Miscible Polymer Research Articles

The performance-stability conundrum of BTP-based organic solar cells

<h2>Summary</h2> As the power conversion efficiency of organic photovoltaic has been dramatically improved to over 18%, achieving long-term stability is now crucial for applications of this promising photovoltaic technology. Among the high-efficiency systems, most are using BTP-4F and its analogs as acceptors. Herein, we determine the thermal transition temperatures (<i>T</i>_g) of seven BTP analogs to develop a structure-<i>T</i>_g framework. Our results point out an unresolved molecular design conundrum on how to simultaneously achieve high performance and intrinsic stability with BTP-based acceptors. We also show that PC₇₁BM has miscibility above the percolation threshold in PM6 and can maintain local charge percolation and improved stability in ternary devices. However, PC₇₁BM is not miscible with BTP-C3-4F and unfavorable vertical gradients that develop during aging still degrade performance. This points to a second thermodynamic conundrum. A compound with differential miscibility in the donor polymer can only impact percolation, and a compound with differential miscibility with the BTP only impacts diffusion.

Formulation of ionic liquid APIs via spray drying processes to enable conversion into single and two-phase solid forms

Ionic liquid (IL) forms of drugs are increasingly being explored to address problems presented by poorly water-soluble drugs and solid-state stability. However, before ILs of active pharmaceutical ingredients (APIs) can be routinely incorporated into oral solid dosage forms (OSDs), challenges surrounding their ease of handling and manufacture must be addressed. To this end a framework for transforming API-ILs into solid forms at high loadings based on spray encapsulation using an immiscible polymer has recently been demonstrated. The current work demonstrates that this framework can be applied to a broad range of newly synthesized low glass transition temperature (Tg) API-ILs. Furthermore, the work explores a second novel approach to solidification of API-ILs based on polymer-API-IL miscibility that, to the best of our knowledge, has not been previously demonstrated. Modulated differential scanning calorimetry (mDSC) and attenuated total reflectance Fourier transform infrared spectroscopy showed that it was possible to produce spray dried solid materials, at acceptable loadings and yields for OSD applications in the form of both two-phase phase encapsulated systems and single phase amorphous solid dispersions (ASDs). This was achieved by the appropriate selection of an API-IL insoluble polymer (ethyl cellulose) for phase separated systems, or a miscible polymer with an exceptionally high Tg (the polysaccharide, maltodextrin) for the ASDs. Both approaches successfully overcame the Tg suppression associated with room temperature ILs.This work represents the first step to understanding the fundamental critical physical attributes of these systems to facilitate a more mechanistic methodology for their design.

Stability of Film-Forming Dispersions: Affects the Morphology and Optical Properties of Polymeric Films.

Starch-based films are promising alternatives to synthetic films in food packaging. They were widely studied in terms of mechanical and optical properties. In food packaging, optical properties are of great interest because ultra violet (UV-light) protection is strictly required. Nevertheless, the characterization of film-forming dispersions was poorly addressed, especially regarding its correlation with the film produced. In this work, we characterized film-forming dispersions at different compositions of starch and carboxymethyl cellulose (CMC) by Turbiscan. This instrument is based on multiple light scattering and gives significant information about the miscibility of polymers in the dispersed phase. Indeed, it identifies the phenomena of destabilization and phase separation before their visibility to the unaided eye. This work aimed to study whether the homogeneous/inhomogeneous morphology of films could be forecast by the analysis of profiles obtained in the dispersed phase. The films produced were investigated by optical microscopy and absorbance analysis. As the CMC fraction increased, Turbiscan showed reduced phase separation. This implies better miscibility of mixture components and higher gelification degree. The related film was more homogeneous and presented higher UV absorbance. Consequently, film-forming dispersions and optical properties of films are strictly correlated and Turbiscan-based analysis is very useful to investigate the dispersion stability and predict the film quality.

