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ABSTRACT: Block copolymers composed of acrylic acid and methyl methacrylate with three topologies of double linear blocks, poly(acrylic acid) (PAA) linear block/poly(methyl methacrylate) (PMMA) G1‐dendron and PAA linear block/PMMA G2‐dendron have been prepared by the combination of atom transfer radical polymerization and azide–alkyne click reaction. Proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography have been adopted thoroughly to identify the chemical structure of those block copolymers with expected topologies. The self‐assembly of those block copolymers in the selective solvent has been performed through two mixing routes of gentle and abrupt variation in solvent selectivity, and the morphology of the obtained self‐assemblies/aggregates was observed by transmission electron microscopy. Because the abrupt variation route altered sharply the solvent quality during the mixing, the intermolecular association of polymer chains resulted in the smaller self‐assemblies but the further growth of smaller self‐assemblies was not observed. On the contrary, the gentle variation route changed gradually the solvent quality during the mixing, favoring not only the intermolecular association but also the further growth of self‐assemblies to result in larger aggregates. The final morphology of those assemblies/aggregates also exhibited the dependence of PMMA dendron generation. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1446–1456 [ABSTRACT FROM AUTHOR]

Narrowly distributed poly(l-lysine-b-N-isopropylacrylamide) (PLL-b-PNIPAM) was prepared through ring-opening polymerization of ε-benzyloxycarbonyl-l-lysine N-carboxy-α-amino anhydride and atom transfer radical polymerization of NIPAM, followed with the removal of ε-benzyloxycarbonyl group. Then gold nanoparticles (AuNPs) grafted with PLL-b-PNIPAM (PNIPAM-PLL-AuNPs) were obtained by the reduction of chloroauric acid with sodium citrate in the presence of PLL-b-PNIPAM. PNIPAM-PLL-AuNPs and its precursors were thoroughly characterized by proton magnetic resonance spectroscope, Fourier transform infrared spectroscope, UV-vis spectroscope, transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, and circular dichroism. The obtained PNIPAM-PLL-AuNPs exhibited high colloid stability even at strong alkaline (pH = 12) and acidic (pH = 2) conditions. The thermal and pH dual-responsive behaviors of the grafting PLL-b-PNIPAM chains was observed to be affected by AuNPs, while not for the secondary structure of PLL chains. Correspondingly, the surface plasmon resonance (SPR) of AuNPs was found to be sensitive to both pH value and temperature. A blue shift in the SPR happened both with increasing pH value and increasing temperature. The stimuli-response was reversible in heating-cooling cycles. The gold nanoparticles with both pH and temperature response may have potential applications in biomedical areas and biosensors. [ABSTRACT FROM AUTHOR]

Photo-luminescent polymers as a kind of talent functional polymer, have been applied in various field such as bioanalysis, detection and materials. Herein we report a novel fluorescent hyperbranched aliphatic polyestertriazole via one-pot azidation and azide-alkynyl cycloaddition of propargyl (2,2-bismethylsulfinyloxymethyl)propionate, an AB 2 pre-monomer, by heat promotion at 110 °C. Under such reaction condition, the methylsulfinyloxy groups were converted into azido groups by NaN 3 , then azide-alkynyl cycloaddition simultaneously happened to give hyperbranched polyestertriazole ( hb -PETA). By the analysis of reaction kinetics monitored with proton nuclear magnetic resonance spectroscopy, the results clarifies that the whole synthesis was achieved efficiently. The obtained hb -PETA exhibited the blue fluorescence in both bulk and solution upon the exposure of UV light although it had no conventional fluorescent group. The emission wavelength and intensity of hb -PETA in solution were dependent on the solvent and the addition of metal ions. Among various metal ions, hb -PETA was particularly sensitive to Hg 2+ , Cu 2+ and Fe 3+ in water, and showed the excellent quenching efficiency for Hg 2+ . Moreover, the Hg 2+ detecting in water could be achieved highly rapidly and sensitively. We believe this kind of functional polymer could be used in other biological and material area. [ABSTRACT FROM AUTHOR]

The degradation of civil engineering structures may lead to a sudden stiffness reduction in a structure and such a sudden damage will cause a discontinuity in the dynamic responses. The detection on structural sudden damage has been actively carried out in this study. The signal singularity of the acceleration responses with sudden stiffness reduction is characterized by the coefficients of continuous wavelet transform with fine scales. A detection approach based on the CWT is proposed in terms of the decomposed detail coefficients of continuous wavelet transform to detect the damage time instant and location. The Lipschitz exponent is mathematically used to estimate the local properties of certain function and is applied to reflect the damage severity. Numerical simulation using a five-story shear building under different types of excitation is carried out to assess the validity of the proposed detection approach for the building at different damage levels. The sensitivity of the damage index to the intensity and frequency range of measurement noise is also investigated. The effects of both measurement noise intensity and frequency range on the damage detection are numerically investigated. [ABSTRACT FROM AUTHOR]

