Mixed micelles of oppositely charged poly(N‐isopropylacrylamide) diblock copolymers

Mixed micelle formation between two oppositely charged diblock copolymers that have a common thermosensitive nonionic block of poly(N‐isopropylacrylamide) (PNIPAAM) has been studied. The block copolymer mixed solutions were investigated under equimolar charge conditions as a function of both temperature and total polymer concentrations by turbidimetry, differential scanning calorimetry, two‐dimensional proton nuclear magnetic nuclear Overhauser effect spectroscopy (2D ¹H NMR NOESY), dynamic light scattering, and small angle X‐ray scattering measurements. Well‐defined and electroneutral cylindrical micelles were formed with a radius and a length of about 3 nm and 35 nm, respectively. In the micelles, the charged blocks built up a core, which was surrounded by a corona of PNIPAAM chains. The 2D ¹H NMR NOESY experiments showed that a minor block mixing occurred between the core blocks and the PNIPAAM blocks. By approaching the lower critical solution temperature of PNIPAAM, the PNIPAAM chains collapsed, which induced aggregation of the micelles. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1457–1469     

Copolymers of 7-Methoxy-2-Acetyl Benzofuryl Methylmethacrylate With Styrene: Synthesis,Characterization, Reactivity Ratios and Determination of Kinetic Parameters With Thermogravimetric Analysis

The 7-methoxy-2-acetyl benzofuryl methylmethacrylate (MABMM) monomer was synthesized by reacting 7-methoxy-2-bromo acetyl benzofurane with sodium methacrylate in acetonitrile solvent at 70°C in the presence of triethylbenzylammoniumchloride (TEBAC). The monomer was characterized by FTIR, ¹H-and ¹³C-NMR spectral studies. Reactivity ratios for the copolymers 7-methoxy-2-acetyl benzofuryl methylmethacrylate (MABMM)-co- styrene (ST) are reported. Copolymers were prepared by free radical polymerization using 2,2′-azobisisobutyronitrile (AIBN) as an initiator at 70°C in 1,4-dioxane solution. FTIR, ¹H-and ¹³C-NMR spectral studies and gel permeation chromatography (GPC) were used the copolymer characterization. The monomer compositions in the copolymer were determined by elementel analyses and the reactivity ratios (ri) were calculated applying diverse linear methods, namely Finemann-Ross (FR) and Kelen-Tüdös (KT) and the nonlinear error invariable model method of a computer program RREVM. By using the latter pr°Cedure, the values of the reactivity ratios were estimated as 2.74 and 0.69 for the system MABMM (1) and ST (2), respectively. These values suggest the formation of nearly-alternating copolymers in the systems. Molecular weights were determined by gel permeation chromatography (GPC). The polydispersity indices of the polymers determined using suggest a strong tendency for chain termination by disproportionation. The glass transition temperature of the polymers were investigated by Shimadzu DSC-60 and the apparent thermal decomposition activation energies (E_d) were calculated by the Ozawa method using the Perkin-Elmer TGA thermobalance, respectively. Tg increases when the concentration of polar monomer (MABMM) in the copolymer increases. It was observed that thermal stabilities of copolymers increased with increasing of MABMM content in copolymers.     

The Zintl Phase Cs7NaSi8 – From NMR Signal Line Shape Analysis and Quantum Mechanical Calculations to Chemical Bonding

Powder samples as well as red and transparent single crystals of the Zintl phase Cs₇NaSi₈ were synthesized and characterized by means of X‐ray diffraction and differential thermal analysis. Cs₇NaSi₈ was found to be isotypic to the recently reported phase Rb₇NaSi₈. It crystallizes in the Rb₇NaGe₈ structure type forming trigonal pyramidal Si₄^4– anions. Two unique environments of the cations are observed, a linear arrangement [Na(Si₄)₂]^7– with short Na–Si distances of 3.0 Å and a Cs2 atom coordinated by six Si₄^4– anions with long Cs–Si distances of 4.2 Å. The bonding situation was investigated by a combined application of ²⁹Si, ²³Na, and ¹³³Cs solid‐state NMR spectroscopy and quantum mechanical calculations of the NMR coupling parameters. In addition the electronic density of states (DOS), the electron localizability indicator (ELI) and the atomic charges using the QTAIM approach were studied. Good agreement of the calculated and experimental values of the NMR coupling parameters was obtained. An anisotropic bonding situation of the silicon atoms is indicated by the chemical shift anisotropy being similar to Rb₇NaSi₈. Confirmation is given by the observation of one lone‐pair‐like feature for each silicon atom and two types of two‐center Si–Si bonds using the ELI. Calculation and NMR spectroscopic determination of the ²³Na and ¹³³Cs electric field gradients prove anisotropies of the charge distribution around the cations. Due to the similar values for the Na atoms in M₇NaSi₈ (M = Rb, Cs) equal bonding situations can be concluded. The much larger anisotropy of the charge distribution of the Cs atoms can be addressed as the main difference to Rb₇NaSi₈.     

