Effect of poly(4‑tert-butylstyrene) block length on the microphase structure of poly(ethylene oxide)-b-poly(4-vinylbenzyl chloride)-b-poly(4‑tert-butylstyrene) triblock terpolymers

A series of linear poly(ethylene oxide)-b-poly(4-vinylbenzyl chloride)-b-poly(4‑tert-butylstyrene) (PEO₁₁₃-b-PVBC₁₃₀-b-PtBS_x or E₁₁₃V₁₃₀T_x) triblock terpolymers with various lengths x (=20, 33, 66, 104, 215) of PtBS block were synthesized via a two-step reversible addition-fragmentation chain transfer (RAFT) polymerization. The E₁₁₃V₁₃₀T_x triblock terpolymers were non-crystalline because the PVBC and PtBS blocks strongly hindered the crystallization of PEO block. The effects of PtBS block length x on the phase structures of E₁₁₃V₁₃₀T_x triblock terpolymers were investigated by combined techniques of small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). It was found that with increasing x from 20 to 215, the phase structure of E₁₁₃V₁₃₀T_x triblock terpolymers became more ordered and changed from disordered structure, hexagonally-packed cylinder (HEX), hexagonally perforated layer (HPL), to lamellar (LAM) phase structures. Temperature-variable SAXS measurements showed that the HEX, HPL and LAM phase structures obtained for E₁₁₃V₁₃₀T₆₆, E₁₁₃V₁₃₀T₁₀₄ and E₁₁₃V₁₃₀T₂₁₅ by thermal annealing, respectively, were thermodynamically stable in the temperature range of 30–170 °C.     

Formation of Single Gyroid Nanostructure by Order–Order Phase Transition Path in ABC Triblock Terpolymers

The kinetics for the formation of the single gyroid (SG) nanostructure in ABC triblock terpolymers is investigated using the self‐consistent field theory combined with the string method. Both simple phases (lamellae, cylinders, and spheres) and networked double diamonds (DD) can transform into SG through order–order phase transition (OOT). In particular, a packing frustration‐induced variation in the epitaxial relationship between DD and SG is demonstrated. By regulating the block interaction, an expected epitaxial phase transition between these two networks without any rotation of the crystallographic directions can be achieved. Interestingly, the hexagonally perforated lamellae (HPL) are encountered in all identified transition pathways to SG. Nucleation kinetics investigation shows that the HPL tends to nucleate from SG easily, which confirms the kinetic origins of the instability of SG in experiments. Therefore, several strategies of preventing the SG being bypassed, such as controlling annealing time and rates during the morphology evolution, are proposed to promote the stabilizing of the SG in kinetic pathways. The findings reported here provide a novel route for fabrication of SG structured materials by manipulating both the epitaxial relationship and the nucleation kinetics in OOT pathways.     

Kinetic pathway to double-gyroid structure

We have investigated the structural development during order-order transitions to the double-gyroid (DG) phase of nonionic surfactant/water systems based on two-dimensional small-angle x-ray scattering patterns from highly oriented ordered mesophases. The lamellar (L) to DG transition proceeds through two intermediate structures, a fluctuating perforated layer structure having ABAB stacking and a hexagonal perforated lamellar structure with ABCABC stacking (HPLABC). For a hexagonally packed cylinder (H) to DG transition, we also observed the HPLABC structure as the intermediate phase, thus the HPLABC is an entrance structure for the DG phase. The hexagonal perforated lamellar (HPL) structure consists of hexagonally packed holes surrounded by the planar tripods, and the transition from HPL structure to the DG phase proceeds by rotation of the dihedral angle of connected tripods. A geometrical consideration shows that large deformations of HPL planes are necessary to form the DG structure from the HPLABC structure, whereas the transition from a HPL structure with ABAB stacking (HPLAB) to the DG structure is straightforward. In spite of the topological constraints, the HPLABC structure is observed in the kinetic pathway to the DG structure.     

