Structure Of Polymer Backbone Research Articles

Mussel-Inspired Polymer Binders for Organic Electrodes.

The development of polymer binders is necessary to meet the growing demands of modern energy storage technologies. While catechol-containing materials are proven successful in silicon anodes, their application in organic batteries remains unexplored. In this contribution, the synthesis of four polymers are described with nearly identical side chain composition but varying backbone structures. The materials are used to investigate the effect of polymer backbone structure on the binding abilities of catechol-containing materials. Comparative analysis with the commonly used polyvinylidene fluoride (PVDF) binder aims to address two critical questions: 1) Can catechol-rich polymers replace PVDF for use in organic cathodes? and 2) Does the choice of polymer backbone affect the performance of the battery?. The investigation reveals that supramolecular interactions, such as π-π stacking and coordination bonding, are pivotal features of catechol binders. Among the catechol-rich polymers, the polyacrylate binder stands out, likely attributed to its high flexibility. Additionally, introducing an oxygen atom into a catechol-rich polynorbornene enhances lithium-ion conductivity and rate performance. Overall, the findings highlight the viability of catechol-containing polymers as organic cathode binders, and that the choice of polymer backbone is a crucial factor for their use as lithium-ion battery binder materials.

Ionic Polybenzimidazoles Crosslinked through Thiol-Ene Reactions for Anion Exchange Membranes

This research introduces a study outlining the synthesis and characteristics of innovative anion exchange membranes that utilize m-polybenzimidazole (m-PBI) as the polymer backbone structure. These membranes incorporate quaternary ammonium groups and alkene groups as side chains. These ionic m-PBI membranes were further crosslinked through thermal thiol-ene reactions. By adeptly manipulating the quantities of attached quaternary ammonium groups and alkene groups, the ion exchange capacity (IEC) values and crosslinking degrees were independently controlled. A comprehensive range of m-PBI based anion exchange membranes was developed, showcasing IEC values ranging from 1.51 to 2.50 mmol/g. This series of membranes demonstrated hydroxide conductivity levels ranging between 14 and 58 mS/cm at an operational temperature of 80 °C. Particularly noteworthy is the comparison between membranes with similar IEC values: the crosslinked membranes exhibited reduced water absorption while effectively maintaining a level of hydroxide conductivity comparable to that of uncrosslinked membranes. Moreover, the crosslinked membranes exhibited enhanced dimensional stability. An intriguing finding emerged from a crosslinked membrane with an IEC value of 2.46 mmol/g, which retained a remarkable 84% of its original hydroxide conductivity after being immersed in a 1.0 M sodium hydroxide solution at 60 °C for a duration of 720 hours. These membranes demonstrated mechanical strength even in their hydrated state, exhibiting tensile strengths ranging from 10.8 to 14.6 MPa. Given their heightened hydroxide conductivity, improved resistance to alkaline conditions, and favorable mechanical attributes, the crosslinked ionic m-PBIs emerge as promising candidates for anion exchange membranes in fuel cell applications. Keywords ; anion exchange membranes, crosslinking reaction, polybenzimidazole, back titration, mechanical strength.

Multicomponent Polymerization of Sulfur, Diynes, and Aromatic Diamines and Facile Tuning of Polymer Backbone Structures

Multicomponent Polymerization of Sulfur, Diynes, and Aromatic Diamines and Facile Tuning of Polymer Backbone Structures

Network Polymer Properties Engineered Through Polymer Backbone Dispersity and Structure

AbstractDispersity (Ð or Mw/Mn) is an important parameter in material design and as such can significantly impact the properties of polymers. Here, polymer networks with independent control over the molecular weight and dispersity of the linear chains that form the material are developed. Using a RAFT polymerization approach, a library of polymers with dispersity ranging from 1.2—1.9 for backbone chain‐length (DP) 100, and 1.4—3.1 for backbone chain‐length 200 were developed and transformed to networks through post‐polymerization crosslinking to form disulfide linkers. The tensile, swelling, and adhesive properties were explored, finding that both at DP 100 and DP 200 the swelling ratio, tensile strength, and extensibility were superior at intermediate dispersity (1.3—1.5 for DP 100 and 1.6—2.1 for DP 200) compared to materials with either substantially higher or lower dispersity. Furthermore, adhesive properties for materials with chains of intermediate dispersity at DP 200 revealed enhanced performance compared to the very low or high dispersity chains.

