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A breakthrough innovation in water-based polymeric nanoparticles has enabled significant progress in mimicking the folding of natural proteins by generating novel "single-chain polymeric nanoparticles" (SCPNs) via supramolecular interactions. In this study, a practical approach to the living polymerization of functionalized oligo(ethylene glycol) methacrylate monomers allows the incorporation of self-constituted multiple hydrogen-bonded groups into physically cross-linked polymer networks, which enables the formation of highly functionalized SCPNs in an aqueous environment. The newly developed materials are particularly attractive from a practical point of view since they have a very low critical micellization concentration and uniform particle diameters of ca. 25 nm, making them extremely stable under dilute conditions. Concentration-dependent experiments showed that SCPNs formed at polymer concentrations up to 40 mg/mL with no significant change in morphology observed. Moreover, the formed SCPNs had a very high stability in an aqueous solution containing surfactant, suggesting potential for a wide variety of applications as a promising candidate nanocarrier for bioimaging, controlled release, and drug delivery systems.

Trophic structure is an integral part of understanding the flow of contaminants within an aquatic system. Persistent, bioacccumulative, and toxic substances and food web perturbations by invasive species are critical ecological issues with far-reaching consequences for the health of the Laurentian Great Lakes. The historically-different aquatic ecosystems of Lakes Superior and Huron were evaluated for mercury (Hg) biomagnification using stable carbon ( δ 13 C) and nitrogen ( δ 15 N) isotope ratios. The results showed that δ values vary significantly with sampling depth, particularly for the lower food web components, reflecting depth- and diet-specific patterns of δ values. The stable isotope assessment of the Lake Superior food webs was consistent with previous results, underscoring the temporal stability of this ecosystem. However, based on stable isotope data, the Lake Huron lake trout appear to be incorporating the exotic round goby in their diet, possibly compensating for the collapse of alewife populations, historically their principal food. Our results suggest that the well-documented perturbations in the Lake Huron ecosystem have likely contributed to increasing Hg concentrations in the lake trout. Similar Hg biomagnification rates were observed suggesting strong similarities in the contemporary contaminant flow in Lakes Superior and Huron.

A new process for modifying a polymeric material for use as a hole injection transport layer in organic light-emitting diodes has been studied, which is through 2π + 2π photodimerization of a DNA-mimetic π-conjugated poly(triphenylamine-carbazole) presenting pendent uracil groups (PTC-U) under 1 h of UV irradiation. Multilayer florescence OLED (Organic light-emitting diodes) device with the PTC-U-1hr as a hole injection/transport layer (ITO (Indium tin oxide)/HITL (hole-injection/transport layer) (15 nm)/N,N'-di(1-naphthyl)- N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPB) (15 nm)/Tris-(8-hydroxyquinoline) aluminum (Alq3) (60 nm)/LiF (1 nm)/Al (100 nm)) is fabricated, a remarkable improvement in performance (Qmax (external quantum efficiency) = 2.65%, Bmax (maximum brightness) = 56,704 cd/m2, and LE (luminance efficiency)max = 8.9 cd/A) relative to the control PTC-U (Qmax = 2.40%, Bmax = 40,490 cd/m2, and LEmax = 8.0 cd/A). Multilayer phosphorescence OLED device with the PTC-U-1hr as a hole injection/transport layer (ITO/HITL (15 nm)/Ir(ppy)3:PVK (40 nm)/BCP (10nm)/Alq3 (40 nm)/LiF (1 nm)/Al (100 nm)) is fabricated by successive spin-coating processes, a remarkable improvement in performance (Qmax = 9.68%, Bmax = 41,466 cd/m2, and LEmax = 36.6 cd/A) relative to the control PTC-U (Qmax = 8.35%, Bmax = 34,978 cd/m2, and LEmax = 30.8 cd/A) and the commercial product (poly(3,4-ethylenedioxythiophene):polystyrenesulfonate) PEDOT:PSS (Qmax = 4.29%, Bmax = 15,678 cd/m2, and LEmax = 16.2 cd/A) has been achieved.

A new concept to supramolecular assembly of existed functional polymers, capable of forming network-like organizational clusters through multiple hydrogen-bonding interactions has been exploited. In this paper, a new adenine-based poly(triphenylamine-carbazole) (PTC-A) has been prepared which exhibits a high self-complementary ability in solution and solid states owing to the formation of adenine–adenine (A–A) pairs by induced hierarchical self-assembly. Comparing with uracil-substituted PTC sample (PTC-U), PTC-A presents a much higher thermal stability, electrochemical stability and solvent-resistance ability due to the formation of the more stable physically cross-linking structure. When the PTC-A is utilized as a hole injection/transport layer in a trilayer OLED device, a remarkable improvement in performance relative to the control PTC and PTC-U under similar experimental conditions has been achieved. Further comparison with a control device using a conventional PEDOT:PSS, the efficiency of the solution-processed phosphorescent PLED device with PTC-A is significantly higher than those of PTC-U and PEDOT:PSS-based devices. Thus, PTC-A represents the next-generation hole injection/transport material for high efficiency LED device and low-cost fabrication process.