Compatibilization of water-soluble polyurethane/poly(lactic acid) blends upon addition of surface-modified CaCO3

We report the fabrication of a polymer composite that is biodegradable and water-soluble. The soluble polymer, water-soluble polyurethane, was fabricated via the acetone process. The biodegradable aspect was obtained from poly(lactic acid) (PLA), which is a biodegradable polyester. The two polymers are made miscible by using glycidyl methacrylate (GM). The GM was binded to the surface of CaCO3 particles, which are used to improve the thermomechanical properties of the WPU/PLA blends. The binding of GM to the surface of the CaCO3 particles was confirmed by FTIR, FE-SEM, qualitatively and quantitatively using TGA. These three analyses have depicted the appearance and dispersion of GM groups on the surface of the CaCO3 particles. The miscibility of the fabricated composites was confirmed with FE-SEM, which displays a miscible polymer blend. The thermomechanical properties of the composites were analyzed with TGA and UTM. We have obtained a high thermal stability with good tensile strength and promising improvements in elongation at break composite. The polymer composite has also shown to be highly hydrophilic.

Synthesis and Characterization of Konjac Gum/Polyethylene Glycol-Silver Nanoparticles and their Potential Application as a Colorimetric Sensor for Hydrogen Peroxide

Green and low-cost synthesis strategies for ultrasonic preparation of polymer blend matrix-based silver nanoparticles (Ag NPs) and the development of rapid and highly sensitive detection routes have a great attention in optical sensor applications. In this study, we investigated the hydrogen peroxide detection performance of Konjac gum/polyethylene glycol—silver nanoparticles (KG/PEG-Ag NPs). The KG/PEG-Ag NPs were synthesized via an ultrasonic process and characterized by different techniques, such as ultraviolet–visible spectroscopy (UV–Vis), Fourier-Transform Infrared spectroscopy (FT-IR), Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX), Transmission Electron Microscope (TEM), and The Xray Photoelectron Spectroscopy (XPS). Furthermore, we determined the experimental optimization on the effect of the rheological parameters of nanostructure with the highest correlation constant (R2:0.989–0.996), and the intrinsic viscosity (14.71–26.77 dl/g). To provide the miscible polymer blends and homogeneous dispersion of the nanostructure, we compared the rheological parameters with the experimental results. The response time was less than 5 s and the lower limit of detection was 0.071 μM. This novel, highly sensitive, rapid, and naked-eye colorimetric biosensor based-Ag NPs, which are prepared using an ultrasonic manufacturing approach, opens up a green approach of development facile detection of hydrogen peroxide in practical biomedical applications.

Modeling the Glass Transition and Glassy Dynamics of Random Copolymers Using the TS2 Mean-Field Approach

Understanding the glass transition and glassy dynamics in random copolymers and miscible polymer blends is crucial for both fundamental and applied polymer science. While there are multiple models describing the dependence of the glass transition temperature on the copolymer or blend composition (Fox, Gordon-Taylor, Kwei, and others), it is still not easy to describe or predict the broader temperature dependence of relaxation times in these systems. Here, we expand our TS2 (two states, two (time)scales) mean-field model to random copolymers and formulate simple and intuitive mixing rules for the model parameters as a function of composition. We obtain a new equation for the characteristic transition temperature, T*, that can serve as an approximate predictor for the glass transition temperature, Tg. The model then allows us to refine the prediction and calculate Tg based on the standard criterion (τα(Tg) = 10² s). We can also calculate the temperature-dependent α- and β-relaxation times for different copolymer compositions. To test the theory, we computed the glass transition temperatures and relaxation times for random styrene-methylmethacrylate (PS-r-PMMA) and statistical styrene-butylmethacrylate (PS-stat-PnBMA) copolymers and found good qualitative and semi-quantitative agreement with published literature data. The described approach can be easily extended to blends and copolymers with multiple components.