Network Polymer Properties Engineered Through Polymer Backbone Dispersity and Structure.

Dispersity (Ð or Mw/Mn) is an important parameter in material design and as such can significantly impact the properties of polymers. Here, polymer networks with independent control over the molecular weight and dispersity of the linear chains that form the material are developed. Using a RAFT polymerization approach, a library of polymers with dispersity ranging from 1.2-1.9 for backbone chain-length (DP) 100, and 1.4-3.1 for backbone chain-length 200 were developed and transformed to networks through post-polymerization crosslinking to form disulfide linkers. The tensile, swelling, and adhesive properties were explored, finding that both at DP 100 and DP 200 the swelling ratio, tensile strength, and extensibility were superior at intermediate dispersity (1.3-1.5 for DP 100 and 1.6-2.1 for DP 200) compared to materials with either substantially higher or lower dispersity. Furthermore, adhesive properties for materials with chains of intermediate dispersity at DP 200 revealed enhanced performance compared to the very low or high dispersity chains.

Poly(fluorenyl-indolinedione) based hydroxide conducting membrane for anion exchange membrane water electrolyzers

Anion exchange membranes (AEMs) serve as the heart of anion exchange membrane water electrolyzers (AEMWE) for green energy conversion electrochemical devices, directly determining the ultimate performance of the electrochemical devices. Conductivity in trade-off with stability (chemical and dimensional stability) is a major target in the development of alkaline membranes. We prepared chemically stable polyisatin-aromatics without ether linkages along the backbone by superacid-catalyzed alkylation. The alkali-stable dimethylpiperidinium cations were covalently linked to the polymer backbone through the aliphatic chain to give comb-type polyelectrolytes. Incorporating the fluorene structural units along the polymer skeleton is expected to improve conductivity and stability. The effect of polymer backbone structure and conformation on AEM properties is systematically elucidated. The results indicate the PipPFTI-25 AEM with 25 mol% dimethylfluorene fragments in the backbone has lower IEC (∼1.36 mmol g−1) but achieves high ionic conductivity (84.6 mS cm−1 at 80 °C). PipPFTI-25 exhibited superior dimensional and alkali stability, mainly reflected in the swelling ratio of less than 10 % while the OH− conductivity remained at 70 % after immersion in 2 M NaOH solution at 80 °C for 1680 h. The AEMWE with PipPFTI-25 operating at 60 °C in 1 M KOH achieves a current of 838 mA cm−2 at 2.5 V. This work demonstrated the feasibility of poly(fluorenyl-indolinedione) AEMs for electrolyzer applications.

Chain-Kinked Design: Improving Stretchability of Polymer Semiconductors through Nonlinear Conjugated Linkers.

The manipulation of the polymer backbone structure has a profound influence on the crystalline behavior and charge transport characteristics of polymers. These strategies are commonly employed to optimize the performance of stretchable polymer semiconductors. However, a universal method that can be applied to conjugated polymers with different donor-acceptor combinations is still lacking. In this study, we propose a universal strategy to boost the stretchability of polymers by incorporating the nonlinear conjugated linker (NCL) into the main chain. Specifically, we incorporate meta-dibromobenzene (MB), characterized by its asymmetric linkage sites, as the NCL into the backbone of diketopyrrolopyrrole-thiophene-based (DPP-based) polymers. Our research demonstrates that the introduction of MB prompts chain-kinking, thereby disrupting the linearity and central symmetry of the DPP conjugated backbone. This modification reshapes the polymer conformation, decreasing the radius of gyration and broadening the free volume, which consequently adjusts the level of crystallinity, leading to a considerable increase in the stretchability of the polymer. Importantly, this method increases stretchability without compromising mobility and exhibits broad applicability across a wide range of donor-acceptor pair polymers. Leveraging this strategy, fully stretchable transistors were fabricated using a DPP polymer that incorporates 10 mol % of MB. These transistors display a mobility of approximately 0.5 cm2 V-1 s-1 and prove remarkably durable, maintaining 90% of this mobility even after enduring 1000 cycles at 25% strain. Overall, we propose a method to systematically control the main-chain conformation, thereby enhancing the stretchability of conjugated polymers in a widely applicable manner.