Complementary nucleobase-functionalized polymers, a combination of base-pair interactions and a blend of two different polymers, can be used for efficient construction of supramolecular polymer networks; these materials exhibit tunable mechanical properties, rapid thermo-responsiveness and self-healing behavior making them highly attractive for a wide range of potential applications. Herein, a multi-uracil functionalized polyhedral oligomeric silsesquioxane (POSS-U) and adenine end-capped three-arm polycaprolactone oligomer (PCL-A) have been successfully developed and show high complementary ability in both solution and the solid state owing to reversible uracil–adenine (U–A)-induced physical cross-linking. The POSS-U/PCL-A blend system demonstrates that physically crosslinked films can be readily tailored to provide the desired mechanical properties and rapidly reprocessed after damage under mild temperature conditions. Importantly, these films can also spontaneously self-heal at room temperature as an autonomously repairing material, without the need for external intervention. Thus, this new system provides a potential route toward the design and fabrication of next-generation self-healing polymers.

We have synthesized TPABZ, a new thermally cross-linkable triphenylamine derivative containing a benzoxazine functional group, for application in organic light-emitting diodes (OLEDs). We used differential scanning calorimetry, thermogravimetric analysis, UV–Vis spectroscopy, and cyclic voltammetry to investigate the thermal, physical, and electrochemical properties of TPABZ, which is readily polymerized, through ring-opening polymerization of its benzoxazine unit, upon heating at 220 °C for 30 min. The cured TPABZ (P-TPABZ) is suitable for use as a hole injection/transport material in OLEDs because it has an appropriate HOMO energy level (−5.16 eV) to form a stepwise energy ladder and a high LUMO energy level (−1.68 eV) with great potential for electron blocking. We fabricated multilayered OLEDs (ITO/TPABZ or P-TPABZ/NPB/Alq3/LiF/Al) through successive spin-coating and vacuum deposition processes; the device incorporating P-TPABZ exhibited good performance (EQE: 2.44%; LEmax: 8.42 cd A−1; PEmax: 4.34 lm W−1).

A series of polylactic acid-polyethylene glycol-polylactic acid diacrylate macromers (PEGLM) were synthesized, and a novel chitosan-PEGLM double network (DN) hydrogel was further successfully fabricated by the sequential interpenetrating technology with highly cross-linked chitosan as the rigid component and PEGLM as the flexible component. Their structures and components were characterized by 1H NMR, FTIR, and XRD. Their fracture morphology was investigated by SEM. It was interesting to found that the compressive strength of hydrogel wound reach its maximum value when the chitosan content was 10%, no matter what the molecular weight of PEGLM component was. What’s more, we found that the compressive strength of 6KL7 could reach 1.07 MPa at gel state, whose PEG segment molecular weight was 6,000, and polymerization degree of PLA was 7. The effects of glutaraldehyde ratio, polymerization degree of PLA, and molecular weight of PEG segment on the mechanical strength of DN hydrogels were also discussed in this article. To further strengthen DN hydrogels, the double network-linear (DNL) hydrogels were fabricated by introducing linear poly(vinyl alcohol) (PVA) into the DN hydrogels. The DN-L hydrogels exhibited better mechanical properties, with the compressive strength up to 1.45 MPa. These hydrogels may have prospective applications in the fields of wound dressing, artificial cartilage and tissue engineering scaffold materials which require high mechanical properties. Open image in new window

A new adenine-functionalized polythiophene (PAT) has been developed which allows the incorporation of multiple self-complementary hydrogen-bonded groups into micelles. After the encapsulation of fullerene derivatives (PCBM) into PAT, their excellent electrochemical storage capacities make the PAT/PCBM micelle a promising candidate for an electron storage/transport layer in the fabrication of high-performance electrochemical devices.

Interfacial mixing of polymers is a critical issue when attempting to improve the charge transport and stabilize the operation of solution-processed organic light-emitting diodes (OLEDs). Herein, we describe a simple methodology for overcoming interfacial mixing, based on the use of a photo-crosslinkable hole injection/transporting material (HITM). We synthesized a conjugated polymer, PTCAzide, bearing ready crosslinking ability and investigated its suitability for use as an HITM. Photo-crosslinking of the PTCAzide copolymer gave X-PTCAzide, which exhibited much higher thermal stability (the glass transition temperature increased by 21 K relative to that of PTCAzide), remarkable electrochemical stability, and excellent solvent-resistance, thereby expanding the operation time of corresponding electronic devices. Such a tris(8-hydroxyquinolinato)aluminum-based trilayer device reached a maximum brightness of 52971 cd m−2, and the maximum luminance efficiency (LE) and power efficiency (ηE) are both higher than those of the corresponding device based on commercial PEDOT:PSS. In addition, a solution-processed phosphorescent OLED device incorporating X-PTCAzide also exhibited good performance (external quantum efficiency: 7.93%; LE: 29.6 cd A−1; ηE: 14.3 lm W−1; maximum brightness: 34484 cd m−2). The efficient and simple photocrosslinking without adding an initiator could facilitate the fabrication process. Thus, PTCAzide appears to be a promising next-generation HITM for the development of highly efficient and inexpensive OLEDs. Its photo-crosslinkable nature allows improvements in morphological stability and hole injection/transporting ability, leading to more stable devices with better operation, without disrupting molecular packing or charge transport.