Investigating crystallization tendency, miscibility, and molecular interactions of drug–polymer systems for the development of amorphous solid dispersions

Crystallization tendencies, thermal analysis [i.e. glass transition temperature (T g)], crystallinity, and melting point depression, along with theoretical calculations such as solubility parameter, of five different drugs [i.e. curcumin (CUR), indomethacin (IND), flutamide (FLU), dipyridamole (DIP), and griseofulvin (GRI)] in the absence and presence of four different polymers in various drug–polymer ratios were determined and analyzed. Physical states of the drug in the solid dispersions (SDs) and their stability were characterized by X-ray diffraction and modulated differential scanning calorimetry. Infrared (IR) and Raman were used in selected systems (i.e. CUR, DIP, and GRI systems) to explore the role of drug–polymer interactions in the amorphization of SDs. The crystallization tendencies of pure drugs were categorized as low (CUR, IND), moderate (FLU), and high (DIP, GRI). In the presence of selected polymers, the crystallization tendency of the drugs changed, though a high polymer concentration was required for high crystallization-tendency drugs [i.e. DIP and GRI (>50% w/w)]. Polymers showing a greater effect on the crystallization tendency of drugs were found to have higher drug–polymer miscibility and stronger molecular interactions. Drug–polymer systems selected from the investigation of physical mixtures formed stable amorphous solid dispersions (ASD). Furthermore, the rank order of the crystallization tendency of drug–polymer systems correlated well with those on miscibility and molecular interactions. Those rank orders also correlated well with the stability of prepared/reported SDs. Hence, the developed approach has significant potential to be a rational screening method for the development of amorphous SDs.

Rheo-optical Near-infrared (NIR) Analysis of Binary Amorphous Polymer Blend Consisting of Polyvinyl Chloride (PVC) and Polymethyl Methacrylate (PMMA).

A binary amorphous polymer blend consisting of polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA) was studied with a rheo-optical characterization technique based on the combination of a near-infrared (NIR) spectrometer and a tensile testing machine. In rheo-optical NIR spectroscopy, tensile deformations were applied to polymers to induce the displacement of molecular chains while being probed by NIR light. The application of this technique was extended to a partially miscible amorphous polymer blend consisting of PVC and PMMA to demonstrate how it can be utilized to detect subtle but important deformation behavior. A change in the NIR spectral feature revealed that the initial deformation of the blend induces the reorientation of the PVC chains. A part of the PMMA connected to the PVC was tagged during the PVC deformation. Further deformation of the sample eventually resulted in necking propagation to the surrounding area.

3D printing of immediate-release tablets containing olanzapine by filaments extrusion

In this work, hot-melt extrusion (HME) is coupled with fused deposition modeling (FDM) mediated 3D printing to demonstrate additive manufacturing to fabricate immediate release (IR) prototypes of olanzapine with the aim of enhanced solubility using a fast disintegrating polymer (Kollicoat® IR). Drug-polymer solubility and interaction parameters were estimated by Hansen solubility parameters and Hildebrand–Scott equation. The obtained values signified drug–polymer miscibility. The detailed in vitro physicochemical evaluations of the developed filament through HME and its derived 3D printed tablet by FDM technique were assessed thoroughly by several analytical means such as light microscopy, DSC, XRD, FT-IR, SEM, etc. The average disintegration time of this developed 3D printed IR tablet was found to be 63.33 (±3.6) sec complying with the USP limit. Additionally, in vitro dissolution study data revealed almost close correlations and both showed 100% of drug release within 15 min, thus complying with the definition of IR tablet. Thus, this study demonstrates the feasibility of directly using olanzapine-Kollicoat® IR through the HME process without the addition of any plasticizers, organic solvents, etc. and coupling of HME with 3D printing technology allowing prototypes of IR tablet of olanzapine.

Controlled Formation of All-Aqueous Janus Droplets by Liquid-Liquid Phase Separation of an Aqueous Three-Phase System.

