant women who underwent regular prenatal examination in Zhujiang Hospital of Southern Medical University during April 1, 2017 to October 31, 2018 were retrospectively analyzed. According to the TSH level before 20 weeks of gestation, they were classified into normal TSH (0.1 mU/L≤TSH0.05). In multi-factor logistic regression analysis results show that the risk of a preterm birth in group D, group E, group F were higher than that in control group, the risk of gestational diabetes in group F was higher than that in control group (OR>1, P

Employing crosslinkable polybenzoxazine (PBz) as the precursor, thermosetting resin based porous membranes possessing interconnected pores are prepared and applied for organic solvent phase microfiltration. The effects of the used solvents and additives on formation of interconnected pores in the obtained membranes are studied. Employing a solvent or an additive, which could build up hydrogen bonding based networks in the PBz solution, favors the formation of interconnected pores in the resulting membranes, as the polymer-solvent and polymer-additive networks could retard the mass transfers to result in a delayed demixing mechanism in the phase separation processes. 2-Pyrrolidone and lignin is an effective solvent and additive for formation of crosslinked PBz with interconnected pores. The crosslinked PBz/lignin membrane shows a high resistance to solvents, a high surface hydrophobicity with a water contact angle of about 141°, a high porosity of 70%, and a small pore size of 0.55 ± 0.05 μm. While being applied to a gravity-driven separation on a surfactant-stabilized water-in-toluene emulsion, the membrane demonstrates a flux of 278 ± 21 Lm−2h−1 and a water content of 474 ± 3 ppm of the permeated toluene, which is close to the natural solubility of water in toluene (411 ppm). This work has explored a new class of thermosetting resin based membrane with interconnected pores suitable for organic solvent microfiltration.

In the present study, poly(ethylene glycol) (PEG) functionalized carbon nanotubes (CNT-PEG) were used as nanoadditives to fabricate hybrid membranes for enhanced CO2 separation in Pebax 1657 matrix...

This work reports the utilization of lignin, a renewable and biomass-based material, as an effective modifying agent for thermally stable and hydrophobic membranes based on crosslinked polybenzoxazine (CRPBz) to significantly enhance their permeation fluxes in pervaporation dehydration tests. Lignin could involve in the crosslinking reaction of polybenzoxazine so as to be chemically embedded in the polymer networks. In addition to the inherent hydrophilicity of lignin, lignin could release the hydrophilic groups (phenol and tertiary amine) of crosslinked polybenzoxazine with formation of hydrogen bonding with crosslinked polybenzoxazine, consequently to significantly enhance the hydrophilicity and water permeation fluxes of the studied membranes. With feeding a 70 wt% tetrahydrofuran aqueous solution at 25 °C, lignin modification increases the permeation flux of the CRPBz based membrane from 237 g m−2 h−1 to 490 g m−2 h−1 and separation factor from 11,920 to 19,440. Lignin modification significantly enhances the water permeation flux of the membrane without scarifying separation ability. A 3.4-folds of pervaporation separation index (PSI, the product of permeation flux and separation factor) has been demonstrated with the lignin modification. Similar performance has also been recorded on the tests on a 70 wt% isopropanol aqueous solution. The effect of lignin has been attributed to increase the membrane hydrophilicity for facilitating water permeation. The results demonstrate the wide application scopes of the lignin-modified CRPBz based membranes in pervaporation dehydration based on their high stability and hydrophilicity.

Simple modification by thermal treatment is the commonly used approach to enhance the performance of electrospun fibers. This was investigated in the thermal treatment of polybenzoxazine (PBz) fibers blended with sulfur copolymers (SDIB) to determine the effect of varying treatment conditions on the microstructure and morphology of PBz fibers with the effect of incorporating sulfur functional groups on resulting properties. Mechanical properties of PBz are greatly improved by thermally-induced ring-opening polymerization (ROP) of the oxazine ring. Blending with sulfur copolymers (SDIB) could have beneficial effects on endowed features on fibers but could also affect the resulting properties of SDIB-blended PBz fibers during crosslinking reactions. Fiber mats were fabricated by electrospinning of PBz (10 wt%) blended with SDIB (10 wt%). Physical modification with varying conditions of sequential thermal treatment were evaluated and compared to the conditions applied on pristine PBz fibers. Changes in morphology and microstructure of fibers after modification were analyzed through scanning electron microscopy (SEM) while elemental compositions were identified after varying the conditions of thermal treatment. Adjustment of treatment conditions using two-step temperature sequential thermal treatment with higher temperatures of 160 °C and 240 °C showed significant changes in microstructure and morphology of fibers. Lower temperatures of 120 °C and 160 °C exhibited microstructure and morphology of fibers which affected the fiber diameter and fiber networks. Cross-sectional SEM images also confirmed the adversed effect of high-temperature treatment conditions on fibrous structures while low-temperature treatment retained the fibrous structures with more compact and stiff fiber networks. SDIB-blended PBz fibers were also evaluated by TGA and DSC to correlate the changes in structure and morphology with the thermal stability and integrity of blended SDIB/PBz fibers as compared to pristine PBz with the effect of change in treatment conditions. Fiber strength indicated slower weight loss for blended fibers and higher onset temperature of degradation which resulted in more thermally stable fibers.

