Showing papers on "Polymer published in 2011"
TL;DR: In this article, the status of worldwide research in the thermal conductivity of carbon nanotubes and their polymer nanocomposites is reviewed, as well as the relationship between thermal conductivities and the micro- and nano-structure of the composites.
2,102 citations
TL;DR: Nano-rGO is established as a novel photothermal agent due to its small size, high photothermal efficiency, and low cost as compared to other NIR photothermal agents including gold nanomaterials and carbon nanotubes.
Abstract: We developed nanosized, reduced graphene oxide (nano-rGO) sheets with high near-infrared (NIR) light absorbance and biocompatibility for potential photothermal therapy. The single-layered nano-rGO sheets were ∼20 nm in average lateral dimension, functionalized noncovalently by amphiphilic PEGylated polymer chains to render stability in biological solutions and exhibited 6-fold higher NIR absorption than nonreduced, covalently PEGylated nano-GO. Attaching a targeting peptide bearing the Arg-Gly-Asp (RGD) motif to nano-rGO afforded selective cellular uptake in U87MG cancer cells and highly effective photoablation of cells in vitro. In the absence of any NIR irradiation, nano-rGO exhibited little toxicity in vitro at concentrations well above the doses needed for photothermal heating. This work established nano-rGO as a novel photothermal agent due to its small size, high photothermal efficiency, and low cost as compared to other NIR photothermal agents including gold nanomaterials and carbon nanotubes.
1,820 citations
TL;DR: In this paper, a review on the tensile properties of natural fiber reinforced polymer composites is presented, where several chemical modifications are employed to improve the interfacial matrix-fiber bonding resulting in the enhancement of tensile strength of the composites.
Abstract: This paper is a review on the tensile properties of natural fiber reinforced polymer composites. Natural fibers have recently become attractive to researchers, engineers and scientists as an alternative reinforcement for fiber reinforced polymer (FRP) composites. Due to their low cost, fairly good mechanical properties, high specific strength, non-abrasive, eco-friendly and bio-degradability characteristics, they are exploited as a replacement for the conventional fiber, such as glass, aramid and carbon. The tensile properties of natural fiber reinforce polymers (both thermoplastics and thermosets) are mainly influenced by the interfacial adhesion between the matrix and the fibers. Several chemical modifications are employed to improve the interfacial matrix–fiber bonding resulting in the enhancement of tensile properties of the composites. In general, the tensile strengths of the natural fiber reinforced polymer composites increase with fiber content, up to a maximum or optimum value, the value will then drop. However, the Young’s modulus of the natural fiber reinforced polymer composites increase with increasing fiber loading. Khoathane et al. [1] found that the tensile strength and Young’s modulus of composites reinforced with bleached hemp fibers increased incredibly with increasing fiber loading. Mathematical modelling was also mentioned. It was discovered that the rule of mixture (ROM) predicted and experimental tensile strength of different natural fibers reinforced HDPE composites were very close to each other. Halpin–Tsai equation was found to be the most effective equation in predicting the Young’s modulus of composites containing different types of natural fibers.
1,757 citations
TL;DR: In this review, recent developments in the area of high-electron-mobility diimides based on rylenes and related aromatic cores, particularly perylene- and naphthalene-diimide-based small molecules and polymers, for application in high-performance organic field-effect transistors and photovoltaic cells are summarized and analyzed.
Abstract: Organic electron-transporting materials are essential for the fabrication of organic p-n junctions, photovoltaic cells, n-channel field-effect transistors, and complementary logic circuits. Rylene diimides are a robust, versatile class of polycyclic aromatic electron-transport materials with excellent thermal and oxidative stability, high electron affinities, and, in many cases, high electron mobilities; they are, therefore, promising candidates for a variety of organic electronics applications. In this review, recent developments in the area of high-electron-mobility diimides based on rylenes and related aromatic cores, particularly perylene- and naphthalene-diimide-based small molecules and polymers, for application in high-performance organic field-effect transistors and photovoltaic cells are summarized and analyzed.
1,494 citations
TL;DR: The resulting fluorinated polymer PBnDT-FTAZ outperforms poly(3-hexylthiophene), the current medium band gap polymer of choice, and thus is a viable candidate for use in highly efficient tandem cells.
