Showing papers on "Polymer published in 2016"
01 Jun 2016
TL;DR: In this paper, the main purpose of this review is to elaborate the mechanical and physical properties that affect its stability, processability, degradation, immiscibility, aging and recyclability, and therefore its potential suitability to fulfill specific application requirements.
Abstract: Poly(lactic acid) (PLA), so far, is the most extensively researched and utilized biodegradable aliphatic polyester in human history. Due to its merits, PLA is a leading biomaterial for numerous applications in medicine as well as in industry replacing conventional petrochemical-based polymers. The main purpose of this review is to elaborate the mechanical and physical properties that affect its stability, processability, degradation, PLA-other polymers immiscibility, aging and recyclability, and therefore its potential suitability to fulfill specific application requirements. This review also summarizes variations in these properties during PLA processing (i.e. thermal degradation and recyclability), biodegradation, packaging and sterilization, and aging (i.e. weathering and hygrothermal). In addition, we discuss up-to-date strategies for PLA properties improvements including components and plasticizer blending, nucleation agent addition, and PLA modifications and nanoformulations. Incorporating better understanding of the role of these properties with available improvement strategies is the key for successful utilization of PLA and its copolymers/composites/blends to maximize their fit with worldwide application needs.
1,360 citations
TL;DR: In this article, state-of-the-art polymer electrolytes are discussed with respect to their electrochemical and physical properties for their application in lithium polymer batteries, and the incorporation of inorganic fillers into GPEs to improve their mechanical strength as well as their transport properties and electrochemical properties is discussed.
Abstract: In this review, state-of-the-art polymer electrolytes are discussed with respect to their electrochemical and physical properties for their application in lithium polymer batteries. We divide polymer electrolytes into the two large categories of solid polymer electrolytes and gel polymer electrolytes (GPE). The performance requirements and ion transfer mechanisms of polymer electrolytes are presented at first. Then, solid polymer electrolyte systems, including dry solid polymer electrolytes, polymer-in-salt systems (rubbery electrolytes), and single-ion conducting polymer electrolytes, are described systematically. Solid polymer electrolytes still suffer from poor ionic conductivity, which is lower than 10−5 S cm−1. In order to further improve the ionic conductivity, numerous new types of lithium salt have been studied and inorganic fillers have been incorporated into solid polymer electrolytes. In the section on gel polymer electrolytes, the types of plasticizer and preparation methods of GPEs are summarized. Although the ionic conductivity of GPEs can reach 10−3 S cm−1, their low mechanical strength and poor interfacial properties are obstacles to their practical application. Significant attention is paid to the incorporation of inorganic fillers into GPEs to improve their mechanical strength as well as their transport properties and electrochemical properties.
969 citations
TL;DR: Preceramic monomers that are cured with ultraviolet light in a stereolithography 3D printer or through a patterned mask, forming 3D polymer structures that can have complex shape and cellular architecture are reported.
Abstract: The extremely high melting point of many ceramics adds challenges to additive manufacturing as compared with metals and polymers. Because ceramics cannot be cast or machined easily, three-dimensional (3D) printing enables a big leap in geometrical flexibility. We report preceramic monomers that are cured with ultraviolet light in a stereolithography 3D printer or through a patterned mask, forming 3D polymer structures that can have complex shape and cellular architecture. These polymer structures can be pyrolyzed to a ceramic with uniform shrinkage and virtually no porosity. Silicon oxycarbide microlattice and honeycomb cellular materials fabricated with this approach exhibit higher strength than ceramic foams of similar density. Additive manufacturing of such materials is of interest for propulsion components, thermal protection systems, porous burners, microelectromechanical systems, and electronic device packaging.
786 citations
TL;DR: A cross-linked polymer containing pendant molecules attached to the polymer framework is shown to form flexible and low-cost membranes, and all-solid-state Li/LiFePO4 cells showed a notably high Coulombic efficiency of 99.8-100% over 640 cycles.