Crosslinked membranes exhibiting in situ crosslinking and micro-cavity generation in membrane fabrication processes have been reported for pervaporation dehydration on methanol aqueous solutions. Meldrum's acid (MA) modified poly(2,6-dimethyl-1,4-phenylene oxide) (PPO-MA) with various MA contents have been synthesized and well characterized with Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. PPO-MA polymers could perform thermally-induced self-crosslinking reaction through cycloaddition reaction between ketene groups generated from MA thermolysis reaction. Meanwhile, MA thermolysis reaction evolves CO2 and acetone molecules which contribute to generation of micro-cavities in the formed membranes. Consequently, compared to the pervaporative separation performance of pristine PPO membrane (permeation flux: 290 g m−2 h−1; separation factor: 57) on a 90 wt% methanol solution at 25 °C, the crosslinked PPO-MA membrane shows a separation factor of 809 with a slight decrease in permeation flux to about 226 g m−2 h−1. Based on the pervaporation separation index (PSI, the product of permeation flux and separation factor), an 11-times enhancement has been achieved.

This study aims to elucidate the effect of magnetic graphene oxide (GO) alignment in a polymer matrix on the ionic conduction and methanol barrier properties of the resulting composites. Magnetic iron oxide (Fe3O4) nanoparticles were fabricated and anchored on GO nanosheets. The magnetic GO-Fe3O4 nanofillers were incorporated into a quaternized polyvinyl alcohol (QPVA) matrix to form a polymeric composite. By applying a magnetic field (MF) along the in-plane direction during the drying and film formation steps, the GO-Fe3O4 nanosheets were aligned in an orientation parallel to the direction of the MF and connected to each other in elongated domains, as confirmed using transmission electron microscopy, field emission scanning electron microscopy/energy dispersive X-ray spectroscopy mapping, and laser scanning microscopy. The MF-aligned QPVA/GO-Fe3O4 electrolyte possessed higher conductivity and lower permeability than the un-aligned QPVA/GO-Fe3O4 membrane and pristine QPVA film. The aligned QPVA/GO-Fe3O4 composite exhibited a peak power density of 172.4 mW cm−2 at 60 °C, which is higher than those of the composite without the MF treatment (67.7 mW cm−2) and the pristine QPVA (50.3 mW cm−2). This research demonstrates the extraordinary benefits of MF assisted GO-Fe3O4 nanofillers in facilitating the ion conduction and barrier property of a polymeric composite at 0.1% filler loading.

On the basis of the reaction between ketene and alcohol groups to result in an ester linkage and Meldrum's acid as an effective precursor of ketene group, a bifunctional aliphatic Meldrum's acid compound (BisMA) is synthesized and used as a monomer to react with ethylene glycol and glycerol for the preparation of linear and cross-linked aliphatic polyesters, respectively. A 62 and 35 wt % of biodegradation fraction have been recorded on the linear and cross-linked aliphatic polyesters after an 8 week biodegradation test, respectively, to demonstrate the good biodegradability of the synthesized polyesters. In addition to conventional linear biodegradable polyesters, this synthetic route also provides a new and convenient method for preparation of cross-linked biodegradable polyesters. The types of the required monomers and reaction methods for preparation of the cross-linked biodegradable polyesters are similar to those used for conventional thermosetting resins. An integration of biodegradable polymers and thermosetting resins in polymer chemistry has been demonstrated.

Polymeric membranes, compared with their inorganic counterparts, usually suffer from insufficient solvent resistance and thermal stability. In this study, an organic solvent–resistant thermally stable polymeric microfiltration membrane is prepared with a self-crosslinkable polybenzoxazine as a precursor. The obtained membranes have pore sizes of approximately 3.4 µm and superior antiswelling stability in organic solvents; thus, they exhibit excellent performance in terms of size-selective particle separation inorganic phases. The membranes are also effective in the gravity-driven separation of surfactant-stabilized water-in-oil emulsions. The water contents of the filtrate oil phases are close to the natural solubility of water in the solvents; for example, a water content of 350 ppm, which is comparable to the water solubility in toluene (330 ppm), has been found in the filtrate toluene from water-in-toluene emulsions. Moreover, the membrane demonstrates pH-induced changes in oil and water selectivity in oil–water separations. When treated with a strong base solution, the oil-selective membrane becomes water-selective and exhibits favorable performance in terms of separating organic solvents from surfactant-stabilized oil-in-water emulsions. These features effectively extend the application scope of the prepared membrane for oil–water separations.

Efficient separation of both immiscible and emulsified oil/water mixtures is achieved by collaborating polybenzoxazine (PBz) with commercially available substrates in this work. Possessing intrinsic low surface energy, crosslinked PBz coating endows various substrates (sponges, filter paper, and ceramic membrane) with surface hydrophobicity and oleophilicity and enables oil-selective penetration. The as-prepared sponge (CR-PBz-sponge) could effectively remove oil floating on water and oil under water with high absorption capacities (up to 120 times its own weight) and good recyclability. The PBz-coated filter paper (CR-PBz-filter paper) is applicable to efficient large-scale oil/water separation based on its high fluxes (about 5000–6000 L m −2 h −1 ) on a wide range of organic solvents and oils. CR-PBz-ceramic membrane shows great effectiveness in removal of tiny water droplets from water-in-oil emulsion and reduces the water contents of the treated oil to the levels of the natural water solubility of the oils. Based on its separation efficiency, processing simplicity, substrate versatility and low cost, the technique of using PBz as coating material to fabricate oil/water separation materials is promising in practical and industrial concerns.