Hole-transport materials based on benzodithiophene-thiazolothiazole-containing conjugated polymers for efficient perovskite solar cells

Conjugated polymers are promising hole-transport materials (HTMs) for designing efficient and stable perovskite solar cells (PSCs). The structure of polymer backbone and position of side substituents greatly influences their electronic properties, film morphology, and hence, the charge extraction and charge transport characteristics of HTMs. Herein, we design two novel donor-acceptor conjugated polymers based on benzodithiophene (BDT) bearing triisopropylsilyl substituents and thiophene-flanked thiazolothiazole block (Tz) with different side chain position. In polymer in-BDTTz alkyl chains are placed “toward” to the Tz moiety, while in aus-BDTTz “outward” to the Tz block. Polymeric HTM in-BDTTz enables 18.7% power conversion efficiency in devices outperforming that of PSCs with aus-BDTTz and reference devices employing poly(triarylamine) (PTAA). Furthermore, PSCs with in-BDTTz as HTM demonstrates stable operation comparable to that of PTAA-based devices. These findings feature alkylsilyl-substituted benzodithiophene-based polymers as promising dopant-free hole-transport materials for efficient and stable perovskite photovoltaics.

Counterion Control and the Spectral Signatures of Polarons, Coupled Polarons, and Bipolarons in Doped P3HT Films

AbstractWhen an electron is removed from a conjugated polymer, such as poly(3‐hexylthiophene‐2,5‐diyl) (P3HT), the remaining hole and associated change in the polymer backbone structure from aromatic to quinoidal are referred to as a polaron. Bipolarons are created by removing the unpaired electron from an already‐oxidized polymer segment. In electrochemically‐doped P3HT films, polarons, and bipolarons are readily observed, but in chemically‐doped P3HT films, bipolarons rarely form. This is explained by studying the effects of counterion position on the formation of polarons, strongly coupled polarons, and bipolarons using both spectroscopic and X‐ray diffraction experiments and time‐dependent density functional theory calculations. The counterion positions control whether two polarons spin‐pair to form a bipolaron or whether they strongly couple without spin‐pairing are found. When two counterions lie close to the same polymer segment, bipolarons can form, with an absorption spectrum that is blueshifted from that of a single polaron. Otherwise, polarons at high concentrations do not spin‐pair, but instead J‐couple, leading to a redshifted absorption spectrum. The counterion location needed for bipolaron formation is accompanied by a loss of polymer crystallinity. These results explain the observed formation order of single polarons, coupled single polarons, and singlet bipolarons in electrochemically‐ and chemically‐doped conjugated polymers.

Poly (aryl piperidinium) anion exchange membranes for acid recovery: The effect of backbone structure

The anion exchange membrane (AEM)-based diffusion dialysis is considered as an efficient strategy for the recovery of acid. Recently, the novel ether-free poly (aryl piperidinium) (PAP) AEMs modified by side chain grafting has been applied in the area of acid separation, showing excellent acid flux. However, there is little study focusing on the influence of polymer backbone structures of AEMs in acid separation. Herein, a series of PAP AEMs with different backbone arrangements based on diphenyl, m-terphenyl, and p-terphenyl were prepared for acid separation via diffusion dialysis. Compared with diphenyl and p-terphenyl, the m-terphenyl-based AEM exhibits a fantastic comprehensive performance, with a dialysis coefficient of 20.1 × 10-3 m h−1 and H+/Fe2+ selectivity of 196. The acid flux and selectivity can be kept after 7 days of acidic stability test in 1 mol/L HCl and 0.25 mol/L FeCl2. This can be attributed to its unique spatial configuration that induces a microphase-separated structure, which is beneficial to H+ conduction. Meanwhile, its high rigidity and low solubility could restrain the water uptake and swelling, and thus reduce the Fe2+ flux and enhance the selectivity. Furthermore, the stability of all PAP AEMs was tested in 2 mol/L HCl at 60 °C for 60 days, and their ionic conductivities still remained above 90 %. This study highlights a simple and reliable strategy to enhance the acid separation performance of AEMs via the facile backbone design.