Supramolecular polymers, a combination of secondary interactions and a polymer material, can be used to control supramolecular self-assembly in a polymeric matrix; these materials exhibit unique stimuli-responsiveness and self-healing properties making them highly attractive for various applications. Herein, we developed a novel supramolecular poly-urea containing a urea–cytosine (UrCy) quadruple hydrogen bonding moiety that undergoes a dynamic healing mechanism, “supramolecular polymer networks (SPN)”, and rapidly repairs after damage under mild conditions. Interestingly, this newly-developed material can also self-heal at room temperature without external intervention, as evidenced by repeated restoration of mechanical properties. Given its simplicity, efficiency and reliability, this material offers a unique paradigm for developing SPN-based self-healing materials.

Novel hybrid diblock copolymers consisting of bidentate ligand-functionalized chains have been synthesized via click reaction and RAFT radical polymerization. The chemical structure and molecular weight of the synthesized poly(methacrylate-POSS)-block-poly(4-vinylbenzyl-2-pyridine-1H-1,2,3-triazole) (PMAPOSS-b-PVBPT) were characterized by NMR and GPC. The copolymers had been utilized to construct metal-containing polymer micelle by the metal–ligand coordination and electrostatic interaction in this study. The self-assembly behaviors of PMAPOSS-b-PVBPT in chloroform, a common solvent, under the effect of Zn(OTf)2 and HAuCl4 were investigated by TEM, DLS, and variable temperature NMR. Besides, micellization of this diblock copolymer was achieved in ethylene glycol, a selective solvent for PMAPOSS-b-PVBPT. The experimental results revealed that the incorporation of heterocyclic rings bearing nitrogen atoms in polymer side chains played an important role in the construction of metal-containing copolymer micelles. The prepared metal-containing PMAPOSS-b-PVBPT micelles had good dynamic and thermal stability due to the strong metal–ligand coordination interaction and electrostatic interaction.

In this study we fabricated a nanopillar array of silicon oxide, involving very-large-scale integration (VLSI) and reactive ion etching (RIE), as two-dimensional periodic relief gratings (2DPRGs) on Si surfaces. Thiolated oligonucleotide was successively immobilized on the thiol functionalized surfaces of 2DPRGs by disulfide bond as an optical probe to detect a human genomic DNA (hgDNA584), related to breast cancer recurrence after surgery, from a biological specimen. The oligonucleotide-bound 2DPRG alone produces insignificant structure change, but upon hybridization with hgDNA584 leads to a dramatic change of the pillar scale due to hgDNA584 filling inside the 2DPRG layers. The performance of the sensor was evaluated by capturing hgDNA584 on the oligonucleotide-bound 2DPRGs and measuring the effective refractive index (neff), resulting of color change from pure blue to red, observed by naked eyes along an incident angle of 20-30°. The surface-bound 2DPRG based assay with the chemoresponsive diffraction grating signal transduction scheme results in an experimentally simple DNA detection protocol, displaying attributes of both detection methodologies: the high sensitivity and selectivity afforded by 2DPRG probes and the experimental simplicity, and miniaturization potential provided by the diffraction-based sensing technology.

New polystyrene (PS)/carbon nanofiber (CNF) and PS/graphite foams with an inter-connected honeycomb-like carbon particulate network of CNF or graphite were prepared by first coating the surface of polymer pellets with either CNF or graphite and then conducting batch foaming using carbon dioxide (CO2) as a blowing agent. It was found that the inter-connected honeycomb-like carbon particulate network could significantly reduce the compression yielding of conventional PS foams. With 1 wt% of CNFs or graphite, the PS foams with inter-connected honeycomb-like carbon particulate network were 5–9 times more electrically conductive than foams made of compounded PS nanocomposite with the same carbon particle loading. In addition, the PS foams with inter-connected honeycomb-like carbon particulate network were more thermally conductive and revealed significantly improved thermal stability comparing to foams made of compounded polymer nanocomposites.

Si, when compared to conventional graphite, offers an order-of-magnitude improvement as a high capacity anode material for Li-ion batteries. Despite significant advances in nanostructured Si-based anodes, the formation of stable Si anodes remains a challenge, due to the significant volume changes that occur during lithiation and delithiation. Si/graphene composites, with graphene sheets and Si nanoparticles bound in a dispersion obtained by a self-assembly technique using non-covalent electrostatic attraction (following thermal processing to remove residual organic material) are used to prepare Sibased anodes for use in Li-ion batteries. A mesoporous structure, obtained by further thermal processing is able to accommodate large Si nanoparticle volume changes during cycling, thereby facilitating Liion diffusion within the electrode. Morphological analysis showed that Si nanoparticles are homogeneously distributed on the graphene sheets, which is thought to account for the excellent electrochemical performance of the resulting Si/graphene composite. A composite containing Si 67.3 wt% exhibits a greatly improved capacity and cycling stability in comparison with bare Si in combination with the thermal reduction of a simple mixture of graphene oxide and Si nanoparticles without electrostatic attraction (Si content ¼ 64.6 wt%; capacity of 512 mAh g

In this paper we demonstrate the use of low-temperature-solution-processable bismuth iodide (BiI3) nanosheets as hole transport layers in organic photovoltaics with an active layer comprising poly(3hexylthiophene) (P3HT) mixed with a fullerene derivative. The performance of the resulting devices was comparable with that of corresponding conventionally used systems incorporating polyethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS). UV–vis spectroscopy revealed that the transparency of a BiI3 layer in the visible (4620 nm) and near-infrared range is greater than that of a PEDOT:PSS layer. X-ray photoemission spectroscopy of a BiI3 film revealed signals at 158.8, 164, 618.6, and 630 eV— characteristic of Bi 4f7/2 ,B i 4f5/2 ,I3 d5/2, and I 3d3/2, respectively—that indicated a stoichiometric BiI3 film. Wet milling of BiI3 crystals resulted in the formation of nanosheets, the presence of which we confirmed using scanning electron microscopy. The resultant power conversion efficiency of the device was approximately 3.5%, with an open-circuit voltage of 0.56 V, a short-circuit current density of