The instability of the lithium and electrolyte interface as well as the lithium dendrite growth could be the major issues for the practical application of lithium metal batteries. This work provides an effective solution to the issues with employing a crosslinked polyimide for preparation of thermally-stable separators. The effect of porous morphology of the separators from various porous membrane-formation methods on their electrochemical properties and the corresponding cell performance has been examined and discussed. The separator made with the non-solvent-induced phase separation (NIPS) has an asymmetric structure possessing a macro-void matrix and a relatively dense layer containing nanoscale pores. This top layer plays as a barrier to prevent the lithium dendrite growth and penetration into the separator. The nanoscale pores in the top layer allows ion migration to ensure the high ionic conductivities. The cells employing the prepared separators are capable of operating at high C rate (10C) and show high stability in cycle tests. A straightforward approach for thermally-stable separators with self-protective layers and inhibition of lithium dendrite growth has been demonstrated.

Membrane pervaporation provides an effective approach for production of desalinated water and treatments of salted water. The water permeation fluxes through the membranes could be the key issue for practical systems. In this work, a surface engineering through introduction of lotus-leaf biomimicked structures and chemical deprotonation has been performed on poly(vinyl alcohol) membrane surfaces. The increased surface area and hydrophilicity of the membranes significantly enhance water dissolution into the membrane, so as to bring a 2.8 times of water permeation flux to the membrane. In addition to a high thickness-normalized water flux of 386 kg-μm h−1 m−2, the surface-engineered PVA membrane also exhibit ability for desalination on high salinity water (15 wt% NaCl(aq)). The surface-engineering method could be integrated with other approaches for membrane modification to exhibit synergistic effect on enhancements of membrane separation performance.

The performance of pervaporation dehydration of a crosslinked polybenzoxazine membrane (CR-PBz-M) on isopropanol (IPA) aqueous solutions has been studied. Compared to the feature showing in dry state, CR-PBz-M exhibits a change in micropore size distribution from a single distribution to a bimodal pattern in wet state being swollen with the feeding solutions. The presence of two groups of micropores in different sizes attributes to the high pervaporation dehydration performance of the membrane, in which the small micropores resist to the permeation of IPA molecules so as to contribute to the high membrane selectivity and the large micropores and high micropore volume fraction contribute to the high permeation fluxes. This feature of CR-PBz-M demonstrates an in situ self-promoted characteristic for pervaporation dehydration membranes. A permeation flux of 330 g h−1m−2 and a 100% of water in the permeate side has been recorded on pervaporation dehydration on a 70 wt% IPA aqueous solution.

This work reports the synthesis of a poly(styrenesulfonic acid)-grafted Nafion (Nafion-g-PSSA) copolymer through atom transfer radical polymerization (ATRP) using Nafion chains as a macroinitiator. The C–F linkages of the –CF– groups and –CF2–SO3H groups serve as the initiating sites for the ATRP of the employed styrenic monomer. The PSSA chains further enhance the hydrophilic–hydrophobic microphase separation in the Nafion-g-PSSA based membrane, demonstrating relatively large ionic cluster domains and small distances between the hydrophilic and hydrophobic domains compared to the neat Nafion based membrane. Consequently, Nafion-g-PSSA is an effective additive for the fabrication of Nafion-based proton exchange membranes. With an optimum fraction of 15 wt% Nafion-g-PSSA, the modified Nafion membrane exhibits a proton conductivity of about 97 mS cm−1 (95 °C, RH = 100%), which is larger than the values measured on the recast neat Nafion membrane (53 mS cm−1) and a commercial Nafion 212 membrane (88 mS cm−1). The Nafion-initiated ATRP is effective for preparation of Nafion derivative materials for proton exchange membranes.

This study proposes a self-healing membrane for pervaporation separation, with a focus on in situ repairing damaged membranes within the separation module. The self-healing membrane is fabricated with a thermally-reversible crosslinked polybenzimidazole (PBI) based on a newly prepared furan-functionalized PBI (PBI-FA) and a commercially-available bismaleimide (BMI) as raw materials. The thermally reversible crosslinked property and self-healing ability of the PBI-FA/BMI membrane have been evaluated using morphological and mechanical tests. The membrane demonstrates a high separation efficiency level (water concentration on the permeate side (Cwater > 99.99 wt%)) and moderate permeation flux (117 ± 11 g m−2 h−1) for pervaporation dehydration with a 70 wt% isopropanol aqueous solution. Membrane damage caused by a knife incision engenders a loss of separation function. However, recovery of the separation function with a Cwater of approximately 94.27 ± 0.14 wt% (self-healing efficiency: 94%) is achievable when the membrane was subjected to the self-healing process. Results from a 50 day long-term stability test indicate that self-healing efficiency could reach 97%, with a recovered Cwater of approximately 96.83 ± 0.24 wt%. The self-healing process can prolong membrane life and reduce cost, effort, and wasted resources associated with total membrane replacement.

