Mechanical Properties and Failure Behavior of Physically Assembled Triblock Copolymer Gels with Varying Midblock Length

Mechanical properties including the failure behavior of physically assembled gels or physical gels are governed by their network structure. To investigate such behavior, we consider a physical gel system consisting of poly(styrene)‐poly(isoprene)‐poly(styrene)[PS‐PI‐PS] in mineral oil. In these gels, the endblock (PS) molecular weights are not significantly different, whereas, the midblock (PI) molecular weight has been varied such that we can access gels with and without midblock entanglement. Small angle X‐ray scattering data reveals that the gels are composed of collapsed PS aggregates connected by PI chains. The gelation temperature has been found to be a function of the endblock concentration. Tensile tests display stretch‐rate dependent modulus at high strain for the gels with midblock entanglement. Creep failure behavior has also been found to be influenced by the entanglement. Fracture experiments with predefined cracks show that the energy release rate scales linearly with the crack‐tip velocity for all gels considered here. In addition, increase of midblock chain length resulted in higher viscous dissipation leading to a higher energy release rate. The results provide an insight into how midblock entanglement can possibly affect the mechanical properties of physically assembled triblock copolymer gels in a midblock selective solvent. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1014–1026     

Erratum to “Fully automated sample treatment method for high throughput proteome analysis”

Science China Chemistry -     

Synthesis and photopolymerization of piperonylamine derivatives as a polymerizable cyclic acetals co‐initiator for light‐cured unfilled dental resins

The aim of this study was to synthesize and characterize N,N‐di(methacryly‐ethoxycarbonyl‐ethyl)‐N‐(1,3‐benzodioxole‐ 5‐methylene)(DMEBM) to replace both triethylene glycol dimethylacrylate(TEGDMA) as a dilute and the non‐polymerizable amine, which is added as a co‐initiator in dental resin mixtures. 2,2‐bis[4‐(2‐Hydroxy‐3‐methacryloxypropoxy) phenyl]‐propane (Bis‐GMA) and camphorquinone (CQ) were used as monomer and photoinitiator in these model dental resin systems, in contrast to ethyl 4‐dimethylaminobenzoate (EDMAB) which was usually used as a co‐initiator. DMEBM was synthesized via Michael‐Addition reaction and characterized using ¹H NMR spectroscopy. A mixture of Bis‐GMA/DMEBM/CQ was found to reach the double bond conversion of 67.5%, slightly higher than that of Bis‐GMA/TEGDMA/CQ/EDMAB (66.8%) and Bis‐GMA/TEGDMA/CQ/DMEBM (64.8%). In addition, the glass transition temperature of Bis‐GMA/TEGDMA/CQ/EDMAB (93.4°C) were higher than that of Bis‐GMA/TEGDMA/CQ/DMEBM (89.3 °C) and Bis‐GMA/DMEBM/CQ (80.4°C). The water sorption and solubility of Bis‐GMA/TEGDMA/CQ/DMEBM were higher than that of Bis‐GMA/TEGDMA/CQ/EDMAB and Bis‐GMA/DMEBM/CQ. However, the values were still within the range of the ISO 4049 standards. DMEBM could be used as a potential co‐initiator and diluent for dental composite. Copyright © 2009 John Wiley & Sons, Ltd.     

A lanthanide metal-organic framework with high thermal stability and available Lewis-acid metal sites

A lanthanide metal-organic framework, Dy(BTC)(H2O).DMF, with excellent thermal stability shows a high surface area, 655 m(2) g(-1), high hydrogen and carbon dioxide storage capability, and available Lewis-acid metal sites which could be anticipated to use in catalysis and metal-site specific chemical sensor.     