Dual Molecular Oxygen Activation Sites on Conjugated Microporous Polymers for Enhanced Photocatalytic Formation of Benzothiazoles

Oxidative formation of high value compounds involving active oxygen species using heterogeneous polymeric photocatalysts has become a useful tool in catalysis. Controlling the interaction between the active sites on polymer photocatalysts and oxygen molecules is still challenging due to the rather large polymer backbone structure. Here, we design a triazine-containing donor acceptor-type conjugated microporous polymer (CMP) containing dual major active sites at F and N atoms for molecular oxygen activation. Introducing fluorine atoms on the CMP backbone led to a combined effect of enhanced adsorption and electron transfer of oxygen. Time-resolved photoluminescence, electronic paramagnetic resonance spectra, and DFT calculation revealed favorable absorption energy and electron transfer kinetics between the CMP and oxygen molecules, thus efficiently generating superoxide radicals (O2•-) and singlet oxygen (1O2) as main active oxygen species. The photocatalytic activity, selectivity, and reusability of the CMP was demonstrated by the photocatalytic formation of a variety of benzothiazoles.

Impact of the Polymer Backbone Structure on the Separation Properties of New Stationary Phases Based on Tricyclononenes

The main purpose of this paper is to compare the chromatographic properties of capillary columns prepared with polymers with different backbone structures and to demonstrate the possibility of polymer differentiation via inverse gas chromatography. With the use of addition and metathesis types of polymerization of tricyclononenes, two new stationary phases were prepared. The metathesis polymer contained double bonds in the polymeric backbone while the backbone of the addition polymer was fully saturated and relatively mobile. A comparison of the separation and adsorption properties of new phases with conventional gas chromatography (GC) stationary phases clearly indicated their non-polar characteristics. However, the difference in the polymer structure appeared to have very little effect on the stationary phase separation properties, so other parameters were used for polymer characterization. The thermodynamic parameters of the sorption of alkanes and aromatic compounds in both polymeric stationary phases were also very similar; however, the entropy of sorption for hydrocarbons with seven or more carbon atoms was different for the two polymers. An evaluation of the specific surface energy of the stationary phases also allowed us to discriminate the two stationary phases.

A comparative study on binary polymer blends comprising rigid planar low-bandgap semiconductor and flexible coil-type insulator

A polymer blend is an essential member of a class of materials analogous to metal alloys, in which two polymers are blended together to create a noble material with different physical properties. Not only the physicochemical properties of each polymer but also their relative interaction and miscibility are a key to eliciting novel materials properties. Here, we investigated the effects of blending a flexible coil-type insulating polymer on the charge transport characteristics of rigid planar semiconducting polymers. To this end, we systematically controlled the blending ratio of the commercial insulating polymer, polystyrene, and one of two different diketopyrrolopyrrole-based donor-acceptor alternating copolymers, and characterized the electrical, microstructural, and morphological properties of the semiconductor–insulator polymer blend films. We found that the electrical properties of the films are strongly correlated with the polymer blend ratio and the resulting films’ vertical segregation and crystalline structures and that hole transport and electron transport alter differently with the polymer backbone structure and blend ratio. These results are expected to be greatly helpful in optimizing the semiconductor–insulator polymer ink formulations for potential use in printed electronics.

