Acid End Groups Research Articles

Evaluation of the impact of the polymer end groups and molecular weight on in vitro and in vivo performances of PLGA based in situ forming implants for ketoprofen

In situ forming implants are appealing long-acting dosage forms for both preclinical and clinical applications due to their simple manufacturing process and easy delivery. This study aims to develop extended-release in situ forming solid implants for subcutaneous administration using two types of commercially available triblock poly (lactic-co-glycolic acid)-poly (ethylene glycol)-poly (lactic-co-glycolic acid) (PLGA-PEG-PLGA) polymers, with either an acid or ester end group. Both types of polymers instantly form in situ implants when injected directly into an aqueous medium. The performance of these implants, containing a model compound ketoprofen, was evaluated by comparing the in vitro drug release profiles with the in vivo performance following subcutaneous administration in rats. Analytical characterizations of two representative in situ implants were conducted to understand their structural impact on polymer degradation and drug release. All tested in situ forming implants demonstrated prolonged drug release profiles both in vitro and in vivo. This study illustrates the successful preparation of sustained-release in situ forming implant formulations for ketoprofen using commercially available polymers, with the molecular weight and the end group of the polymers affecting their degradation and the drug release from the in situ formed implants.

Supramolecular assembled macroscopic soft scaffolds of thioindigo amphiphiles as cell-material interfaces

Biocompatible synthetic supramolecular systems have been proven success in fabricating regenerative biomedical materials with intrinsic functionality, tunability, and stimuli-responsiveness. However, it remains highly challenging to develop a supramolecular soft scaffold that allows transferring intrinsic microscopic aligned structural properties to cell attachments. Herein, we report a thioindigo bola-amphiphile (TIA) that is equipped with long alkyl-linker to connect the carboxylic acid end-group on the opposite side. Though photoresponsiveness of TIA is hindered in aqueous medium, it can be slightly improved by utilizing a co-solvent system or doping TIA with other amphiphiles. Electron microscopies and X-ray diffraction analysis suggest that a large aspect ratio of TIA nanostructures assembled into macroscopic soft scaffold with high degree of unidirectional alignment. The fabricated TIA macroscopic soft scaffold is further incubated with hMSCs, in revealing unidirectional aligned cell attachments. This work could provide an alternative strategy towards development of next-generation biocompatible soft functional materials.

Direct Reactive Extrusion of PLA in the Presence of a Multifunctional Chain Extender

The environmental impact of non-renewable, fossil fuel-based polymers has led to growing interest in sustainable alternatives such as Poly(lactic acid) (PLA). PLA is biodegradable and suitable for packaging application, however due to limited number of efforts to effectively recycle PLAs, its disposal still contributes to the plastic pollution problem. In general, plastic recycling methods could be categorized into three main groups: (i) incineration for energy generation, (ii) chemical recycling, and (iii) mechanical recycling. Among those strategies, mechanical recycling would be the optimal choice due to its applicability to current plastic production lines. However, limited thermal stability of PLA during melt mixing make its mechanical recycling challenging. This study explores the direct use of ketene-based chain extenders in the melt mixing step without any pre-treatments to enhance PLA's properties during thermal recycling. Those ketene-based chain extenders could increase the molecular weight and hence melt viscosity of PLA by reacting its hydroxyl and carboxylic acid end groups. For this purpose, copolymers of styrene, methyl methacrylate and 2,2,5-trimethyl-5-(4-vinylbenzyl)-1,3-dioxane-4,6-dione (MA) were synthesized and directly melt mixed with PLA in micro compounder at 210 °C for 3 mins. Final molecular weights and thermal properties of PLAs were analyzed through GPC and DSC analyses.