Synthesis, structure, and luminescent properties of microporous lanthanide metal-organic frameworks with inorganic rod-shaped building units

A series of microporous lanthanide metal-organic frameworks, Tb3(BDC)(4.5)(DMF)2(H2O)3.(DMF)(H2O) (1) and Ln3(BDC)(4.5)(DMF)2(H2O)3.(DMF)(C2H5OH)(0.5)(H2O)(0.5) [Ln = Dy (2), Ho (3), Er (4)], have been synthesized by the reaction of the lanthanide metal ion (Ln3+) with 1,4-benzenedicarboxylic acid and triethylenetetramine in a mixed solution of N,N'-dimethylformamide (DMF), water, and C(2)H(5)OH. X-ray diffraction analyses reveal that they are extremely similar in structure and crystallized in triclinic space group P. An edge-sharing metallic dimer and 4 metallic monomers assemble with 18 carboxylate groups to form discrete inorganic rod-shaped building units [Ln6(CO2)18], which link to each other through phenyl groups to lead to three-dimensional open frameworks with approximately 4 x 6 A rhombic channels along the [0,-1,1] direction. A water sorption isotherm proves that guest molecules in the framework of complex 1 can be removed to create permanent microporosity and about four water molecules per formula unit can be adsorbed into the micropores. These complexes exhibit blue fluorescence, and complex 1 shows a Tb3+ characteristic emission in the range of 450-650 nm.     

Calix[4]arene-thiacrown-5 di(carboxylic acid) regioisomers as metal ion extractants

A regioisomer of a previously reported p-tert-butylcalix[4]arene-1,3-thiacrown-5 di(carboxylic acid) is prepared in which the thiacrown ring attachment sites are moved from distal phenolic oxygens of a cone p-tert-butylcalix[4]arene scaffold to proximal phenolic oxygens. The influence of this structural variation in the di-ionizable calixcrown ligand on competitive solvent extractions of alkali metal cations and of alkaline earth metal cations and single species solvent extractions of Hg²⁺ and Pb²⁺ from aqueous solutions into chloroform is evaluated.     

Identification and structural characterisation of carboxy-terminal polypeptides and antibody epitopes of Alzheimer's amyloid precursor protein using high-resolution mass spectrometry

Alzheimer's disease (AD) is the most common cause for human age-related dementia, characterised by formation of diffuse plaques in brain that are directly involved in AD pathogenesis. The major component of AD plaques is beta-amyloid, a 40 to 42 amino acid polypeptide derived from the amyloid precursor protein (APP) by proteolytic degradation involving the specific proteases, beta-and gamma-secretase acting at the N- and C- terminal cleavage site, respectively. In this study we have prepared polypeptides comprising the carboxy-terminal and transmembrane sequences of APP, by bacterial expression and chemical synthesis, as substrates for studying the C-terminal processing of APP and its interaction with the gamma-secretase complex. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was used as a major tool for structure analysis. Immunisation of transgenic mouse models of AD with Abeta42 has been recently shown to be effective to inhibit and disaggregate Abeta-fibrils, and to reduce AD-related neuropathology and memory impairments. However, the mechanism underlying these therapeutic effects has been as yet unclear. Using proteolytic epitope excision from immune complexes in combination with FT-ICR-MS, we identified the epitope recognised by the therapeutically active antibody as the N-terminal Abeta(4-10) sequence; this soluble, nontoxic epitope opens new lead structures for AD vaccine development. A monoclonal antibody (Jonas; JmAb) directed against the cytosolic APP domain was used in studies of APP biochemistry and metabolism. Here we report the identification of the epitope recognised by the JmAb, using the combination of epitope excision and peptide mapping by FT-ICR-MS. The epitope was determined to be located at the C-terminal APP(740-747) sequence; it was confirmed by ELISA binding assays and authentic synthetic peptides and will be an efficient tool in the development of new specific vaccines. These results demonstrate high-resolution FT-ICR-MS as a powerful method for characterising biochemical pathways and molecular recognition structures of APP.     

Thermal Expansion Properties and Mechanochemical Synthesis of Stoichiometric Cocrystals Containing Tetrabromobenzene as a Hydrogen- and Halogen-Bond Donor

The solution and mechanochemical synthesis of two cocrystals that differ in the stoichiometric ratio of the components (stoichiometric cocrystals) is reported. The components in the stoichiometric cocrystals interact through hydrogen or hydrogen/halogen bonds and differ in π-stacking arrangements. The difference in structure and noncovalent interactions affords dramatically different thermal expansion behaviors in the two cocrystals. At certain molar ratios, the cocrystals are obtained concomitantly; however, by varying the ratios, a single stoichiometric cocrystal is achieved using mechanochemistry.