A facile method was developed to prepare MWCNT/POSS nanocomposites by direct esterification between carboxylic acid functionalized MWCNT and octa(phenol) octasilsesquioxane. Completeness of the MWCNT surface modification was confirmed by FT-IR. The hybrid nano-MWCNT–OP-POSS composite structure and properties was characterized using DSC, TGA, optical microscopy, WAXD, and AFM. The results indicated the solubility and processability of MWCNT–COOH improved because of OP-POSS grafting on MWCNT surface. The Tg and thermal stability of the nanocomposites was higher than that of the OP-POSS as a result of the cross-linking reaction. AFM observations revealed that the nanocomponents were reacted in a homogeneous phase at nanoscale level.

Nucleobase-grafted polycaprolactone has been prepared which exhibits amorphous nature, rapid photoresponse and controlled surface properties in the solid state owing to the formation of uracil–diamidopyridine (U–DAP) pairs by induced physical cross-linking. In addition, they can self-organize to alter material behavior with light, switching both optical and thermal properties. Remarkable changes in the surface morphology and the contact angle with water were also observed.

Crosslinking is an efficient and simple approach for enhancing the thermal and mechanical properties of polymers. Numerous studies have reported such enhancements by the incorporation of benzoxazine (a cross-linker) in the polymer's structures. The great majority of these studies have focused on the effect of the benzoxazine content on the polymer matrix. As far as we know, there has been no discussion related to the effects arising from the position of benzoxazine incorporation. In order to investigate any such effects, we synthesized new benzoxazine monomers (SBz and MBz), containing bis-propargyl functional groups and new main chain and side chain benzoxazine functionalized polytriazole polymers, with the above benzoxazine moieties in the repeat unit, using click chemistry. The resulting thermal and mechanical properties of Cured-PTA-SBz-10 were better than those of Cured-PTA-MBz-10, and the Cured-PTA-SBz-4 and Cured-PTA-SBz-6 were close or even better than those of Cured-PTA-MBz-10. To better understand any thermal curing effects related to the positions of benzoxazine moieties in the polymer chain, we performed dynamic differential scanning calorimetric measurements by Kissinger and Ozawa methods. Significant enhancement of the thermal and mechanical properties comparing neat PTA with Cured-PTA-SBz-10 were noted: e.g. (i) a ∼110 °C improvement of Tg; (ii) a ∼205% improvement in storage modulus, a ∼232% improvement of tensile strength, and a ∼262% improvement in Young's modulus. Therefore, when designing the polymer, by giving consideration to the position of the cross-linker, the resulting thermal and mechanical properties can be enhanced to the extent that an equivalent polymer can be formed with a reduced amount of cross-linker leading to cost reduction.

In this study, we synthesized amphiphilic poly(3-hexylthiophene)-graft-poly(ethylene oxide) (P3HT-g-PEO) rod–coil conjugated random copolymers through oxidative polymerization with FeCl3 and facile click chemistry and characterized them using 1H nuclear magnetic resonance spectroscopy, size exclusion chromatography, differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy, UV-Vis spectroscopy, and fluorescence spectroscopy. We then used atomic force microscopy, transmission electron microscopy, and dynamic light scattering to investigate the self-assembled structures formed from these amphiphilic random copolymers in solution and in the bulk state. In the bulk state, DSC analyses revealed that after PEO had been grafted onto P3HT, the crystallization temperature of PEO decreased from +20 to −26 °C as a result of hard confinement of microphase separation in the copolymer system. In addition, we found that the amphiphilic conjugated random copolymers could form micelle structures in the DMF–water system.

National Natural Science Foundation of China [51273164, U1205113]; Natural Science Foundation of the Fujian Province of China [2012J01233]; Fundamental Research Funds for the Central Universities [2012121031]; NCET

It is often difficult to observe nanoscale structures of polymeric materials using conventional transmission electron microscopy (TEM) because of their weak scattering contrast. To produce quantitative image contrast without any staining, low-angle annular dark-field scanning transmission electron microscopy (LAADF-STEM) was studied for its applicability for observing fine structures in block copolymers. The LAADF-STEM images displayed microphase-separated morphologies of block copolymers with high S/N contrast depending on the intrinsic density difference because of nonstaining. We found that the temperature dependence of the image contrast showed a kink around the glass-transition of the constituent phase, from which one can estimate glass transition temperatures and thermal expansion coefficients at nanoscale. This indicates that the LAADF-STEM imaging is an effective tool to quantitatively image nanoscale phases of polymers.