Nafion chains have been reacted onto graphene oxide (GO) through atom transfer radical addition (ATRA) reaction between the C–F groups of Nafion and the C=C groups of GO. The obtained nanohybrids of GO and Nafion (GO-Nafion) are characterized with Fourier transform Infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy to support the performance of the ATRA reaction between GO and Nafion and the chemical structure of GO-Nafion. Morphological observation on GO-Nafion with transmission electron microscopy and atomic force microscopy further demonstrates the organic-inorganic hybrid nanosheet structure of GO-Nafion. GO-Nafion has been used as a nanoadditive for fabrication of Nafion-based nanocomposite proton exchange membranes for fuel cells. Compared to the neat recast Nafion membrane, addition of GO-Nafion results in a 1.6-folds of proton conductivity to the corresponding nanocomposite PEM. The single cell tests on the nanocomposite PEM also exhibit an about 35–40% increase in the fuel cell performance.

Electrospun quaternized polyvinyl alcohol (Q-PVA) nanofibers are prepared, and a potassium hydroxide (KOH)-doped nanofiber mat demonstrates enhanced ionic conductivity compared with a dense Q-PVA film with KOH doping. The Q-PVA composite containing 5.98% electrospun Q-PVA nanofibers exhibits suppressed methanol permeability. Both the high conductivity and suppressed methanol permeability are attributed to the quasi-coaxial structure of the electrospun nanofibers. The core of the fibers exhibits a more amorphous region that forms highly conductive paths, while the outer shell of the nanofibers contains more polymer crystals that serve as a hard sheath surrounding the soft core. This shell induces mass transfer resistance and creates a tortuous fuel pathway that suppresses methanol permeation. Such a Q-PVA composite is an effective solid electrolyte that makes the use of alkaline fuel cells viable. In a direct methanol alkaline fuel cell operated at 60 °C, a peak power density of 54 mW cm−2 is obtained using the electrospun Q-PVA composite, a 36.4% increase compared with a cell employing a pristine Q-PVA film. These results demonstrate that highly conductive coaxial electrospun nanofibers can be prepared through a single-opening spinneret and provide a possible approach for high-performance electrolyte fabrication.

The ultra-micropores in polymeric membranes play a key role on the separation performance. This work demonstrates that liberation of small molecules in the membrane formation process is an effective approach to create ultra-micropores in a narrow size distribution in polymeric membranes. A crosslinkable Meldrum's acid derivative is used as the effective agent that liberates CO 2 and acetone molecules in the polyimide (PI) membrane formation process and to chemically crosslink the PI-based membranes. Compared to the neat PI membrane, the modified membrane shows small ultra-micropores in a narrow size distribution measured with a positron annihilation lifetime spectroscopy. Consequently, the modified PI membranes become highly-selective toward H 2 gas. With a small reduction of permeability (from 23.1 to 15.5 barrer), the ideal selectivity for H 2 /N 2 (155) and H 2 /CO 2 (5.3) of the modified PI membrane are about 3-fold of the values recorded with the neat PI membrane. In a binary mixed gas test at 20 atm, the modified PI membrane shows a high H 2 permeability of 24.5 barrer and a high H 2 /CO 2 selectivity 14.1. The results demonstrate an effective and simple method to enhance the gas separation performance of polymeric membranes with modulation of the cavity sizes and size distribution of the membranes.

Three approaches for directly reacting chemical agents and polymer chains with multi-walled CNTs (MWCNTs) are presented, including (i) sequential atom transfer radical addition/polymerization to MWCNTs; (ii) ozone-mediated addition reaction to MWCNTs; and (iii) Diels–Alder reaction-mediated MWCNT functionalization. On the basis of the reaction routes, the scopes and functions of MWCNT-based nanohybrids and nanocomposites have been extended.

This study investigates the application of a polyvinyl alcohol (PVA)/functionalized carbon nano-tubes (m-CNTs) composite in alkaline direct ethanol fuel cells (ADEFC). The m-CNTs are functionalized with PVA using the ozone mediation method, and the PVA composite containing the modified CNTs is prepared. Adding m-CNT into the PVA matrix enhances the alkaline uptake and the ionic conductivity of the KOH-doped electrolyte. Meanwhile, the m-CNT-containing membrane exhibited a lower swelling ratio and suppressed ethanol permeability compared to the pristine PVA film. The optimal condition for the ADEFC is determined to be under operation at an anode feed of 3 M ethanol in a 5 M KOH solution (at a flow rate of 5 cm3 min−1) with a cathode feed of moisturized oxygen (with a flow rate of 100 cm3 min−1) and the KOH-doped PVA/m-CNT electrolyte. We achieved a peak power density value of 65 mW cm−2 at 60 °C, which is the highest among the ADEFC literature data and several times higher than the proton-exchange direct ethanol fuel cells using sulfonated membrane electrolytes. Therefore, the KOH-doped PVA/m-CNT electrolyte is a suitable solid electrolyte for ADEFCs and has potential for commercialization in alkaline fuel cell applications.

Polymers with integrated functions might have greater possibility to meet the various requirements for a specific application. This work demonstrates a molecule-design based development of multi-functional polymers with a branched polysiloxane polymer which exhibits integrated functions including good thermal stability, high thermal resistance, high flame retardancy and self-extinguishing properties, high transparency in the ultraviolet to blue light region, and relatively high RI value (1.59). This multi-functional polymer is potentially applicable in high performance LED encapsulants.