The vibration control and performance evaluation on a transmission-tower line system by using friction dampers subjected to wind excitations are carried out in this study. The three-dimensional finite element (FE) model of a transmission tower is firstly constructed. A two-dimensional lumped mass model of a transmission tower is developed for dynamic analysis. The analytical model of transmission tower-line system is proposed by taking the dynamic interaction between the tower and the transmission lines into consideration. The mechanical model of passive friction damper is presented by involving the effects of damper axial stiffness. The equation of motion of the transmission tower-line system incorporated with the friction dampers disturbed by wind excitations is established. A real transmission tower-line system is taken as an example to examine the feasibility and reliability of the proposed control approach. An extensive parameter study is carried out to find the optimal parameters of friction damper and to assess the effects of slipping force axial stiffness and hysteresis loop on control performance. The work on an example structure indicates that the application of friction dampers with optimal parameters could significantly reduce wind-induced responses of the transmission tower-line system. [ABSTRACT FROM AUTHOR]

Macro-porous poly(lauryl acrylate) cryogel sheets as oil-sorbents were prepared through UV-radiation cryo-polymerizations in 1, 4-dioxane at low temperatures (−5, −2 and 0 °C) within 30 min. The influences of total monomer concentration, crosslinking monomer amount and polymerization temperature on the formation of cryogels were studied. The chemical structure and porous morphology were characterized through the techniques of Fourier transform infrared spectroscopy, thermal gravimetric analysis, contact angle measurement and scanning electron microscopy, confirming the features of high hydrophobicity, macro-porosity and good thermal stability. As well, the comparison between conventional gels prepared at room temperature and cryogels at lower temperatures was made, showing the higher rate of cryo-polymerization than conventional polymerization under the same UV-radiation condition. The swelling investigation was carried out with several organic solvents and oils. Enhanced performance of oil absorption was observed for those cryogels considering the absorption capacity and absorption rate. Variation of initiator amount and acrylate monomers could also modulate the absorption capacity. Those cryogel oil-sorbents exhibited wide adaptability, good reusability and high-temperature tolerance. Thus, this rapid and low-cost fabrication opens out a novel pathway to prepare efficient oil-sorbents used in waste water treatment. • Polyacrylate cryogels were prepared under UV-radiation within 30 min. • Cryogel morphology were modulated with various parameters, principally temperature. • Macro-porosity and pore-wall feature are extremely important to oil-sorbent capacity. • Oil-sorbents have wide adaptability, good reusability and high-temperature tolerance. [ABSTRACT FROM AUTHOR]

Ring-opening polymerization (ROP) of N-carboxy-α-amino acid anhydride (NCA) of γ-benzyl l -glutamate (BLG) was investigated under frozen condition for the first time. This cryo-ROP was performed in DMSO or 1,4-dioxane below the freezing point of polymerization mixture. The kinetics was monitored with proton nuclear magnetic resonance spectroscopy and gel permeation chromatography, disclosing the well control over molecular weight, living polymerization features and considerable polymerization rate. Compared with the polymerization proceeded at 30 °C, which showed weak linearity regarding the reaction kinetics and relatively broad distribution of molecular weight, the cryo-ROP exhibited excellent first-order kinetics as well as narrow molecular distribution. [ABSTRACT FROM AUTHOR]

Ternary hydrogels composed of poly[acrylamide- co -2-(dimethylamino)ethyl methacrylate] [P(AM- co -DMAEMA)], poly(vinyl alcohol) (PVA) and β -cyclodextrin ( β -CD) were fabricated based on the multiple physical interactions such as inclusion complexation, hydrogen bonding and polymer crystallinity, and exhibited high storage modulus. To illustrate the individual role of each physical interaction, symmetrical investigation has been performed. P(AM- co -DMAEMA)s with two compositions, prepared by radical polymerization at −20 °C below the freezing point of reaction medium of water, were served as the inclusion guest for the inclusion host of β -CD. The inclusion complex between dimethylaminoethyl group of DMAEMA and β -CD was identified through 2D NOESY NMR spectroscopy. Hydrogen bonding between each pairs of hydrogel components was confirmed with FTIR analysis and contributed the second form of crosslinkage. Under freezing polymerization and further freezing-thawing treatment, PVA component tended to crystallize to serve as the third type of physical crosslinkage, which was recognized with X-ray diffraction. Rheological and thermo-gravimetrical analysis was used to inspect the modulus and thermal stability of the hydrogels, respectively. Three hydrogels of P(AM- co -DMAEMA)/PVA-g- β -CD, P(AM- co -DMAEMA)/PVA/ β -CD and P(AM- co -DMAEMA)/PVA were synthesized under the same condition to make the comparison. The whole results disclosed the strong dependence of hydrogel properties on the hydrogel components, reflecting the synergistic effects of different physical crosslinkages for the formation of those physical hydrogels. [ABSTRACT FROM AUTHOR]