Alkaline stable piperidinium-based biphenyl polymer for anion exchange membranes

Long-term alkaline stability of the anion exchange membrane is a critical requirement for its practical application under a high pH operation environment. It is an effective strategy to improve the alkaline stability of the membrane from the three aspects of the polymer backbone, cationic groups, and linkage structure. A type of alkaline stable piperidinium-based biphenyl polymer (PBP-PIP) was prepared via super electrophilic activated reaction. The all carbon-bond backbone was chosen to ensure the alkaline stability of the polymer backbone by preventing it from reacting with hydroxide. Based on the stable polymer backbone, the piperidinium group with a ring structure and β‑hydrogen-free linkage structure was considered to improve the alkaline stability of cationic groups and linkage structure by slowing down the occurrence of nucleophilic substitution and Hofmann elimination reaction. The PBP-PIP membrane exhibited hydroxide conductivity of 57 mS cm−1 at 80 °C and tensile strength of 28.2 MPa. Meanwhile, the PBP-PIP membrane showed good alkaline stability with a 76% retention of conductivity and 77% retention of tensile strength after being immersed in a 1 M NaOH aqueous solution at 80 °C for 750 h.

Screening semiconducting polymers to discover design principles for tuning charge carrier mobility.

We employ a rapid method for computing the electronic structure and orbital localization characteristics for a sample of 36 different polymer backbone structures. This relatively large sample derived from recent literature is used to identify the features of the monomer sequence that lead to greater charge delocalization and, potentially, greater charge mobility. Two characteristics contributing in equal measure to large localization length are the reduced variation of the coupling between adjacent monomers due to conformational fluctuations and the presence of just two monomers in the structural repeating units. For such polymers a greater mismatch between the HOMO orbitals of the fragments and, surprisingly, a smaller coupling between them is shown to favour greater delocalization of the orbitals. The underlying physical reasons for such observations are discussed and explicit and constructive design rules are proposed.

Origin of Proteolytic Stability of Peptide-Brush Polymers as Globular Proteomimetics.

Peptide-brush polymers (PBPs), wherein every side-chain of the polymers is peptidic, represent a new class of proteomimetic with unusually high proteolytic resistance while maintaining bioactivity. Here, we sought to determine the origin of this behavior and to assess its generality via a combined theory and experimental approach. A series of PBPs with various polymer backbone structures were prepared and examined for their proteolytic stability and bioactivity. We discovered that an increase in the hydrophobicity of the polymer backbones is predictive of an elevation in proteolytic stability of the side-chain peptides. Computer simulations, together with small-angle X-ray scattering (SAXS) analysis, revealed globular morphologies for these polymers, in which pendant peptides condense around hydrophobic synthetic polymer backbones driven by the hydrophobic effect. As the hydrophobicity of the polymer backbones increases, the extent of solvent exposure of peptide cleavage sites decreases, reducing their accessibility to proteolytic enzymes. This study provides insight into the important factors driving PBP aqueous-phase structures to behave as globular, synthetic polymer-based proteomimetics.

Effects of microplastics on soil microbiome: The impacts of polymer type, shape, and concentration

Increasing research has recognized that the ubiquitous presence of microplastics in terrestrial environments is undeniable, which potentially alters the soil ecosystem properties and processes. The fact that microplastics with diverse characteristics enter into the soil may induce distinct effects on soil ecosystems. Our knowledge of the impacts of microplastics with different polymers, shapes, and concentrations on soil bacterial communities is still limited. To address this, we examined the effects of spherical microplastics (150 μm) with different polymers (i.e., polyethylene (PE), polystyrene (PS), and polypropylene (PP)) and four shapes of PP microplastics (i.e., fiber, film, foam, and particle) at a constant concentration (1%, w/w) on the soil bacterial community in an agricultural soil over 60 days. Treatments with different concentrations (0.01–20%, w/w) of PP microplastic particles (150 μm) were also included. The bacterial communities in PE and PP treatments showed a similar pattern but separated from those in PS-treated soils, indicating the polymer backbone structure is an important factor modulating the soil bacterial responses. Fiber, foam, and film microplastics significantly affected the soil bacterial composition as compared to the particle. The community dissimilarity of soil bacteria was significantly (R2 = 0.592, p < 0.001) correlated with the changes of microplastic concentration. The random forest model identified that certain bacteria belonging to Patescibacteria were closely linked to microplastic contamination. Additionally, analysis of the predicted function further showed that microplastics with different characteristics caused distinct effects on microbial community function. Our findings suggested that the idiosyncrasies of microplastics should not be neglected when studying their effects on terrestrial ecosystems.