Abstract: A cross-linked polymer containing pendant molecules attached to the polymer framework is shown to form flexible and low-cost membranes, to be a solid Li+ electrolyte up to 270 °C, much higher than those based on poly(ethylene oxide), to be wetted by a metallic lithium anode, and to be not decomposed by the metallic anode if the anions of the salt are blocked by a ceramic electrolyte in a polymer/ceramic membrane/polymer sandwich electrolyte (PCPSE). In this sandwich architecture, the double-layer electric field at the Li/polymer interface is reduced due to the blocked salt anion transfer. The polymer layer adheres/wets the lithium metal surface and makes the Li-ion flux at the interface more homogeneous. This structure integrates the advantages of the ceramic and polymer. With the PCPSE, all-solid-state Li/LiFePO4 cells showed a notably high Coulombic efficiency of 99.8–100% over 640 cycles.
774 citations
TL;DR: In this paper, the widely used non-derivatizing cellulose solvents are summarized, including their dissolution mechanisms, with emphasis on the neat regenerated cellulose materials and the composite materials.
710 citations
TL;DR: Much stronger chemical/mechanical interactions between monodispersed 12 nm diameter SiO2 nanospheres and poly(ethylene oxide) (PEO) chains were produced by in situ hydrolysis, which significantly suppresses the crystallization of PEO and thus facilitates polymer segmental motion for ionic conduction.
Abstract: High ionic conductivity solid polymer electrolyte (SPE) has long been desired for the next generation high energy and safe rechargeable lithium batteries. Among all of the SPEs, composite polymer electrolyte (CPE) with ceramic fillers has garnered great interest due to the enhancement of ionic conductivity. However, the high degree of polymer crystallinity, agglomeration of ceramic fillers, and weak polymer–ceramic interaction limit the further improvement of ionic conductivity. Different from the existing methods of blending preformed ceramic particles with polymers, here we introduce an in situ synthesis of ceramic filler particles in polymer electrolyte. Much stronger chemical/mechanical interactions between monodispersed 12 nm diameter SiO2 nanospheres and poly(ethylene oxide) (PEO) chains were produced by in situ hydrolysis, which significantly suppresses the crystallization of PEO and thus facilitates polymer segmental motion for ionic conduction. In addition, an improved degree of LiClO4 dissociati...
702 citations
TL;DR: In this paper, the authors present a comprehensive understanding on synthesis, morphology control, electrochemical performances and solid-state devices of the nanostructured polypyrrole (PPy) and its nanocomposites.
568 citations
TL;DR: A new approach to designing crosslinked, rigid polymer nanofilms with enhanced microporosity by manipulating the molecular structure is reported, showing outstanding separation performance in organic solvents.
Abstract: Here it is shown how ultrathin and microporous polymer membranes, fabricated using sterically contorted monomers, can achieve enhanced performance for solvent-based separations.
543 citations
TL;DR: Three novel solution-processable small molecules, which contain π-bridges with gradient-decreased electron density and end acceptors substituted with various fluorine atoms, exhibit excellent inverted device performance and an average power conversion efficiency of 11.08% are reported.
Abstract: Solution-processable small molecules for organic solar cells have attracted intense attention for their advantages of definite molecular structures compared with their polymer counterparts. However, the device efficiencies based on small molecules are still lower than those of polymers, especially for inverted devices, the highest efficiency of which is <9%. Here we report three novel solution-processable small molecules, which contain π-bridges with gradient-decreased electron density and end acceptors substituted with various fluorine atoms (0F, 1F and 2F, respectively). Fluorination leads to an optimal active layer morphology, including an enhanced domain purity, the formation of hierarchical domain size and a directional vertical phase gradation. The optimal morphology balances charge separation and transfer, and facilitates charge collection. As a consequence, fluorinated molecules exhibit excellent inverted device performance, and an average power conversion efficiency of 11.08% is achieved for a two-fluorine atom substituted molecule.
530 citations
TL;DR: Porosity is a rare property for molecular materials but, surprisingly, porous solids built from discrete organic cage molecules have emerged as a versatile functional-materials platform as mentioned in this paper, and the surface areas of molecular organic cage solids now rival those of metal-organic frameworks.