ABSTRACT The emergency of antibiotic-resistant bacteria and their wide spread has posed a worldwide threat to public health, and traditional antibiotics are gradually overwhelmed by infectious bacteria. Herein, we report an efficient and economical strategy to construct antimicrobial polymers with net cationic component and hyperbranched architecture, which exhibit highly selective toxicity toward bacteria over human cells. To this aim, cationic poly(aminoethyl acrylate) (PAEA) without hydrophobicity is chosen for low hemolysis activity and targeting the negative bacterial membranes, and hyperbranched architecture is introduced to solve the dilemma of low antimicrobial activity. Long-subchain hyperbranched PAEA ( lhb-PAEA) samples kills >99.99% gram-negative Escherichia coli and >98% gram-positive Staphylococcu aureus at the dose of ≤4 μg/mL. Moreover, lhb-PAEA samples exhibit great biocompatibility, for the hemolysis percentage was ≤35% even at the high dose of 1024 μg/mL. Thus, enhanced antimicrobial activity, reduced hemolytic toxicity, the feasible and low-cost production are achieved for lhb-PAEA as antimicrobial agents. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3462-3469 [ABSTRACT FROM AUTHOR]

Mitochondria play a pivotal role in cellular function, not only acting as the powerhouse of the cell, but also regulating ATP synthesis, reactive oxygen species (ROS) production, intracellular Ca2+ cycling, and apoptosis. During the past decade, extensive progress has been made in the technology to assess mitochondrial functions and accumulating evidences have shown that mitochondrial dysfunction is a key pathophysiological mechanism for many diseases including cardiovascular disorders, such as ischemic heart disease, cardiomyopathy, hypertension, atherosclerosis, and hemorrhagic shock. The advances in methodology have been accelerating our understanding of mitochondrial molecular structure and function, biogenesis and ROS and energy production, which facilitates new drug target identification and therapeutic strategy development for mitochondrial dysfunction-related disorders. This review will focus on the assessment of methodologies currently used for mitochondrial research and discuss their advantages, limitations and the implications of mitochondrial dysfunction in cardiovascular disorders. [Display omitted] [ABSTRACT FROM AUTHOR]

Temperature-responsive macro-porous cryogels of poly(N -iospropylacryamide- co -acrylamido-2-methylpropane sulfonic acid) [P(NIPAM- co -AMPS)] were prepared through redox-initiated cryo-polymerization at −12, −18 and −24 °C. Silver or gold nanoparticles (AgNPs or AuNPs) were formed inside P(NIPAM- co -AMPS) cryogels through the thermal reduction of absorbed AgNO 3 or HAuCl 4 , resulting in hybrid cryogels immobilized with AgNPs or AuNPs. Fourier transform infrared spectroscopy, thermal gravimetric analysis and X-ray diffraction confirmed the chemical composition. Cryogel morphology and nanoparticle distribution were investigated through scanning and transmission electron microscopies. By checking swelling ratio in neutral water, the temperature response of cryogels was identified. The hybrid cryogels were used as the catalysts to reduce p -nitrophenol with NaBH 4 at different temperatures and pHs. The hybrid cryogel with AuNPs had the higher catalytic activity than the counterpart hybrid cryogel with AgNPs. The catalytic activity of hybrid cryogels increased with temperature and pH. The temperature response of cryogels facilitated their isolation from the reaction mixture. Since AuNPs were fixed tightly onto the cryogel pore-wall and hardly lost, hybrid cryogels with AuNPs demonstrated no decrease in catalytic activity for 5 cycles of p -nitrophenol reduction. P(NIPAM- co -AMPS) hybrid cryogels with gold or/and silver nanoparticle was used to catalyze the reduction of p -nitrophenol with the performances of high rate and reusability. Image 1 • Thermo-responsive and macro-porous cryogels of P(NIPAM- co -AMPS) were prepared. • AgNPs or AuNPs were incorporated through in-situ thermal reduction inside the cryogels. • Hybrid cryogels exhibited the high catalytic activity for p -nitrophenol conversion. • Cryogel morphology and metal nanoparticle affected greatly the catalytic activity. [ABSTRACT FROM AUTHOR]