Diversity of morphological patterns in supramolecular polymers formed from the amphiphilic oligomers of pyrenes

Very important aspects of the modern nanotechnology are control and prediction of arraying patterns of opto- and electroactive molecules in discrete objects on nanoscale level both on surface and solution. Consequqntly, a self-assembly of small molucules provides such an opportunity.For example, oligopyrenotides (OPs, short amphiphilic pyrene oligomers) represent a novel class of amphiphilic molecules which tend to aggegate in aqueous phase. As has been already shown, OPs are able to form 1D supramolecular polymer only under high salt concentration. Since programmed arraying of polyaromatic hydrocarbons in structurally defined objects could offer enhanced performance over the individual components, prediction and controlling of their spatial arrangement remains challenging. Herein we demonstrate that substitution type of the pyrene is crutial, and it determines a morphology of the assemblies. Thus, a 1.6-linkage causes a formation of large, free-standing 2D supromolecular polymers with a thickness 2 nm. These assemblies possess a high degree of an internal order: the interior consists of hydrophobic pyrenes and alkyl chains, whereas the exterior exists as a net of hydrophilic negatively charged phosphates. Contrary, a 1.8-linkage exclusiveley leads to a formation of long (up to a few micrometer), nanometer thick helical supramolecular polymers. These structures tend to form even more complex structures (bundles, superhelixes). Moreover for both molecules, the polymerizations occurs via a nucleation-elongation mechanism. To study Py3 self-assembly, we carried out whole set of spectroscopic (UV/vis, fluorescence, DLS) and microscopic experiments (AFM).

Diversity of morphological patterns in supramolecular polymers formed from the amphiphilic oligomers of pyrenes

Herein we demonstrate that a substitution type of the pyrene in short amphiphilic oligomers determines a morphology of the assemblies formed. Thus, 1.6- and 2.7-linkages lead to a formation of micrometer-sized 2D supromolecular polymers with a constant thickness 2 nm (pictures A and B). These assemblies possess a high degree of an internal order: the interior consists of hydrophobic pyrenes and alkyl chains, whereas the exterior exists as a net of hydrophilic negatively charged phosphates. Contrary, a 1.8-linkage exclusiveley leads to a formation of long nanometer thick helical supramolecular polymers (picturee C). These structures tend to form even more complex assemblies (bundles, superhelixes). Moreover, for all samples the polymerization process occurs via a nucleation-elongation mechanism. To study Py3 self-assembly, we carried out whole set of spectroscopic (UV/vis, fluorescence, DLS) and microscopic experiments (AFM).

Formation of supramolecular polymers by chrysene oligomers

Supramolecular assembly of π-conjugated systems is of large interested due to the possibility to use them in electronic devices.[1] Chrysene is a polyaromatic hydrocarbon which has been studied e.g for organic light-emitting diodes (OLEDs).[2] In continuation of our previous work involving the supramolecular polymerisation of pyrene oligomers [3] an oligomer consisting of three chrysenes linked by phophodiesters was synthesised (Chry3). UV-Vis measurements show that aggregates of Chry3 are formed in aqueous medium. This is illustrated by general hypochromicity, a change in vibronic band intensities and, in particular, the appearance of a red-shifted absorption band in the S0 → S2 transition. The data suggest the formation of J-aggregates. The formation of supramolecular polymers is further studied by temperature-dependent absorption- and fluorescence measurements, and by atomic force microscopy (AFM).

Long-Distance Electronic Energy Transfer in Light-Harvesting Supramolecular Polymers.

The efficient collection of solar energy relies on the design and construction of well-organized light-harvesting systems. Herein we report that supramolecular phenanthrene polymers doped with pyrene are effective collectors of light energy. The linear polymers are formed through the assembly of short amphiphilic oligomers in water. Absorption of light by phenanthrene residues is followed by electronic energy transfer along the polymer over long distances (>100 nm) to the accepting pyrene molecules. The high efficiency of the energy transfer, which is documented by large fluorescence quantum yields, suggests a quantum coherent process.

