Synthesis and characterization of poly(pentabromostyrene) micrometer-sized particles of narrow size distribution for flame-retardant applications

Flame-retardant microspheres are important due to their ability to increase the thermal stability of host materials. Bromine-containing compounds have been used for centuries due to their flame-retardant properties. A problem with many currently used fire retardants is their escape from their host material, decreasing their effectiveness as well as polluting the environment. In this work, a pentabromostyrene (PBS) monomer was synthesized and polymerized by dispersion polymerization for preparation of flame-retardant microspheres. The effect of various polymerization parameters on their size and size distribution was also elucidated. In order to demonstrate the potential of poly(PBS) microspheres as flame retardants, poly(PBS)/polystyrene (poly(PBS)/PS) blends were prepared, and it was shown that the higher the percentage of poly(PBS) in the blend, the higher the combustion temperature. An additional test for the performance of the poly(PBS) microparticles as flame-retardant additives was performed by coating polyethylene terephthalate (PET) films with the poly(PBS) microspheres, decreasing their flammability, as was illustrated by a vertical burn test. The high thermal stability and low flammability of both the poly(PBS) particles and the poly(PBS)/polymer blends indicate the potential of these microspheres as flame-retardant additives.     

Bi-phasic nanostructures for functional applications

Biphasic solid state composites of the type metal/metal oxide or element/element oxide can be synthesized in one pot chemical reactions using so called molecular "single source precursors". Due to their singular genesis these composites show peculiar hetero-structures based on core-shell hierarchies such as superlattices and composite nanospheres or nanowires. They exhibit superior or new functional properties compared to their individual constituent compounds. In the current work, we review in particular the synthetical and mechanistical approach of bi-phasic (Al/Al(2)O(3)) nanostructures such as nanospheres, nanowires and nanoloops using a single source precursor. Other bi-phasic materials of the general formula M/MO(x) (for example M = Ge, Sn, Pb) are addressed for comparison. The impact of different synthetical conditions as well as of modification of surfaces by laser techniques and their technological relevance are presented briefly. Additionally, functional applications of the prepared surfaces are explained with some outstanding case studies. These case studies are primarily concerned with their use as biomaterials and their application in medicine as well as with their use as thin films for optics and functional surfaces.     

From Prebiotic Chemistry to Supramolecular Biomedical Materials: Exploring the Properties of Self-Assembling Nucleobase-Containing Peptides

Peptides and their synthetic analogs are a class of molecules with enormous relevance as therapeutics for their ability to interact with biomacromolecules like nucleic acids and proteins, potentially interfering with biological pathways often involved in the onset and progression of pathologies of high social impact. Nucleobase-bearing peptides (nucleopeptides) and pseudopeptides (PNAs) offer further interesting possibilities related to their nucleobase-decorated nature for diagnostic and therapeutic applications, thanks to their reported ability to target complementary DNA and RNA strands. In addition, these chimeric compounds are endowed with intriguing self-assembling properties, which are at the heart of their investigation as self-replicating materials in prebiotic chemistry, as well as their application as constituents of innovative drug delivery systems and, more generally, as novel nanomaterials to be employed in biomedicine. Herein we describe the properties of nucleopeptides, PNAs and related supramolecular systems, and summarize some of the most relevant applications of these systems.     

Electro-optic properties of organic nanotubes

In this review article the theoretical and experimental possibilities of applying EO-methods for estimation of the physico-chemical properties of the organic nanotubes (ONTs) are studied. The ONTs are highly organized nanostructures of strongly elongated, anysometric, and hollow cylinders with a size range of 1 nm to 10,000 nm, e.g. in aqueous solutions they could behave as colloid (disperse) particles. They have high interaction ability due to their extremely large curved, rolled-up external surfaces (bilayers of membrane walls) and unique properties because of their specific electric charge distribution and dynamics that make possible the functionalization of their surfaces. Thus they could template guestsubstances such as membrane proteins and protein complexes on the exterior surfaces and in the membrane. We performed our investigations for the case of ONT aqueous colloid suspension. Following our earlier proposition of the general expression for the electro-optic (EO) effect we derived equations for the evaluation of the electric properties of ONT particles such as mechanism of electric polarization and identification of their most important electric Dipole Moments (DM), permanent (pDM) and induced (iDMs). Further we recommend ways for the calculation of their magnitude and direction. Also we evaluated some geometrical properties such as length of the ONT particles and their polydispersity. The knowledge that we provided about the ONT properties may enable us to elucidate and predict their biological activity. Templating biological active ligands (such as membrane proteins and protein complexes) on the inner and outer surfaces as well as in the surface membrane creates their potential usefulness as carrier and deliverer of biopharmaceuticals in bio-nanodevices. The theoretical equations were compared with the experimental data for ONTs such as (lipid) LNT, Tobacco Mosaic Virus (TMV) and microtubules (MT). Comparison of EO methods with other methods used till now shows that the EO methods are faster, not invasive and do not alter the studied particles.     