Molecularly imprinted polymer based potentiometric sensor for the determination of hydroxyzine in tablets and biological fluids

Molecular imprinting is a useful technique for the preparation of functional materials with molecular recognition properties. In this work, a biomimetic potentiometric sensor, based on a non-covalent imprinted polymer, was fabricated for the recognition and determination of hydroxyzine in tablets and biological fluids. The molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization, using hydroxyzine dihydrochloride as a template molecule, methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylat (EGDMA) as a cross-linking agent. The sensor showed a high selectivity and a sensitive response to the template in aqueous system. The MIP-modified electrode exhibited a Nernstian response (29.4 ± 1.0 mV decade⁻¹) in a wide concentration range of 1.0 × 10⁻⁶ to 1.0 × 10⁻¹ M with a lower detection limit of 7.0 × 10⁻⁷ M. The electrode demonstrated a response time of ∼15 s, a high performance and a satisfactory long-term stability (more than 5 months). The method has the requisite accuracy, sensitivity and precision to assay hydroxyzine in tablets and biological fluids.     

Interpenetration of a 3D Icosahedral M@Ni12 (M=Al,Ga) Framework with Porphyrin‐Reminiscent Boron Layers in MNi9B8

Two ternary borides MNi₉B₈ (M=Al, Ga) were synthesized by thermal treatment of mixtures of the elements. Single‐crystal X‐ray diffraction data reveal AlNi₉B₈ and GaNi₉B₈ crystallizing in a new type of structure within the space group Cmcm and the lattice parameters a=7.0896(3) Å, b=8.1181(3) Å, c=10.6497(4) Å and a=7.0897(5) Å, b=8.1579(4) Å, c=10.6648(7) Å, respectively. The boron atoms build up two‐dimensional layers, which consist of puckered [B₁₆] rings with two tailing B atoms, whereas the M atoms reside in distorted vertices‐condensed [Ni₁₂] icosahedra, which form a three‐dimensional framework interpenetrated by boron porphyrin‐reminiscent layers. An unusual local arrangement resembling a giant metallo‐porphyrin entity is formed by the [B₁₆] rings, which, due to their large annular size of approximately 8 Å, chelate four of the twelve icosahedral Ni atoms. An analysis of the chemical bonding by means of the electron localizability approach reveals strong covalent B?B interactions and weak Ni?Ni interactions. Multi‐center dative B?Ni interaction occurs between the Al–Ni framework and the boron layers. In agreement with the chemical bonding analysis and band structure calculations, AlNi₉B₈ is a Pauli‐paramagnetic metal.     

Sol–gel-based silver nanoparticles-doped silica – Polydiphenylamine nanocomposite for micro-solid-phase extraction

A nanocomposite of silica-polydiphenylamine doped with silver nanoparticles (Ag–SiO₂-PDPA) was successfully synthesized by the sol–gel process. For its preparation, PDPA was mixed with butanethiol capped Ag nanoparticles (NPs) and added to the silica sol solution. The Ag NPs were stabilized as a result of their adsorption on the SiO₂ spheres. The surface characteristic of nanocomposite was investigated using scanning electron microscopy (SEM). In this work the Ag–SiO₂-PDPA nanocomposite was employed as an efficient sorbent for micro-solid-phase extraction (μ-SPE) of some selected pesticides. An amount of 15 mg of the prepared sorbent was used to extract and determine the representatives from organophosphorous, organochlorine and aryloxyphenoxy propionic acids from aqueous samples. After the implementation of extraction process, the analytes were desorbed by methanol and determined using gas chromatography–mass spectrometry (GC–MS). Important parameters influencing the extraction and desorption processes such as pH of sample solution, salting out effect, type and volume of the desorption solvent, the sample loading and eluting flow rates along with the sample volume were experimentally optimized. Limits of detection (LODs) and the limits of quantification (LOQs) were in the range of 0.02–0.05 μg L⁻¹ and 0.1–0.2 μg L⁻¹, respectively, using time scheduled selected ion monitoring (SIM) mode. The relative standard deviation percent (RSD %) with four replicates was in the range of 6–10%. The applicability of the developed method was examined by analyzing different environmental water samples and the relative recovery (RR %) values for the spiked water samples were found to be in the range of 86–103%.     