Reactive blends of polymers provide a convenient and effective approach to prepare functional materials exhibiting integrated or synergistic properties. In this work we report the first electrically-induced self-healing anticorrosion material composed of (a) an electrically-responsive crosslinked polymer of ferrocene modified poly(glycidylmethacrylate) and a difunctional β-cyclodextrin compound and (b) an electroactive polymer of aniline trimer. The two components exhibit synergistic effects on both self-healing and anticorrosion properties. A 94% of protection efficiency for anticorrosion and a 92.5% self-healing recovery of anticorrosion protection efficiency have been recorded.

Carbon nanotubes (CNTs) could be an effective additive for polymeric anticorrosion coatings due to their electrical conductivity. For enhancement of the interfacial compatibility and dispersion homogeneity of CNTs in the polymer matrix, functionalization of CNTs with matrix polymer is attractive. In this work, polybenzoxazine (PBz) as the matrix polymer is chemically bonded to multiwalled CNT (MWCNT) without altering the benzoxazine reactive groups through the radical transfer and addition reaction. The PBz-functionalized MWCNT (PBz-MWCNT) has been carried out with FTIR, XPS, and Raman spectroscopies. The PBz fraction of PBz-MWCNT is also quantitatively and qualitatively observed with thermogravimetric analysis and high resolution TEM, respectively. PBz-MWCNT has been utilized as an additive for crosslinked PBz based anticorrosion coatings for cold roll steel. An effective protection efficiency of 99.91% with an ultralow corrosion rate of 0.179 μm y−1 is recorded with the anticorrosion coating with 3.0 wt% of PBz-MWCNT. As the neat crosslinked PBz based anticorrosion coating shows a 90.28% protection efficiency and a 20 μm y−1 corrosion rate, the effectiveness of PBz-MWCNT on enhancement of the anticorrosion coating of crosslinked PBz is demonstrated.

Elemental sulfur (S8) is largely available resource as by-product from petroleum refining process which is causing “excess sulfur problem’ due to its limited usage. The utilization of sulfur as valuable material will not only address environmental concerns but provide cost-effective ways of consuming this huge amount of waste to develop new high-value, high-volume products. One facile synthetic method of utilizing sulfur directly as feedstock to produce polymeric material is inverse vulcanization. In this study, sulfur copolymers (SDIB) was synthesized via inverse vulcanization from S8 and processed into polymer blend with component polymers, polybenzoxazine (PBz) and poly(methyl methacrylate) (PMMA) to show its potential processability into polymer blend. Initially, synthesis of SDIB with varying feed ratios of sulfur to comonomer 1, 3-diisopropenylbenzene (DIB) was evaluated for its resulting properties. Spectroscopy showed copolymerization reactions occurred based on the change in characteristic absorption peaks (C=C-H, C=C, C-H) present in the spectra. Thermogravimetric analysis (TGA) indicated that SDIB is more thermally stable with the increase in onset temperature of degradation. Differential scanning calorimetry (DSC) profile exhibited new single glass transition temperature (Tg) that slightly increased with higher DIB ratio indicating evolution of microstructures of copolymers produced. The processability of SDIB into polymer blend was investigated by using SDIB (50 wt% S) with PBz and PMMA. Blending process using simple mixing technique with solvents was carried out for SDIB/PBz (10/10 wt%) and SDIB/PMMA (7.65/7.65 wt%) blend compositions. The results of this study demonstrated that polymercopolymers interactions influenced the phase structure and behaviour with polymer blend of SDIB/PBz showing higher degree of miscibility with more homogeneous and transparent blend as compared to SDIB/PMMA blend. The suitability of polymer blend in electrospinning of nanofibers could provide variety of new applications for SDIB.

Deciduous teeth are the first dentition of humans and play an important role in children's physical and mental development. Dental caries are one of the most common oral diseases in children. According to the data of the World Health Organization, 60%-90% of school children worldwide develop dental caries. In China, dental caries of primary teeth feature high incidence and low rate of visits. Without timely treatment, the deep caries lesions of primary teeth can lead to teeth defect, pulpitis, apical periodontitis, and maxillofacial space infection. Moreover, the premature loss of deciduous teeth can cause malocclusion and eruption disorder of subsequent permanent teeth. These conditions all cause considerable effects on children's oral health and physical and mental development. Performing active and effective measures to treat deciduous teeth with deep caries lesions is important to maintain the integrity and normal physiological function of dentition and facilitate normal eruption of permanent teeth. The current situation of indirect pulp therapy in China was studied in this paper. Basic concepts, including indirect pulp capping, interim therapeutic restoration, partial caries removal, stepwise caries removal, and atraumatic restorative therapy, have been defined by consulting domestic and foreign literature. A theoretical basis for improving the clinical pathway of deciduous teeth with deep caries lesions is provided by explaining the technical connotation and therapeutic importance of indirect pulp therapy in primary teeth.乳牙是人类的第一副牙齿，其正常萌出建并行使生理功能对儿童的身心发育具有重要意义。乳牙龋病是儿童慢性疾病之首，是儿童口腔医学临床最常见的疾病之一。根据世界卫生组织调查数据显示，世界范围内60%~ 90%的学龄儿童患有龋病。乳牙龋病在我国具有患龋率高，就诊率低下的特点，如不及时治疗，可导致牙体组织缺损、生理间隙丢失、牙髓和根尖周病变及颌面间隙感染，严重者可致乳牙早失并伴发牙列畸形及后续恒牙萌出障碍等不良结果，影响儿童口腔健康及身心发育。因此，对深龋乳牙采取积极有效的治疗措施对保存必要乳牙及其牙髓活力，恢复正常生理功能，维持牙列完整性，诱导后续恒牙正常萌出建具有重要意义。本文从目前深龋乳牙间接牙髓治疗的研究认识现状出发，通过文献资料收集整理，对间接牙髓治疗、间接盖髓术、暂时性保髓充填、部分去龋法、分步去龋法和非创伤性修复治疗等相关概念进行了对比分析，阐明了乳牙间接牙髓治疗的技术内涵和治疗意义，对乳牙深龋的临床治疗路径完善提供了理论依据。.