Janus droplets have been demonstrated in a wide range of applications, ranging from drug delivery, to biomedical imaging, to bacterial detection. However, existing fabrication strategies often involve nonaqueous solvents, such as organic solvent or oil, which largely limits their use in fields that require a high degree of biocompatibility. Here, we present a method to achieve all-aqueous Janus droplets by liquid-liquid phase separation of an aqueous three-phase system (A3PS). An aqueous droplet containing two initially miscible polymers is first injected into an aqueous solution of another concentrated polymer, and then it spontaneously phase-separates into a Janus droplet due to the diffusive mass exchange between the drop and bulk phases during equilibration. To achieve continuous generation of the Janus droplets, the A3PS is further integrated with microfluidics and electrospray. The size and shape of the phase-separated Janus droplets can be easily controlled by tuning the operation parameters, such as the flow rate and/or the initial composition of the drop phases. Dumbbell-shaped and snowman-shaped Janus droplets with average sizes between 100 and 400 μm can be generated by both coflow microfluidics and electrospray. In particular, the phase-separated Janus droplets can simultaneously load two different liposomes into each compartment, which are promising carriers for combination drugs. The obtained Janus droplets are superior templates for biocompatible materials, which can serve as building blocks such as high-order droplet patterns for constructing advanced biomaterials.

Dielectric Performance of Silica-Filled Nanocomposites Based on Miscible (PP/PP-HI) and Immiscible (PP/EOC) Polymer Blends

This study compares different polymer-nanofiller blends concerning their suitability for application as insulating thermoplastic composites for High Voltage Direct Current (HVDC) cable application. Two polymer blends, PP/EOC (polypropylene/ethylene-octene copolymer) and PP/PP-HI (polypropylene/ propylene - ethylene copolymer) and their nanocomposites filled with 2 wt.% of fumed silica modified with 3-aminopropyltriethoxysilane were studied. Morphology, thermal stability, crystallization behavior dynamic relaxation, conductivity, charge trap distribution and space charge behavior were studied respectively. The results showed that the comprehensive performance of the PP/PP-HI composite is better than the one of the PP/EOC composite due to better polymer miscibility and flexibility, as well as lower charging current density and space charge accumulation. Nanosilica addition improves the thermal stability and dielectric properties of both polymer blends. The filler acts as nucleating agent increasing the crystallization temperature, but decreasing the degree of crystallinity. Dynamic mechanical analysis results revealed three polymer relaxation transitions: PP glass transition ( $\beta$ ), weak crystal reorientation ( $\alpha 1$ ) and melting ( $\alpha 2$ ). The nanosilica introduced deep traps in the polymer blends and suppressed space charge accumulation, but slightly increased the conductivity. A hypothesis for the correlation of charge trap distribution and polymer chain transition peaks is developed: In unfilled PP/EOC and PP/PP-HI matrices, charges are mostly located at the crystalline-amorphous interface, whereas in the filled PP/EOC/silica and PP/PP-HI /silica composites, charges are mostly located at the nanosilica-polymer interface. Overall, the PP/PP-HI (55/45) nanocomposite with 2 wt.% modified silica and 0.3 wt.% of antioxidants making it $a$ promising material for PP based HVDC cable insulation application with $a$ reduced space charge accumulation and good mechanical properties.

Controlling the Film Microstructure in Organic Thermoelectrics

Doping is a vital method to increase the charge carrier concentration of conjugated polymers, thus improving the performance of organic electronic devices. However, the introduction of dopants may cause phase separation. The miscibility of dopants and polymers as well as the doping-induced microstructure change are always the barriers in the way to further enhance the thermoelectrical performance. Here, recent research studies about the influence of molecular doping on the microstructures of conjugated polymers are summarized, with an emphasis on the n-type doping. Highlighted topics include how to control the distribution and density of dopants within the conjugated polymers by modulating the polymer structure, dopant structure, and solution-processing method. The strong Coulombic interactions between dopants and polymers as well as the heterogeneous doping process of polymers can hinder the polymer film to achieve better miscibility of dopants/polymer and further loading of the charge carriers. Recent developments and breakthroughs provide guidance to control the film microstructures in the doping process and achieve high-performance thermoelectrical materials.