Abstract: Recent research advances on conjugated polymers for photovoltaic devices have focused on creating low band gap materials, but a suitable band gap is only one of many performance criteria required for a successful conjugated polymer. This work focuses on the design of two medium band gap (∼2.0 eV) copolymers for use in photovoltaic cells which are designed to possess a high hole mobility and low highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels. The resulting fluorinated polymer PBnDT−FTAZ exhibits efficiencies above 7% when blended with [6,6]-phenyl C61-butyric acid methyl ester in a typical bulk heterojunction, and efficiencies above 6% are still maintained at an active layer thicknesses of 1 μm. PBnDT−FTAZ outperforms poly(3-hexylthiophene), the current medium band gap polymer of choice, and thus is a viable candidate for use in highly efficient tandem cells. PBnDT−FTAZ also highlights other performance criteria which contribute to high photovoltaic efficiency, bes...
1,463 citations
TL;DR: In this paper, a review of the preparation of polymer nanoparticles and the crucial parameters involved in techniques designed to obtain the desired properties is presented, and the choice of method depends on a number of factors, such as particle size, particle size distribution, area of application, etc.
1,393 citations
TL;DR: Mussels attach to solid surfaces in the sea and their adhesion must be rapid, strong, and tough, or else they will be dislodged and dashed to pieces by the next incoming wave.
Abstract: Mussels attach to solid surfaces in the sea. Their adhesion must be rapid, strong, and tough, or else they will be dislodged and dashed to pieces by the next incoming wave. Given the dearth of synthetic adhesives for wet polar surfaces, much effort has been directed to characterizing and mimicking essential features of the adhesive chemistry practiced by mussels. Studies of these organisms have uncovered important adaptive strategies that help to circumvent the high dielectric and solvation properties of water that typically frustrate adhesion. In a chemical vein, the adhesive proteins of mussels are heavily decorated with Dopa, a catecholic functionality. Various synthetic polymers have been functionalized with catechols to provide diverse adhesive, sealant, coating, and anchoring properties, particularly for critical biomedical applications.
1,380 citations
TL;DR: In this article, a simple method to control catechol-Fe3+ interpolymer cross-linking via pH was developed, inspired by the pH jump experienced by proteins during maturation of a mussel byssus secretion, and the resonance Raman signature was similar to that from native mussel thread cuticle and the gels displayed elastic moduli that approach covalently crosslinked gels as well as self-healing properties.
Abstract: Growing evidence supports a critical role of metal-ligand coordination in many attributes of biological materials including adhesion, self-assembly, toughness, and hardness without mineralization [Rubin DJ, Miserez A, Waite JH (2010) Advances in Insect Physiology: Insect Integument and Color, eds Jerome C, Stephen JS (Academic Press, London), pp 75–133]. Coordination between Fe and catechol ligands has recently been correlated to the hardness and high extensibility of the cuticle of mussel byssal threads and proposed to endow self-healing properties [Harrington MJ, Masic A, Holten-Andersen N, Waite JH, Fratzl P (2010) Science 328:216–220]. Inspired by the pH jump experienced by proteins during maturation of a mussel byssus secretion, we have developed a simple method to control catechol-Fe3+ interpolymer cross-linking via pH. The resonance Raman signature of catechol-Fe3+ cross-linked polymer gels at high pH was similar to that from native mussel thread cuticle and the gels displayed elastic moduli (G′) that approach covalently cross-linked gels as well as self-healing properties.
1,286 citations
TL;DR: In this critical review, ionogels are presented as a new class of hybrid materials, in which the properties of the IL are hybridized with those of another component, which may be organic, inorganic or hybrid organic-inorganic, which opens new routes for designing advanced materials, especially (bio)catalytic membranes, sensors and drug release systems.
Abstract: The current interest in ionic liquids (ILs) is motivated by some unique properties, such as negligible vapour pressure, thermal stability and non-flammability, combined with high ionic conductivity and wide electrochemical stability window. However, for material applications, there is a challenging need for immobilizing ILs in solid devices, while keeping their specific properties. In this critical review, ionogels are presented as a new class of hybrid materials, in which the properties of the IL are hybridized with those of another component, which may be organic (low molecular weight gelator, (bio)polymer), inorganic (e.g.carbon nanotubes, silicaetc.) or hybrid organic–inorganic (e.g.polymer and inorganic fillers). Actually, ILs act as structuring media during the formation of inorganic ionogels, their intrinsic organization and physicochemical properties influencing the building of the solid host network. Conversely, some effects of confinement can modify some properties of the guest IL, even though liquid-like dynamics and ion mobility are preserved. Ionogels, which keep the main properties of ILs except outflow, while allowing easy shaping, considerably enlarge the array of applications of ILs. Thus, they form a promising family of solid electrolyte membranes, which gives access to all-solid devices, a topical industrial challenge in domains such as lithium batteries, fuel cells and dye-sensitized solar cells. Replacing conventional media, organic solvents in lithium batteries or water in proton-exchange-membrane fuel cells (PEMFC), by low-vapour-pressure and non flammable ILs presents major advantages such as improved safety and a higher operating temperature range. Implementation of ILs in separation techniques, where they benefit from huge advantages as well, relies again on the development of supported IL membranes such as ionogels. Moreover, functionalization of ionogels can be achieved both by incorporation of organic functions in the solid matrix, and by encapsulation of molecular species (from metal complexes to enzymes) in the immobilized IL phase, which opens new routes for designing advanced materials, especially (bio)catalytic membranes, sensors and drug release systems (194 references).