Multifunctional methacrylated polyhedral oligomeric silsesquioxanes (MMA-POSS) and furfurylamine (FA) are utilized as the monomers to demonstrate an example of utilization of nanosized inorganic molecule as a reactive building block in preparation of nanohybrids materials. Both of the MA-amine Michael addition and MA-furan Diels–Alder (DA) reaction occur between the two monomers and contribute to build up the hybrid structures of the resulting materials. Based on the strong interaction between the POSS units, the nanohybrids materials exhibit self-assembled lamellar structures with a spacing width of about 455 nm. Moreover, the residual methacrylate groups of the POSS-based hybrid materials make them are thermally crosslinkable. The corresponding crosslinked nanocomposite exhibits thermally-induced self-healing ability based on the thermally-reversible MA-furan DA adducts built in the nanocomposites structure.

Chemical modification has been carried out on polybenzimidazole (PBI) membranes for pervaporation dehydration on tetrahydrofuran (THF)/water mixtures. The PBI membrane crosslinked with 30 wt% of a polybenzoxazine (CR-PBI-30) shows good stability and high separation performance for pervaporation dehydration on the THF aqueous solutions in a wide range of concentrations above 50 wt%. Incorporation of poly(styrene sulfonic acid) (PSSA) chains to CR-PBI-30 membrane surface increases the surface hydrophilicity and water dissolution/absorption of the resulting membrane (CR-PBI-30-PSSA), so as to increase its water permeability without sacrificing membrane selectivity. The CR-PBI-30-PSSA membrane shows extremely high separation factors (the water concentrations at the permeate side ( C w )>99.99 wt%) and moderate permeation fluxes (about 180 g h −1 m −2 ) for pervaporation dehydration on the THF aqueous solutions in concentrations above 80 wt%. The membrane also shows a C w >97.5 wt% and a water flux of 220 g h −1 m −2 for a 70 wt% THF aqueous solution. This work demonstrates an effective approach to prepare membranes for pervaporation dehydration on aqueous solutions of high polar solvents, especially for the feed solutions possessing high water contents.

Hierarchical poly(vinylidene difluoride) (PVDF) electrospun fiber mats anchored with flower-like CuO spheres (F–CuO@PVDF) have been prepared in a one-step redox reaction mediated process using copper foil as the copper source at a low temperature of 80 °C. Structural and morphological studies have been carried out by X-ray diffraction, scanning electron microscopy, and high resolution transmission electron microscopy. The optimized reaction conditions have been studied and discussed in detail. The amount of flower-like CuO on the F–CuO@PVDF has been gravimetrically determined to be 10.4 μg cm−2. The obtained F–CuO@PVDF could be utilized as a catalytic separation membrane and has shown effective catalytic ability and photostability for the photodegradation of rhodamine B (10−5 M in aqueous solution) in cycled tests. Catalyst separation, recovery, and regeneration are not necessary for F–CuO@PVDF in the cycled tests.

Surface-initiated atom transfer radical polymerization has been performed on poly(vinylidene fluoride) electrospun nanofibers (PVDFNF) to incorporate poly(styrenesulfonic acid) (PSSA) chains tethered on PVDFNF surfaces. The obtained PSSA-g-PVDFNF nanofibers are used as reinforcement for Nafion to prepare Nafion/PSSA-g-PVDFNF composite membrane (Nafion/NF-CM). The PSSA chains tethered on the nanofiber surfaces improve the interfacial compatibility between the nanofiber reinforcement and the Nafion matrix, and might provide a proton-conducting pathway along the nanofibers. As a result, the proton conductivity of Nafion/NF-CM membrane is 2.5-fold of the value recorded with the nanofiber-free recasting Nafion membrane. The H2/O2 single cell employing Nafion/NF-CM membrane shows a maximum power density of 770 mW cm−2 which is 1.5-fold of the value recorded with the commercial Nafion 212 membrane and a current density at 0.6 V of 940 mA cm−2 which is about 2.7-fold of the value recorded with Nafion 212. The Nafion/NF-CM membrane is also suitable for direct methanol fuel cell, in which it could be operated at a 5 M methanol solution to show a cell performance of 91.2 mW cm−2 for maximum power density and 464 mA cm−2 for current density at 0.2 V, which are about 1.5-fold of the values recorded with the commercial Nafion 117 membrane at 2 M methanol solution.

