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The polymers can be found in different forms in solution (particles, capsules, pseudo-micelles, hydrogels…) or on surface with important prospects in many field applications. These polymer systems are particularly very good candidates to entrap, transport and deliver an active substance in biomedical applications however with many limitations on control of release of a given target. The stimuli-sensitive polymers, also called smart or environmentally sensitive polymers, present physical or chemical changes under the action of small variations of an external stimulus. This signal acts as a stimulus which causes the change of conformation and/or solvation of the macromolecular chains by modifying their various interactions. The stimuli are classified into two broad categories: physical or external stimuli: temperature, mechanical stress, light, magnetic and electric fields; chemical and biochemical or internal stimuli: pH, ionic strength, chemical molecule (glucose, redox) or biochemical (enzymes, antigens…). The use of stimuli-sensitive pathway is widely used in the literature to enhance or trigger the release of an active compound. In this paper, we present the different stimuli addressing the theoretical aspects, polymers corresponding to these stimuli. Some examples illustrate these systems for the controlled release of active compounds., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

This article explores the field of nanomedicine and its potential applications in targeted drug delivery. It discusses the concept of "nanocarriers" that can transport drugs to specific organs and infected tissues, minimizing side effects. The article presents two experimental series that demonstrate the synthesis and loading of nanoparticles using polymers and various cargos. The experiments investigate the behavior of the nanoparticles in response to changes in pH, showing promising results for targeted drug delivery. The article highlights the educational opportunities and interdisciplinary connections that can be made through the teaching of nanomedicine in chemistry, biology, and physics classes. [Extracted from the article]

• Polymer desiccant wheel with high water uptake and low regeneration temperature is studied. • Polymer's adsorption capacity of 1.15 g kg−1 at 90 %RH is five times that of silica gel. • Polymer's desorption rate coefficient is 1.32–1.64 times that of silica gel at 40–70 °C heat sources. • The maximum ∆ Y and DCOP of the polymer desiccant wheel are 4.0 g kg−1 and 0.66, respectively. • Polymer desiccant wheel offers a promising measure for ultra-low dew point humidity control. Desiccant wheels have been widely used in humidity control, particularly under conditions with ultra-low dew point temperatures. However, traditional desiccants such as silica gel and zeolites are subject to relatively low adsorption capacity and high regeneration temperature. To address these challenges, a type of polymer material with high water uptake and low regeneration temperature is investigated in this paper. Firstly, the adsorption/desorption capacity of this polymer is thoroughly tested. Results reveal that its remarkable equilibrium adsorption capacity and desorption rate coefficients k LDF,de are 350% and 32–64% higher than that of silica gel, respectively. Moreover, its required regeneration temperature is just about 40–70 °C. The performance of the desiccant wheel using this polymer is simulated by a model validated by experiments tests. Parameter analysis demonstrates that the desiccant wheel is suitable for cool and humid conditions, reaching the maximum moisture removal (∆ Y) and dehumidification coefficient of performance (DCOP) of 4.0 g kg−1 and 0.66, respectively. Furthermore, the corresponding relationship between other parameters and the optimal rotation speed is discussed in detail. The ω opt is around 18 rph, enabling the attainment of the highest ∆ Y. Finally, the performance comparison with a traditional silica gel desiccant wheel is carried out. The results indicate that the polymer one performs 17–53.9% higher in terms of both ∆ Y and DCOP than the silica gel counterpart. And the most significant improvement is observed in low relative humidity conditions (45%RH), where ∆ Y and DCOP are 1.25–1.53 times that of the silica gel's, highlighting the advantageous utilization of the polymer material. [ABSTRACT FROM AUTHOR]

Copyright of Technisches Messen is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Für eine nachhaltige Kreislaufwirtschaft müssen Polymere auf rezyklierte und biobasierte Rohstoffe umgestellt werden, und sie müssen bezüglich der Emissionen CO2‐neutral werden. Dies gilt nicht nur für Strukturpolymere, z. B. in Verpackungen oder technischen Anwendungen, sondern auch für Funktionspolymere in flüssigen Formulierungen: in Klebstoffen oder Schmiermitteln, als Verdickungs‐ oder Dispersionsmittel. Am Ende ihrer Lebensdauer müssen Polymere entweder gesammelt und technisch rezykliert werden oder biologisch abbaubar sein, wenn sie nicht sammelbar sind. Fortschritte in der Polymerchemie, in Anwendungen und durch zunehmend rechnergestützte Methoden der Materialwissenschaft ermöglichen einen ganzheitlichen Ansatz: Polymere werden bereits für ihre Rezyklierbarkeit oder biologische Abbaubarkeit konzipiert. Dieser Aufsatz zeigt, wie neue wissenschaftliche Erkenntnisse in Verbindung mit entsprechenden rechtlichen, gesellschaftlichen und wirtschaftlichen Randbedingungen den Weg zu einer umfassenden Kreislaufwirtschaft für Polymere weisen können. [ABSTRACT FROM AUTHOR]