Biolimus-eluting stent with biodegradable polymer improves clinical outcomes in patients with acute myocardial infarction

OBJECTIVE To investigate clinical outcomes of coronary intervention using a biolimus-eluting stent (BES) compared with a sirolimus-eluting stent (SES) in patients with acute myocardial infarction (AMI) in the Limus Eluted from A Durable versus ERodable Stent (LEADERS) coating trial at the final 5-year follow-up. METHODS The LEADERS trial is a multicentre all-comer study, where patients (n=1707) were randomised to percutaneous intervention with either BES containing biodegradable polymer or SES containing durable polymer. Out of 1707 patients enrolled in this trial, 573 patients had percutaneous coronary intervention for AMI (BES=280, SES=293) and were included in the current analysis. Patient-oriented composite endpoint (POCE, including all death, all myocardial infarction (MI) and all revascularisations), major adverse cardiac events (MACE, including cardiac death, MI and clinically indicated target vessel revascularisation) and stent thrombosis were assessed at 5-year follow-up. RESULTS The baseline clinical, angiographic and procedural characteristics were well matched between BES and SES groups. In all patients with AMI, coronary intervention with a BES, compared with SES, significantly reduced POCE (28.9% vs 42.3%; relative risk (RR) 0.61, 95% CI 0.47 to 0.82, p=0.001) at 5-year follow-up. There was also a reduction in MACE rate in the BES group (18.2% vs 25.9%; RR 0.67, 95% CI 0.47 to 0.95, p=0.025); however, there was no difference in cardiac death and stent thrombosis. In patients with ST-elevation MI (STEMI), coronary intervention with BES significantly reduced POCE (24.4% vs 39.3%; RR 0.55, 95% CI 0.36 to 0.85, p=0.006), MACE (12.6% vs 25.0%; RR 0.47, 95% CI 0.26 to 0.83, p=0.008) and cardiac death (3.0% vs 11.4%; RR 0.25, 95% CI 0.08 to 0.75, p=0.007), along with a trend towards reduction in definite stent thrombosis (3.7% vs 8.6%; RR 0.41, 95% CI 0.15 to 1.18, p=0.088), compared with SES. CONCLUSIONS BES, compared with SES, significantly improved safety and efficacy outcomes in patients with AMI, especially those with STEMI, at 5-year follow-up. TRIAL REGISTRATION NUMBER NCT 00389220.

Synthesis, structure and magnetic properties of cobalt(II) and copper(II) coordination polymers assembled by phthalate and 4-methylimidazole

New coordination polymers [M(Pht)(4-MeIm)2(H2O)]n (M=Co (1), Cu (2); Pht2−=dianion of o-phthalic acid; 4-MeIm=4-methylimidazole) have been synthesized and characterized by IR spectroscopy, X-ray crystallography, thermogravimetric analysis and magnetic measurements. The crystal structures of 1 and 2 are isostructural and consist of [M(4-MeIm)2(H2O)] building units linked in infinite 1D helical chains by 1,6-bridging phthalate ions which also act as chelating ligands through two O atoms from one carboxylate group in the case of 1. In complex 1, each Co(II) atom adopts a distorted octahedral N2O4 geometry being coordinated by two N atoms from two 4-MeIm, three O atoms of two phthalate residues and one O atom of a water molecule, whereas the square-pyramidal N2O3 coordination of the Cu(II) atom in 2 includes two N atoms of N-containing ligands, two O atoms of two carboxylate groups from different Pht, and a water molecule. An additional strong O–H⋯O hydrogen bond between a carboxylate group of the phthalate ligand and a coordinated water molecule join the 1D helical chains to form a 2D network in both compounds. The thermal dependences of the magnetic susceptibilities of the polymeric helical Co(II) chain compound 1 were simulated within the temperature range 20–300 K as a single ion case, whereas for the Cu(II) compound 2, the simulations between 25 and 300 K, were made for a linear chain using the Bonner–Fisher approximation. Modelling the experimental data of compound 1 with MAGPACK resulted in: g=2.6, |D|=62 cm−1. Calculations using the Bonner–Fisher approximation gave the following result for compound 2: g=2.18, J=–0.4 cm−1.

DNA-Grafted Supramolecular Polymers: Helical Ribbon Structures Formed by Self-Assembly of Pyrene-DNA Chimeric Oligomers

The controlled arraying of DNA strands on adaptive polymeric platforms remains a challenge. Here, the noncovalent synthesis of DNA-grafted supramolecular polymers from short chimeric oligomers is presented. The oligomers are composed of an oligopyrenotide strand attached to the 5′-end of an oligodeoxynucleotide. The supramolecular polymerization of these oligomers in an aqueous medium leads to the formation of one-dimensional (1D) helical ribbon structures. Atomic force and transmission electron microscopy show rod-like polymers of several hundred nanometers in length. DNA-grafted polymers of the type described herein will serve as models for the development of structurally and functionally diverse supramolecular platforms with applications in materials science and diagnostics.