Abstract: Porosity is a rare property for molecular materials but, surprisingly, porous solids built from discrete organic cage molecules have emerged as a versatile functional-materials platform. From modest beginnings less than a decade ago, there are now organic cage solids with surface areas that can rival extended metal–organic frameworks. In contrast to network polymers and frameworks, these organic cages are synthesized first and then assembled in the solid state in a separate step. This offers solution-processing options that are not available for insoluble organic and inorganic frameworks. In this Review, we highlight examples of porous organic cages and focus on the unique features that set them apart, such as their molecular solubility, their increased tendency to exhibit polymorphism and the scope for modular co-crystallization. The surface areas of molecular organic cage solids now rival those of metal–organic frameworks. In this Review, the synthesis and structures of various porous organic cages are outlined together with a discussion of the characteristics — such as solubility, polymorphism and modular co-crystallization — that distinguish these cages from their inorganic or hybrid counterparts.
498 citations
TL;DR: The structural modifications applied to DPP polymers are focused on and rationalize and explain the relationships between chemical structure and organic photovoltaic performance are rationalized.
Abstract: ConspectusConjugated polymers have been extensively studied for application in organic solar cells. In designing new polymers, particular attention has been given to tuning the absorption spectrum, molecular energy levels, crystallinity, and charge carrier mobility to enhance performance. As a result, the power conversion efficiencies (PCEs) of solar cells based on conjugated polymers as electron donor and fullerene derivatives as electron acceptor have exceeded 10% in single-junction and 11% in multijunction devices. Despite these efforts, it is notoriously difficult to establish thorough structure–property relationships that will be required to further optimize existing high-performance polymers to their intrinsic limits.In this Account, we highlight progress on the development and our understanding of diketopyrrolopyrrole (DPP) based conjugated polymers for polymer solar cells. The DPP moiety is strongly electron withdrawing and its polar nature enhances the tendency of DPP-based polymers to crystalliz...
TL;DR: It is reported that the ROP of γ-BL can, with a suitable catalyst, proceed smoothly to high conversions under ambient pressure to produce PγBL materials with a number-average molecular weight up to 30 kg mol(-1) and with controlled linear and/or cyclic topologies.
Abstract: Ring-opening polymerization (ROP) is a powerful synthetic methodology for the chemical synthesis of technologically important biodegradable aliphatic polyesters from cyclic esters or lactones. However, the bioderived five-membered γ-butyrolactone (γ-BL) is commonly referred as ‘non-polymerizable’ because of its low strain energy. The chemical synthesis of poly(γ-butyrolactone) (PγBL) through the ROP process has been realized only under ultrahigh pressure (20,000 atm, 160 °C) and only produces oligomers. Here we report that the ROP of γ-BL can, with a suitable catalyst, proceed smoothly to high conversions (90%) under ambient pressure to produce PγBL materials with a number-average molecular weight up to 30 kg mol–1 and with controlled linear and/or cyclic topologies. Remarkably, both linear and cyclic PγBLs can be recycled back into the monomer in quantitative yield by simply heating the bulk materials at 220 °C (linear polymer) or 300 °C (cyclic polymer) for one hour, which thereby demonstrates the complete recyclability of PγBL. Bio-derived γ-butyrolactone (γ-BL) is commonly referred to as ‘non-polymerizable’ due to its low strain energy. Now it has been shown that ring-opening polymerization of γ-BL can in fact proceed to high conversions under ambient pressure with a suitable catalyst, producing high-molecular-weight polymers with controlled topologies and complete recyclability.
TL;DR: This work demonstrates a rational design for fine-tuned crystallinity of polymer acceptors, and reveals the high potential of all-PSCs through structure and morphology engineering of semicrystalline polymer:polymer blends.
Abstract: Growing interests have been devoted to the design of polymer acceptors as potential replacement for fullerene derivatives for high-performance all polymer solar cells (all-PSCs). One key factor that is limiting the efficiency of all-PSCs is the low fill factor (FF) (normally <0.65), which is strongly correlated with the mobility and film morphology of polymer:polymer blends. In this work, we find a facile method to modulate the crystallinity of the well-known naphthalene diimide (NDI) based polymer N2200, by replacing a certain amount of bithiophene (2T) units in the N2200 backbone by single thiophene (T) units and synthesizing a series of random polymers PNDI-Tx, where x is the percentage of the single T. The acceptor PNDI-T10 is properly miscible with the low band gap donor polymer PTB7-Th, and the nanostructured blend promotes efficient exciton dissociation and charge transport. Solvent annealing (SA) enables higher hole and electron mobilities, and further suppresses the bimolecular recombination. As expected, the PTB7-Th:PNDI-T10 solar cells attain a high PCE of 7.6%, which is a 2-fold increase compared to that of PTB7-Th:N2200 solar cells. The FF of 0.71 reaches the highest value among all-PSCs to date. Our work demonstrates a rational design for fine-tuned crystallinity of polymer acceptors, and reveals the high potential of all-PSCs through structure and morphology engineering of semicrystalline polymer:polymer blends.