The relevance of shape and size of Au55 clusters

This critical review deals with the history of Au(55)(PPh(3))(12)Cl(6) and its derivatives from the very beginning in 1981 to date. Au(55) clusters obtain their special interest from their ultimate size and their ideal cuboctahedral structure. They are part of the family of so-called full-shell clusters, particles with perfectly completed geometries, also represented by icosahedral Au(13) clusters. Bare as well as ligand protected Au(55) clusters not only exhibit special chemical and physical stability, but draw their attention particularly from their unique electronic properties. Single electron switching at room temperature becomes possible, giving rise for development of applications in future nanoelectronic devices. A predominantly size-determined property of the 1.4 nm particles becomes obvious with respect of biological response. Au(55) clusters indicate an unusual cytotoxicity which seems to be caused by the unusually strong interaction between the 1.4 nm particles and the major grooves of DNA. Only marginally smaller or larger particles show drastically reduced toxicity, whereas significantly larger gold nanoparticles are completely non-toxic. Both, the electronic perspectives as well as the relevance in toxicology are at very early stages of development (75 references).     

Detection of ATP-binding to growth factors

It was shown in previous work that the interaction of growth factors (GFs) with adenosine triphosphate (ATP) is essential for their neuroprotective effect. Here we investigated the nature of the association of human basic fibroblast growth factor (bFGF), nerve growth factor (NGF), and brain-derived neurotrophic factor (BDNF) with ATP. It was demonstrated that this interaction involves the formation of non-covalent ATP-GF complexes that are labile at low pH and that could be selectively purified and subjected to electrospray and MALDI-TOF mass spectrometry. The results obtained with these techniques indicated that the stability of the complexes is high. Main features of the procedure used here are: (1) reversed-phase purification of nucleotide-protein non-covalent complexes, (2) their detection with MALDI-TOF-MS using acid-free matrix, and/or (3) their measurement with ESI-MS using soft desolvation conditions. The methodology was successful in providing proof for the presence of various nucleotide-GF complexes. It was extended to other nucleotide-binding proteins (ribonuclease A) as well as proteins that do not exhibit nucleotide binding (lysozyme) as positive and negative control, respectively. Thus, the method demonstrated its general use for the investigation of a wide range of proteins interacting with nucleotides as long as their complexes are sufficiently stable to accommodate the experimental conditions.     

Cyclic acylimines and cyclic carbinolamides III. Piperidone and isoindolone

6-Phenyl-2,3,4,5-tetrahydro-3,3,5,5-tetramethyl-2-pyridone ( 6 ), 1-phenyl-3-isoindolone, and their methanol ( 5 ) and butanol ( 19 ) addition products, as well as 6-methoxy-3,3,5,5-tetramethyl-2-piperidone ( 4 ) and 1-methoxy-3-isoindolinone ( 11 ) were prepared and their chemical properties studied. The cyclic acylimines and their methanol addition products were found to react with weak nucleophiles (amides, alcohols), active methylene compounds (acetone, dimedone) or dienes (1,2,3,4-tetramethyl and 2,3-dimethylbutadiene) to give addition products.     

Glass‐transition temperatures of nanostructured amorphous bulk polymers and their blends

Nanostructured amorphous bulk polymer samples were produced by processing them with small molecule hosts. Urea (U) and gamma‐cyclodextrin (γ‐CD) were utilized to form crystalline inclusion compounds (ICs) with low and high molecular weight as‐received (asr‐) poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA), and their blends as included guests. Upon careful removal of the host crystalline U and γ‐CD lattices, nanostructured coalesced (c‐) bulk PVAc, PMMA, and PVAc/PMMA blend samples were obtained, and their glass‐transition temperatures, T_gs, measured. In addition, non‐stoichiometric (n‐s)‐IC samples of each were formed with γ‐CD as the host. The T_gs of the un‐threaded, un‐included portions of their chains were observed as a function of their degree of inclusion. In all the cases, these nanostructured PVAc and PMMA samples exhibited T_gs elevated above those of their as‐received and solution‐cast samples. Based on their comparison, several conclusions were reached concerning how their molecular weights, the organization of chains in their coalesced samples, and the degree of constraint experienced by un‐included portions of their chains in (n‐s)‐γ‐CD‐IC samples with different stoichiometries affect their chain mobilities and resultant T_gs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1041–1050     