Energy dependent XPS measurements on thin films of a poly(vinyl methyl ether)/polystyrene blend concentration profile on a nanometer resolution to understand the behavior of nanofilms.

The composition of the surface layer in dependence from the distance of the polymer/air interface in thin films with thicknesses below 100 nm of miscible polymer blends in a spatial region of a few nanometers is not investigated completely. Here, thin films of the blend poly(vinyl methyl ether) (PVME)/polystyrene (PS) with a composition of 25/75 wt% are investigated by Energy Resolved X-ray Photoelectron Spectroscopy (ER-XPS) at a synchrotron storage ring using excitation energies lower than 1 keV. By changing the energy of the photons the information depth is varied in the range from ca. 1 nm to 10 nm. Therefore, the PVME concentration could be estimated in dependence from the distance of the polymer/air interface for film thicknesses below 100 nm. Firstly, as expected for increasing information depth the PVME concentration decreases. Secondly, it was found that the PVME concentration at the surface has a complicated dependence on the film thickness. It increases with decreasing film thickness until 30 nm where a maximum is reached. For smaller film thicknesses the PVME concentration decreases. A simplified layer model is used to calculate the effective PVME concentration in the different spatial regions of the surface layer.

Rouse Mode Analysis of Relaxation in Polymer Blends

AbstractThe relaxation spectra of the components in polymer blends determine the dynamic mechanical properties of the corresponding composite materials, which, in thermo‐rheological studies, show a delicate dependence on their chemical and physical properties as well as its bulk composition. A molecular dynamics simulation based Rouse mode analysis is performed to detect the relaxation spectra of the component chains on all length scales ranging from one monomer to the whole chain size, indicating that the bulk composition dominates the relaxation dynamics of the components in miscible polymer blends. The relaxation of component chains accelerates on all length scales as increasing the free volume available to monomers to move, with the dependence of mobility shift on composition being quantified by a Williams–Landel–Ferry like function governing the time‐composition superposition. Role of the chain connectivity induced self‐concentration effect on chain relaxation in polymer blends is discussed and proved to be limited, which leads to a visible but subtle length‐scale dependent rheological complexity as the composition is varied.

Phase behavior of ASDs based on hydroxypropyl cellulose

Novel polymeric carriers for amorphous solid dispersions (ASDs) are highly demanded in pharmaceutical industry to improve the bioavailability of poorly-soluble drug candidates. Besides established polymer candidates, hydroxypropyl celluloses (HPC) comes more and more into the focus of ASD production since they have the availability to stabilize drug molecules in aqueous media against crystallization. The thermodynamic long-term stability of HPC ASDs with itraconazole and fenofibrate was predicted in this work with PC-SAFT and compared to three-months enduring long-term stability studies. The glass-transition temperature is a crucial attribute of a polymer, but in case of HPC hardly detectable by differential scanning calorimetry. By investigating the glass transition of HPC blends with a miscible polymer, we were for the first time able to estimate the HPC glass transition. Although both, fenofibrate and itraconazole reveal a very low crystalline solubility in HPC regardless of the HPC molecular weight, we observed that low-molecular weight HPC grades such as HPC-UL prevent fenofibrate crystallization for a longer period than the higher molecular weight HPC grades. As predicted, the ASDs with higher drug load underwent amorphous phase separation according to the differential scanning calorimetry thermograms. This work thus showed that it is possible to predict critical drug loads above which amorphous phase separation and/or crystallization occurs in HPC ASDs.

Fabrication and Characterization of PEEK/PEI Multilayer Composites.