High-level hierarchical morphology reinforcing covalent adaptable networks

High-level hierarchical morphology reinforcing covalent adaptable networks

Ionic liquid-based molecular design for transparent, flexible, and fire-retardant triboelectric nanogenerator (TENG) for wearable energy solutions

Transparent and flexible triboelectric nanogenerator (TENG) represent an efficient and invisible energy solution for generating eco-friendly electricity from mechanical human motion for wearable electronic devices and systems. In addition to boosting the output performance of TENG, the molecular design relying on non-flammable materials and anti-ignition invulnerability should be considered when designing TENG devices, to ensure the safety of personnel working under extreme temperature conditions. However, the requirement for non-flammability of conventional transparent triboelectric materials in wearable applications remains either unmet or almost unexamined to date. Here, we propose bi-continuous and flame-retarding epoxy-based ion-gel films that retain mechanical flexibility, optical transparency, and fast ionic polarization for high-performance and deformable TENG. It is found that our transparent and flexible TENG devices produce an output voltage and current as high as approximately 150 V and 45 μA, respectively, from an external mechanical stimulus while also retaining their fire retardancy and low flammability. This TENG is not flammable even after 20 s of trying, whereas conventional triboelectric materials were completely burned by the fire under the same conditions. Therefore, we propose that our synergistic design of triboelectric ion-gel films, including fire-retardant epoxy-based dual cation-incorporated ionic liquid, represents a significant step toward a high-performance, durable, and transparent wearable energy solution. A new type of ionic liquid-based molecular design for our TENG device structure containing dual-positive ions and forming the electrical double layer (EDL) due to the rapid movement of internal ions during friction. It was intended that the dual ILs including Li+ and EMIM+ positive ions can easily transport through the bi-continuous structure of fire-resistant polymer backbone upon the mechanical surface friction as depicted in the right image. • Ionic liquid-based molecular design for high-performance and mechanically durable TENG film. • Flame-retarding, transparent and flexible epoxy-based ion-gel films. • Transparent and flexible triboelectric nanogenerators (TENGs) producing an output voltage and current of ~150 V and ~45 μA from an external mechanical stimulus.

Metal ion cross-linked nanoporous polymeric membranes with improved organic solvent resistance for molecular separation

The strategy of chemical cross-linking has been well used in the system of polyimide membranes for organic solvent nanofiltration (OSN). However, this method significantly affects the permeability and mechanical properties of polyimide membranes, as the opening of imide bond during the chemical cross-linking reaction damages the original polymer backbone structure. This work presents the formation of a new generation of OSN membranes through facile metal ion cross-linking of integrally skinned asymmetric polyimide membranes. A type of specially designed polyimide is synthesized with carboxyl functional groups introduced into the polymer backbone as organic ligands, and metal ion coordination cross-linking reaction takes place between the functionalized polyimide membranes and metal ions. Especially, the Cu2+ ion cross-linked polyimide membranes exhibit good stability in a variety of organic solvents including toluene, DMF, acetone, methanol, acetonitrile, etc., with >99% rejection to Coomassie brilliant blue (MW = 854) in acetone. Meanwhile, no significant attenuation of membrane permeability is observed after the cross-linking, as the metal ion does not occupy as much free volume as traditional chemical cross-linkers. Furthermore, the metal ion cross-linking is found to greatly improve the compaction resistance of the membrane due to the enhanced polymer-chain rigidity. This work confirms the feasibility of ion coordination based polymeric membranes for organic solvent separation applications and provides a brand-new route for the fabrication of OSN membranes with unique advantages.