Mist-control of polyalphaolefin (PAO) lubricants using long pairwise end-associative polymers

Accidental release of pressurized hydrocarbon fuels and lubricants are a major fire hazard due to the formation of small droplet mists that can readily evaporate and ignite. Mist control through increasing droplet size and suppressing droplets has been previously demonstrated with high molecular weight polymer additives, but traditional long polymer additives do not survive the pumping that would usually precede accidental release. This constraint inspired associative polymer additives that can transiently form the high molecular weights needed for mist control, while reversibly breaking during pumping. A prior study demonstrated the efficacy of such a system in fuel: long telechelic polycyclooctadiene (PCOD) with pairwise associating acid and base end-groups. Here, we address an obstacle to applying this same polymeric system in a polyalphaolefin (PAO) solvent—its poorer solvent quality for PCOD than fuel. We measured the effects of the end-associative PCOD compared to a non-associative control on the rheological properties of solutions in both PAO (a common lubricant and heat transfer fluid) and decahydronapthalene (decalin, a solvent with PCOD solubility similar to fuel) in shear and extension, and connect those rheological modifications to observed changes in PAO spray under simulated accidental release conditions. The PCOD additives demonstrated substantial mist control in PAO, both in terms of reduced spray angle and droplet suppression. Despite the worse solubility in PAO and thus smaller effective coil size, these associative PCOD additives are effective at the low concentrations (¡0.1 wt %) necessary for practical use as a safety measure.

Waxes from Long-Chain Aliphatic Difunctional Monomers.

Petrochemical polyethylene waxes (Mn = 800-8000 g/mol for commercial Ziegler waxes) as additives, lubricants, and release agents are essential to numerous products and production processes. The biodegradability of this class of compounds when unintentionally released to the environment is molar mass dependent and subject to ongoing discussions, and alternatives to conventional polyethylene waxes are desirable. By employing bottom-up and top-down approaches, that is nonstoichiometric A2 + B2 polycondensation and chain scission, respectively, linear waxes with multiple in-chain ester groups as biodegradation break points could be obtained. Specifically, waxes with 12,12 (WLE-12,12, WLE = waxes linear ester) and 2,18 (WLE-2,18) carbon atom linear ester repeat unit motifs were accessible over a wide range of molar masses (Mn ≈ 600-10 000 g/mol). In addition to the molar mass, the type of end group functionality (i.e., methyl ester, hydroxy, or carboxylic acid end groups) significantly impacts the thermal properties of the waxes, with higher melting points observed for carboxylic acid end groups (e.g., Tm = 83 °C for carboxylic acid-terminated WLE-12,12 with Mn,NMR = 1900 g/mol, Tm = 92 °C for WLE-2,18 with Mn,NMR = 2200 g/mol). A HDPE-like orthorhombic crystalline structure and rheological properties comparable to a commercial polyethylene wax suggest WLE-12,12 and WLE-2,18 are viable biodegradable and biosourced alternatives to conventional, petrochemical polyethylene waxes.

Exploring the Potential of Azo Compounds in Leukemia Treatment: Synthesis and Characterization of New Derivatives with Dimedone and Meldrum's Acid End Groups

AbstractThis scholarly investigation presents pioneering drug candidates for combating leukemia, distinguished by reduced side effects and elevated efficacy. The study focuses on azo compounds for their selective targeting against cancerous cells, and customizable properties. Novel azo compounds, DMTPC and DMTPD, were skillfully synthesized via diazotization of 3‐(4‐Methyl‐1H‐imidazol‐1‐yl)‐5‐(trifluoromethyl)aniline with dimedone and meldrum‘s acid. Comprehensive characterization employed advanced analytical techniques like 1H‐NMR, 13C‐NMR, LC‐MS, FT‐IR, and XRD. UV‐Vis and fluorescence spectrophotometers scrutinized absorption and fluorescence properties in diverse solvents. Theoretical DFT computations provided optimized geometries, vibrational frequencies, NMR chemical shifts, absorption wavelengths, HOMOs‐LUMOs, Mulliken charges, and molecular orbital energies. Encouragingly, experimental and theoretical values aligned well. ADME properties and toxicity profiles were evaluated using online web servers. Molecular dynamics simulations explored interactions of DMTPC and DMTPD with the leukemia inhibitory factor protein (PDB ID: 1EMR) compared to Nilotinib. Molecular docking studies indicated DMTPC′s promising potential with a binding energy of −8.8 kcal/mol, approaching Nilotinib's −9.4 kcal/mol. This investigation accentuates the burgeoning research paradigm of exploiting azo compounds in the formidable battle against leukemia, opening new avenues for breakthroughs in this field.