Polyetheretherketone (PEEK)/polyetherimide (PEI) blends (50/50, v/v) keeping the crystal phase of PEEK have been manufactured by alternate PEEK/PEI layer stacking. This strategy avoided the complete miscibility of both polymers, keeping layers of PEEK and PEI unmixed along the sample thickness, as well as promoting the formation of a smooth interfacial layer where PEEK and PEI were mixed. The properties of this interface after processing at molten state and different times was studied by DSC, DMA, and X-Ray synchrotron. These techniques allowed monitoring the evolution of glass transition, where isolated Tg’s for both pristine polymers were observed even after long processing time. PEEK crystallinity slightly decreased during manufacturing, whereas PEEK crystal parameters did not vary. These observations show that, although the interface—the zone where both polymers are mixed—grew, layers with pristine polymers remained even after prolonged processing time. The preservation of the PEEK crystallinity was also observed in the mechanical properties of the multilayer PEEK/PEI films, which were compared with pristine PEEK and PEI films. Multilayer samples processed for shorter times rendered higher young modulus, tensile strength, and strain at break.

Effect of Silicone-Containing Charge-Transfer Polymer Blend Membrane for PEFC Application

Introduction Silicone polymers generally have characteristics such as thermal/chemical stability compared to hydrocarbon polymer [1,2]. As such, we have focused on silicone polymers as new alternative polymer electrolyte membranes (PEMs) in this study. However, silicone polymers have some drawback such as low glass transition temperature (Tg) and relatively high gas permeability. We attempt to develop PEMs consisting of a blend of silicone polymer and a hydrocarbon polymer, to enhance the merits of silicone polymers, while suppressing the demerits (Fig. 1). Our group has previously developed the polymer blend method applied to supramolecular interactions to prepare PEMs [3-5], and charge-transfer (CT) interaction has been used as supramolecular interaction. Polymer blends using the CT interaction are composed of two different polymers. One polymer is an electron-donating unit, and the other polymer is an electron-accepting unit [3-5]. In CT blend membranes, the donor polymer and the acceptor polymer can align alternatively due to the CT interaction, and miscible polymer blend at the molecular level can be prepared. In addition, the CT polymer blend method can be used to control several properties such as mechanical strength and the Tg [3-5]. In this study, we developed silicone-containing polymer, Si-Epoxy, and evaluated their mechanical, thermal stability, and performance.Experimental Silicon-containing polymer, Si-Epoxy, was synthesized by epoxy ring open reaction from 2,6-dihydroxynaphthalene and 1,3-Bis (3-glycidyloxypropyl) tetramethyldisiloxane using phosphine catalyst. Si-Epoxy was used as the electron-donating polymer while sulfonated polyimide homopolymer (SPI) was used as the electron-accepting polymer. CT blend membranes (SPI/Si-Epoxy) were prepared by solvent casting method. Tg of Si-Epoxy, SPI and SPI/Si-Epoxy were measured by differential scanning calorimetry (DSC). To confirm CT complex formation, visible spectroscopy was used. Thermal stability and mechanical strength of the SPI/Si-Epoxy membranes were evaluated by TGA, tensile test. IEC, proton conductivity and fuel cell performance were also evaluated.Results and discussion From the DSC results, Tg of Si-Epoxy was observed at 12.5°C. The reason for the relatively high Tg is that Si-Epoxy have naphthalene moiety into main chain. The Tg of the SPI was not observed within the measured temperature range. But Tg of the CT blend membrane (SPI/Si-Epoxy-0.5) also was not observed. This phenomenon is a result of blending which eliminates the Tg of Si-Epoxy. The TGA result of Si-Epoxy has no weight loss until 350 ˚C. This result indicates that Si-Epoxy is very thermally stable and will not thermally decompose under PEFC operation conditions. For the SPI/Si-Epoxy, The TGA tendency was similar with SPI, not Si-Epoxy. It means that thermal property of SPI/Si-Epoxy membrane depends on property of SPI. Mechanical properties of SPI/Si-Epoxy membranes with different ratio, Nafion 211 and SPI were measured. The stress at break of SPI/Si-Epoxy was similar with Nafion 211. Elongation of SPI/Si-Epoxy was less than 20 %, and there was almost no deformation compared to Nafion 211. This is a great advantage for mechanical durability, such as buckling deformation. The proton conductivity of SPI/Si-Epoxy was measured at 80 ˚C, 90 % RH (Fig. 2). The proton conductivity of SPI/Si-Epoxy 0.5 (SPI : Si-Epoxy = 1 : 1 (mol eq.)), SPI, Nafion was 23.1, 49.1, 56.8 mS/cm, respectively. The proton conductivity of SPI/Si-Epoxy depends on the amount of sulfonic acid. In fuel cell test, OCV was decreased with increase of Si-Epoxy in SPI/Si-Epoxy membranes. For CT membranes with low Si-Epoxy ratio (< 30 %), OCV and mechanical strength will have a positive effect on improvement. In addition, SPI/Si-Epoxy can be used as an ionomer by using the advantage of high gas permeability.