Copyright of Matériaux et Techniques is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mechanophore sind molekulare Einheiten, die in Polymere eingebaut werden und auf Kraft mit konstitutionellen, konfigurativen oder konformationellen Bindungsumlagerungen reagieren, um Funktionalität zu ermöglichen. Bis heute wurden bereits einige chemisch latente Motive durch mechanochemische Methoden in Polymeren aktiviert, aber die Erzeugung sekundärer Amine blieb unerforscht. Hier berichten wir über Carbamoyloxime als mechanochemische Schutzgruppen für sekundäre Amine. Wir zeigen, dass Carbamoyloxime eine kraftinduzierte homolytische Bindungsspaltung an der N−O‐Oximbindung in Polymeren eingehen und so das freie Amin erzeugen. Die Reaktion verläuft analog zu ihrem photochemischen Gegenstück über Carbamoyloxyl‐ und Aminylradikale. Schließlich wenden wir das Carbamoyloxim‐Motiv in einer kraftaktivierten organokatalytischen Knoevenagel‐Reaktion an. Wir glauben, dass diese Schutzgruppenstrategie universell für viele andere sekundäre und primäre Amine in Polymermaterialien angewendet werden kann. [ABSTRACT FROM AUTHOR]

When tunnelling with a TBM (Tunnel Boring Machine) in rock and soil, mostly the machine is described and often reduced to a slogan. Such descriptions say little about geotechnical processes at the tunnel face that are key to the success of tunnel driving and must be considered when selecting a tunnelling system. In soil tunnels the tunnel face must be safely supported and extracting material must be possible. For a slurry shield the slurry must not escape and pressure must act on the face. In the literature mostly bentonite content is considered. With an Earth‐Pressure balance machine the soil has to have characteristics that it can be remoulded and transformed in a mass of adequate consistency with mechanical means, adding water and additives such that this mass can support the face and be extracted. Long‐term experience shows that the fine content and polymers are also important factors. Flow channels (pores) in open gravel may be clogged, and the face supported by seepage forces. Also, the drag forces in the slurry circuit are increased and the operation of the slurry circuit became more stable. Rates of advance exceeding 10 m/day were achieved with a 11.6 m slurry shield. The limited depth of penetration of the slurry could be determined in‐situ. For fine‐grained soils the characteristics of the fines are crucial and are described by the Atterberg limits. Soil mechanics strength properties may be vastly different. [ABSTRACT FROM AUTHOR]

Copyright of Tribologie und Schmierungstechnik is the property of Narr Francke Attempto Verlag GmbH & Co.KG and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vitrimere sind kovalent vernetzte Polymere, die ihre Netzwerktopologie durch aktivierbaren assoziativen Bindungsaustausch neu organisieren können, wenn die Topologie‐Einfriertemperatur (Tv) überschritten wird. Trotz zahlreicher entwickelter Vitrimersysteme besteht ein gravierender Mangel an Methoden für eine kontrollierte und ortsaufgelöste Aktivierung des Bindungsaustauschs oberhalb der Tv. Hier präsentieren wir ein Konzept, das die lokale Freisetzung des effizienten Umesterungskatalysators 1,5,7‐Triazabicyclo[4.4.0]dec‐5‐en (TBD) durch UV‐induzierte Spaltung einer photolatenten Base in einem kovalent vernetzten Thiol‐Epoxid‐Polymer ermöglicht. Mittels Spannungsrelaxationsmessungen, die weit über der Tv des Netzwerks durchgeführt wurden, konnte gezeigt werden, dass nur die kontrollierte Freisetzung von TBD Umesterungen und die damit verbundene Relaxation der Netzwerkspannung ermöglicht. Zudem konnte durch lokal induzierte permanente Formänderungen im Material eine ortsaufgelöste UV‐vermittelte Photoaktivierung der vitrimeren Eigenschaften demonstriert werden. [ABSTRACT FROM AUTHOR]

Wood has numerous advantages: It is sustainable, has a good CO2 and energy balance, is environmentally friendly due to its biodegradability, and its mechanical properties are so good that it is used as a building material, e.g. for multilevel houses. Moreover, thanks to modern research, obvious disadvantages of wood compared to other materials can now be improved by chemical modifications: Chemically modified wood has a higher durability and does not swell or shrink as much as natural wood upon changing environmental conditions. Therefore, besides bio‐based plastics or wood‐plastic composites, chemically modified wood might contribute to more sustainability as well as climate and environmental protection in the future.This article presents fundamentals of the hierarchical structure and chemical modification of wood and curriculum‐related experiments that provide insights into current research on this topic and is suitable to teach aspects of polymer chemistry in the context of sustainability and climate protection at school or in a student laboratory. [ABSTRACT FROM AUTHOR]