Biocompatible Polymer-Grafted TiO2 Nanoparticle Sonosensitizers Prepared Using Phosphonic Acid-Functionalized RAFT Agent.

Sonodynamic therapy is widely used in clinical studies including cancer therapy. The development of sonosensitizers is important for enhancing the generation of reactive oxygen species (ROS) under sonication. Herein, we have developed poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)-modified TiO2 nanoparticles as new biocompatible sonosensitizers with high colloidal stability under physiological conditions. To fabricate biocompatible sonosensitizers, a grafting-to approach was adopted with phosphonic-acid-functionalized PMPC, which was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) using a newly designed water-soluble RAFT agent possessing a phosphonic acid group. The phosphonic acid group can conjugate with the OH groups on the TiO2 nanoparticles. We have clarified that the phosphonic acid end group is more crucial for creating colloidally stable PMPC-modified TiO2 nanoparticles under physiological conditions than carboxylic-acid-functionalized PMPC-modified ones. Furthermore, the enhanced generation of singlet oxygen (1O2), an ROS, in the presence of PMPC-modified TiO2 nanoparticles was confirmed using a 1O2-reactive fluorescent probe. We believe that the PMPC-modified TiO2 nanoparticles prepared herein have potential utility as novel biocompatible sonosensitizers for cancer therapy.

Compatibilization of Polymer Blends by Ionic Bonding

Chemically dissimilar polymers are rarely miscible due to a specific entropy of mixing that scales as 1/N, where N is the degree of polymerization. As a consequence, the compatibilization of immiscible polymer blends presents a major challenge to plastics recycling efforts. We demonstrate that when the chain ends of two highly immiscible polymers are functionalized with reacting acid and base groups, ionic junctions form in situ by proton transfer, leading to the stabilization of interfaces and the suppression of macroscopic phase separation. Due to the dynamic nature of proton transfer, the microstructure can be tuned via ionic bond energy (h) and segregation strength (χN). In this work, a library of ionically end-functionalized polystyrene (PS) and polydimethylsiloxane (PDMS) is used to demonstrate the importance of end-group acidity/basicity and molecular weight on compatibilization. Well-ordered lamellae result from blending polymers with strong acid and base units, while less ordered, more swollen microphases occur in systems with weak acid and base end groups or larger molar mass. Heating the ionic blends results in reverse proton transfer and destruction of the close-contact ion pairs. As a result, domains are swollen with the resulting unbonded homopolymers, which in sufficient amounts, leads to macrophase separation. Moreover, external salt ions screen the electrostatic attractions and disturb ionic compatibilization. The self-consistent field theory (SCFT) of this system reveals that the ionic interactions can be tuned to create a broad range of morphologies, from microphases to macrophases.

High impact strength of aliphatic polyketone/polyamide 6 blends induced by a chemical reaction

Compatibility and physical properties of aliphatic polyketon (PK)/polyamide 6 (PA6) blend were investigated. The PK and PA6 showed high adhesion strength and thus impact strength of PK/PA6 blends was very high. It was observed that PK-PA6 copolymers are formed by a chemical reaction between the two polymers and the copolymers act as a reactive compatibilizer in the PK/PA6 blends. The presence of the PK-PA6 copolymer was confirmed by FTIR analysis. The adhesion strength between PK and PA6 was very high compared to a typical incompatible polymer pair. PA6 investigated herein has two end groups, NH2 and carboxylic acid. We also adopted end-capped PA6 that has two carboxylic acid end groups. The adhesion strength and impact strength of the PK/end-capped PA6 blends was much lower than that of PK/PA6 blends. More importantly, the PK-PA6 copolymer was not formed in the PK/end-capped PA6 blends. Thus, it was concluded that the chemical reaction occurs between the carbonyl of PK and the primary amine end group of PA6. Due to the high impact strength of PK/PA6 blends, possible applications could be automotive parts where higher impact strength is required.