Despite the intensive effort directed at the synthesis of anion exchange membranes (AEMs) only a few studies show enhanced ionic conductivity with simultaneous suppression of unfavourable mass transport and improved thermal and mechanical properties. Here we report an alkaline nanocomposite membrane based on fully exfoliated graphene nanosheets and poly(vinyl alcohol) (PVA) prepared by a simple blending process. The composite membrane shows improved ionic transport due to the homogeneous distribution of the graphene nanosheets which are able to form continuous, well-connected ionic channels. Significant enhancement of the ionic conductivity for the prepared graphene/PVA composite membranes is observed with a 0.7 wt% graphene loading resulting in a ∼126% improvement in ionic conductivity and a ∼55% reduction in methanol permeability. The resulting maximum power density obtained by incorporating the membrane in a cell is increased by ∼148%. A higher graphene loading (1.4 wt%) enhances the adhesion of the nanofiller–matrix, giving a ∼73% improvement in the tensile strength. This study provides a simple route to designing and fabricating advanced AEMs.

An easy and effective method for producing low methanol-crossover membranes is developed by dispersing sulfonated graphene oxide (SGO) into a Nafion matrix. A SGO/Nafion mixture with low SGO content exhibits unique viscosity behavior and allows for better SGO dispersion within the Nafion. After film casting, the composite membranes show lower methanol and water uptakes, a reduced swelling ratio, improved proton conductivity in low relative humidity, and extremely high methanol selectivity, which can be implemented in direct methanol fuel cells (DMFCs). The regular backbone of the composite membrane shows a higher storage modulus, increased α-relaxation (transition temperature), and improved tolerance to pressure during membrane electrode assembly (MEA). The small angle X-ray spectra indicate the shrinkage of the ionic clusters in the composite membranes, which thus reduce methanol crossover. The hybrid membranes applied to DMFCs demonstrate performances superior to that of the commercial Nafion 115 in 1 M and 5 M methanol solutions.

A high water retention membrane is developed by co-assembling poly(ethylene glycol) (PEG) grafted activated carbon (AC-PEG) with Nafion. The AC-PEG is prepared via a sol–gel process. The use of PEG as a transporting medium in AC-PEG shows a largely improved water retention ability, a higher proton conductivity and a reduced swelling ratio, making it well suited for proton exchange membrane fuel cells (PEMFCs). Further, the composite membranes show improved mechanical properties at high temperature, thus ensuring the structural stability of membranes during the fuel cell operation. Compositional optimized AC-PEG/Nafion composite membrane (15 wt% compared to Nafion) demonstrates a better performance than the commercially available counterpart, Nafion 212, in fuel cell measurements. To identify the key factor of the improved performance, current interrupt technique is used to quantitatively verify the changes of resistance under different relative humidity environment.

In this study, we tethered terminal uracil groups onto short-chain poly(ethylene glycol) (PEG) to form the polymers, uracil (U)-PEG and U-PEG-U. Through AC impedance measurements, we found that the conductivities of these polymers increased upon increasing the content of the lithium salt, LiAsF6, until the Li-to-PEG ratio reached 1:4, with the conductivities of the LiAsF6/U-PEG blends being greater than those of the LiAsF6/U-PEG-U blends. The ionic conductivity of the LiAsF6/U-PEG system reached as high as 7.81 × 10−4 S/cm at 30 °C. Differential scanning calorimetry, wide-angle X-ray scattering, 7Li nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy revealed that the presence of the uracil groups in the solid state electrolytes had a critical role in tuning the glass transition temperatures and facilitating the transfer of Li+ ions.

A cost-effective and high-throughput method for producing high-water-uptake membranes is developed by combining high-porosity and superior-surface-area activated carbon with Nafion. The resultant activated carbon/Nafion hybrid composite exhibits high water uptake and an improved proton conductivity, which can be exploited in a proton exchange membrane fuel cell (PEMFC). This hybrid membrane displays a superior performance to that of the commercial Nafion 211 when used in fuel-cell measurements. Electrochemical impedance spectroscopy (EIS) is used to simulate the changes in resistance during the operation of the fuel cells and conclusively explains the improved performance of the composite membranes.

We blended poly(3-phenyl-3,4-dihydro-2H-1,3-benzoxazine) (PBA) into polyacrylonitrile (PAN) to generate low-surface-free-energy fibers without fluorine and silicon elements for electrospinning. Liquid-state BA at room temperature can be solidified in electrospinning process using PAN as a medium through their miscible behavior. Results indicate that the mixing below 50 wt% BA into PAN matrix for electrospinning has no significant dropping beads, indicated a miscible PAN/BA system. Above 70 wt% BA in PAN solution could not be solidified completely after electrospinning, revealed apparent beaded fibers. The PAN/PBA blend fibers, obtained after curing at 300 °C, generated a superhydrophobicity because of the low-surface-free-energy PBA. In addition, laser scanning confocal microscope (LSCM) measurements were included to determine the relative amount of antibody that adsorbed to these PAN/PBA fibers to examine the biofouling-resistant property. The results showed an obviously decreased protein adsorption with increasing PBA fraction. The correlations between PAN and PBA would provide insight into the designing and developing of low-surface-free-energy fibers without fluorine and silicon elements to improve biofouling-resistant property.