Wood has numerous advantages: It is sustainable, has a good CO2 and energy balance, is environmentally friendly due to its biodegradability, and its mechanical properties are so good that it is used as a building material, e.g. for multilevel houses. Moreover, thanks to modern research, obvious disadvantages of wood compared to other materials can now be improved by chemical modifications: Chemically modified wood has a higher durability and does not swell or shrink as much as natural wood upon changing environmental conditions. Therefore, besides bio‐based plastics or wood‐plastic composites, chemically modified wood might contribute to more sustainability as well as climate and environmental protection in the future.This article presents fundamentals of the hierarchical structure and chemical modification of wood and curriculum‐related experiments that provide insights into current research on this topic and is suitable to teach aspects of polymer chemistry in the context of sustainability and climate protection at school or in a student laboratory. [ABSTRACT FROM AUTHOR]

Copyright of Tribologie und Schmierungstechnik is the property of Narr Francke Attempto Verlag GmbH & Co.KG and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The electrochemical splitting of water holds promise for the storage of energy produced intermittently by renewable energy sources. The evolution of hydrogen currently relies on the use of platinum as a catalyst—which is scarce and expensive—and ongoing research is focused towards finding cheaper alternatives. In this context, 2D polymers grown as single layers on surfaces have emerged as porous materials with tunable chemical and electronic structures that can be used for improving the catalytic activity of metal surfaces. Here, we use designed organic molecules to fabricate covalent 2D architectures by an Ullmann‐type coupling reaction on Au(111). The polymer‐patterned gold electrode exhibits a hydrogen evolution reaction activity up to three times higher than that of bare gold. Through rational design of the polymer on the molecular level we engineered hydrogen evolution activity by an approach that can be easily extended to other electrocatalytic reactions. [ABSTRACT FROM AUTHOR]

2D polymer sheets with six positively charged pyrylium groups at each pore edge in a stacked single crystal can be transformed into a 2D polymer with six pyridines per pore by exposure to gaseous ammonia. This reaction furnishes still a crystalline material with tunable protonation degree at regular nano‐sized pores promising as separation membrane. The exfoliation is compared for both 2D polymers with the latter being superior. Its liquid phase exfoliation yields nanosheet dispersions, which can be size‐selected using centrifugation cascades. Monolayer contents of ≈30 % are achieved with ≈130 nm sized sheets in mg quantities, corresponding to tens of trillions of monolayers. Quantification of nanosheet sizes, layer number and mass shows that this exfoliation is comparable to graphite. Thus, we expect that recent advances in exfoliation of graphite or inorganic crystals (e.g. scale‐up, printing etc.) can be directly applied to this 2D polymer as well as to covalent organic frameworks. [ABSTRACT FROM AUTHOR]

Imprinting nanopatterns on flexible substrates has diverse applications in advanced fabrication. However, the traditional thermal nanoimprint lithography (T‐NIL) often causes shrinkage upon cooling. Here, a simple yet versatile method is introduced to fabricate multiple nanopatterns on a flexible substrate coated with an azopolymer by combining athermal nanoimprint lithography (AT‐NIL) and photolithography. The azopolymer has various mechanical properties upon photoirradiation: 1) phototunable glass‐transition temperatures (Tg) and concomitantly photoinduced switch from glassy plastic to viscoplastic polymer; 2) prominent modulation of viscoplasticity under light illumination at different wavelengths. Regionally selective multiple nanopatterns are conveniently fabricated, presenting angle‐dependent structural color images on poly(ethylene terephthalate) (PET) substrates. The flexible, athermal and multiple nanopatterning method has the potential for on‐demand fabrication of complex nanopatterns. [ABSTRACT FROM AUTHOR]

In various nickel(II) salicylaldiminato ethylene polymerization catalysts, which are a versatile mechanistic probe for substituent effects, longer perfluoroalkyl groups exert a strong effect on catalytic activities and polymer microstructures compared to the trifluoromethyl group. This effect is accounted for by a reduced electron density on the active sites, and is also supported by electrochemical studies. Thus, β‐hydride elimination, the key step of chain transfer and branching pathways, is disfavored while chain‐growth rates are enhanced. This enhancement occurs to an extent that enables living polymerizations in aqueous systems to afford ultra‐high‐molecular‐weight polyethylene for various chelating salicylaldimine motifs. These findings are mechanistically instructive as well as practically useful for illustrating the potential of perfluoroalkyl groups in catalyst design. [ABSTRACT FROM AUTHOR]