1,017 citations
TL;DR: In this paper, the synthesis of polyhedral oligomeric silsesquioxane (T8-POSS) compounds, the miscibility of POSS derivatives and polymers, the preparation of both multifunctional and monofunctional monomers, and 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.
886 citations
TL;DR: This tutorial review will cover polymer-based optical chemosensors from 2007 to 2010.
Abstract: Recently, fluorescent or colorimetric chemosensors based on polymers have attracted great attention due to several important advantages, such as their simplicity of use, signal amplification, easy fabrication into devices, and combination of different outputs, etc. This tutorial review will cover polymer-based optical chemosensors from 2007 to 2010.
TL;DR: Recently, several series of new fullerene derivatives with higher-lying LUMO energy level and better solubility were reported in recent years for further improving the power conversion efficiency of the PSCs.
Abstract: Polymer solar cells (PSCs) are composed of a blend film of a conjugated polymer donor and a soluble fullerene derivative acceptor sandwiched between a PEDOT : PSS coated ITO positive electrode and a low workfunction metal negative electrode. The conjugated polymer donor and the fullerene derivative acceptor are the key photovoltaic materials for high performance PSCs. For the acceptors, although [6,6]-phenyl-C61-butyric acid methyl ester (PC60BM) and its corresponding C70 derivative PC70BM are dominantly used as the acceptors in PSC at present, several series of new fullerene derivatives with higher-lying LUMO energy level and better solubility were reported in recent years for further improving the power conversion efficiency of the PSCs. In this perspective paper, we reviewed the recent research progress on the new fullerene derivative acceptors, including various PC60BM-like C60 derivatives, PC60BM bisadduct, PC70BM bisadduct, indene-C60 bisadduct and indene-C70 bisadduct, trimetallic nitride endohedral fullerenes and other C60 derivatives with multi side chains. The synthesis and physicochemical properties of PC60BM and PC70BM were also introduced considering the importance of the two fullerene acceptors.
TL;DR: The synthesis and polymerization of a novel thieno[3,2-b]thiophene-diketopyrrolopyrrole-based monomer is reported, which has a maximum hole mobility of 1.95 cm(2) V(-1) s(-1), which is the highest mobility from a polymer-based OFET reported to date.
Abstract: We report the synthesis and polymerization of a novel thieno[3,2-b]thiophene−diketopyrrolopyrrole-based monomer. Copolymerization with thiophene afforded a polymer with a maximum hole mobility of 1.95 cm2 V−1 s−1, which is the highest mobility from a polymer-based OFET reported to date. Bulk-heterojunction solar cells comprising this polymer and PC71BM gave a power conversion efficiency of 5.4%.
TL;DR: In this article, a review examines the inspiration for high temperature proton exchange membrane fuel cells (PEMFCs) development, the technological constraints, and recent advances, and a detailed discussion of the synthesis of polymer, membrane fabrication and physicochemical characterizations is provided.
TL;DR: In this article, the structure, preparation and properties of the blends of natural and man-made polymers are discussed in general, and detailed examples are also drawn from scientific literature and practical work.
TL;DR: In this paper, notable recent advances in the field of shape memory polymers are highlighted, focusing on how the new developments have changed the conventional view of SMPs, what they mean for practical applications, and where the future opportunities are.
TL;DR: A facile and versatile synthesis using dopamine as a carbon source gives hollow carbon spheres and yolk-shell Au{at}Carbon nanocomposites that endow the products with high structural integrity.
Abstract: A facile and versatile synthesis using dopamine as a carbon source gives hollow carbon spheres and yolk-shell Au{at}Carbon nanocomposites. The uniform nature of dopamine coatings and their high carbon yield endow the products with high structural integrity. The Au{at}C nanocomposites are catalytically active.