1H and 13C NMR Study of Oligosuccinimide Prepared by Thermal Condensation and Evaluation of Its Scale Inhibition

<p>The presence of scale is a serious problem in the petroleum industry, and some efforts should be made to control scale formation. Oligosuccinimide (OSI) is an oligomer with several repeating units of succinimide. The structure of the OSI main chain and end groups has never been comprehensively analyzed. Meanwhile, OSI is potentially a scale inhibitor due to chelating properties, high polarity, and high solubility. This study investigates the molecular structure of oligosuccinimide, focusing on the main chain and end groups. Synthesis was carried out by thermal condensation between maleic anhydride and ammonium carbonate using a <sup>1</sup>H and <sup>13</sup>C NMR spectroscope equipped with Distortionless Enhancement by Polarization Transfer 135, Heteronuclear Multiple Quantum Coherence, and Single Quantum Coherence. The NMR analysis results detected the presence of the main chain and several synthesized OSI end groups, such as the amino, succinimide, and maleimide end groups. However, the dicarboxylic acid end group and other irregular structures, as in polysuccinimide (various synthesis methods), were not identified. It confirmed that our thermal condensation method produced OSI with less irregular structures than previous methods. Evaluation of OSI as CaCO<sub>3</sub> and CaSO<sub>4</sub> scales inhibitor showed reasonably good performance in very small concentrations. The inhibition efficiency was 73.20% for the CaCO<sub>3</sub> scale with 10 mg.L<sup>-1</sup> and 55.29% for the CaSO<sub>4</sub> scale with 10 mg.L<sup>-1</sup> inhibitor concentration. Analysis of thermal stability informed OSI has good thermal stability because it started to be degraded at 353.38 °C.</p>

MRI Contrast Agents in Glycobiology

Molecular recognition involving glycoprotein-mediated interactions is ubiquitous in both normal and pathological natural processes. Therefore, visualization of these interactions and the extent of expression of the sugars is a challenge in medical diagnosis, monitoring of therapy, and drug design. Here, we review the literature on the development and validation of probes for magnetic resonance imaging using carbohydrates either as targeting vectors or as a target. Lectins are important targeting vectors for carbohydrate end groups, whereas selectins, the asialoglycoprotein receptor, sialic acid end groups, hyaluronic acid, and glycated serum and hemoglobin are interesting carbohydrate targets.

Polyhedral oligomeric silsesquioxane (POSS)-modified citric-acid coated magnetic Fe3O4 nanoparticles for anticancer drug delivery

In this work, magnetic nanoparticles coated with citric acid (Fe3O4@Cit) were synthesized via co-precipitation strategy. Then, Fe3O4@Cit was modified with octa-aminopropyl polyhedral oligomeric silsesquioxane hydrochloride salt nanoparticles (OAPOSS NPs) by amidation reaction between carboxylic acid end groups on Fe3O4@Cit and the amine groups of OAPOSS surface (Fe3O4@Cit@OAPOSS). The key point of this approach is utilizing a symmetric nanosized cagelike POSS NPs as coating material to obtain novel hybrid drug nanocarrier. The successful preparation of nanocarrier (Fe3O4@Cit@OAPOSS) was confirmed by various techniques. Drug loading and release behaviors of Fe3O4@Cit@OAPOSS were evaluated using doxorubicin (DOX), a standard anticancer model drug, in neutral and acidic conditions. Moreover, Higuchi and Korsmeyer-Peppas models were used to study the release kinetics of DOX. Obtained results confirmed the suitability of Fe3O4@Cit@OAPOSS as a potential novel nanocarrier for drug delivery.