Asymmetric synthesis of aminocyclooctenecarbonitriles: Cyclooctene β-lactam and hydroxyaminocyclooctene carboxylic precursors

Enantiopure β-aminocyclooctenenitriles, as precursors of β-amino acids and β-lactams, were synthesized from a readily available chloroalkene nitrile and (S)-methylbenzylamine via a straightforward substitution reaction and purified by crystallization. Acidic hydrolysis of the nitrile groups to their corresponding amides followed by DCC assisted carbonyl group activation gave novel α,β-unsaturated lactams. The treatment of 3-bromo-8-chlorocyclooctenecarbonitrile with (S)-methylbenzylamine furnished a diastereomeric mixture of bromoaminocyclooctenecarbonitriles via an S_N2′ pathway rather than bromide substitution via an S_N2 pathway. The diastereomeric mixture of bromoaminocyclooctanecarbonitriles provided two novel aziridines upon heating. TFA catalyzed aziridine ring opening gave γ-hydroxyl-β-aminocyclooctenecarbonitriles and γ-amino-β-hydroxycyclooctenecarbonitriles.     

On the definition of interfacial excesses in a system consisting of an insoluble solid adsorbent and a binary liquid mixture

The paper deals with the problem whether the interfacial excess volumeV ^σ has to be set zero in the case of the systems in question as stated by D. H. Everett, or eventually different from zero as proposed by G. Schay. First it is shown that the current operational definitions of the interfacial excess amounts as relative or reduced excesses are quite independent of the choice of the reference volume (or amount) of equilibrium bulk liquid. Everett operates with the Gibbs dividing surface, letting it coincide with the surface of the solid, the corresponding operational definition of the interfacial excess amount being then that ofn ^σ(v). It is shown that this definition, while compatible with those of the relative or reduced excesses, is not cogent. Relative and reduced excesses are usually interpreted as the values resulting when the adsorption of either one selected component or the total adsorption is set arbitrarily zero. With this interpretation, the assumptionV ^σ =0 for the total system could be maintained only by admitting an adsorption excess of the solid different from zero which appears, however, unnatural.     

The Effects of Hydrophobicity and Textural Properties on Hexamethyldisiloxane Adsorption in Reduced Graphene Oxide Aerogels

To expand the applications of graphene-based materials to biogas purification, a series of reduced graphene oxide aerogels (rGOAs) were prepared from industrial grade graphene oxide using a simple hydrothermal method. The influences of the hydrothermal preparation temperature on the textural properties, hydrophobicity and physisorption behavior of the rGOAs were investigated using a range of physical and spectroscopic techniques. The results showed that the rGOAs had a macro-porous three-dimensional network structure. Raising the hydrothermal treatment temperature reduced the number of oxygen-containing groups, whereas the specific surface area (S_BET), micropore volume (V_micro) and water contact angle values of the rGOAs all increased. The dynamic adsorption properties of the rGOAs towards hexamethyldisiloxane (L2) increased with increasing hydrothermal treatment temperature and the breakthrough adsorption capacity showed a significant linear association with S_BET, V_micro and contact angle. There was a significant negative association between the breakthrough time and inlet concentration of L2, and the relationship could be reliably predicted with a simple empirical formula. L2 adsorption also increased with decreasing bed temperature. Saturated rGOAs were readily regenerated by a brief heat-treatment at 100 °C. This study has demonstrated the potential of novel rGOA for applications using adsorbents to remove siloxanes from biogas.     

Oxidation induction time and oxidation onset temperature of polyethylene in air

Oxidation induction times (OIT) and oxidation onset temperatures (OOT) of a low density polyethylene melt were evaluated in air using DSC. Good regression fits to OOT data were obtained using global values for the activation energy (E) that are specific for each antioxidant but assumed independent of concentration. Gimzewski’s postulate that OIT and OOT correspond to the same level of antioxidant depletion was tested by attempting to predict OIT values from OOT generated model parameters. The deviations between predicted and experimental OIT values were comparable in magnitude to the inherent scatter in the data. However, regression of the dynamic OOT data yielded statistically significant lower values for the activation energy than are obtained by direct regression of isothermal data.     

Activation and Stabilization of The Hydroperoxide Lyase Enzymatic Extract from Mint Leaves (Mentha spicata) Using Selected Chemical Additives

The effects of selected lyoprotecting excipients and chemical additives on the specific activity and the thermal stability of the hydroperoxide lyase (HPL) enzymatic extract from mint leaves were investigated. The addition of KCl (5%, w/w) and dextran (2.5%, w/w) to the enzymatic extract, prior to lyophilization, increased the HPL specific activity by 2.0- and 1.2-fold, respectively, compared to the control lyophilized extract. From half-life time (t _1/2), it can be seen that KCl has enhanced the HPL stability by 1.3- to 2.3-fold, during long-period storage at ?20 °C and 4 °C. Among the selected additives used throughout this study, glycine appeared to be the most effective one. In addition to the activation effect conferred by glycine, it also enhanced the HPL thermal stability. In contrast, polyhydroxyl-containing additives were not effective for stabilizing the HPL enzymatic extract. On the other hand, there was no signification increase in HPL activity and its thermal stability with the presence of Triton X-100. The results also showed that in the presence of glycine (10%), the catalytic efficiency of HPL was increased by 2.45-fold than that without additive.     