Chelating DTPA amphiphiles: ion-tunable self-assembly structures and gadolinium complexes

A series of chelating amphiphiles and their gadolinium (Gd(iii)) metal complexes have been synthesized and studied with respect to their neat and lyotropic liquid crystalline phase behavior. These amphiphiles have the ability to form ion-tunable self-assembly nanostructures and their associated Gd(III) complexes have potential as magnetic resonance imaging (MRI) contrast enhancement agents. The amphiphiles are composed of diethylenetriaminepentaacetic acid (DTPA) chelates conjugated to one or two oleyl chain(s) (DTPA-MO and DTPA-BO), or isoprenoid-type chain(s) of phytanyl (DTPA-MP and DTPA-BP). The thermal phase behavior of the neat amphiphiles was examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and cross polarizing optical microscopy (POM). Self-assembly of neat amphiphiles and their associated Gd complexes, as well as their lyotropic phase behavior in water and sodium acetate solutions of different ionic strengths, were examined by POM and small and wide angle X-ray scattering (SWAXS). All neat amphiphiles exhibited lamellar structures. The non-complexed amphiphiles showed a variety of lyotropic phases depending on the number and nature of the hydrophobic chain in addition to the ionic state of the hydration. Upon hydration with increased Na-acetate concentration and the subtle changes in the effective headgroup size, the interfacial curvature of the amphiphile increased, altering the lyotropic liquid crystalline structures towards higher order mesophases such as the gyroid (Ia3d) bicontinuous cubic phase. The chelation of Gd with the DTPA amphiphiles resulted in lamellar crystalline structures for all the neat amphiphiles. Upon hydration with water, the Gd-complexed mono-conjugates formed micellar or vesicular self-assemblies, whilst the bis-conjugates transformed only partially into lyotropic liquid crystalline mesophases.     

Synthesis,in vitro antimicrobial assessment,and computational investigation of pharmacokinetic and bioactivity properties of novel trifluoromethylated compounds using in silico ADME and toxicity prediction tools

1,3-Dipolar cycloaddition reactions of a sugar-based trifluoromethylated nitrone-to-maleimide and allyl bromide afforded a series of cycloadducts in good yield. The same nitrone reacts with propargyl acetate lead, after rearrangement of 4-isoxazoline, to aziridine with good yield. The obtained compounds were evaluated for their in vitro antimicrobial potency. Additionally, we are interested in predicting their physicochemical parameters such as lipophilicity and bioactivity score as well as their pharmacokinetic properties such as absorption, distribution, metabolism, and excretion (ADME) such as plasma protein binding (PPB) penetration of the blood–brain barrier (BBB), human intestinal absorption (HIA), cellular permeability (PCaco-2), cell permeability of Madin–Darby canine kidney (PMDCK), P-glycoprotein (P-gp) efflux, CYP inducers, substrates and inhibitors’ skin and permeability (PS), and their toxicological behavior [mutagenicity, carcinogenicity, acute, environmental, cardiotoxicity (hERG inhibition)] using in silico computational methods. Also, we aimed to validate QSAR models for the elucidation of their antitarget using 32 sets of end-points (IC50, Ki and Kact). The obtained result provides good information about the pharmacotherapy potential and toxicity of the examined molecules with good compliance between in vitro antimicrobial and the predicted properties. Findings indicated and encouraged the use of these compounds and their derivatives for further in vivo evaluations in the design and the elucidation of the intrinsic mechanisms as well as the efficacy of the selected powerful drug.     

Synthesis and characterization of novel poly(amide urea)s,materials with outstanding mechanical properties

Four novel A‐B condensation monomers containing an amine and a carboxylic acid function are described, along with their polymerization to give main chain aromatic poly(amide urea)s. The monomers, and the polymer structural unit, are N,N′‐diphenylurea derivatives. When comparing wholly aromatic polyamides, or aramids, with the poly(amide urea)s described herein, we find that the chemical resistance to hydrolysis of the later polymers increases and their thermal resistance is diminished due to the main chain urea groups, whereas their water uptake is not greatly modified. The most striking result of the new poly(amide urea)s is their outstanding mechanical resistance: their Young's modulus rises as high as 5.5 GPa and their tensile strengths as high as 170 MPa for unoriented films prepared at laboratory scale by casting. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5398–5407, 2007     

Amphiphilic properties of dumbbell-shaped inorganic-organic-inorganic molecular hybrid materials in solution and at an interface