Surface-modification of polybenzoimidazole (PBI) membrane with chitosan chains has been performed using 4-isocyanato-4′-(3,3′-dimethyl-2,4-dioxo-azetidino)diphenylmethane (IDD) as a coupling agent to build up chemical linkages between the PBI membrane surface and chitosan chains. Incorporation of chitosan chains to PBI membrane surface increases its surface hydrophilicity and enhances its performance of pervaporation dehydration on isopropanol aqueous solutions. The surface chemical structure of the chitosan-modified PBI membrane (PBI-CS) has been characterized with attenuated total reflectance Fourier transform infrared and X-ray photoelectron spectroscopies. The scanning electron micrographs of PBI-CS indicate the surface reaction between PBI and IDD might take place at the top surface of the PBI matrix in a thickness of about 2 μm as the PBI membrane is swollen with the used solvent. PBI-CS is effective for pervaporation dehydration on isopropanol aqueous solutions in a wide concentration range from 30 to 90 wt%. The chitosan layer increases the dissolution rate of water into the PBI-CS membrane so as to simultaneously increase the water permeability and selectivity of the membrane. PBI-CS shows high pervaporation separation indexes which are about 3.9-fold of the value measured with the neat PBI membrane.

Nanocomposites of thermally stable polybenzimidazole (PBI) containing small amounts ( −2 at 90 °C. These KOH-doped PBI/CNT composites have the potential to be used in high temperature alkaline fuel cell applications.

Surface modification of poly(vinylidene fluoride) (PVDF) membrane is performed for preparation of multiple stimuli-responsive membrane. Poly(N-isopropylacrylamide) (PNIPAAm), poly(acrylic acid), and Fe 3 O 4 nanoparticles are incorporated to the PVDF membrane surface to bring temperature-, pH-, and magnetism-responsive property to the membrane, respectively. The chemical structures and surface morphology of the modified PVDF membrane have been characterized with reflectance Fourier transform infrared, X-ray photoelectron spectroscopy, and scanning electron microscopy. The stimuli-responsive property of the membrane has been examined with the change of the water permeation fluxes. A dramatic change of water permeation flux appear at about 30 and 42 °C under the operation at pH=3.7 and pH=6.6, respectively The results demonstrates the dual temperature- and pH-responsive characteristic of the membrane. Moreover, incorporation of the magnetic Fe 3 O 4 nanoparticles to the membrane surface makes the membrane becoming a magnetism-responsive material and brings the magnetothermal property to the membrane. Under an alternating magnetic field (100 kHz) for 5 min the membrane has shown a temperature increase from 29 to 40 °C due to the magnetothermal effect. The possibility to trigger the temperature-responsive property of the membrane with a remote magnetic field manner has been demonstrated. The temperature- and magnetism-responsive property also provide a driving force for release of protein foulants from the membrane surface in bioseparation. As a result, the surface-modified PVDF membrane shows multiple stimuli-responsive characteristics and high efficiency of membrane clean in protein separation.

In this work, multi-walled carbon nano-tubes (CNTs) were modified with pendant Fe3O4 nanoparticles and polyvinyl alcohol (PVA) polymer chains. These functionalized CNTs (FeCNT) were incorporated into a PVA solution and used to prepare a cast film. The use of the pendant Fe3O4 nanoparticles resulted in a loose crystal structure with low crystallinity for the PVA matrix. With an increased fractional free volume, the water solubilities and diffusivities were enhanced in the FeCNT-containing composite membranes. The methanol permeability was reduced in the PVA–FeCNT sample. The PVA and PVA–FeCNT films were doped with a potassium hydroxide (KOH) solution to prepare hydroxide-conducting solid electrolytes. The ionic conductivity of the KOH-doped PVA–FeCNT composite membrane was improved by the FeCNT addition. This improvement was ascribed to the increased polymeric amorphous region with the ionic conducting micro-channels provided by the FeCNT. These electrolytes were used in direct methanol alkaline fuel cells. An open-circuit potential and a peak power density of 0.87 V and 87.8 mW cm−2, respectively, were obtained using a 2 M methanol fuel in 6 M KOH at 60 °C with the PVA-based electrolyte containing 0.15% FeCNT. This peak power density was more than double the value observed without the FeCNT incorporation.

Hybrids and nanocomposites of polymer and magnetic Fe3O4 nanoparticles have been utilized as magnetically-responsive materials and magnetically-directed nanoparticles. In this work, we prepare polymer-functionalized Fe3O4 nanoparticles through in situ Diels–Alder polymerization using maleimide-functionalized Fe3O4 nanoparticle as a precursor. Polybenzoxazine-functionalized Fe3O4 nanoparticles (MNP-PBz) have been obtained and characterized with Fourier Transform Infrared, X ray photoelectron, and Raman spectroscopies. The high saturation magnetization value of 51.9 emu g−1 of the MNP-PBz nanoparticles demonstrates its superparamagnetism. Moreover, MNP-FBz has been utilized as a nanofiller for preparation of cured PBz/MNP-PBz nanocomposites, which contain various MNP-PBz contents of 67, 50, 33, and 17 wt.%. The sample of PBz/MNP-PBz-67 shows a storage modulus of 8.0 GPa, a saturation magnetization value of 37.6 emu g−1, and a glass transition temperature above 380 °C. As a result, the PBz/MNP-PBz nanocomposites could be classified as magnetically-responsive high performance materials.

