Putting aromatic compounds to work: Rational synthesis of organic 2D polymers

This contribution describes two different approaches aimed at the synthesis of monolayer molecular sheets with internal order, or, in other words, 2D polymers. First, an interfacial strategy is presented in which terpyridene-based hexafunctional monomers spread at the air/water interface are connected to one another with the help of metal salts. While this approach leads to micrometer-sized monolayer sheets that are mechanically stable enough to be spanned over several micrometer-sized holes, their internal structure could not yet be proven. The second approach rests upon solid-state photochemistry, and properly designed monomers are covalently connected with one another while being held in layered geometries owing to crystal packing. Exfoliation to single sheets can be achieved, and molecular structure is supported by a Raman spectroscopic analysis. We consider this the first case of a rational synthesis of 2D polymers and briefly touch on the impact this may hav

Scalable Synthesis of Two-dimensional Polymer Crystals and Exfoliation into Nanometer-thin Sheets

Two-dimensional materials have moved into the spotlight of researchers. The isolation of single graphene sheets has shown that restricted dimensionality can lead to interesting properties. Bottom-up synthesis of organic, covalently-bonded structures is, however, still challenging. In this publication we give a synopsis of a recently published monomer that is easily accessible and reversibly provides chiral two-dimensional polymer single crystals, which can be exfoliated into nanometer-thin sheets and show promise for applications in, for example, nonlinear optics and ultrathin membranes

Polymers Going Rigid, Thick, and Laterally Infinite

This short review article provides insight into the impact organic chemistry can have on state-of-the-art materials creation. Three cases were selected from the authors' laboratory, the first being 'Suzuki polycondensation', a powerful method with which innovative organic chemistry was successfully transferred to polymer synthesis and which meanwhile has even found technical scale application. The second describes the decoration of linear polymers with a dense layer of regular branch work. Though seemingly a rather esoteric enterprise, these decorations resulted in considerable property changes as compared to other linear polymers and, additionally, led to the discovery of novel properties. Consequently, this area which is commonly referred to as 'dendronized polymers' in a world-wide activity has been developed into a ripe research field, presently under exploration for possible technical application. Finally, an example still very much in its first tumbling steps was selected to give yet another perspective of the role of organic chemistry in a materials-oriented chemistry. It aims at the generation of ultrathin, yet internally strictly defined, sheet-like macromolecules for which a great future is foreseen, e.g. as a 2D platform for the systematic construction of 3D matter

Modeling nanosized single molecule objects: dendronized polymers adsorbed onto mica

We attempt to provide direct evidence for the suggested behavior of dendronized polymers as molecular objects (i.e., single shape persistent macromolecules). For this purpose, the microscopic structure of dendronized polymers adsorbed onto mica has been investigated using atomistic molecular dynamics simulations. We find that the shape of the second to fourth generation dendronized polymers is basically kept upon adsorption due to substantial backfolding within their interior. The fluctuation strength of the polymer backbones, which is seen to decrease with increasing generation, also indicates that these individual macromolecules exhibit molecular object behavior in the nanosize rangePostprint (published version

a new level of hierarchical structure control by use of supramolecular self-assembled dendronized block copolymers

Complexation of dendronized block copolymers with sulfate alkyl tails forms unprecedented hierarchically ordered bulk structures, including rectangular-in-lamellar, tetragonal-in-lamellar, hexagonal-in-lamellar and lamellar-in-lamellar. These novel liquid-crystalline morphologies, which can be designed at low length scales in these systems, are expected to provide final materials with not only unprecedented structural complexity, but also tunable physical properties

In-situ nanospectroscopic imaging of plasmon-induced two-dimensional [4+4]-cycloaddition polymerization on Au(111)

From Springer Nature via Jisc Publications RouterHistory: received 2021-01-14, accepted 2021-06-16, registration 2021-07-13, pub-electronic 2021-07-27, online 2021-07-27, collection 2021-12Publication status: PublishedFunder: EC | EU Framework Programme for Research and Innovation H2020 | H2020 Priority Excellent Science | H2020 European Research Council (H2020 Excellent Science - European Research Council); doi: https://doi.org/10.13039/100010663; Grant(s): 741431-2DNanoSpecFunder: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (Swiss National Science Foundation); doi: https://doi.org/10.13039/501100001711; Grant(s): URPP-LightChECFunder: EC | Horizon 2020 Framework Programme (EU Framework Programme for Research and Innovation H2020); doi: https://doi.org/10.13039/100010661; Grant(s): 841653-2DvdWHsFunder: the Swiss National Supercomputing Centre (CSCS) under Project ID uzh1 and s965Abstract: Plasmon-induced chemical reactions (PICRs) have recently become promising approaches for highly efficient light-chemical energy conversion. However, an in-depth understanding of their mechanisms at the nanoscale still remains challenging. Here, we present an in-situ investigation by tip-enhanced Raman spectroscopy (TERS) imaging of the plasmon-induced [4+4]-cycloaddition polymerization within anthracene-based monomer monolayers physisorbed on Au(111), and complement the experimental results with density functional theory (DFT) calculations. This two-dimensional (2D) polymerization can be flexibly triggered and manipulated by the hot carriers, and be monitored simultaneously by TERS in real time and space. TERS imaging provides direct evidence for covalent bond formation with ca. 3.7 nm spatial resolution under ambient conditions. Combined with DFT calculations, the TERS results demonstrate that the lateral polymerization on Au(111) occurs by a hot electron tunneling mechanism, and crosslinks form via a self-stimulating growth mechanism. We show that TERS is promising to be plasmon-induced nanolithography for organic 2D materials