Morphing Simulations Reveal Architecture Effects on Polymer Miscibility

The Flory–Huggins interaction parameter χ quantifies the excess free energy of mixing unlike species and governs phase behavior in polymer blends and block copolymers. Chain architecture affects ho...

Miscibility Studies of Hyaluronic Acid and Poly(Vinyl Alcohol) Blends in Various Solvents.

In this study, blends based on hyaluronic acid (HA) and poly(vinyl alcohol) (PVA) were characterized by the viscometric method, steady shear rheological tests and FTIR spectroscopy (Fourier Transform Infrared Spectroscopy). Viscometric studies showed the miscibility of HA and PVA in distilled water: 0.1 mol dm−3 NaCl and 0.1 mol dm−3 HCl. The method proposed by Garcia et al. was applied to assess the miscibility of polymers, while Δ[η] and Δb were introduced to determine of miscibility from the Huggins plots. The viscometric data showed that the attractive forces of HA and PVA were dominant when dissolved in 0.1 mol dm−3 NaCl and 0.1 mol dm−3 HCl, while, in distilled water, repulsive forces played the leading role. All polymer solutions were well characterized using a power law model, and exhibited non-Newtonian behavior with pseudoplasticity increasing with the increasing weight fraction of HA in 0.1 mol dm−3 NaCl and 0.1 mol dm−3 HCl. FTIR studies exhibited the formation of new intermolecular interactions between HA and PVA via hydrogen bonding.

Fluorinated benzotriazole-modified random terpolymer acceptors towards less thickness-sensitive all-polymer solar cells

Naphthalene diimide (NDI)-based n-type polymers have been reported as the most widely employed polymer acceptors so far. However, all-polymer solar cells (all-PSCs) based on NDI-typed acceptors commonly suffer from low short-circuit current density (Jsc) due to the deficient absorption coefficients of polymer acceptors and unsatisfactory morphologies. In this work, based on the most widely used copolymer acceptor N2200, we designed terpolymer acceptors named PNDI-BTzx (x = 5 and 10) by randomly embedding a certain amount of fluorinated benzotriazole (2f-BTz) into N2200 backbone. The enhanced absorption coefficients, relatively weakened polymer crystallinities and improved polymer miscibility were obtained from terpolymer acceptors compared to N2200. Synchronously benefited from improved absorption and optimized morphology, all-PSCs based on PNDI-BTz5 demonstrated enhanced photovoltaic performance with power conversion efficiency (PCE) and Jsc of 6.72% and 12.54 mA cm−2 than 5.67% and 10.80 mA cm−2 from N2200-control. In addition, satisfactory reproducibility was obtained with comparable performance among different batches of PNDI-BTzx (x = 5 and 10). And more interestingly, all-PSCs based on PNDI-BTz5 possessed better thickness tolerance than N2200. These results offered useful guidelines to realize reproducible-performance and thick-film practical all-polymer photovoltaic applications through designing random terpolymer acceptors.