Clinical Outcomes According to Diabetic Status in Patients Treated With Biodegradable Polymer Sirolimus-Eluting Stents Versus Durable Polymer Everolimus-Eluting Stents: Prespecified Subgroup Analysis of the BIOSCIENCE Trial.

BACKGROUND Ultrathin strut biodegradable polymer sirolimus-eluting stents (BP-SES) proved noninferior to durable polymer everolimus-eluting stents (DP-EES) for a composite clinical end point in a population with minimal exclusion criteria. We performed a prespecified subgroup analysis of the Ultrathin Strut Biodegradable Polymer Sirolimus-Eluting Stent Versus Durable Polymer Everolimus-Eluting Stent for Percutaneous Coronary Revascularisation (BIOSCIENCE) trial to compare the performance of BP-SES and DP-EES in patients with diabetes mellitus. METHODS AND RESULTS BIOSCIENCE trial was an investigator-initiated, single-blind, multicentre, randomized, noninferiority trial comparing BP-SES versus DP-EES. The primary end point, target lesion failure, was a composite of cardiac death, target-vessel myocardial infarction, and clinically indicated target lesion revascularization within 12 months. Among a total of 2119 patients enrolled between February 2012 and May 2013, 486 (22.9%) had diabetes mellitus. Overall diabetic patients experienced a significantly higher risk of target lesion failure compared with patients without diabetes mellitus (10.1% versus 5.7%; hazard ratio [HR], 1.80; 95% confidence interval [CI], 1.27-2.56; P=0.001). At 1 year, there were no differences between BP-SES versus DP-EES in terms of the primary end point in both diabetic (10.9% versus 9.3%; HR, 1.19; 95% CI, 0.67-2.10; P=0.56) and nondiabetic patients (5.3% versus 6.0%; HR, 0.88; 95% CI, 0.58-1.33; P=0.55). Similarly, no significant differences in the risk of definite or probable stent thrombosis were recorded according to treatment arm in both study groups (4.0% versus 3.1%; HR, 1.30; 95% CI, 0.49-3.41; P=0.60 for diabetic patients and 2.4% versus 3.4%; HR, 0.70; 95% CI, 0.39-1.25; P=0.23, in nondiabetics). CONCLUSIONS In the prespecified subgroup analysis of the BIOSCIENCE trial, clinical outcomes among diabetic patients treated with BP-SES or DP-EES were comparable at 1 year. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT01443104.

Hierarchical self-assembly of the DNA-grafted supramolecular polymers

Conjugation of functional entities with a specific set of optical, mechanical or biological properties to DNA strands allows engineering of sophisticated DNA-containing architectures. Among various hybrid systems, DNA-grafted polymers occupy an important place in modern materials science. In this contribution we present the non-covalent synthesis and properties of DNA-grafted linear supramolecular polymers (SPs), which are assembled in a controllable manner from short chimeric DNA-pyrene oligomers. The synthetic oligomers consist of two parts: a 10 nucleotides long DNA chain and a covalently attached segment of variable number of phosphodiester-linked pyrenes. The temperature-dependent formation of DNA-grafted SPs is described by a nucleation-elongation mechanism. The high tendency of pyrenes to aggregate in water, leads to the rapid formation of SPs. The core of the assemblies consists of stacked pyrenes. They form a 1D platform, to which the DNA chains are attached. Combined spectroscopic and microscopic studies reveal that the major driving forces of the polymerization are π-stacking of pyrenes and hydrophobic interactions, and DNA pairing contributes to a lesser extent. AFM and TEM experiments demonstrate that the 1D SPs appear as elongated ribbons with a length of several hundred nanometers. They exhibit an apparent helical structure with a pitch-to-pitch distance of 50±15 nm. Since DNA pairing is a highly selective process, the ongoing studies are aimed to utilize DNA-grafted SPs for the programmable arrangement of functional entities. For example, the addition of non-modified complementary DNA strands to the DNA-grafted SPs leads to the cooperative formation of higher-order assemblies. Also, our experiments suggest that the fluorescent pyrene core of 1D ribbons serves as an efficient donor platform for energy transfer applications.