Temporal trend analysis of the latest Great Lake Fish Monitoring and Surveillance Program (GLFMSP) data showed statistically significant decreases in persistent bioaccumulative and toxic (PBT) contaminant (polychlorinated biphenyls (PCBs), dichloro-diphenyl-trichlorethane and its metabolites (DDTs), dieldrin, cis-chlordane, oxychlordane, cis-nonachlor) concentrations in Lakes Huron, Ontario, and Michigan lake trout over the period of 1999 to 2009. In contrast, for most contaminants, no statistically significant concentration trends were found in top predator fish in Lakes Superior and Erie during the same period. For Lakes Huron, Ontario, and Michigan 5.0 ± 2.6% average annual concentration decreases were found for PCBs, DDTs, dieldrin, and other organochlorine pesticides (OCs) decreased at a faster rate, ranging from 10 ± 4.3% to 20 ± 7.1% per year. For these three lakes, with the exception of PCBs, these current decreases are greater than were shown by an earlier trend analysis that estimated an annual contaminant decrease of about 2–5% for the period of 1980 to 2003. For Lakes Superior and Erie, the finding of no statistically significant trend is in agreement with previously reported results for these lakes.

In this study, we synthesized core/shell structures comprising monodisperse 3-μm SiO(2) microspheres and gold nanoparticles (AuNPs, ca. 6.7 nm) as the core and shell components, respectively. Using a layer-by-layer cross-linking process with a dithiol cross-linking agent, we prepared low-permittivity AuNP-encapsulated high-permittivity SiO(2) core/shell microspheres with variable AuNP shell thicknesses. The dispersivity of the microspheres in solution was enhanced after grafting poly(ethylene glycol) monomethyl ether thiol (PEG-SH) onto the AuNP layer on the SiO(2) microspheres. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images revealed sesame ball-like structures for these SiO(2)@AuNP@PEG microspheres. We encapsulated aqueous dispersions of these SiO(2)@AuNP microspheres into sandwich structured displays (SSDs) to investigate their electrorheological properties, observing reversibly electroresponsive transmittance that is ideally suited for display applications. Increasing the thickness of the AuNP layer dramatically enhanced the stringing behavior of the SiO(2) microspheres, resulting in increased transmittance of the SSD. The response time of the electroresponsive electrorheological fluids also decreased significantly after modifying the SiO(2) with the AuNP layers. The effective permittivities of these composites could be predicted from the real (έ) and imaginary (έ́) parts of the Clausius-Mossotti formalism.

This study successfully prepared zirconia ultrathin films from the sol–gel solution with dispersion of zirconium halide in 1-octanol solvent. The film was subjected to annealing treatments after sol–gel spin-coating, and the films of interest were evaluated. The amorphous morphology of the zirconia film was identified using high-resolution transmission electron microscopy and X-ray diffractometry. The plot of the current density with respect to the electric field demonstrates that the as-deposited film at 500 °C annealing exhibited an inferior leakage current, whereas 600 °C annealing stabilized the film with a satisfactory leakage current of 10−8 to 10–9 A/cm2. The out-gassing behavior of the sol–gel-derived thin film was evaluated using a thermal desorption system, that is, atmospheric pressure ionization mass spectrometry. The dielectric constant of the film was dependent on the retention effect of the preparation solvents. The low residual solvent for the preparation of the thin film with 1-octanol solvent and 600 °C annealing contributed to the superior high-k property.

Developing powerful and reliable strategies to covalently functionalize graphene for efficient grafting and achieving precise interface control remains challenging due to the strong interlayer cohesive energy and the surface inertia of graphene. Here, we present versatile and efficient grafting strategies to functionalize graphene nanosheets. An alkyne-bearing graphene core was used to prepare polymer-functionalized graphene using ‘grafting to’ and ‘grafting from’ strategies in combination with reversible chain transfer and click chemistry. The use of the ‘grafting to’ approach allows full control over limited length grafted polymer chains, while permitting a high grafting density to a single graphene face, resulting in good solubility and processability. The ‘grafting from’ approach offers complementary advantages, such as the grafting of high molecular weight polymer chains and a better coverage ratio on the graphene surface; however, the extra steps introduced, the presence of initiating groups, and di...

Sulfonated polytriazole-clay (SPTA-clay) nanocomposites are successfully prepared by in situ polymerization of SPTA using click chemistry in the presence of propargyl-functionality modified clay. The clay layers are exfoliated and well dispersed within the SPTA matrix resulting in improvements in thermal stability, mechanical strength, methanol permeability, water retention, ion channel size, and ionic cluster distribution. The SPTA-clay nanocomposite membranes with small amounts of clay in the SPTA matrices possess higher selectivity's; defined as the ratio of proton conductivity to methanol permeability, and thus have potential as proton exchange membranes (PEMs) in direct methanol fuel cells (DMFCs).

In this paper, we discuss liquid lenses driven by various mechanisms. By properly designing the device structure and choosing the optimal materials, the liquid lenses offer great potential for practical uses. The driving mechanism dictates the application and performance of the liquid lenses. Here we categorize the driving mechanisms into mechanical and electrical ones. In general, mechanical driving with an elastic membrane and an external pump drives liquids in a cavity by controlling the hydraulic pressure. The mechanical driving method can be applied to most of the liquids, but the application of the electrical driving method would be limited by the conductivity or the permittivity of the liquids. Therefore, the properties of the different liquids, e.g., dielectric liquids, liquid crystal molecules, and conductive liquids, deeply affect the mechanism we may choose to realize a liquid lens. Among various electrical methods, dielectrophoresis (DEP), electrostatic forces, and electrowetting-on-d...