TL;DR: Three self-exfoliated guanidinium halide based ionic covalent organic nanosheets with antimicrobial property are synthesized and a mixed matrix membrane is devised which could be useful for antimicrobial coatings with plausible medical benefits.
Abstract: Covalent organic nanosheets (CONs) have emerged as functional two-dimensional materials for versatile applications. Although π–π stacking between layers, hydrolytic instability, possible restacking prevents their exfoliation on to few thin layered CONs from crystalline porous polymers. We anticipated rational designing of a structure by intrinsic ionic linker could be the solution to produce self-exfoliated CONs without external stimuli. In an attempt to address this issue, we have synthesized three self-exfoliated guanidinium halide based ionic covalent organic nanosheets (iCONs) with antimicrobial property. Self-exfoliation phenomenon has been supported by molecular dynamics (MD) simulation as well. Intrinsic ionic guanidinium unit plays the pivotal role for both self-exfoliation and antibacterial property against both Gram-positive and Gram-negative bacteria. Using such iCONs, we have devised a mixed matrix membrane which could be useful for antimicrobial coatings with plausible medical benefits.
TL;DR: New methods for linking fluorophores to the polymer that now enable expansion microscopy with conventional fluorescently labeled antibodies and fluorescent proteins are developed and characterized.
Abstract: Expansion microscopy is a technique in which fluorophores on fixed specimens are linked to a swellable polymer that is physically expanded to enable super-resolution microscopy with ordinary microscopes. We have developed and characterized new methods for linking fluorophores to the polymer that now enable expansion microscopy with conventional fluorescently labeled antibodies and fluorescent proteins. Our methods simplify the procedure and expand the palette of compatible labels, allowing rapid dissemination of the technique.
TL;DR: It is suggested that the degradation of plastic debris proceeds relatively quickly in salt marshes and that surface delamination is the primary mechanism by which microplastic particles are produced in the early stages of degradation.
Abstract: As part of the degradation process, it is believed that most plastic debris becomes brittle over time, fragmenting into progressively smaller particles. The smallest of these particles, known as microplastics, have been receiving increased attention because of the hazards they present to wildlife. To understand the process of plastic degradation in an intertidal salt marsh habitat, strips (15.2 cm × 2.5 cm) of high-density polyethylene, polypropylene, and extruded polystyrene were field-deployed in June 2014 and monitored for biological succession, weight, surface area, ultraviolet (UV) transmittance, and fragmentation. Subsets of strips were collected after 4 wk, 8 wk, 16 wk, and 32 wk. After 4 wk, biofilm had developed on all 3 polymers with evidence of grazing periwinkles (Littoraria irrorata). The accreting biofilm resulted in an increased weight of the polypropylene and polystyrene strips at 32 wk by 33.5% and 167.0%, respectively, with a concomitant decrease in UV transmittance by approximately 99%. Beginning at 8 wk, microplastic fragments and fibers were produced from strips of all 3 polymers, and scanning electron microscopy revealed surface erosion of the strips characterized by extensive cracking and pitting. The results suggest that the degradation of plastic debris proceeds relatively quickly in salt marshes and that surface delamination is the primary mechanism by which microplastic particles are produced in the early stages of degradation. Environ Toxicol Chem 2016;35:1632-1640. © 2016 SETAC.
TL;DR: In this paper, the authors reviewed recent advances in different polymer-based reverse osmosis (RO) and forward osmotic (FO) desalination membranes in terms of materials and strategies developed for improving properties and performances.
TL;DR: A liquid crystalline polymer film doped with a visible light responsive fluorinated azobenzene capable of continuous chaotic oscillatory motion when exposed to ambient sunlight in air is described.