Complex capacitance in the representation of modulus of the lithium niobate crystals

The lithium niobate (LiNbO₃ or LN) single crystal is grown in-house. The ac small-signal electrical characterization is conducted over a temperature range 35≤T≤150 °C as a function of measurement frequency (10≤f≤10⁶ Hz). Meaningful observation is noted only in a narrow temperature range 59≤T≤73 °C. These electrical data when analyzed via complex plane formalisms revealed single semicircular relaxation both in the complex capacitance (C^?) and in the modulus (M^?) planes. The physical meaning of this kind of observation is obtained on identifying the relaxation type, and then incorporating respective equivalent circuit model. The simplistic non-blocking nature of the equivalent circuit model obtained via M^?-plane is established as the lumped relaxation is identified in the C^?-plane. The feature of the eventual equivalent circuit model allows non-blocking aspect for the LN crystal attributing to the presence of the operative dc conduction process. Identification of this leakage dc conduction via C^?-plane is portrayed in the M^?-plane where the blocking nature is removed. The interacting interpretation between these two complex planes is successfully presented.     

High-pressure high-temperature synthesis and crystal structure of the isotypic rare earth (RE)-thioborate-sulfides RE9[BS3]2[BS4]3S3, (RE=Dy-Lu)

Application of high-pressure high-temperature conditions (3.5 GPa at 1673 K for 5 h) to mixtures of the elements (RE:B:S=1:3:6) yielded crystalline samples of the isotypic rare earth-thioborate-sulfides RE₉[BS₃]₂[BS₄]₃S₃, (RE=Dy-Lu), which crystallize in space group P6₃ (Z=2/3) and adopt the Ce₆Al_3.33S₁₄ structure type. The crystal structures were refined from X-ray powder diffraction data by applying the Rietveld method. Dy: a=9.4044(2) Å, c=5.8855(3) Å; Ho: a=9.3703(1) Å, c=5.8826(1) Å; Er: a=9.3279(12) Å, c=5.8793(8) Å; Tm: a=9.2869(3) Å, c=5.8781(3) Å; Yb: a=9.2514(5) Å, c=5.8805(6) Å; Lu: a=9.2162(3) Å, c=5.8911(3) Å. The crystal structure is characterized by the presence of two isolated complex ions [BS₃]^3- and [BS₄]^5- as well as [□(S^2-)₃] units.     

BPS Quivers and Spectra of Complete {\mathcal{N} = 2} Quantum Field Theories

We study the BPS spectra of ${\mathcal{N}=2}$ N = 2 complete quantum field theories in four dimensions. For examples that can be described by a pair of M5 branes on a punctured Riemann surface we explain how triangulations of the surface fix a BPS quiver and superpotential for the theory. The BPS spectrum can then be determined by solving the quantum mechanics problem encoded by the quiver. By analyzing the structure of this quantum mechanics we show that all asymptotically free examples, Argyres-Douglas models, and theories defined by punctured spheres and tori have a chamber with finitely many BPS states. In all such cases we determine the spectrum.     

Higgs boson searches via dileptonic bottomonium decays

We explore the pseudoscalar ηb${\eta }_b$ and the scalar χ_b0${\chi }_{b0}$ decays into ?⁺?⁻${?}^{+}{?}^{-}$ to probe whether it is possible to probe the Higgs sectors beyond that of the Standard Model. We, in particular, focus on the Minimal Supersymmetric Standard Model, and determine the effects of its Higgs bosons on the aforementioned bottomonium decays into lepton pairs. We find that the dileptonic branchings of the bottomonia can be sizeable for a relatively light Higgs sector.