Triblock copolymer surfactant, HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H (i.e. P123)-based nanocrystalline (nc)-TiO2 thin film had been synthesized on organic flexible polyimide (PI) sheet for their application in organic metal–insulator–semiconductor (MIS) device. The nc-TiO2 film over PI was successfully deposited for the first time by a systematic solution proceeds dip-coating method and by the assistance of triblock copolymer surfactant. The effect of annealing temperature (270 °C, 5 h) on the texture, morphology and time-induced hydrophilicity was studied by X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle system, respectively, to examine the chemical composition of the film and the contact angle. The surface morphology of the semiconducting layer of organic pentacene was also investigated by using AFM and XRD, and confirmed that continuous crystalline film growth had occurred on the nc-TiO2 surface over flexible PI sheet. The semiconductor–dielectric interface of pentacene and nc-TiO2 films was characterized by current–voltage and capacitance–voltage measurements. This interface measurement in cross-link MIS structured device yielded a low leakage current density of 8.7 × 10−12 A cm−2 at 0 to −5 V, maximum capacitance of 102.3 pF at 1 MHz and estimated dielectric constant value of 28.8. Furthermore, assessment of quality study of nc-TiO2 film in real-life flexibility tests for different types of bending settings with high durability (c.a. 30 days) demonstrated a better comprehension of dielectric properties over flexible PI sheet. We expected them to have a keen interest in the scientific study, which could be an alternate opportunity to the excellent dielectric–semiconductor interface at economic and low temperature processing for large-area flexible field-effect transistors and sensors.

Two kinds of novel reduction-sensitive rapid degradable poly(urethane-urea)s were synthesized and characterized based on a cystine derivative chain extender which provided active sites for reductive degradation. In vitro degradation study was carried out under physiological conditions mediated by glutathione and dithiothreitol respectively, and was assessed by 1 H NMR, GPC and SEM. The results indicated that the disulfide bonds in poly(urethane-urea)s were effectively cleaved while the structures of urethane groups and soft segments remained almost unaffected. Still, the rate and degree of reductive degradation could be controlled by the structures of the polymers. The influence of the poly(urethane-urea)s on human umbilical vein endothelial cells was investigated by WST-1 assay. The results indicated that the polymers sustained much higher cell viability than the controls. It is possible that the poly(urethane-urea)s can be potentially applied for temporary biomaterials such as wound closure devices, cell scaffolds and sophisticated drug delivery systems.

In this study, we partially grafted geminal silanol groups in the protecting organic shells on the surfaces of gold nanoparticles (AuNPs) and then assembled the alkyl-AuNP-Si(OH)4 particles onto the surfaces of silicon (Si) wafers. The density of assembled AuNPs on the Si surface was adjusted by varying the geminal silanol group content on the AuNP surface; at its optimal content, it approached the high assembly density (0.0254 particles/nm2) of an AuNP assembled monolayer. Using reactive-ion etching (RIE) with the templates as masks, we transferred the patterned AuNP assemblies to form large-area, size-tunable, Si nanopillar arrays, the assembly density of which was controlled by the dimensions of the AuNPs. Using this colloidal lithography (CL) process, we could generate Si nanopillars having sub-10-nm diameters and high aspect ratios. The water contact angles of the high-aspect-ratio Si nanopillars approached 150°. We used another fabrication process, involving electron beam lithography and oxygen plasma treatment, to generate hydrophilic 200-nm-resolution line patterns on a Si surface to assemble the AuNPs into 200-nm-resolution dense lines for use as an etching mask. Subsequent CL provided a patterned Si nanopillar array having a feature size of 200 nm on the Si surface. Using this approach, it was possible to pattern sub-10-nm Si nanopillar arrays having densities as high as 0.0232 nm−2.

New star poly(N-isopropylacrylamide)-b-polyhedral oligomeric silsesquioxane (PNIPAm-b-POSS) copolymers were synthesized from octa-azido functionalized POSS (N3-POSS) and alkyne-PNIPAm, which was prepared using an alkyne-functionalized atom transfer radical polymerization (ATRP) initiator (propargyl 2-bromo-2-methylpropionamide), via click chemistry. These star PNIPAm-b-POSS copolymers undergo a sharp coil-globule transition in water at above 32°C changing from a hydrophilic state below this temperature to a hydrophobic state above it, which is similar to linear PNIPAm homopolymers. More interestingly, we found that these star polymers exhibited strong blue photoluminescence in water above a lower critical solution temperature (LCST). This photoluminescence was likely due to the constrained geometric freedom and relatively rigid structure caused by intramolecular hydrogen bonding within the star PNIPAm polymers, which exhibit an intrinsic fluorescent behavior.

A new polyhedral oligomeric silsesquioxane ionomer (HCl-doped POSS-C11-Py) has been investigated. This new ionomer is able to self-assemble through macromers by quadruple hydrogen bonding interactions into a physically crosslinked polymer-like material that can be easily fabricated into films with micro-phase separation. This HCl-doped POSS-C11-Py membrane exhibits higher proton conductivity than a typical Nafion® membrane at high temperature, which is extremely rare for a non-sulfonic acid system. This newly developed material may provide an alternative route toward design and fabrication of a new type of proton exchange membranes.

Two kinds of novel peptide mimetic pepsin-inspired degradable polyurethanes were synthesized and characterized. A synthetic pseudo tripeptide acted as chain extender and provided active sites for pepsin biodegradation. In vitrodegradation behavior was investigated in simulated gastric fluid containing pepsin, and assessed by 1H NMR, mass loss and SEM. The results indicated that the pseudo peptide bonds in polyurethanes were effectively digested by the action of pepsin. Furthermore, the rate and degree of pepsin-inspired polyurethanes in simulated gastric fluid containing pepsin could be controlled by alteration of the soft segments and activity of pepsin. The influence of the polymers on human umbilical vein endothelial cells was evaluated by WST-1 assay. The results indicated that the polymers sustained much higher cell viability than the controls.