A facile approach for grafting ion imprinted polymer onto magnetic multi-walled carbon nanotubes for selective removal and preconcentration of cadmium in food and wastewater samples prior to atomic spectrometric determination

A 3D Fe3O4@MWCNT-CdIIP was synthesized by the oxidizing surface of multi-walled carbon nanotubes with carboxylic acid end groups and its subsequent termination with an ion imprinted polymer. An artificial neural network manifests better predictability than the central composite design methodology for optimising the adsorption procedure. The adsorption capacity was 109 mg g−1 (2.5 times more than non-imprinted polymer) under optimized conditions (pH; 5.6, time; 15 min, concentration; 800 μg mL−1 temperature; 25 °C), which was in accord with Toth isotherm. Fractal-like pseudo-second-order kinetics was found reasonably fast, with 66 % adsorption in 5 min. Solid phase extraction coupled Flame atomic absorption spectrometry method provides selective recognition towards Cd(II), with limit of detection; 1.13 µg/L, limit of quantification; 3.21 µg/L after preconcentration (preconcentration factor; 50) and good robustness. The developed method was applied for Cd(II) determination in food (tea, coffee, bread, tobacco, radish, spinach), water and wastewater (>99 % removal as well). Cd(II) loaded IIP was further utilized to remove anionic dyes with >95 % removal.

Cationic polymerization of cyclic trimethylene carbonate induced with initiator and catalyst in one molecule: Polymer structure, kinetics and DFT

Trimethylene carbonate, the monomer that can be prepared from CO2 and 1,3-propanediol, was polymerized cationically, according to the activated monomer mechanism, as it follows from the polymerization kinetics and the DFT studies. Polymerization provides the biocompatible, degradable polymer and was conducted with initiator and catalyst in one molecule (CINICAT). This is in contrast to the known processes when protonic acids (organocatalysts) require addition of an independent initiator and then the low molar mass catalyst, left free in the polymer, may diffuse to its surface, changing the properties. The used CINICAT: hydroxymethylphosphonic acid {HOCH2P(=O)(OH)2} is quantitatively embedded in the polymer molecules. Polymerization is living/controlled and provides at 100 °C, in bulk, polymers with molar masses ∼104 g/mol. The acidic end groups were further used for polymer functionalization and in reaction with diepoxybutane were quantitatively converted into reactive epoxy groups.

Glycerol-based enzymatically synthesized renewable polyesters: Control of molecular weight, degree of branching and functional endgroups

The catalytic specificity of Lipase B from Candida antarctica (CALB) has been exploited to achieve specific terminal groups for the synthesis of glycerol poly(ester)s. This permits the preparation of glycerol-derived macromers able to undergo further reactions/chemical modifications for customization as functional systems and building blocks for polymer synthesis. Poly(glycerol adipate) based macromers with different terminal structures were achieved from the reaction between glycerol and divinyl adipate by varying the stoichiometry (from equimolar to 1.5 and 3.0 excess either of glycerol or divinyl adipate) and amount of catalyst (1 and 3 wt%). In the course of polymerization, transesterification and hydrolysis reactions occur over vinyl functionalities that result in acid endgroups. Thus, the resulting macromers are either terminated with hydroxyl groups and/or acid groups and/or vinyl groups. Therefore, an understanding of how acid functionality appears (from vinyl groups hydrolysis) and its quantification under various conditions may provide an opportunity for the design of synthetic strategies to avoid acid production and obtain the desired structures. Endgroup analysis was carried out using 1H NMR and 13C NMR spectroscopies and MALDI-TOF spectrometry. Mainly linear hydroxyl and vinyl-terminated macromers were obtained with high efficiency without significant hydrolysis of the chain ends (for vinyl terminated).

Reactive Oxygen Species and Folate Receptor-Targeted Nanophotosensitizers Composed of Folic Acid-Conjugated and Poly(ethylene glycol)-Chlorin e6 Tetramer Having Diselenide Linkages for Targeted Photodynamic Treatment of Cancer Cells.