Constructing a solid electrolyte interface (SEI) is a highly effective approach to overcome the poor reversibility of lithium (Li) metal anodes. Herein, an adhesive and self‐healable supramolecular copolymer, comprising of pendant poly(ethylene oxide) (PEO) segments and ureido‐pyrimidinone (UPy) quadruple‐hydrogen‐bonding moieties, is developed as a protection layer of Li anode by a simple drop‐coating. The protection performance of in‐situ‐formed LiPEO–UPy SEI layer is significantly enhanced owing to the strong binding and improved stability arising from a spontaneous reaction between UPy groups and Li metal. An ultrathin (approximately 70 nm) LiPEO–UPy layer can contribute to stable and dendrite‐free cycling at a high areal capacity of 10 mAh cm−2 at 5 mA cm−2 for 1000 h. This coating together with the promising electrochemical performance offers a new strategy for the development of dendrite‐free metal anodes. [ABSTRACT FROM AUTHOR]

The synthesis of conjugated polymers with ionic substituents directly bound to their main chain repeat units is a strategy for generating strongly electron‐accepting conjugated polyelectrolytes, as demonstrated through the synthesis of a series of ionic azaquinodimethane (iAQM) compounds. The introduction of cationic substituents onto the quinoidal para‐azaquinodimethane (AQM) core gives rise to a strongly electron‐accepting building block, which can be employed in the synthesis of ionic small molecules and conjugated polyelectrolytes (CPEs). Electrochemical measurements alongside theoretical calculations indicate notably low‐lying LUMO values for the iAQMs. The optical band gaps measured for these compounds are highly tunable based on structure, ranging from 2.30 eV in small molecules down to 1.22 eV in polymers. The iAQM small molecules and CPEs showcase the band gap reduction effects of combining the donor‐acceptor strategy with the bond‐length alternation reduction strategy. As a demonstration of their utility, the iAQM CPEs so generated were used as active agents in photothermal therapy. [ABSTRACT FROM AUTHOR]

The polydimethylsiloxane (PDMS) membrane commonly used for separation of biobutanol from fermentation broth fails to meet demand owing to its discontinuous and polluting thermal fabrication. Now, an UV‐induced polymerization strategy is proposed to realize the ultrafast and continuous fabrication of the PDMS membrane. UV‐crosslinking of synthesized methacrylate‐functionalized PDMS (MA‐PDMS) is complete within 30 s. The crosslinking rate is three orders of magnitude larger than the conventional thermal crosslinking. The MA‐PDMS membrane shows a versatile potential for liquid and gas separations, especially featuring an excellent pervaporation performance for n‐butanol. Filler aggregation, the major bottleneck for the development of high‐performance mixed matrix membranes (MMMs), is overcome, because the UV polymerization strategy demonstrates a freezing effect towards fillers in polymer, resulting in an extremely high‐loading silicalite‐1/MA‐PDMS MMM with uniform particle distribution. [ABSTRACT FROM AUTHOR]

Polymerizing epoxides after cyclic esters remains a major challenge, though their block copolymers have been extensively studied and used for decades. Reported here is a simple catalytic approach based on a metal‐free Lewis pair that addresses the challenge. When the Lewis acid is used in excess of a base, selective (transesterification‐free) polymerization of epoxides occurs in the presence of esters, while selectivity toward cyclic esters is achieved by an oppositely biased catalyst. Hence, one‐pot block copolymerization can be performed in both ester‐first and ether‐first orders with selectivity being switchable at any stage, yielding ether‐ester‐type block copolymers with unlimited ordering of sequences as well as widely variable compositions and architectures. The selectivity can also be switched back and forth several times to generate a multiblock copolymer. Experimental and calculational results indicate that the selectivity originates mainly from the state of catalyst‐activated hydroxy species. [ABSTRACT FROM AUTHOR]

Mechanical initiation of polymerization offers the chance to generate polymers in new environments using an energy source with unique capabilities. Recently, a renewed interest in mechanically controlled polymerization has yielded many techniques for controlled radical polymerization by ultrasound. However, other types of polymerizations induced by mechanical activation are rare, especially for generating high‐molecular‐weight polymers. Herein is an example of using piezoelectric ZnO nanoparticles to generate free‐radical species that initiate chain‐growth polymerization and polymer crosslinking. The fast generation of high amounts of reactive radicals enable the formation of polymer/gel by ultrasound activation. This chemistry can be used to harness mechanical energy for constructive purposes in polymeric materials and for controlled polymerizations for bulk‐scale reactions. [ABSTRACT FROM AUTHOR]