Transforming Growth Factor β1 Oppositely Regulates the Hypertrophic and Contractile Response to β-Adrenergic Stimulation in the Heart

BACKGROUND: Neuroendocrine activation and local mediators such as transforming growth factor-β₁ (TGF-β₁) contribute to the pathobiology of cardiac hypertrophy and failure, but the underlying mechanisms are incompletely understood. We aimed to characterize the functional network involving TGF-β₁, the renin-angiotensin system, and the β-adrenergic system in the heart. METHODS: Transgenic mice overexpressing TGF-β₁ (TGF-β₁-Tg) were treated with a β-blocker, an AT₁-receptor antagonist, or a TGF-β-antagonist (sTGFβR-Fc), were morphologically characterized. Contractile function was assessed by dobutamine stress echocardiography in vivo and isolated myocytes in vitro. Functional alterations were related to regulators of cardiac energy metabolism. RESULTS: Compared to wild-type controls, TGF-β₁-Tg mice displayed an increased heart-to-body-weight ratio involving both fibrosis and myocyte hypertrophy. TGF-β₁ overexpression increased the hypertrophic responsiveness to β-adrenergic stimulation. In contrast, the inotropic response to β-adrenergic stimulation was diminished in TGF-β₁-Tg mice, albeit unchanged basal contractility. Treatment with sTGF-βR-Fc completely prevented the cardiac phenotype in transgenic mice. Chronic β-blocker treatment also prevented hypertrophy and ANF induction by isoprenaline, and restored the inotropic response to β-adrenergic stimulation without affecting TGF-β₁ levels, whereas AT₁-receptor blockade had no effect. The impaired contractile reserve in TGF-β₁-Tg mice was accompanied by an upregulation of mitochondrial uncoupling proteins (UCPs) which was reversed by β-adrenoceptor blockade. UCP-inhibition restored the contractile response to β-adrenoceptor stimulation in vitro and in vivo. Finally, cardiac TGF-β₁ and UCP expression were elevated in heart failure in humans, and UCP--but not TGF-β₁--was downregulated by β-blocker treatment. CONCLUSIONS: Our data support the concept that TGF-β₁ acts downstream of angiotensin II in cardiomyocytes, and furthermore, highlight the critical role of the β-adrenergic system in TGF-β₁-induced cardiac phenotype. Our data indicate for the first time, that TGF-β₁ directly influences mitochondrial energy metabolism by regulating UCP3 expression. β-blockers may act beneficially by normalizing regulatory mechanisms of cellular hypertrophy and energy metabolism

Toxoplasma gondii Actively Inhibits Neuronal Function in Chronically Infected Mice

Upon infection with the obligate intracellular parasite Toxoplasma gondii, fast replicating tachyzoites infect a broad spectrum of host cells including neurons. Under the pressure of the immune response, tachyzoites convert into slow-replicating bradyzoites, which persist as cysts in neurons. Currently, it is unclear whether T. gondii alters the functional activity of neurons, which may contribute to altered behaviour of T. gondii–infected mice and men. In the present study we demonstrate that upon oral infection with T. gondii cysts, chronically infected BALB/c mice lost over time their natural fear against cat urine which was paralleled by the persistence of the parasite in brain regions affecting behaviour and odor perception. Detailed immunohistochemistry showed that in infected neurons not only parasitic cysts but also the host cell cytoplasm and some axons stained positive for Toxoplasma antigen suggesting that parasitic proteins might directly interfere with neuronal function. In fact, in vitro live cell calcium (Ca2+) imaging studies revealed that tachyzoites actively manipulated Ca2+ signalling upon glutamate stimulation leading either to hyper- or hypo-responsive neurons. Experiments with the endoplasmatic reticulum Ca2+ uptake inhibitor thapsigargin indicate that tachyzoites deplete Ca2+ stores in the endoplasmatic reticulum. Furthermore in vivo studies revealed that the activity-dependent uptake of the potassium analogue thallium was reduced in cyst harbouring neurons indicating their functional impairment. The percentage of non-functional neurons increased over time In conclusion, both bradyzoites and tachyzoites functionally silence infected neurons, which may significantly contribute to the altered behaviour of the host

Respiratory chain signalling is essential for adaptive remodelling following cardiac ischaemia

Abstract Cardiac ischaemia-reperfusion (I/R) injury has been attributed to stress signals arising from an impaired mitochondrial electron transport chain (ETC), which include redox imbalance, metabolic stalling and excessive production of reactive oxygen species (ROS). The alternative oxidase (AOX) is a respiratory enzyme, absent in mammals, that accepts electrons from a reduced quinone pool to reduce oxygen to water, thereby restoring electron flux when impaired and, in the process, blunting ROS production. Hence, AOX represents a natural rescue mechanism from respiratory stress. This study aimed to determine how respiratory restoration through xenotopically expressed AOX affects the re-perfused post-ischaemic mouse heart. As expected, AOX supports ETC function and attenuates the ROS load in post-anoxic heart mitochondria. However, post-ischaemic cardiac remodelling over 3 and 9 weeks was not improved. AOX blunted transcript levels of factors known to be up-regulated upon I/R such as the atrial natriuretic peptide (Anp) whilst expression of pro-fibrotic and pro-apoptotic transcripts were increased. Ex vivo analysis revealed contractile failure at nine but not 3 weeks after ischaemia whilst label-free quantitative proteomics identified an increase in proteins promoting adverse extracellular matrix remodelling. Together, this indicates an essential role for ETC-derived signals during cardiac adaptive remodelling and identified ROS as a possible effector.Peer reviewe