Photocurable resins, bisphenol A propoxylate glycerolate diacrylate (BPA-PGDA, containing two hydroxyl) and bisphenol A propoxylate diacrylate (BPA-PDA), with fixed photoinitiator (Irgacure 907) concentration and various contents of methacrylisobutyl polyhedral oligomeric silsesquioxane (MI-POSS) were prepared and characterized by FTIR spectroscopy, scanning electron microscope and differential photocalorimetry. The MI-POSS molecules form crystals or aggregated particles in the cured resin matrix. The BPA-PGDA series photocurable resins show higher viscosity and lower photo-polymerization reactivity than the BPA-PDA series resins. The photo-polymerization rate and conversion of BPA-PGDA series are improved with increasing MI-POSS content. On the contrary, the photo-polymerization behavior of BPA-PDA series photocurable resins remains nearly unchanged by the addition of MI-POSS. Hydrogen-bonding interaction between the hydroxyl of BPA-PGDA and the siloxane of MI-POSS tends to attract and concentrate these acrylate double bonds around MI-POSS particles and thus enhances the photo-polymerization rate and conversion.

In this paper, we have synthesized poly(4-vinylphenol) (PVPh) and polyhedral oligomeric silsesquioxanes-poly(4-vinylphenol) (POSS-PVPh) with low surface energies and investigated their surface properties. Experimental results reveal that the surface properties of PVPh and POSS-PVPh can be manipulated with the length of PVPh segment and POSS contents, respectively, resulting in the variation of intermolecular hydrogen bonding interactions. In addition, the surface energies of PVPh after thermal treatment of 180 °C for 24 h can be less than 20 mJ m −2 and those of POSS-PVPh without thermal treatment can be less than 25 mJ m −2 while those of poly(tetrafluoroethylene) (PTFE) are 22 mJ m −2 .

This review describes the syntheses of polyhedral oligomeric silsesquioxane (T8-POSS) compounds, the miscibility of POSS derivatives and polymers, the preparation of both multifunctional and monofunctional monomers and polymers containing POSS including styryl-POSS, methacrylate-POSS, norbornyl–POSS, vinyl-POSS, epoxy–POSS, phenolic–POSS, benzoxazine–POSS, amine-POSS, and hydroxyl-POSS. The thermal, dynamic mechanical, electrical, and surface properties of POSS-related polymeric nanocomposites prepared from both monofunctional and multifunctional POSS monomers are discussed. In addition, we describe the applications of several high-performance POSS nanocomposites in such systems as light emitting diodes, liquid crystals, photo-resist materials, low-dielectric constant materials, self-assembled block copolymers, and nanoparticles.

Sulfonated polytriazole (SPTA) in which the acidic sulfonic acid and basic triazole groups act as physical crosslinking sites within a polymer backbone has been successfully prepared, for use as a proton exchange membrane, using the click reaction. The acid-base interactions of the SPTA membranes leads to the formation of well-dispersed ionic clusters and the random distribution of ion channels with good connectivity resulting in lower methanol permeabilities at ambient temperatures and similar or higher proton conductivities than Nafion 117 at 80 °C in conditions of near zero relative humidity. Proton conductivities (σ) of 0.149 S cm−1 at 80 °C and 9 × 10−5 S cm−1 in anhydrous conditions together with low methanol permeability (P) at 0.1 × 10−6 cm2 s−1 that are comparable or superior to Nafion 117 (σT=80 : 0.151 S cm−1; σRH=0 : 3 × 10−5 S cm−1; PT=30: 1.31 × 10−6 cm2 s−1) were achieved. Additionally, the selectivity of SPTA is approximately four times higher than that of Nafion 117, thus it may have potential for use in direct methanol fuel cells (DMFCs).

A new and fully flexible Si 3 N 4 –HfO 2 stacked poly-(3-hexylthiophene) p-type thin film transistor (P3HT-TFT) was successfully fabricated on thin semi-transparent polyimide (PI) substrate. The success of the TFT manufacturing adopts: (a) very simple and cost-effective sol–gel spin-coating technique to obtain 10-nm high- k HfO 2 as dielectric layer over fully flexible PI substrate; (b) 50-nm silicon nitride (Si 3 N 4 ) as the most efficient passivation layer on top of HfO 2 film; (c) bendable 30-nm P3HT channel film by spin-coating method. Current–electric field characteristics of HfO 2 layer in metal–insulator–metal (MIM) and TFT configurations, with or without Si 3 N 4 passivation layer, were carefully evaluated. The origin of unsatisfactory leakage current in MIM and TFT structures could be effectively suppressed by means of Si 3 N 4 film as the efficient passivation layer. The bottom-gate TFT demonstrated the on-to-off ratio 2 × 10 4 for drain current, −1.9 V threshold voltage and good saturation mobility (0.041 cm 2 V −1 s −1 ). The proposed devices were examined in convex and concave types of various radii of curvature ( R c ) in order to explore the manufacturing feasibility and electrical reliability of the fully flexible TFT for practical applications. In addition, various folding times and environmental stability on aforementioned devices with respective to electrical performances were also evaluated.