Abstract: Nature provides much inspiration for the design of materials capable of motion upon exposure to external stimuli, and many examples of such active systems have been created in the laboratory. However, to achieve continuous motion driven by an unchanging, constant stimulus has proven extremely challenging. Here we describe a liquid crystalline polymer film doped with a visible light responsive fluorinated azobenzene capable of continuous chaotic oscillatory motion when exposed to ambient sunlight in air. The presence of simultaneous illumination by blue and green light is necessary for the oscillating behaviour to occur, suggesting that the dynamics of continuous forward and backward switching are causing the observed effect. Our work constitutes an important step towards the realization of autonomous, persistently self-propelling machines and self-cleaning surfaces powered by sunlight.
TL;DR: This work addresses the issue of accelerating polymer dielectrics design by extracting learning models from data generated by accurate state-of-the-art first principles computations for polymers occupying an important part of the chemical subspace.
Abstract: The ability to efficiently design new and advanced dielectric polymers is hampered by the lack of sufficient, reliable data on wide polymer chemical spaces, and the difficulty of generating such data given time and computational/experimental constraints. Here, we address the issue of accelerating polymer dielectrics design by extracting learning models from data generated by accurate state-of-the-art first principles computations for polymers occupying an important part of the chemical subspace. The polymers are 'fingerprinted' as simple, easily attainable numerical representations, which are mapped to the properties of interest using a machine learning algorithm to develop an on-demand property prediction model. Further, a genetic algorithm is utilised to optimise polymer constituent blocks in an evolutionary manner, thus directly leading to the design of polymers with given target properties. While this philosophy of learning to make instant predictions and design is demonstrated here for the example of polymer dielectrics, it is equally applicable to other classes of materials as well.
TL;DR: By regulating the mobility of classic −EO− based backbones, an innovative polymer electrolyte system can be architectured and allows the construction of all solid lithium-based polymer cells having outstanding cycling behaviour in terms of rate capability and stability over a wide range of operating temperatures.
Abstract: Here we demonstrate that by regulating the mobility of classic −EO− based backbones, an innovative polymer electrolyte system can be architectured. This polymer electrolyte allows the construction of all solid lithium-based polymer cells having outstanding cycling behaviour in terms of rate capability and stability over a wide range of operating temperatures. Polymer electrolytes are obtained by UV-induced (co)polymerization, which promotes an effective interlinking between the polyethylene oxide (PEO) chains plasticized by tetraglyme at various lithium salt concentrations. The polymer networks exhibit sterling mechanical robustness, high flexibility, homogeneous and highly amorphous characteristics. Ambient temperature ionic conductivity values exceeding 0.1 mS cm−1 are obtained, along with a wide electrochemical stability window (>5 V vs. Li/Li+), excellent lithium ion transference number (>0.6) as well as interfacial stability. Moreover, the efficacious resistance to lithium dendrite nucleation and growth postulates the implementation of these polymer electrolytes in next generation of all-solid Li-metal batteries working at ambient conditions.
TL;DR: The basic concepts and synthetic strategies leading to the development of organometallic and coordination compounds featuring properties that are relevant for potential applications in diverse areas of research are summarized and discussed.
Abstract: The incorporation of metal centers into the backbone of polymers has led to the development of a broad range of organometallic and coordination compounds featuring properties that are relevant for potential applications in diverse areas of research, ranging from energy storage/conversion to bioactive or self-healing materials. In this review, the basic concepts and synthetic strategies leading to these types of materials as well as the scope of available characterization techniques will be summarized and discussed.
TL;DR: It is found that the high optical absorption of a diketopyrrolopyrrole-thienothiophene copolymer can be explained by the high persistence length of the polymer, and high absorption in other polymers with high theoretical persistence length is demonstrated.