Folic acid-conjugated nanophotosensitizers composed of folic acid (FA), poly(ethylene glycol) (PEG) and chlorin e6 (Ce6) tetramer were synthesized using diselenide linkages for reactive oxygen species (ROS)- and folate receptor-specific delivery of photosensitizers. Ce6 was conjugated with 3-[3-(2-carboxyethoxy)-2,2-bis(2-carboxyethoxymethyl)propoxy]propanoic acid (tetra acid, or TA) to make Ce6 tetramer via selenocystamine linkages (TA-sese-Ce6 conjugates). In the carboxylic acid end group of the TA-sese-Ce6 conjugates, FA-PEG was attached again using selenocystamine linkages to make FA-PEG/TA-sese-Ce6 conjugates (abbreviated as FAPEGtaCe6 conjugates). Nanophotosensitizers were fabricated by a dialysis procedure. In the morphological observations, they showed spherical shapes with small diameters of less than 200 nm. Stability of the aqueous FAPEGtaCe6 nanophotosensitizer solution was maintained (i.e., their particle sizes were not significantly changed until 7 days later). When H2O2 was added to the nanophotosensitizer solution, the particle size distribution was changed from a monomodal pattern to a multimodal pattern. In addition, the fluorescence intensity and Ce6 release rate from the nanophotosensitizers were also increased by the addition of H2O2. These results indicated that the nanophotosensitizers had ROS-sensitive properties. In an in vitro cell culture study, an FAPEGtaCe6 nanophotosensitizer treatment against cancer cells increased the Ce6 uptake ratio, ROS generation and light-irradiated cytotoxicity (phototoxicity) compared with Ce6 alone against various cancer cells. When the folic acid was pretreated to block the folate receptors of the Y79 cells and KB cells (folate receptor-overexpressing cells), the intracellular Ce6 uptake, ROS generation and thereby phototoxicity were decreased, while the MCF-7 cells did not significantly respond to blocking of the folate receptors. These results indicated that they could be delivered by a folate receptor-mediated pathway. Furthermore, an in vivo pulmonary metastasis model using Y79 cells showed folate receptor-specific delivery of FAPEGtaCe6 nanophotosensitizers. When folic acid was pre-administered, the fluorescence intensity of the lungs was significantly decreased, indicating that the FAPEGtaCe6 nanophotosensitizers had folate receptor specificity in vitro and in vivo. We suggest that FAPEGtaCe6 nanophotosensitizers are promising candidates for a targeted photodynamic therapy (PDT) approach against cancer cells.

Improved chemical resistance of transparent bisphenol A polycarbonate materials

AbstractBisphenol A polycarbonate (BPA‐PC) is an important engineering plastic with unique properties. However, it has some inherent flaws like chemical resistance toward greases and oils. Hence, to improve the chemical resistance the effect of small amounts of polybutylene terephthalate (PBT) functionalized with allyl glycidyl epoxy (AGE) were evaluated. Low amounts of PBT and AGE provided a transparent blend composition with an allyl functionality. Detailed structural analysis by 1H‐NMR showed the addition reaction of AGE‐epoxy with acid end group of PBT, followed by an expected substitution reaction of the modified PBT with BPA‐PC. This unique blend composition exhibited Tg of 131°C and melting temperature (Tm) of 221°C by differential scanning calorimetry (DSC). Further, the microscopy study of blend revealed the stable morphology of PBT domain distributed into PC matrix indicating chemical compatibilization. The mechanical property evaluation of the blend demonstrated an improved flow, an increase in modulus, tensile strength, and higher elongation at break. Thus, a chemical compatible transparent blend of BPA‐PC and PBT with allyl group functionalization has been achieved and first evaluations show slight improvement of chemical resistance toward Banana Boat Sun cream over the BPA‐PC homopolymer.