Volumetric properties and volumetric interaction parameters for the CsCl–monosaccharide (d-galactose,d-xylose and d-arabinose)–water systems at T=298.15 K

Density measurements have been carried out at T=298.15 K for the CsCl–monosaccharide (d-galactose, d-xylose and d-arabinose)–water systems. The apparent molar volume of saccharides V_φ,S in the ternary solutions, the corresponding infinite dilution apparent molar volume V_φ,S^∘, and the standard transfer volume Δ_tV_φ,S^∘ of saccharides from water to aqueous CsCl solutions have been determined. The McMillan–Mayer theory was employed to relate the excess thermodynamic functions to a series of interaction parameters to obtain the volumetric interaction parameters of CsCl with monosaccharide in water. These parameters are interpreted by the group additivity principle and the stereochemistry of these monosaccharide molecules.     

Label-free photoelectrochemical sensor based on 2D/2D ZnIn2S4/g-C3N4 heterojunction for the efficient and sensitive detection of bisphenol A

Photoelectrochemical （PEC） sensor is an emerging technology in analysis as the advantage of fast response,high sensitivity and uncomplicated operation.In this study,an effective label-free PEC sensor for bisphenol A （BPA） detecting is constructed,in which Zn In₂S₄/g-C₃N₄heterojunction is prepared via a simple hydrothermal method.The characterization outcomes display that the formation of p-n heterojunction helps for promoting the separation efficiency ...     

Dissolution kinetics of silver metal nanoparticles in their reaction with nitric acid in an reverse micelle solution of AOT

The dissolution of silver nanoparticles in their reaction with aqueous HNO₃ solubilized to an reverse micelle solution of sodium bis(2-ethylhexyl)sulfosuccinate in decane is studied spectrophotometrically. A physicochemical model is advanced for quantifying the process kinetics on th basis of the following autocatalytic scheme: Ag⁰ + H⁺ + NO ₃ ^? → Ag⁺ + products (k ₁), and Ag⁰ + Ag⁺ + NO ₃ ^? → 2Ag⁺ + products (k ₂). The effective rate constant k ₂ decreases with decreasing solubilization capacity V _S/V _O (where V _S is the volume of the solubilized dispersed aqueous phase and V _O is the volume of the micelle solution); the solubilization capacity determines the size of the micelle cavities in which the reaction between Ag⁰ and HNO₃ occurs: k ₂ = 74 (V _S/V _O) · 100% ≈ 3.8%), 41 (2.9), and 35 (2.0) L/(mol s). The effective constant k ₁ is determined with a high uncertainty; the effect of V _S/V _O on k ₁ has the opposite tendency.     

Aggregation-induced emission and self-assembly of functional tetraphenylethene-based tetracationic dicyclophanes for selective detection of ATP in water

Functional dicyclophanes with various substituents (e.g., NO₂, Br, OCH₃ and OH) were synthesized via one-pot S_N2 reaction. Dicyclophanes can form nanospheres via the head-to-tail self-assembly between the cavities and the TPE units to exhibit aggregation-induced emission (AIE) in aqueous solution. These AIE-active nanospheres with cationic feature exhibited selective recognition with fluorescence response for anionic ATP via electrostatic interactions and hydrophobic effects in water.     

Structural analysis of ethyl 2-Z-phenylhydrazono-3-E-methylthio(thioxo)methylhydrazone-butanoate

A new compound of ethyl 2-Z-phenylhydrazono-3-E-methylthio(thioxo) methylhydrazone-butanoate is synthesized via the reaction between ethyl 2-Z-phenylhydrazono-3-oxo-butanoate and S-methyldithio-carbazate at room temperature. A single crystal of the titled compound is obtained and the structure is determined by X-ray diffraction. It belongs to a monoclinic P2₁ space group with the cell parameters: a = 5.335(1) Å, b = 15.907(4) Å, c = 9.507(2) Å, β = 90.21(1)°, V = 806.8(4) ų. A one-dimensional parallel structure is constructed by an unclassic hydrogen bond and a weak p-π interaction.     