Lithium‐metal anodes are recognized as the most promising next‐generation anodes for high‐energy‐storage batteries. However, lithium dendrites lead to irreversible capacity decay in lithium‐metal batteries (LMBs). Besides, the strict assembly‐environment conditions of LMBs are regarded as a challenge for practical applications. In this study, a workable lithium‐metal anode with an artificial hybrid layer composed of a polymer and an alloy was designed and prepared by a simple chemical‐modification strategy. Treated lithium anodes remained dendrite‐free for over 1000 h in a Li–Li symmetric cell and exhibited outstanding cycle performance in high‐areal‐loading Li–S and Li–LiFePO4 full cells. Moreover, the treated lithium showed improved moisture stability that benefits from the hydrophobicity of the polymer, thus retaining good electrochemical performance after exposure to humid air. [ABSTRACT FROM AUTHOR]

Selective activation of photocatalysts under constant light conditions has recently been targeted to produce multi‐responsive systems. However, controlled activation, with easy recovery of the photocatalysts, induced by external stimuli remains a major challenge. Mimicking the responsiveness of biological systems to multiple triggers can offer a promising solution. Herein, we report dual‐responsive polymer photocatalysts in the form of nanogels consisting of a cross‐linked poly‐N‐isopropylacrylamide nanogel, copolymerised with a photocatalytically active monomer. The dual‐responsive polymer nanogels undergo a stark decrease in diameter with increasing temperature, which shields the photocatalytic sites, decreasing the activity. Temperature‐dependent photocatalytic formation of NAD+ in water demonstrates the ability to switch photocatalysis on and off. Moreover, the photocatalysed syntheses of several fine chemicals were carried out to demonstrate the utility of the designed material. [ABSTRACT FROM AUTHOR]

Upon heating, polyesters decompose to small molecules and release flammable volatiles and toxic gases, primarily through chain scission of their ester linkages, and therefore exhibit poor fire‐safety properties, thus restricting their applications. Reported herein is an end‐group‐capturing effect of (bis)oxazoline groups, generated from the thermal rearrangement of the N‐(2‐hydroxyphenyl)phthalimide (HPI) moiety which was incorporated into the polyester chain by copolymerization. These copolyesters, as a result, exhibit high efficiency in retarding decomposition by capturing the decomposed products, particularly for the carbonyl‐terminated fragments, thus increasing the fire‐safety properties, such as self‐extinguishing, anti‐dripping, and inhibiting heat release and smoke production. The successful application of this method in both semi‐aromatic and aliphatic polyesters provide promising perspectives to designing versatile fire‐safe polymers. [ABSTRACT FROM AUTHOR]

The presented work deals with the application of artificial neural networks in the modelling of the thermal decomposition process of friction composite systems based on polymer matrices reinforced by yarns. The thermal decomposition of the automotive clutch friction composite system consisting of a polymer blend reinforced by yarns from organic, inorganic and metallic fibres impregnated with resin, as well as its individual components, was monitored by a method of non‐isothermal thermogravimetry over a wide temperature range. A supervised feed‐forward back‐propagation multi‐layer artificial neural network model, with temperature as the only input parameter, has been developed to predict the thermogravimetric curves of weight loss and time derivative of weight loss of studied friction composite system and its individual components acquired at a fixed constant heating rate under a pure dry nitrogen atmosphere at a constant flow rate. It has been proven that an optimized model with a 1‐25‐6 architecture of an artificial neural network trained by a Levenberg‐Marquardt algorithm is able to predict simultaneously all the analyzed experimental thermogravimetric curves with a high level of reliability and that it thus represents the highly effective artificial intelligence tool for the modelling of thermal stability also of relatively complicated friction composite systems. [ABSTRACT FROM AUTHOR]

The first main‐group element radical based one‐dimensional magnetic chain (1K)n was realized by one‐electron reduction of the pyridinyl functionalized borane 1 with elemental potassium in THF in the absence of 18‐crown‐6 (18‐c‐6). The electron spin density of (1K)n mainly resides at the boron centers with a considerable contribution from central benzene and pyridine moieties. The spin centers exhibit an antiferromagnetic interaction as demonstrated by magnetic measurements and theoretical calculations. In contrast, the reduction in the presence of 18‐c‐6 afforded the separated radical anion salt 1K(Crown), in which the potassium cation was trapped by THF and 18‐c‐6 molecules. Further one‐electron reduction of 1K(Crown) and (1K)n led to the diamagnetic monomer and polymer, respectively. [ABSTRACT FROM AUTHOR]