Hierarchical self-assembly of the DNA-grafted supramolecular polymers

Conjugation of functional entities with a specific set of optical, mechanical or biological properties to DNA strands allows engineering of sophisticated DNA-containing architectures. Among various hybrid systems, DNA-grafted polymers occupy an important place in modern materials science. In this contribution we present the non-covalent synthesis and properties of DNA-grafted linear supramolecular polymers (SPs), which are assembled in a controllable manner from short chimeric DNA-pyrene oligomers. The synthetic oligomers consist of two parts: a 10 nucleotides long DNA chain and a covalently attached segment of variable number of phosphodiester-linked pyrenes. The temperature-dependent formation of DNA-grafted SPs is described by a nucleation-elongation mechanism. The high tendency of pyrenes to aggregate in water, leads to the rapid formation of SPs. The core of the assemblies consists of stacked pyrenes. They form a 1D platform, to which the DNA chains are attached. Combined spectroscopic and microscopic studies reveal that the major driving forces of the polymerization are π-stacking of pyrenes and hydrophobic interactions, and DNA pairing contributes to a lesser extent. AFM and TEM experiments demonstrate that the 1D SPs appear as elongated ribbons with a length of several hundred nanometers. They exhibit an apparent helical structure with a pitch-to-pitch distance of 50±15 nm. Since DNA pairing is a highly selective process, the ongoing studies are aimed to utilize DNA-grafted SPs for the programmable arrangement of functional entities. For example, the addition of non-modified complementary DNA strands to the DNA-grafted SPs leads to the cooperative formation of higher-order assemblies. Also, our experiments suggest that the fluorescent pyrene core of 1D ribbons serves as an efficient donor platform for energy transfer applications.

Influence of polymers on microstructure and adhesive strength of cementitious tile adhesive mortars

The impact of polymer modification on the physical properties of cementitious mortars is investigated using a multimethod approach. Special emphasis is put on the identification and quantification of different polymer components within the cementitious matrix. With respect to thin-bed applications, particularly tile adhesives, the spatial distributions of latex, cellulose ether (CE), polyvinyl alcohol (PVA), and cement hydration products can be quantified. It is shown that capillary forces and evaporation induce water fluxes in the interconnected part of the pore system, which transport CE, PVA, and cement ions to the mortar interfaces. In contrast, the distribution of latex remains homogeneous. In combination with results from qualitative experiments, the quantitative findings allow reconstruction of the evolution from fresh to hardened mortar, including polymer film formation, cement hydration, and water migration. The resulting microstructure and the failure modes can be correlated with the final adhesive strength of the tile adhesive. The results demonstrate that skinning prior to tile inlaying can strongly reduce wetting properties of the fresh mortar and lower final adhesive strength.

From Ribbons to Networks: Hierarchical Organization of DNA-Grafted Supramolecular Polymers

DNA-grafted supramolecular polymers (SPs) allow the programmed organization of DNA in a highly regular, one-dimensional array. Oligonucleotides are arranged along the edges of pyrene-based helical polymers. Addition of complementary oligonucleotides triggers the assembly of individual nanoribbons resulting in the development of extended supramolecular networks. Network formation is enabled by cooperative coaxial stacking interactions of terminal GC base pairs. The process is accompanied by structural changes in the pyrene polymer core that can be followed spectroscopically. Network formation is reversible, and disassembly into individual ribbons is realized either via thermal denaturation or by addition of a DNA separator strand.

Interaction of the Trinuclear Triangular Secondary Building Unit [Cu 3 (μ 3 -OH)(μ-pz) 3 ] 2+ with 4,4′-Bipyridine. Structural Characterizations of New Coordination Polymers and Hexanuclear Cu II Clusters. 2°

By reacting 4,4′-bipyridine (bpy) with selected trinuclear triangular CuII complexes, [Cu3(μ3-OH)(μ-pz)3(RCOO)2(LL′)] [pz = pyrazolate anion; R = CH3, CH3CH2, CH2═CH, CH2═C(CH3); L, L′ = Hpz, H2O, MeOH] in MeOH, the substitution of monotopic ligands by ditopic bpy was observed. Depending on the stoichiometric reaction ratios, different compounds were isolated and structurally characterized. One- and two-dimensional coordination polymers (CPs), as well as two hexanuclear CuII clusters were identified. One of the hexanuclear clusters self-assembles into a supramolecular three-dimensional structure, and its crystal packing shows the presence of two intersecting channels, one of which is almost completely occupied by guest bpy, while in the second one guest water molecules are present. This compound also shows a reversible, thermally induced, single-crystal-to-single-crystal transition.