A5066101201- Advanced NMR Techniques and Applications
- NMR spectroscopy and applications
- Polymer crystallization and properties
- Polymer Nanocomposites and Properties
- Crystallization and Solubility Studies
- Advanced MRI Techniques and Applications
- Block Copolymer Self-Assembly
- Solid-state spectroscopy and crystallography
- Analytical Chemistry and Chromatography
- Zeolite Catalysis and Synthesis
- Fiber-reinforced polymer composites
- Advanced Polymer Synthesis and Characterization
- Advanced Battery Materials and Technologies
- Perovskite Materials and Applications
- Polymer Surface Interaction Studies
- Polymer composites and self-healing
- Innovative Microfluidic and Catalytic Techniques Innovation
- biodegradable polymer synthesis and properties
- Rheology and Fluid Dynamics Studies
- Conducting polymers and applications
- Chemical Synthesis and Characterization
- Building materials and conservation
- Muon and positron interactions and applications
- Mesoporous Materials and Catalysis
- Chemical and Physical Properties in Aqueous Solutions
University of Massachusetts Amherst
2014-2025
Beijing Institute of Nanoenergy and Nanosystems
2024
Chinese Academy of Sciences
2024
University of Chinese Academy of Sciences
2024
Central South University
2006-2024
State Key Laboratory of Chemical Engineering
2021-2023
Tianjin University
2018-2023
Ningbo University
2019-2021
Amherst College
2019
China National Pharmaceutical Group Corporation (China)
2018
The pursuit of materials, particularly plastics, with a minimal ecological footprint throughout their circular lifecycle, is crucial for advancing sustainable materials development. Living composed embedded yet active organisms can leverage endogenous biotic resources to achieve functional that align sustainability goals. However, current living material systems face challenges such as weak mechanical properties, limited environmental adaptability, and restricted cellular functionality. In...
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTCenterband-Only Detection of Exchange: Efficient Analysis Dynamics in Solids by NMRE. R. deAzevedo, W.-G. Hu, T. J. Bonagamba, and K. Schmidt-RohrView Author Information Department Polymer Science & Engineering University Massachusetts Amherst, 01003 Instituto de Física São Carlos Universidade Paulo, Brazil Cite this: Am. Chem. Soc. 1999, 121, 36, 8411–8412Publication Date (Web):August 31, 1999Publication History Received15 June 1999Revised5...
An explanation of the varying (ultra)drawability semicrystalline polymers is proposed, based on NMR evidence αc-relaxation-associated helical jumps and chain diffusion through crystallites polyethylene several similarly "αc-mobile" polymers; these include isotactic polypropylene, poly(ethylene oxide), poly(oxymethylene), poly(tetrafluoroethylene), poly(vinyl alcohol), others. The motions provide a mechanism by which hot drawing can extend an initially formed fiber morphology order magnitude...
Crystalline domains composed of poly(methylene) chains have been detected by solid-state NMR and wide-angle X-ray scattering (WAXS) in several samples soil organic matter, including humins, surface (peat), humic acids extracted from young coal. From the melting range 60−>80 °C 1H spin diffusion experiments, a crystallite thickness ca. 3 nm or 25 CH2 units is deduced. The overall fraction (CH2)n carbons these materials up to 9%. Nearly half this crystalline, while rest noncrystalline more...
By using a combination of wide-angle X-ray diffraction (WAXD), mass density, and 13C solid-state nuclear magnetic resonance (NMR) measurements, quantification the absolute degree crystallinity in regioregular poly(3-hexylthiophene) (rr-P3HT) is presented. A regiorandom P3HT (rra-P3HT), lacking long-range order, was used to separate crystalline contribution from total scattering WAXD, thus yielding degrees range 47–56% at room temperature for three different rr-P3HTs. For same rr-P3HT with...
Theoretical principles and experimental details of the centerband-only detection exchange (CODEX) nuclear magnetic resonance (NMR) experiment for characterizing slow segmental dynamics in solids are described. The experiment, which is performed under magic-angle spinning, employs recoupling chemical-shift anisotropy before after a long mixing time during molecular reorientations may occur. By an analysis terms difference tensor chemical shifts time, dependence on reorientation angle obtained...