Five novel dumbbell-shaped polyoxometalate (POM)-based inorganic-organic-inorganic molecular hybrids are investigated both in polar solvents and at interfaces for potential amphiphilic properties, which are compared with those of conventional surfactants. These hybrids with the general formula {P(2)V(3)W(15)}(2)-bis(TRIS)-linker are formed by linking two Wells-Dawson-type clusters, [P(2)V(3)W(15)O(62)](9-), with different linear bis(TRIS) linker ligands between the two TRIS moieties. Laser light scattering (LLS) studies reveal the presence of self-assembled vesicular structures in water/acetone mixed solvents, and the vesicle size increases with increasing acetone content, suggesting a charge-regulated process. The elastic constants, which are used to calculate the bending energy during vesicle formation, reveal that the organic ligands play an important role in determining the self-assembly process and that the hybrids do demonstrate amphiphilic behavior at the water/air interface. Furthermore, it is shown that some of the hybrids form monolayers at the interface, with an average molecular area that can be correlated with their organic linkers, as determined from their π-A isotherms. Finally, the hybrids not only display amphiphilic behavior akin to that of a surfactant but also exhibit an unusually high entropy contribution to vesicle formation as a result of their unique large, polar head groups, complex organic linkers, and their special molecular architectures as well as because of the involvement of the amphiphilic tetrabutylammonium (TBA) counterions.     

全共轭聚噻吩类和聚硒吩类嵌段共聚物的凝聚态结构调控

嵌段共聚物可发生微相分离形成丰富的介观尺度上的相结构,而共轭聚合物是一类具有特殊的力学、导电性能或光电功能的半刚性链高分子.全共轭嵌段共聚物因其兼具两者的特性而备受瞩目.本文着重介绍了近年来课题组在基于全共轭聚(3-烷基噻吩)和聚(3-烷基硒吩)嵌段共聚物体系的研究进展,通过改变体系的分子结构包括主侧链结构、侧链的烷基长度及取代基团等以及对体系在溶液状态及薄膜状态进行后处理包括改变溶剂、热处理、溶剂蒸气处理等来调控体系的微相分离行为和结晶行为,实现对材料凝聚态结构的调控.在此基础上,以有机场效应晶体管和聚合物太阳能电池器件作为最终体现聚噻吩或聚硒吩类体系凝聚态结构与性能关系的平台,将获得的调控体系凝聚态结构的有效策略用于实现其半导体材料物理性能的提升.     

Cyclodextrin-functionalised gold nanoparticles via streptavidin: a supramolecular approach

Biofunctionalised nanoparticles (NPs) have received increased attention both for their potential use as drug carriers and imaging agents and for their applications in medical diagnostics. Functionalised gold nanoparticles (AuNPs) bring together their unique electronic and optical properties (including strong plasmon absorption bands and enhanced light scattering) with the specific capabilities of the functionalising biological molecule. Cyclodextrins (CDs) have been used to functionalise NPs with different approaches. CDs are able to protect from physical, chemical and enzymatic degradation drugs that are included in their cavity. In this study, we report on a new supramolecular approach for the fabrication of CD-functionalised AuNPs. Particularly, we synthesised streptavidin (SA)-coated NPs modified with biotinylated β- and γ-CD, in order to exploit the interaction with SA.     

Stereoselective Synthesis of (+)-Boronolide

(+)-Boronolide (1) and its deacetylated products have attracted much attention of synthetic chemists due to their diverse biological properties as well as their structural complexities.[1] Many of these reported synthesis involved dehydrogenation of δ-lactone by using benzeneseleninic anhydride or ring-closing olefin metathesis (RCM) to introduce the requisite α,β-unsaturated δ-lactone in boronolide. Here, we report the synthesis of boronolide with diastereoselective propargylation of α-hydroxy aldehyde as the key step and D-gluconolactone as the starting material.     

Tuning, via counter anions, the morphology and catalytic activity of CeO2 prepared under mild conditions

Advanced synthetic methods under mild and controlled conditions for the synthesis of nanocrystals with specific shapes and exposed surfaces are very important for understanding the surface related properties and to explore their structure-property relationship for various potential applications. Here, we report the synthesis of highly uniform CeO(2) nanorods and nanoflowers in large scale using non-hydrothermal homogeneous precipitation method with urea as a precipitating agent and CTAB as a shape directing agent. Uniform microstructures of CeO(2) samples were selectively synthesized using chloride and nitrate as the counter anions. The samples were characterized by thermal analysis, X-ray diffraction, N(2) adsorption-desorption isotherms, SEM, TEM, UV-Vis-DRS, and Raman spectroscopy, and temperature programmed reduction as well as desorption methods. The results show that the physicochemical and optical properties of CeO(2) samples significantly differ with their surface microstructure and morphology. They also strongly influence the redox property, oxygen storage capacity, and surface acidity of the CeO(2) samples. The CeO(2) samples with different morphologies were tested for their soot oxidation activity. The CeO(2) sample with nanorod morphology was found to be more active due to larger CeO(2)/soot interface than the CeO(2) sample with nanoflower morphology.     

