Trivalent Titanium Salen Complex: Thermally Robust and Highly Active Catalyst for Copolymerization of CO₂ and Cyclohexene Oxide

A trivalent titanium complex combining salen ligand (salen-H₂<i>N,N</i>-bis­(3,5-di-<i>tert</i>-butylsalicylidene)-1,2-benzenediamine) was synthesized as catalyst for copolymerization of CO₂ and cyclohexene (CHO). In combination with onium salt [PPN]­Cl, (Salen)­Ti­(III)Cl showed impressive activity and selectivity, yielding completely alternating copolymer without the formation of cyclohexene carbonate (CHC), with turnover frequency (TOF) of 557 h^–1 at 120 °C, which was more than 10 times higher than that of our previously reported (Salalen)­Ti­(IV)­Cl, and close to the Cr counterparts. In addition to the biocompatibility of Ti, thermally robust character resulting from the reducibility of trivalent Ti was industrially desirable

Reversible Sol–Gel Transition of Oligo(<i>p</i>‑phenylenevinylene)s by π–π Stacking and Dissociation

Methyl sulfide terminated <i>trans</i>-oligo­(<i>p</i>-phenylenevinylene) derivatives (<b>OPV</b><i><b>n</b></i>, <i><b>n</b></i> is the number of phenyl rings) were synthesized, and reversible sol–gel transition was observed in a variety of organic solvents. Investigations with UV–vis, fluorescence, and ¹H NMR spectroscopy revealed that aromatic π–π stacking and van der Waals forces were important in the formation of the gels, with the former being the main driving force for sol–gel transition. The π-conjugation length showed a key influence on self-assembly and gelation property: the gel-to-sol transition temperature (<i>T</i>_gel) increased with π-conjugation length. The gels of <b>OPV4–7</b> can self-assemble into one-dimensional fibers with different sizes and shapes, depending on their π-conjugation length. On the basis of X-ray diffraction measurements and spectroscopic data, a self-assembly model was proposed. Our observation may be useful for designing functional π-gelators based on π–π stacking

Enhancing Molecular Conductance of Oligo(<i>p</i>‑phenylene ethynylene)s by Incorporating Ferrocene into Their Backbones

Designing and preparing the molecular wires with good charge transport performance is of crucial importance to the development of molecular electronics. By incorporating ferrocene into molecular backbones, we successfully enhanced the molecular conductance of OPEs in both tunneling and hopping conduction regimes. Furthermore, we found that the increase degree of molecular conductance in the hopping regime is much more than that in the tunneling regime. Via this approach, the molecular conductance of a long molecule exceeds the molecular conductance of a short one at room temperature. A theoretical calculation provided a possible and preliminary explanation for these novel phenomena in terms of molecular electronic structures. The current work opens the opportunity for designing excellent charge transport performance molecules. An increasing number of new types of molecular wires with this unusual phenomenon are expected to be discovered in the future

Study on the Thermal Degradation Kinetics of Biodegradable Poly(propylene carbonate) during Melt Processing by Population Balance Model and Rheology

The degradation behavior of poly­(propylene carbonate) (PPC) was investigated during melt processing to infer the mechanism and kinetics of thermal degradation. First, the degradation experiments were carried out in a miniature conical twin-screw extruder at different temperatures, rotating speeds, and processing times. Gel permeation chromatography (GPC) was applied to analyze the molecular weight and molecular weight distributions (MWDs) of melt processed PPC samples. The degradation process at various processing conditions was described by the population balance equations (PBEs) with random chain scission and chain end scission. By comparing the prediction of PBE model with the experimental evolution of molecular weight, it is proposed that random chain scission and chain end scission occur simultaneously. At temperature higher than 160 °C, random chain scission dominates with the activation energy about 120 kJ/mol. Second, a method combining the PBE model and rheology was suggested to determine the kinetics of degradation directly from the torque of mixer during melt processing without further measurements on molecular weight. Such method was applied to melt mixing of PPC in a batch mixer, from which a higher kinetic parameter of thermal degradation and similar activation energy were successfully determined as compared to those obtained from extrusion experiments

Additional file 1: Table S1. of Activation of the Keap1/Nrf2 stress response pathway in autophagic vacuolar myopathies

Summary of diagnostic criteria used for PM and IBM case classification; adapted from reference [15]. (PDF 11 kb

Additional file 3: Table S2. of Activation of the Keap1/Nrf2 stress response pathway in autophagic vacuolar myopathies

mRNA expression level for a subset of the Nrf2-regulated genes (individual subject data; summary graphs are shown in Fig. 6a). (PDF 97 kb