Syntheses of L‐Glutamic Acid Analogues for Neuroexcitatory Activity Studies

Starting from D–serine, (2S,3S)‐, (2S,3R)‐substituted‐L‐glutamic acids were prepared via Claisen rearrangement methodology. A variety of the substituents can be introduced at the C‐3 of the L‐glutamic acid backbone.     

Formation of Two Kinds of Hexagonally Arranged Structures in ABC Triblock Copolymer Thin Films Induced by a Strongly Selective Solvent Vapor

An order–order transition (OOT) in the sequence of a hexagonally arranged core–shell cylinder to a double‐hexagonally arranged dot in polystyrene‐block‐poly(butadiene)‐block‐poly(2‐vinylpyridine) (SBV) triblock copolymer thin films is reported to be induced upon exposure to a solvent vapor that is strongly selective for the two end blocks. These two kinds of hexagonally arranged structures could form when the film thickness is 44, 123, and 223 nm. When the film thickness is decreased to 13 nm, the ordered structure is absent. The sizes of the core–shell cylinder structures formed with the same annealing time in films of different thickness are compared to address the effects of film thickness on the phase structure. The mechanism is analyzed from the total surface area of the blocks and the effective interaction parameter in the solvent vapor.

     

The phase study of the TlVS system and the properties of TlV6S8 and TlV5S8 phases

The ternary phase diagram of the TlVS system was investigated using samples quenched from 400°C, especially in the neighborhood of TlV₆S₈ and TlV₅S₈ phases. The TlV₆S₈ phase (Tl_xV₆S_y) exists between 0.75 < x < 1.00 and 7.55 < y < 7.90, and the TlV₅S₈ phase (Tl_x′V₅S_y′) between 0.70 < x′ < 1.00 and 7.54 < y′ < 7.98. A new ternary phase with the nominal composition of TlV₂S₄ was found in addition to the three known ternary phases. The entirely deintercalated V₆S_7.8 with the framework structure was obtained by using 1 N AlCl₃ + 0.01 N FeCl₃ aqueous solution, while the lower phase limit of the TlV₅S₈ phase was Tl_0.33V₅S₈ consistent with the earlier work. The electrical resistivity and the magnetic susceptibility measurements show that these compounds are expected to be weakly magnetic itinerant-electron systems.     

Distribution of reaction products (theory). XI. H + F2

The availability for the first time of detailed rate constants k(V′, R′, T′) (where V′, R′ and T′ are product vibrational, rotational and translational excitation) for the highly exothermic reaction H + F₂ → HF(V′, R′) + F has prompted the 3D classical-trajectory study reported here. The potential-energy surface is found to be predominantly repulsive ($\text{A}$_⊥ ≈ 42%, R_⊥ ≈ 58%) corresponding to the rather low fractional conversion of reaction energy into vibration ((f′V) = 0.58 from experiment, and 0.56 from theory). In the homologous series of reactions H + X₂ (X  F, Cl, Br, I) the percentage of repulsive energy-release decreases for X  Cl, Br, I, but increases from X  F to Cl. It is shown that this cannot be due to charge in mass-combination, but can plausibly be explained by the anomolously short range of interaction between the separating X atoms in the case X  F. It is predicted that the more-forward scattered HF will be more rotationally excited. The form of the cross section function S_r(T) (where T is reagent translation) is analysed. In accordance with the expectation for a strongly exothermic reaction, it is found that S_r(T) rises more steeply than S_r(V) (where V is reagent vibrational energy). The effect on the product energy distribution conforms qualitatively to the “adiabatic” behaviour noted in previous work: ΔT → ΔT′ + ΔR′; ΔV → ΔV′. The explanation is to be found in reaction through more-compressed or more-extended intermediate configurations than are characteristic of room temperature reaction. We note the existence of an amplification effect: (ΔT′ + ΔR′)/ΔT ≈ 2, and ΔV′/ΔV ≈ 2.     