Abstract: The specific optical absorption of an organic semiconductor is critical to the performance of organic optoelectronic devices. For example, higher light-harvesting efficiency can lead to higher photocurrent in solar cells that are limited by sub-optimal electrical transport. Here, we compare over 40 conjugated polymers, and find that many different chemical structures share an apparent maximum in their extinction coefficients. However, a diketopyrrolopyrrole-thienothiophene copolymer shows remarkably high optical absorption at relatively low photon energies. By investigating its backbone structure and conformation with measurements and quantum chemical calculations, we find that the high optical absorption can be explained by the high persistence length of the polymer. Accordingly, we demonstrate high absorption in other polymers with high theoretical persistence length. Visible light harvesting may be enhanced in other conjugated polymers through judicious design of the structure.
TL;DR: Fluorescence spectroscopy on a series of aqueous solutions of poly(acrylic acid) containing a luminescent label showed that polymers with molar mass, Mn < 16.5 kDa did not exhibit a pH responsive conformational change, which is typical of higher molarMass poly(Acrylic acid), while large molarmass polymers did exhibit pH-dependent diffusion.
Abstract: Fluorescence spectroscopy on a series of aqueous solutions of poly(acrylic acid) containing a luminescent label showed that polymers with molar mass, Mn < 16.5 kDa did not exhibit a pH responsive conformational change, which is typical of higher molar mass poly(acrylic acid). Below this molar mass, polymers remained in an extended conformation, regardless of pH. Above this molar mass, a pH-dependent conformational change was observed. Diffusion-ordered nuclear magnetic resonance spectroscopy confirmed that low molar mass polymers did not undergo a conformational transition, although large molar mass polymers did exhibit pH-dependent diffusion.
TL;DR: In this article, it was shown that poly(ethylene glycol) bis(3-aminopropyl) with 1,3,5-triformylbenzene with an equal molar ratio of amine and aldehyde functionalities in organic solvents with varying polarity and in neat condition exhibits malleability and self-healing characteristics.
Abstract: Covalent polymeric networks composed of imine cross-linkages have been prepared by condensation polymerization of poly(ethylene glycol) bis(3-aminopropyl) with 1,3,5-triformylbenzene with an equal molar ratio of amine and aldehyde functionalities in organic solvents with varying polarity and in neat condition. The polymer networks exhibit malleability and self-healing characteristics. Rheological measurements revealed that longer reaction time is required to reach the gel point (i.e., crossover of G′ and G″) in polar solvents than in nonpolar solvents. The malleability of the solvent-swelled polymer network is also strongly dependent on the solvent polarity. Polymer gels in polar solvents are more malleable than those in nonpolar solvents, as supported by the dynamic mechanical analysis. These results are consistent with faster dynamic imine bond exchange in the polar solvents relative to the nonpolar solvents, thus requiring higher functionality conversion to form an elastic network in the polar solvent ...
TL;DR: This review discusses the synthesis and properties of thermosets and thermoplastic polymers prepared from vanillin, ferulic acid, guaiacol, syringaldehyde, or 4-hydroxybenzoic acid.
Abstract: Nowadays, the synthesis of (semi)aromatic polymers from lignin derivatives is of major interest, as aromatic compounds are key intermediates in the manufacture of polymers and lignin is the main source of aromatic biobased substrates. Phenols with a variety of chemical structures can be obtained from lignin deconstruction; among them, vanillin and ferulic acid are the main ones. Depending on the phenol substrates, different chemical modifications and polymerization pathways are developed, leading to (semi)aromatic polymers covering a wide range of thermomechanical properties. This review discusses the synthesis and properties of thermosets (vinyl ester resins, cyanate ester, epoxy, and benzoxazine resins) and thermoplastic polymers (polyesters, polyanhydrides, Schiff base polymers, polyacetals, polyoxalates, polycarbonates, acrylate polymers) prepared from vanillin, ferulic acid, guaiacol, syringaldehyde, or 4-hydroxybenzoic acid.
TL;DR: This review focuses on the synthesis of CO2-responsive polymers using reversible deactivation radical polymerization (RDRP), a powerful technique for the preparation of well-defined (co)polymers with precise control over molecular weight distribution, chain-end functional groups, and polymer architectural design.