Chiral packing of ligands on the surface of nanoparticles (NPs) is of fundamental and practical importance, as it determines how NPs interact with each other and with the molecular world. Herein, for gold nanorods (NRs) capped with end‐grafted nonchiral polymer ligands, we show a new mechanism of chiral surface patterning. Under poor solvency conditions, a smooth polymer layer segregates into helicoidally organized surface‐pinned micelles (patches). The helicoidal morphology is dictated by the polymer grafting density and the ratio of the polymer ligand length to nanorod radius. Outside this specific parameter space, a range of polymer surface structures was observed, including random, shish‐kebab, and hybrid patches, as well as a smooth polymer layer. We characterize polymer surface morphology by theoretical and experimental state diagrams. The helicoidally organized polymer patches on the NR surface can be used as a template for the helicoidal organization of other NPs, masked synthesis on the NR surface, as well as the exploration of new NP self‐assembly modes. [ABSTRACT FROM AUTHOR]

A novel continuous flow system for automated high‐throughput screening, autonomous optimization, and enhanced process control of polymerizations was developed. The computer‐controlled platform comprises a flow reactor coupled to size exclusion chromatography (SEC). Molecular weight distributions are measured online and used by a machine‐learning algorithm to self‐optimize reactions towards a programmed molecular weight by dynamically varying reaction parameters (i.e. residence time, monomer concentration, and control agent/initiator concentration). The autonomous platform allows targeting of molecular weights in a reproducible manner with unprecedented accuracy (<2.5 % deviation from pre‐selected goal) for both thermal and light‐induced reactions. For the first time, polymers with predefined molecular weights can be custom made under optimal reaction conditions in an automated, high‐throughput flow synthesis approach with outstanding reproducibility. [ABSTRACT FROM AUTHOR]

Hybridization of metal–organic frameworks (MOFs) and polymers into composites yields materials that display the exceptional properties of MOFs with the robustness of polymers. However, the realization of MOF–polymer composites requires efficient dispersion and interactions of MOF particles with polymer matrices, which remains a significant challenge. Herein, we report a simple, scalable, bench‐top approach to covalently tethered nylon–MOF polymer composite materials through an interfacial polymerization technique. The copolymerization of a modified UiO‐66‐NH2 MOF with a growing polyamide fiber (PA‐66) during an interfacial polymerization gave hybrid materials with up to around 29 weight percent MOF. The covalent hybrid material demonstrated nearly an order of magnitude higher catalytic activity for the breakdown of a chemical warfare simulant (dimethyl‐4‐nitrophenyl phosphate, DMNP) compared to MOFs that are non‐covalently, physically entrapped in nylon, thus highlighting the importance of MOF–polymer hybridization. [ABSTRACT FROM AUTHOR]

Inspired by the adhesive proteins of mussels, polydopamine (pDA) has emerged as one of the most widely employed materials for surface functionalization. Despite numerous attempts at characterization, little consensus has emerged regarding whether pDA is a covalent polymer or a noncovalent aggregate of low molecular weight species. Here, we employed single‐molecule force spectroscopy (SMFS) to characterize pDA films. Retraction of a pDA‐coated cantilever from an oxide surface shows the characteristic features of a polymer with contour lengths of up to 200 nm. pDA polymers are generally weakly bound to the surface through much of their contour length, with occasional "sticky" points. Our findings represent the first direct evidence for the polymeric nature of pDA and provide a foundation upon which to better understand and tailor its physicochemical properties. [ABSTRACT FROM AUTHOR]

Repeatable topological transformation of polymers for the modulation of material functions is a challenge. We have developed a method for repeatedly resetting a cyclic macromolecular architecture to a linear architecture by photostimulation, namely, topology‐reset execution (T‐rex) based on the photochemistry of hexaarylbiimidazoles (HABIs). We synthesized cyclic poly(dimethylsiloxane)s (PDMSs) of various ring sizes with HABIs linked in the chains. UV irradiation of the cyclic PDMSs produced telechelic linear PDMSs with triphenylimidazolyl radical (TPIR) end groups. After termination of UV irradiation, end‐to‐end recyclization occurred by the recoupling of TPIRs. The cyclic PDMSs also responded to ultrasound, which decreased their molecular weight (MW) by site‐specific cleavage of in‐chain HABI moieties, and we are able to reset the MWs by subsequent phototriggered T‐rex. Furthermore, T‐rex enabled solvent‐free switching of the rheological properties of the materials while retaining the liquid character of PDMS. [ABSTRACT FROM AUTHOR]