TL;DR: In this paper, non-covalent functionalization was used to functionalize graphene nanosheets (GNSs) through ππ stacking of pyrene molecules with a functional segmented polymer chain, which results in a remarkable improvement in the thermal conductivity of GNS-filled polymer composites.
TL;DR: It is indicated that the deposition behavior of pDA is not strongly dependent on the nature of the substrates, and effective strategies for exploiting the properties of dopamine to create novel functional polymer materials are found.
Abstract: This study aims to explore the fundamental surface characteristics of polydopamine (pDA)-coated hydrophobic polymer films. A poly(vinylidene fluoride) (PVDF) film was surface modified by dip coating in an aqueous solution of dopamine on the basis of its self-polymerization and strong adhesion feature. The self-polymerization and deposition rates of dopamine on film surfaces increased with increasing temperature as evaluated by both spectroscopic ellipsometry and scanning electronic microscopy (SEM). Changes in the surface morphologies of pDA-coated films as well as the size and shape of pDA particles in the solution were also investigated by SEM, atomic force microscopy (AFM), and transmission electron microscopy (TEM). The surface roughness and surface free energy of pDA-modified films were mainly affected by the reaction temperature and showed only a slight dependence on the reaction time and concentration of the dopamine solution. Additionally, three other typical hydrophobic polymer films of polytetrafluoroethylene (PTFE), poly(ethylene terephthalate) (PET), and polyimide (PI) were also modified by the same procedure. The lyophilicity (liquid affinity) and surface free energy of these polymer films were enhanced significantly after being coated with pDA, as were those of PVDF films. It is indicated that the deposition behavior of pDA is not strongly dependent on the nature of the substrates. This information provides us with not only a better understanding of biologically inspired surface chemistry for pDA coatings but also effective strategies for exploiting the properties of dopamine to create novel functional polymer materials.
TL;DR: In this paper, a review of the preparation of copolymers and polymeric materials as starting materials for solid alkaline fuel cells membranes is presented, and the requirements for such membranes are also summarized.
TL;DR: A panoramic overview of recent progress in the most relevant areas related to such materials, including the polymerisation of natural monomers and their derivatives, the exploitation of biopolymers, as such, or after appropriate modifications, as well as the preparation of composites and blends, can be found in this article.
TL;DR: Donor-acceptor conjugated polymers PBDT-DTBT and PBDt-DTNT, based on 2,1,3-benzothiadiazole (BT) and naphtho[1,2-c:5,6-c]bis[ 1,2,5]thiad Diazole (NT), have been designed and synthesized for polymer solar cells.
Abstract: Donor–acceptor conjugated polymers PBDT-DTBT and PBDT-DTNT, based on 2,1,3-benzothiadiazole (BT) and naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole (NT), have been designed and synthesized for polymer solar cells NT contains two fused 1,2,5-thiadiazole rings that lower the band gap, enhance the interchain packing, and improve the charge mobility of the resulting polymer Consequently, the NT-based polymer PBDT-DTNT exhibited considerably better photovoltaic performance with a power conversion efficiency (PCE) of 600% when compared with the BT-based polymer PBDT-DTBT, which gave a PCE of 211% under identical device configurations
TL;DR: Methods for encapsulation and release, triggering methods, and mechanisms, and opinions on interesting obstacles for chemically induced activation with relevance for controlled release are presented.
Abstract: Stimuli-responsive capsules are of interest in drug delivery, fragrance release, food preservation, and self-healing materials. Many methods are used to trigger the release of encapsulated contents. Here we highlight mechanisms for the controlled release of encapsulated cargo that utilize chemical reactions occurring in solid polymeric shell walls. Triggering mechanisms responsible for covalent bond cleavage that result in the release of capsule contents include chemical, biological, light, thermal, magnetic, and electrical stimuli. We present methods for encapsulation and release, triggering methods, and mechanisms and conclude with our opinions on interesting obstacles for chemically induced activation with relevance for controlled release.
TL;DR: It was found that perfluorination of the polymer backbone resulted in poor photochemical stability against singlet oxygen attack and poor solar energy conversion efficiency, and the polymer containing mono-fluorinated thienothiophene gave the best solar cell performance.