Abstract: CO2 is an ideal trigger for switchable or stimuli-responsive materials because it is benign, inexpensive, green, abundant, and does not accumulate in the system. Many different CO2-responsive materials including polymers, latexes, solvents, solutes, gels, surfactants, and catalysts have been prepared. This review focuses on the preparation, self-assembly, and functional applications of CO2-responsive polymers. Detailed discussion is provided on the synthesis of CO2-responsive polymers, in particular using reversible deactivation radical polymerization (RDRP), formerly known as controlled/living radical polymerization (CLRP), a powerful technique for the preparation of well-defined (co)polymers with precise control over molecular weight distribution, chain-end functional groups, and polymer architectural design. Self-assembly in aqueous dispersed media is highlighted as well as emerging potential applications.
TL;DR: A key finding reveals that maintenance of a planar conformation of the phenoxazine catalyst during the catalytic cycle encourages the synthesis of well-defined macromolecules.
Abstract: N-Aryl phenoxazines have been synthesized and introduced as strongly reducing metal-free photoredox catalysts in organocatalyzed atom transfer radical polymerization for the synthesis of well-defined polymers. Experiments confirmed quantum chemical predictions that, like their dihydrophenazine analogs, the photoexcited states of phenoxazine photoredox catalysts are strongly reducing and achieve superior performance when they possess charge transfer character. We compare phenoxazines to previously reported dihydrophenazines and phenothiazines as photoredox catalysts to gain insight into the performance of these catalysts and establish principles for catalyst design. A key finding reveals that maintenance of a planar conformation of the phenoxazine catalyst during the catalytic cycle encourages the synthesis of well-defined macromolecules. Using these principles, we realized a core substituted phenoxazine as a visible light photoredox catalyst that performed superior to UV-absorbing phenoxazines as well as previously reported organic photocatalysts in organocatalyzed atom transfer radical polymerization. Using this catalyst and irradiating with white LEDs resulted in the production of polymers with targeted molecular weights through achieving quantitative initiator efficiencies, which possess dispersities ranging from 1.13 to 1.31.
TL;DR: In this paper, a systematic study was conducted for the analysis of polymer backbone chemical stability in alkaline media, including poly(arylene ethers, poly(biphenyl alkylene)s, and polystyrene block copolymers.
Abstract: Anion exchange membranes are an important component in alkaline electrochemical energy conversion and storage devices, and their alkaline stability plays a crucial role for the long-term use of these devices. Herein, a systematic study was conducted for the analysis of polymer backbone chemical stability in alkaline media. Nine representative polymer structures including poly(arylene ether)s, poly(biphenyl alkylene)s, and polystyrene block copolymers were investigated for their alkaline stability. Polymers with aryl ether bonds in their repeating unit showed poor chemical stability when treated with KOH and NaOCH3 solutions, whereas polymers without aryl ether bonds [e.g., poly(biphenyl alkylene)s and polystyrene block copolymers] remained stable. Additional NMR studies and density functional theory (DFT) calculations of small molecule model compounds that mimic the chemical structures of poly(arylene ether)s confirmed that electron-withdrawing groups near to the aryl ether bonds in the repeating unit acc...
TL;DR: An overview of the chemistry that is used in interfacial polymerization, discusses the (dis)advantages of derived material types, and assesses the future prospects for synthesis of ultrathin functional materials via interfacial polymers.
TL;DR: It is shown that proper and precise tuning of both donor and acceptor polymer Mns is critical for optimizing APSC performance and the importance of optimizing Mn for both polymer components to realize the full potential of AP SC performance is highlighted.
Abstract: The influence of the number-average molecular weight (Mn) on the blend film morphology and photovoltaic performance of all-polymer solar cells (APSCs) fabricated with the donor polymer poly[5-(2-hexyldodecyl)-1,3-thieno[3,4-c]pyrrole-4,6-dione-alt-5,5-(2,5-bis(3-dodecylthiophen-2-yl)thiophene)] (PTPD3T) and acceptor polymer poly{[N,N′-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} (P(NDI2OD-T2); N2200) is systematically investigated. The Mn effect analysis of both PTPD3T and N2200 is enabled by implementing a polymerization strategy which produces conjugated polymers with tunable Mns. Experimental and coarse-grain modeling results reveal that systematic Mn variation greatly influences both intrachain and interchain interactions and ultimately the degree of phase separation and morphology evolution. Specifically, increasing Mn for both polymers shrinks blend film domain sizes and enhances donor–acceptor polymer–polymer interfacial areas, affording increased...