In den letzten Jahren sind die Vermüllung durch Kunststoffe und deren Persistenz in der Umwelt zu einem Schwerpunkt in Forschung und Nachrichten geworden. Bioabbaubare Polymere wie Polymilchsäure gelten als geeignete Alternativen zu Standardkunststoffen. Polymilchsäure ist jedoch im Meerwasser grundsätzlich nur schlecht abbaubar. In ähnlicher Weise hängt die Abbaurate von anderen bioabbaubaren Polymeren auch entscheidend von der Umgebung ab, in der sie enden. Dieser Kurzaufsatz zeigt, dass Abbautests unter Laborbedingungen nicht auf reale Bedingungen übertragbar sind und daher ökologisch authentische und relevante Feldtestbedingungen erforderlich sind. Zudem werden ökotoxikologische Folgen von bioabbaubaren Polymeren erwogen. Auch soziale Aspekte werden betrachtet, und die Frage wird gestellt, wie bioabbaubare Polymere das Konsumverhalten und die kommunale Abfallwirtschaft beeinflussen. Dies soll einen Beitrag zur Bewertung des Potenzials bioabbaubarer Polymere als alternative Materialien zu Standardkunststoffen leisten. Wir leben im Plastikzeitalter – für die meisten von uns ist ein Leben ohne Polymere und Kunststoffe undenkbar. Ein wachsendes Problem besteht jedoch in der Vermüllung durch Kunststoffe und deren Persistenz in der Umwelt. Dieser Kurzaufsatz befasst sich mit der Frage, ob bioabbaubare Polymere wie Polymilchsäure tatsächlich eine geeignete Alternative zu Standardkunststoffen bieten können. [ABSTRACT FROM AUTHOR]

Structural heterogeneity defines the properties of many functional polymers and it is often crucial for their performance and ability to withstand mechanical impact. Such heterogeneity, however, poses a tremendous challenge for characterization of these materials and limits our ability to design them rationally. Herein we present a practical methodology capable of resolving the complex mechanical behavior and tracking mechanical impact in discrete phases of segmented polyurethane—a typical example of a structurally complex polymer. Using direct optical imaging of photoluminescence produced by a small‐molecule organometallic mechano‐responsive sensor we observe in real time how polymer phases dissipate energy, restructure, and breakdown upon mechanical impact. Owing to its simplicity and robustness, this method has potential in describing the evolution of complex soft‐matter systems for which global characterization techniques fall short of providing molecular‐level insight. [ABSTRACT FROM AUTHOR]

Amino functionalized boron nitride nanosheets (FBN) were incorporated into a crosslinked, thermally rearranged polyimide (XTR) to fabricate FBN‐XTR nanocomposite membrane. The FBN‐XTR membrane exhibited a small decrease in H2 permeability but demonstrated a remarkably increased H2 gas selectivity over other gases, compared with XTR. The XTR membrane heat‐treated at 425 °C had a H2 permeability of 210 Barrers and a H2/CH4 separation factor of 24.1, whereas the nanocomposite membrane with 1 wt % FBN exhibited a H2 permeability of 110 Barrers and H2/CH4 separation factor of 275, an order of magnitude greater. At 1 wt % FBN loading, the FBN‐XTR membrane showed three times higher tensile strength and 60 % higher elongation than pristine XTR membrane. In addition, FBN‐XTR was found to be able to be readily processed into thin‐film membranes for practical H2 separation applications. [ABSTRACT FROM AUTHOR]

The magnitudes of the charges developed on contact‐electrified polymers depend on not only the properties of these materials but also the nature of distant substrates on which the polymers are supported. In particular, image charges induced in conductive substrates can decrease charges on the polymers by arc discharge through the surrounding gas. This mode of charge dissipation occurs on timescales of milliseconds and can be prevented by insulating the sharp edges of the conductive supports. [ABSTRACT FROM AUTHOR]

Abstract: Polymer carbon dots (PCDs) are proposed as a new class of room‐temperature phosphorescence (RTP) materials. The abundant energy levels in PCDs increase the probability of intersystem crossing (ISC) and their covalently crosslinked framework structures greatly suppress the nonradiative transitions. The efficient methods allow the manufacture of PCDs with unique RTP properties in air without additional metal complexation or complicated matrix composition. They thus provide a route towards the rational design of metal‐free RTP materials that may be synthesized easily. Furthermore, we find that RTP is associated with a crosslink‐enhanced emission (CEE) effect, which provides further routes to design improved PCDs with diverse RTP performance. Our results show the potential of PCDs as a universal route to achieve effective metal‐free RTP. [ABSTRACT FROM AUTHOR]

Abstract: Contrary to normal materials, the auxetic/meta‐materials expand transversally as well as longitudinally when subjected to longitudinal load and contract in both directions on compression. In this work, auxeticity is obtained in composites reinforced with carbon woven fabrics placed at certain angles. The auxetic effect on the mechanical properties of the prepared carbon/epoxy composites was investigated. The mechanical properties include the tensile, flexural and impact properties. It is found that the tensile properties are not affected by the auxetic effect; however, the flexural and impact properties are significantly enhanced by the auxetic effect. [ABSTRACT FROM AUTHOR]