Boosting photovoltaic performance of ternary organic solar cells by integrating a multi-functional guest acceptor

Constructing ternary structure is one of the most effective design strategies to break the efficiency ceiling of traditional binary organic solar cells (OSCs). Here, a new Y-series non-fullerene acceptor (Y-T) featuring 1,3-diethyl-2-thiobarbituric acid (DTBA) end groups is developed as a third component for the classical PM6:Y6 binary system. The champion power conversion efficiency of ternary OSCs is increased from 15.64% to 17.37% via incorporating 10 wt% Y-T, with the simultaneously enhanced open-circuit voltage (Voc) of 0.865 V, a short-circuit current density (Jsc) of 26.90 mA/cm2, and a fill factor (FF) of 74.97%. The positive contribution of Y-T in the ternary blend can be ascribed to the improved spectroscopic complementarity and enhanced exciton utilization ratio due to the additional energy transfer process. Moreover, Y-T guest acceptor plays a critical role in adjusting the active layer morphology and facilitating three-dimension phase separation, resulting in a balanced charge transport and enhanced FF of ternary OSCs. This work provides insight into the molecular design of non-fullerene acceptor and suggest guidelines to rationally select guest component for ternary OSCs.

Carboxyl functional group-assisted defects passivation strategy for efficient air-processed perovskite solar cells with excellent ambient stability

Because the perovskites materials tend to decompose in humid air and at high temperature, a controlled inert condition is usually necessary to obtain high-performance perovskite solar cells (PSCs), which is inconvenient for large-scale commercial production. Furthermore, defects/traps in the perovskite layer, as non-radiative charge recombination centers, dramatically deteriorate the device efficiency and stability. Inspired by the Lewis acid-base adduct theory, herein we report a terephthalic acid (PTA)-assisted defect passivation strategy for fabricating highly efficient and stable devices in ambient air. Density functional theory calculation confirms that electrons are located at two carboxylic acid end groups in the PTA molecule, which can serve as Lewis base to form the Lewis acid-base adduct with uncoordinated Pb2+ defects. The PTA-treatment effects promote high performance of PSCs, the champion device provides power conversion efficiency (PCE) of 18.22%, in sharp contrast to 17.41% of control sample. More importantly, unencapsulated devices retain over 80% of their original PCE after being stored for 4500 h in air (≈45% average relative humidity (RH)), exhibiting one of the best long-term stability to date. Correspondingly, PTA-treatment gives the device favorable thermal stability. Our strategy provides a simple yet effective path for passivating defects and improving performance of PSCs.

Electrospray Ionization-Mass Spectrometry of Synthetic Polymers Functionalized with Carboxylic Acid End-Groups.

Electrospray ionization-mass spectrometry (ESI-MS) of low-charging synthetic polymers typically produces mass spectra exhibiting a bias toward the low-mass region of the polymer mass distribution. To examine the origin(s) of this ionization bias, narrow dispersity polystyrene polymers (Đ < 1.10) were prepared with ionizable carboxylic acid end-groups at one or both chain termini. The mixture complexity was further reduced through preparative size-exclusion chromatography (SEC), and these well-defined polymers were subjected to negative ion ESI-MS on a high-resolution instrument with a mass-to-charge (m/z) range up to 8000. Incorporation of one carboxylic acid end-group facilitated the generation of singly charged [M - H]- ions across the entire range of the mass analyzer. The comparison of mass spectra with size-exclusion chromatograms of the same polymer revealed an ionization bias toward lower masses, which was partially overcome through fractionation, modification of electrospray solvent, and increased declustering potentials. Incorporation of a second ionizable moiety within polymers of equivalent size facilitated multiply charged [M - 2H]2- ion formation with significantly improved ionization efficiency, spectral coverage of the molar mass distribution, and minimal cluster ion formation. These findings indicate that increased charging of polymers through multiple, well-defined sites of ionization can enhance volatilization and ionization of higher-mass polymers. Generation of higher-molecular-weight polymers in low-charge states-while possible under ideal conditions-competes ineffectively with either nonspecific, multiple-charging of similar sized polymers or ionization of the smaller polymers in the distribution.