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Hydroxyl radical (OH) is a key oxidant that triggers atmospheric oxidation chemistry in both gas and aqueous phases. The current understanding of its aqueous sources is mainly based on known bulk (photo)chemical processes, uptake from gaseous OH, or related to interfacial O3 and NO3 radical-driven chemistry. Here, we present experimental evidence that OH radicals are spontaneously produced at the air-water interface of aqueous droplets in the dark and the absence of known precursors, possibly due to the strong electric field that forms at such interfaces. The measured OH production rates in atmospherically relevant droplets are comparable to or significantly higher than those from known aqueous bulk sources, especially in the dark. As aqueous droplets are ubiquitous in the troposphere, this interfacial source of OH radicals should significantly impact atmospheric multiphase oxidation chemistry, with substantial implications on air quality, climate, and health.

Substituted 2,1,3-benzothiadiazole (BTD) is a widely used electron acceptor unit for functional organic semiconductors. Difluorination or annulation on the 5,6-position of the benzene ring is among the most adapted chemical modifications to tune the electronic properties, though each sees its own limitations in regulating the frontier orbital levels. Herein, a hitherto unreported 5,6-annulated BTD acceptor, denoted as ssBTD, is designed and synthesized by incorporating an electron-withdrawing 2-(1,3-dithiol-2-ylidene)malononitrile moiety via aromatic nucleophilic substitution of the 5,6-difluoroBTD (ffBTD) precursor. Unlike the other reported BTD annulation strategies, this modification leads to the simultaneous decrease in both frontier orbital energies, a welcoming feature for photovoltaic applications. Incorporation of ssBTD into conjugated polymers results in materials boasting broad light absorption, dramatic solvatochromic and thermochromic responses (>100 nm shift and a band gap difference of ∼0.28 eV), and improved crystallinity in the solid state. Such physical properties are in accordance with the combined electron-withdrawing effect and significantly increased polarity associated with the ssBTD unit, as revealed by detailed theoretical studies. Furthermore, the thiolated ssBTD imbues the polymer with ambipolar charge transport property, in contrast to the ffBTD-based polymer, which transports holes only. While the low mobilities (10-4 to 10-5 cm2 V-1 s-1) could be further optimized, detailed studies validate that the thioannulated BTD is a versatile electron-accepting unit for the design of functional stimuli-responsive optoelectronic materials.

New polyurethane-based polycaprolactone copolymer networks, with shape recovery properties, are presented here. Once deformed at ambient temperature, they show 100% shape fixation until heated above the melting point, where they recover the initial shape within 22 s. In contrast to current shape memory materials, the new materials do not require deformation at elevated temperature. The stable polymer structure of polyurethane yields a copolymer network that has strength of 10 MPa with an elongation at break of 35%. The copolymer networks are self-healing at a slightly elevated temperature (70 degrees C) without any external force, which is required for existing self-healing materials. This allows for the new materials to have a long life of repeated healing cycles. The presented copolymers show features that are promising for applications as temperature sensors and activating elements., QC 20180307

Time- and temperature-dependent structural relaxation (physical aging) of poly (styrene-b-methyl methacrylate) (PS-b-PMMA) block copolymers was investigated by calorimetry. Our study reveals the interplay of the relaxation responses of the two components of the copolymer in an intermediate temperature regime. That is, when the testing temperature is closely below the glass transition temperatures of PS and PMMA, structural relaxation in these polymer phases takes place concurrently, the corresponding thermogram displays partially superposed dual endothermic peaks as a feature of physical aging in the diblock copolymers. The aging response for each component is identified from a curve fitting method and analyzed by the relaxation of enthalpy. Comparing with the homopolymer analogs, the PS and PMMA in diblock copolymers show enhanced aging rate. © 2017 Elsevier Ltd

The aim of this research is to reconstruct a metaphysical interpretation of the philosophy of history with regard to the spirit of historical thinking. The spirit of historical thinking is to emphasize the relation between what happened in the past and historical thinking about the past in the present. However, current philosophies of history, which are largely epistemologically oriented, have not adequately explored this relation. In order to investigate the relation between past and present, I refer to an Aristotelian philosophy of practice and politics, and adapt it to the domain of the philosophy of history, and argue the case for a metaphysical science of history. A metaphysical science of history contains two primary parts. They are the part on physis and the part on technê/phronēsis. With regard to physis that metaphysically investigates the natural generating progress of entities, I argue that the existence of historical events can be understood as a natural developing progress in which the events are ordered in a chronological sequence. Such chronological sequence is essentially the physis of history in the metaphysical sense (I characterize it as ‘Ordnungszeit’). For the part on technê/phronēsis, I demonstrate that Aristotelian knowing is for itself an action of knowing, which is located beyond a given temporal position in the past to both the past and the thinking present, and indicates the fundamental Beingness of history (I characterize it as ‘Geschehenszeit’). Finally I conclude that the historical eudaimonia, namely the pursuing of the completeness of historical knowledge, is the final presentation of actualizing Geschehenszeit, as it bridges the past and the present in accordance to the spirit of historical thinking.

The aim of this research is to reconstruct a metaphysical interpretation of the philosophy of history with regard to the spirit of historical thinking. The spirit of historical thinking is to emphasize the relation between what happened in the past and historical thinking about the past in the present. However, current philosophies of history, which are largely epistemologically oriented, have not adequately explored this relation. In order to investigate the relation between past and present, I refer to an Aristotelian philosophy of practice and politics, and adapt it to the domain of the philosophy of history, and argue the case for a metaphysical science of history. A metaphysical science of history contains two primary parts. They are the part on physis and the part on technê/phronēsis. With regard to physis that metaphysically investigates the natural generating progress of entities, I argue that the existence of historical events can be understood as a natural developing progress in which the events are ordered in a chronological sequence. Such chronological sequence is essentially the physis of history in the metaphysical sense (I characterize it as ‘Ordnungszeit’). For the part on technê/phronēsis, I demonstrate that Aristotelian knowing is for itself an action of knowing, which is located beyond a given temporal position in the past to both the past and the thinking present, and indicates the fundamental Beingness of history (I characterize it as ‘Geschehenszeit’). Finally I conclude that the historical eudaimonia, namely the pursuing of the completeness of historical knowledge, is the final presentation of actualizing Geschehenszeit, as it bridges the past and the present in accordance to the spirit of historical thinking.