Abstract: Herein, we describe the synthesis of fluorinated polythienothiophene-co-benzodithiophenes (PTBFs) and the characterization of their physical properties, especially their performance in solar cells. Fluorination of the polymer backbone lowered both the HOMO and LUMO energy levels and simultaneously widened the energy bandgap of the polymer (0.1-0.2 eV). Incorporation of fluorine into the various positions of the polymer backbone significantly affected the solar cells' power conversion efficiency from 2.3% to 7.2%. Detailed studies revealed that the polymer containing mono-fluorinated thienothiophene gave the best solar cell performance. Perfluorination of the polymer backbone led to poor compatibility with PC(71)BM molecules, thus poor solar energy conversion efficiency. This is possibly due to the enhanced self-organization properties of the polymer chains and the fluorophobicity effect. Furthermore, it was found that perfluorination of the polymer backbone resulted in poor photochemical stability against singlet oxygen attack. Theoretical studies indicated that the internal polarization caused enhancement of the negative charge density on thienothiophene rings, which rendered them vulnerable to [2+4] cycloaddition reaction with singlet oxygen.
TL;DR: This review explores several aspects of antimicrobial polymer silver nanocomposites, giving special focus to the critical analysis of the reported synthetic routes including their advantages, drawbacks, possible improvements, and real applicability in antibacterial and antifungal therapy.
TL;DR: In this paper, the authors provide an overview of the present situation with special attention to the use of olefin metathesis and thiol-ene chemistry as synthetic methods and as polymerization techniques.
TL;DR: Polymer-based nanocomposites (PNCs) have received increasing attention in both academia and industry as discussed by the authors, and they present outstanding mechanical properties and compatibility owing to their polymer matrix, the unique physical and chemical properties caused by the unusually large surface area to volume ratios and high interfacial reactivity of the nanofillers.
TL;DR: Lowering the modulus of hydrogel microparticles altered their biodistribution properties, allowing them to bypass several organs, such as the lung, that entrapped their more rigid counterparts, resulting in increasingly longer circulation times well past those of conventionalmicroparticles.
Abstract: It has long been hypothesized that elastic modulus governs the biodistribution and circulation times of particles and cells in blood; however, this notion has never been rigorously tested. We synthesized hydrogel microparticles with tunable elasticity in the physiological range, which resemble red blood cells in size and shape, and tested their behavior in vivo. Decreasing the modulus of these particles altered their biodistribution properties, allowing them to bypass several organs, such as the lung, that entrapped their more rigid counterparts, resulting in increasingly longer circulation times well past those of conventional microparticles. An 8-fold decrease in hydrogel modulus correlated to a greater than 30-fold increase in the elimination phase half-life for these particles. These results demonstrate a critical design parameter for hydrogel microparticles.
TL;DR: The general properties and applications of different water soluble polymers in the formulation of different dosage forms, novel delivery systems and biomedical applications will be discussed.
Abstract: Advances in polymer science have led to the development of novel drug delivery systems. Some polymers are obtained from natural resources and then chemically modified for various applications, while others are chemically synthesized and used. A large number of natural and synthetic polymers are available. In the present paper, only water soluble polymers are described. They have been explained in two categories (1) synthetic and (2) natural. Drug polymer conjugates, block copolymers, hydrogels and other water soluble drug polymer complexes have also been explained. The general properties and applications of different water soluble polymers in the formulation of different dosage forms, novel delivery systems and biomedical applications will be discussed.
TL;DR: Stable dispersions of uniform high-aspect-ratio aramid nanofibers (ANFs) with diameters between 3 and 30 nm and up to 10 μm in length were successfully obtained and revealed distinct morphological features similar to carbon nanotubes.
Abstract: Stable dispersions of nanofibers are virtually unknown for synthetic polymers. They can complement analogous dispersions of inorganic components, such as nanoparticles, nanowires, nanosheets, etc. as a fundamental component of a toolset for design of nanostructures and metamaterials via numerous solvent-based processing methods. As such, strong flexible polymeric nanofibers are very desirable for the effective utilization within composites of nanoscale inorganic components such as nanowires, carbon nanotubes, graphene, and others. Here stable dispersions of uniform high-aspect-ratio aramid nanofibers (ANFs) with diameters between 3 and 30 nm and up to 10 μm in length were successfully obtained. Unlike the traditional approaches based on polymerization of monomers, they are made by controlled dissolution of standard macroscale form of the aramid polymer, that is, well-known Kevlar threads, and revealed distinct morphological features similar to carbon nanotubes. ANFs are successfully processed into films using layer-by-layer (LBL) assembly as one of the potential methods of preparation of composites from ANFs. The resultant films are transparent and highly temperature resilient. They also display enhanced mechanical characteristics making ANF films highly desirable as protective coatings, ultrastrong membranes, as well as building blocks of other high performance materials in place of or in combination with carbon nanotubes.