Abstract: The first well‐controlled aqueous atom‐transfer radical polymerization (ATRP) conducted in the open air is reported. This air‐tolerant ATRP was enabled by the continuous conversion of oxygen to carbon dioxide catalyzed by glucose oxidase (GOx), in the presence of glucose and sodium pyruvate as sequential sacrificial substrates. Controlled polymerization using initiators for continuous activator regeneration (ICAR) ATRP of oligo(ethylene oxide) methyl ether methacrylate (OEOMA, Mn=500) yielded polymers with low dispersity (1.09≤Đ≤1.29) and molecular weights (MWs) close to theoretical values in the presence of pyruvate. Without added pyruvates, lower MWs were observed due to generation of new chains by H2O2 formed by reaction of O2 with GOx. Successful chain extension of POEOMA500 macroinitiator with OEOMA300 (Đ≤1.3) and Bovine Serum Albumin bioconjugates (Đ≤1.22) confirmed a well‐controlled polymerization. The reactions in the open air in larger scale (25 mL) were also successful. [ABSTRACT FROM AUTHOR]

Mechanical gradients are often employed in nature to prevent biological materials from damage by creating a smooth transition from strong to weak that dissipates large forces. Synthetic mimics of these natural structures are highly desired to improve distribution of stresses at interfaces and reduce contact deformation in manmade materials. Current synthetic gradient materials commonly suffer from non-continuous transitions, relatively small gradients in mechanical properties, and difficult syntheses. Inspired by the polychaete worm jaw, we report a novel approach to generate stiffness gradients in polymeric materials via incorporation of dynamic monodentate metal-ligand crosslinks. Through spatial control of metal ion content, we created a continuous mechanical gradient that spans over a 200-fold difference in stiffness, approaching the mechanical contrast observed in biological gradient materials. [ABSTRACT FROM AUTHOR]

A new superbase, the cyclic trimeric phosphazene base (CTPB), was prepared with high yield and purity. In the presence of alcohol, the CTPB serves as a highly efficient organocatalyst for ring-opening polymerization of the 'non-polymerizable' γ-butyrolactone to offer well-defined poly(γ-butyrolactone) with high conversions (up to 98 %) at −60 °C. The produced polymers have high molecular weights (up to 22.9 kg mol−1) and low polydispersity distributions (1.27-1.50). NMR analysis of initiation process and the structural analysis of resulting polymers by MALDI-TOF suggest a mechanism involving an activating initiator which leads only to linear polymers with BnO/H chain ends. [ABSTRACT FROM AUTHOR]

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An upper critical solution temperature (UCST)-type self-oscillating polymer was designed that exhibited rhythmic soluble–insoluble changes induced by the Belousov–Zhabotinsky (BZ) reaction. The target polymers were prepared by conjugating Ru(bpy)3, a catalyst for the BZ reaction, to ureido-containing poly(allylamine-co-allylurea) (PAU) copolymers. The Ru(bpy)3-conjugated PAUs exhibited a UCST-type phase-transition behavior, and the solubility of the polymer changed in response to the alternation in the valency of Ru(bpy)3. The ureido content influences the temperature range of self-oscillation, and the oscillation occurred at higher temperatures than conventional LCST-type self-oscillating polymers. Furthermore, the self-oscillating behavior of the Ru-PAU could be regulated by addition of urea, which is a unique tuning strategy. We envision that novel self-oscillating polymers with widely tunable soluble-insoluble behaviors can be rationally designed based these UCST-type polymers. [ABSTRACT FROM AUTHOR]

A microfluidic assembly approach was developed for efficiently producing hydrogel spheres with reactive multidomains that can be employed as an advantageous platform to create spherical porous networks in a facile manner with well-defined multicompartments and spatiotemporally controlled functions. This strategy allows for not only large scale fabrication of various robust hydrogel microspheres with controlled size and porosity, but also the domains embedded in hydrogel network could be introduced in a modular manner. Additionally, the number of different domains and their ratio could be widely variable on demand. More importantly, the reactive groups distributed in individual domains could be used as anchor sites to further incorporate functional units in an orthogonal fashion, leading to well-defined multicompartment systems. The strategy provides a new and efficient route to construct well-defined functional multicompartment systems with great flexibility and extendibility. [ABSTRACT FROM AUTHOR]

Oligomeric phosphaalkenes are readily characterized using electrospray ionization mass spectrometry (ESI-MS). The high affinity of phosphines for silver ions permits the detection of the unadulterated polymer as [M + xAg] x+ ions ( x = 2-3). When the oligomers are oxidized using H2O2, the resulting phosphine oxide polymer may be treated with sodium ions to produce [M + xNa] x+ ions ( x = 2-3). Both methods predict a similar distribution of oligomers: Mn values of 3450 ± 100 Da and a PDI of 1.09 ± 0.01 cover both analyses. This distribution represents oligomers of the general formula Me(PMesCPh2) nH from n = 4-20, maximizing at ∼ n = 10. [ABSTRACT FROM AUTHOR]