Polybenzimidazole (PBI) has been chemically bonded to silica nanoparticles (SNPs) through an ozone-mediated process using N-(p-carboxyphenyl)maleimide (pCPM) functionalized SNPs (SNP-pCPM) as precursors, to enhance the interfacial compatibility between SNPs and PBI in PBI/SNP nanocomposites. The PBI-functionalized SNPs (SNP-PBI) have been well characterized and used as inorganic nanofillers for preparation of PBI/SNP-PBI membranes for fuel cells. Addition of PBI-SNP to PBI membranes enhances their thermal and mechanical properties as well as decreases their phosphoric acid uptakes. For the PBI/SNP-PBI membrane with 10 wt% of SNP-PBI, it shows a proton conductivity of about 50 mS cm−1 at 160 °C, which is 25% higher compared to the pristine PBI membrane. Consequently, the PBI/SNP-PBI membrane demonstrates a maximum power density of 650 mW cm−2 in a single cell test, compared to the value of 530 mW cm−2 read from the test for pristine PBI membrane.

This research focuses on improving direct methanol alkaline fuel cell (DMAFC) performance using hydroxide-potassium-doped polyvinyl alcohol/carbon nano-tube (PVA/CNT/KOH) electrolytes. The CNTs must be functionalized with PVA polymer chains to improve their dispersion in the polymer matrix and enhance the cell performance. A functionalized CNT load of 0.05% exhibits the highest cell voltage and power density among the PVA electrolytes containing 0–0.1% CNT. The cell voltage increases with the cell temperature between 30 and 60 °C. The open-circuit voltage and peak power density (Pmax) are highest at 6 M KOH concentration in the anode feed. A methanol concentration of 2 M produces a higher Pmax compared to concentrations of 1 M and 6 M methanol. The cell performance is enhanced by increasing the fuel flow rate into the anode. A Pmax of 68.1 mW cm−2 is obtained for a DMAFC employing PVA/0.05%CNT/KOH electrolyte at 60 °C with 2 M methanol and 6 M KOH as the anode feed at a flow rate of 30 mL min−1 and humidified oxygen at a flow rate of 100 mL min−1 to the cathode. To the best of our knowledge, this Pmax is the highest reported value in the literature for DMAFCs.

Highly proton-conducting polymer electrolyte membrane (PEMs) materials are presented as alternatives to state-of-the-art perfluorinated polymers such as Nafion®. To achieve stable PEMs with efficient ionic nanochannels, novel fully aromatic ABA triblock copolymers (SP3O-b-PAES-b-SP3O) based on sulfonated poly(2,6-diphenyl-1,4-phenylene oxide)s (A, SP3O) and poly(arylene ether sulfone)s (B, PAES) were synthesized. This molecular design for a PEM was implemented to promote the nanophase separation between the hydrophobic polymer chain and hydrophilic ionic groups, and thus to form well-connected hydrophilic nanochannels that are responsible for the water uptake and proton conduction. Relative to other hydrocarbon-based PEMs, the triblock copolymer membranes showed a dramatic enhancement in proton conductivity under partially hydrated conditions, and superior thermal, oxidative and hydrolytic stabilities, suggesting that they have the potential to be utilized as alternative materials in applications operating under partly hydrated environments.

A novel route to functionalize polyvinyl alcohol (PVA) onto multi-walled carbon nano-tube (MWCNT) is reported in this work. FTIR, XPS, Raman spectroscopy, and TGA data confirmed PVA grafting onto the MWCNT. The grafted PVA content was estimated to be 25% in the PVA–functionalized MWCNT. A nano-composite consisting of PVA and 0.05% functionalized CNT was successfully prepared using a solution casting method. Water solubility and diffusivity were enhanced in the CNT-containing membranes. The ionic conductivity of the potassium hydroxide (KOH)-doped PVA/CNT membrane was improved by adding the functionalized CNT, which might be ascribed to the ionic channels provided by the CNT. The methanol permeability was suppressed in the CNT-containing sample. The alkali-doped electrolytes were applied in direct methanol alkaline fuel cells. An open-circuit potential and a peak power density of 0.86 V and 39 mW cm −2 were obtained using a 2 M methanol fuel in 6 M KOH at 60 °C with the PVA/CNT/KOH electrolyte, significantly higher than those without CNT incorporation.

This work reports the preparation of chitosan hollow nanospheres and their uses as the ultrasound-induced imaging agents. Reaction of chitosan to the 4-isocyanato-4′-(3,3-dimethyl-2,4-dioxo-azetidino)diphenylmethane modified silica nanoparticles forms silica@chitosan core shell nanoparticles. Removal of the silica cores with hydrofluoride generates the chitosan hollow nanospheres. Structures and morphology of the silica@chitosan core–shell nanoparticles and chitosan hollow nanospheres are characterized with an X-ray photoelectron spectroscopy and electron microscopies. Moreover, perfluoropentane is used an imaging gas to be filled into the chitosan hollow nanospheres. The gas-filled chitosan hollow nanospheres show ultrasonic-induced imaging behavior, demonstrating their potentials of applications in ultrasound-induced image.