Structure and total synthesis of (-)-myrionidine and (-)-schoberine, antimalarial alkaloids from Myrioneuron nutans

Two new alkaloids, (5S,9S,10R)-myrionidine (1) and (5S,9S,10R,13S)-myrionamide (2), along with the known schoberine (3), were isolated from the leaves of Myrioneuron nutans (Rubiaceae), and their structures were determined from spectral analysis, including mass spectrometry and 2D NMR. The total asymmetric syntheses of (-)-myrionidine (1), (-)-schoberine (3), their enantiomers as well as their 9-epimers derivatives were performed, allowing the determination of their absolute configuration together with that of myrionamide (2). (-)-Myrionidine (1) and its synthetic enantiomer (18) showed a significant antimalarial activity on Plasmodium falciparum.     

Effect of chloroform on the structure and gas-separation properties of poly(ether imides)

The FTIR spectra of poly(ether imide) films prepared from their chloroform solutions were recorded in a wide temperature interval. The cast films were shown to contain residual solvent. This residual solvent existed in films as unbound chloroform that may be removed by heating to 60–70°C and as bound chloroform that is involved in complex formation with polymers and may be removed by heating at temperatures close to their glass transition temperatures (180°C). Quantum-chemical calculations were performed for structures that model fragments and monomer units of poly(ether imides), as well as their complexes with chloroform. Chloroform was shown to be capable of preferential binding with an oxygen atom in a Ph-O-Ph′ fragment via hydrogen bonds. In this case, the conformational set of poly(ether imide) chains is changed. The above evidence is invoked to explain changes in transport characteristics with time for poly(ether imide) films cast from chloroform solutions.     

Continuum of outer- and inner-sphere mechanisms for organic electron transfer. Steric modulation of the precursor complex in paramagnetic (ion-radical) self-exchanges

Transient 1:1 precursor complexes for intermolecular self-exchange between various organic electron donors (D) and their paramagnetic cation radicals (D+*), as well as between different electron acceptors (A) paired with their anion radicals (A-*), are spectrally (UV-NIR) observed and structurally (X-ray) identified as the cofacial (pi-stacked) associates [D, D+*] and [A-*, A], respectively. Mulliken-Hush (two-state) analysis of their diagnostic intervalence bands affords the electronic coupling elements (HDA), which together with the Marcus reorganization energies (lambda) from the NIR spectral data are confirmed by molecular-orbital computations. The HDA values are found to be a sensitive function of the bulky substituents surrounding the redox centers. As a result, the steric modulation of the donor/acceptor separation (rDA) leads to distinctive electron-transfer rates between sterically hindered donors/acceptors and their more open (unsubstituted) parents. The latter is discussed in the context of a continuous series of outer- and inner-sphere mechanisms for organic electron-transfer processes in a manner originally formulated by Taube and co-workers for inorganic (coordination) donor/acceptor dyads-with conciliatory attention paid to traditional organic versus inorganic concepts.     

Allopurinol- and Hypoxanthine-Copper(II) Compounds. Spectral and Magnetic Studies of Novel Dinuclear Coordination Compounds with Bridging Hypoxanthine

The synthesis in aqueous solution and pH = 1.0 of several novel Cu(II) compounds with allopurinol and hypoxanthine as heterocyclic ligands and X = Cl(-), Br(-), NO(3)(-), SO(4)(2-), and ClO(4)(-) as anions, together with their spectral and magnetic characterization, is reported. The studies of the Cu(II) systems with these heterocycles and Cl(-) or Br(-) support their Cu(II)(L)(2)(X)(2) character and their interactions through halogen atoms as bridging ligands, leading to a very weak antiferromagnetic coupling. For the Cu(II) compounds with hypoxanthine and X = NO(3)(-), SO(4)(-), or ClO(4)(-), new examples of the cupric acetate type are obtained, showing in all cases similar strong antiferromagnetic coupling. These three cases are new examples of the scarce Cu(II) dinuclear compounds with bridging hypoxanthine which have been reported up to now.