Long chain branched isotactic polypropylene (LCB-PP) was synthesized using metallocene catalyst (rac-dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride activated by methylaluminoxane). The branching in situ generated a diluted polymerization condition hexane or toluene as diluent. polymers have significant population of molecules evidenced multiangle laser light scattering analysis. More importantly, such structure has been, for the first time, identified 13C NMR spectroscopy....
The chain conformation of glassy poly(ethylene terephthalate) (PET) was characterized by two-dimensional double-quantum nuclear magnetic resonance (NMR). In amorphous carbon-13-labeled PET, the statistics O-13CH2-13CH2-O torsion angle were determined, on basis distinct shapes NMR patterns trans and gauche conformations. crystalline content is 100 percent, but in PET it only 14 percent (+/-5 percent). An average 70 degrees (+/-9 degrees) obtained. Implications for materials properties...
Abstract Siliceous zeolites are ideally suited for emerging applications in gas separations, sensors, and the next generation of low‐ k dielectric materials, but use fluoride synthesis significantly hinders their commercialization. Herein, we show that dry gel conversion (DGC) technique can overcome this problem. Fluoride‐free two siliceous zeolites—AMH‐4 (CHA‐type) AMH‐5 (STT‐type), has been achieved first time using method. *BEA‐, MFI‐, *MRE‐type have also synthesized to obtain insights...
Here, we explore the effect of copolymer chemistry on phase behavior and viscoelasticity complex coacervates. To this end, utilized a library methacrylate copolymers with varying charge densities hydrophobicity. Our results show that changing density hydrophobicity drastically affects behavior─with dictating salt stability controlling polymer concentration Small-amplitude oscillatory shear measurements were used to study viscoelastic response coacervates, leveraging knowledge coacervate in...
A nonflammable eutectic electrolyte, with wide electrochemical (3.0 V vs. Zn/Zn 2+ ) and thermal (−70 to 160 °C) windows, eliminates hydrogen evolution, induces robust solid–electrolyte interphase broadens temperature/voltage range of Zn batteries.
The occurrence and rate of 180° chain-flip motions in the crystalline regions two polyethylenes were studied by 13C NMR. In high-density polyethylene (HDPE) ultradrawn ultrahigh molecular weight (UHMWPE) fibers, changes 13C−13C dipolar couplings brought about reorientations internuclear vectors crystallites observed. HDPE sample, which was labeled with 4% pairs, rotational motion observed directly via two-dimensional exchange spectroscopy, stimulated-echo decays, 1D line shape monitoring...
Using fluorinated probes for 19F MRI imaging is an emerging field with potential utility in cellular and cell tracking vivo, which complements conventional 1H MRI. An attractive feature of 19F-based that this a bio-orthogonal nucleus the naturally abundant isotope NMR active. A significant hurdle however arises from tendency organic macromolecules, multiple fluorocarbon substitutions, to aggregate aqueous phase. This aggregation results loss sensitivity, because T2 relaxation times these...
This study investigates the molecular dependencies of dynamic stiffening and strengthening through comparison high strain rate impact responses various polyurethanes polyureas. We use an in-house designed tabletop microimpact experimental platform—the laser-induced particle test—to perform impacts measure corresponding material response. Dynamic mechanical analysis differential scanning calorimetry are used to show that glass transition temperature is a useful predictor response at ambient...
Functional polymer ligands are used to prepare perovskite nanoparticles that disperse in matrices.
Silicon carbide (SiC) and silicon oxycarbide (SiOC) ceramic/carbon (C) nanocomposites are prepared via photothermal pyrolysis of cross-linked polycarbosilanes polysiloxanes using a high-intensity pulsed xenon flash lamp in air at room temperature to yield crystalline amorphous phases SiC SiOC ceramics, graphitic, carbon phases. The millisecond duration the radiation pulse is shorter than thermal equilibrium time preceramic polymers (PCPs), enabling precursor phase crystallization product...
To push upper boundaries of thermal conductivity in polymer composites, understanding transport mechanisms is crucial. Despite extensive simulations, systematic experimental investigation on composites limited. better understand processes, we design with perfect fillers (graphite) and defective (graphite oxide), using polyvinyl alcohol (PVA) as a matrix model. Measured conductivities ~1.38 ± 0.22 W m −1 K PVA/defective filler higher than those ~0.86 0.21 PVA/perfect while measured are lower...