Tough while Recyclable Plastics Enabled by Monothiodilactone Monomers

The current scale of plastics production and the attendant waste disposal issues represent an underexplored opportunity for chemically recyclable polymers. Typical recyclable polymers are subject to the trade-off between the monomer’s polymerizability and the polymer’s depolymerizability as well as insufficient performance for practical applications. Herein, we demonstrate that a single atom oxygen-by-sulfur substitution of relatively highly strained dilactone is an effective and robust strategy for converting the “non-recyclable” polyester into a chemically recyclable polymer by lowering the ring strain energy in the monomer (from 16.0 kcal mol–1 in dilactone to 9.1 kcal mol–1 in monothiodilactone). These monothio-modification monomers enable both high/selective polymerizability and recyclability, otherwise conflicting features in a typical monomer, as evidenced by regioselective ring-opening, minimal transthioesterifications, and quantitative recovery of the pristine monomer. Computational and experimental studies demonstrate that an n→π* interaction between the adjacent ester and thioester in the polymer backbone has been implicated in the high selectivity for propagation over transthioesterification. The resulting polymer demonstrates high performance with its mechanical properties being comparable to some commodity polyolefins. Thio-modification is a powerful strategy for enabling conversion of six-membered dilactones into chemically recyclable and tough thermoplastics that exhibit promise as next-generation sustainable polymers

Additional file 2: Figure S1. of Activation of the Keap1/Nrf2 stress response pathway in autophagic vacuolar myopathies

Keap1 immunohistochemistry with a lower antibody dilution. A. When a lower antibody dilution (1:250) was used for Keap1 immunohistochemistry in the normal skeletal muscle (representative subject #1), diffuse sarcoplasmic staining showed a checkerboard distribution, raising a possibility that Keap1 protein is differentially expressed by slow and fast twitch muscle fibers. B-C. Under these experimental conditions, sequestration of Keap1 into sarcoplasmic puncta was still apparent in the toxic AVM muscle (B, HCQ-treated subject #29; C, colchicine-treated subject #20) but was partially obscured by the background Keap1 staining. Scale bar, 20 μm. (PDF 3954 kb

Synthesis and Properties of Alternating Polypeptoids and Polyampholytes as Protein-Resistant Polymers

Alternating polypeptoids are particularly appealing because alternating sequence may impart highly ordered structure and special functions, while their simple synthesis still remains a key challenge. We describe that natural amino acid monomers can be polymerized via Ugi reaction in a step-growth fashion as an AA′ BB′ system, which leads to alternating polypeptoids with molecular weight up to 15 kg/mol. These alternating polypeptoids are thermally responsive and exhibit cloud points (<i>T</i>_cp) between 27 and 37 °C. Importantly, the marriage of high functionality of amino acids with Ugi reaction also enables the preparation of polypeptoids encoding both protected amino and carboxyl groups in the side chains with alternating arrangement. The cleavage of the protecting groups leads to alternating polyampholytes without any compositional drift. Such alternating polyampholytes not only exhibit high water solubility (>100 mg/mL) but also demonstrate the ability to resist aggregation with proteins. Moreover, the cell viability measurements reveal that these materials have minimal cytotoxicity to HeLa cells. Overall, this study offers us a simple way to prepare a variety of polypeptoids and polyampholytes as new protein-resistant materials for bioapplications

A Multifunctional Polypeptide via Ugi Reaction for Compact and Biocompatible Quantum Dots with Efficient Bioconjugation

The growing application of quantum dots (QDs) in biomedical research necessitates, in turn, continuous development of surface functionalizing ligands to optimize their performance for ever more challenging and diverse biological applications. Here, we demonstrate the novel multifunctional polypeptide ligands for compact and biocompatible QDs. The target ligand preparation exploits the efficient, activating agent-free Ugi reaction of four functional components to incorporate lipoic acid, pyridine, zwitterion motifs, and reactive functionalities in a one-pot procedure under mild conditions. Cap exchange with these multifunctional polypeptide ligands generates hydrophilic QD dispersions, which are colloidally stable for prolonged periods of time. The zwitterionic ligation delivers compact and small QDs, and the existence of reactive functionalities enables coupling of the QDs to biologics through bio-orthogonal coupling chemistry, such as ligation of azide-modified QDs to DNA. Therefore, this QD functionalization strategy via Ugi reaction is believed to be a viable approach for compact and biocompatible QDs with efficient bioconjugation