Ta4P4S29: A new tunnel structure with inserted polymeric sulfur

Ta₄P₄S₂₉ was prepared from the elements heated together in stoichiometric proportions in an evacuated Pyrex tube for 10 days at 500°C. The crystal symmetry is tetragonal, space group P4₃2₁2, with the cell parameters: a = b = 15.5711(7) Å, c = 13.6516(8) Å, V = 3309.9(5) ų, and Z = 4. The structure calculations were conducted from 2335 reflections and 146 variables, leading to R = 0.033. The structure basic framework, corresponding to the chemical composition [TaPS₆], is made of biprismatic bicapped [Ta₂S₁₂] units (average d_TaS = 2.539 Å), including sulfur pairs (average d_SS = 2.039 Å), bonded to each other through [PS₄] tetrahedral groups (average d_PS = 2.044 Å) sharing sulfurs. This framework leaves large tunnels running along the c axis of the cell and in which (S₁₀)_∞ sulfur chains are found to be inserted (average d_SS = 2.052 Å and SSS = 105.75°). Diamagnetic and semiconducting Ta₄P₄S₂₉ can be formulated: Ta^V₄P^V₄(S^?II)₁₆(S^?II₂)₄(S⁰₅).     

Location of energy barriers. VI. The dynamics of endothermic reactions,ab + c

A systematic 3D classical-trajectory study has been made of the effect of reagent energy distribution and mass combination on the dynamics of endothermic reaction. The potential-energy hypersurface was endothermic by 35.7 kcal mole^?1. Reagent translation, T′, and vibration, V′, was varied in the range up to T′ + V′ = 90 kcal mole^?. Among the principal findings for the equal-mass case were the following. (i) There is an orders-of-magnitude increase in reaction cross section when energy is transferred from T′ to V′, until an optimal distribution over T′ and V′ is achieved at V′ ?, T′. There is a qualitative difference between the forms of the reactive cross section dependences S(T′) V′ and S(V′)_T′. (ii) The greater efficacy of V′ than T′ in promoting endothermic reaction is marked even at total reagent energies ≈ 3 x the endothermic barrier height. (iii) The total reactive cross section for endothermic reaction increases to large values (≈ gas kinetic) as V′ increased to several times the barrier height. (iv) Reagent energy in excess of that required to cross the endothermic barrier is subject to the same “adiabatic” transformation into product energy as was previously observed for exothermic reactions: ΔT′ → ΔT + ΔR (where R is enhanced product rotational energy), and ΔV′ → ΔV. This is explained in terms of induced repulsive energy release in the former case, and induced attractive energy release in the latter. (v) The molecular product is backwards or sideways scattered. Enhanced V′ at constant T′ diminishes product repulsion, giving rise to more-forward scattering. (vi) These findings remain qualitatively unchanged when extreme mass combinations H H + L and L H + H (L = 1 amu, H = 80 amu) are substituted for the equal-mass combination, L L + L. Effects ascribable to a “late” barrier are accentuated for HH + L. and diminished for L H + H. (vii) The total reactive cross section at a given reagent energy increases in the sequence H H + L, L L + L, L H + H, for simple kinematic reasons. (viii) The dynamics on this endothermic potential-energy surface resemble, in all the points listed above, the dynamics on a thermoneutral surface which has its barrier crest in the coordinate of separation (surface II of part I of this series).     

Synthesis and structure determination of a new layered compound: V2P4S13

V₂P₄S₁₃ was prepared from the elements taken in stoichiometric proportions and heated in an evacuated Pyrex tube for 10 days at 450°C. The crystal symmetry is triclinic, space group P1¯ with the parameters: a = 9.112(1) Å, b = 9.680(1) Å, c = 11.620(1) Å, α = 72.15(1)°, β = 110.82(1)°, γ = 110.13(1)°, V = 879.5(1) ų, and Z = 2. The structure was solved from 3052 independent reflections and 173 parameters, the least-squares refinement yielding R = 0.033. The building units of the structure are made up of two distorted (VS₆) octahedra and four distorted (PS₄) tetrahedra sharing edges to form (V₂P₄S₁₆) groups. These share sulfur atoms through their four (PS₄) tetrahedra with the same neighbor groups. Infinite (V₂P₄S₁₃) planes parallel to (101) are thus obtained, with no bonds other than van der Waals' ones between them. Within the slabs, the layered phase presents the following average distances: d_V-S = 2.471(1) Å, d_P-S = 2.050(1) Å, d_V-V = 3.715(2) Å. From the various oxydation states of the atoms, the developed formula can be written V^III₂P^V₄S^?II₁₃. The phase is semiconducting and magnetic susceptibility measurements show a Curie behavior with the occurrence of high spin d² vanadium. Antiferromagnetic ordering is observed below 10 K.