Scan Science and Technology
Contact Leading Edge Experts & Companies
The Experts below are selected from a list of 8094 Experts worldwide ranked by ideXlab platform
Dennis W. Smith – One of the best experts on this subject based on the ideXlab platform.
Perfluorocyclohexenyl (PFCH) Aromatic Ether polymers from perfluorocyclohexene and polycyclic Aromatic bisphenolsPolymer Chemistry, 2020Co-Authors: Ganesh Narayanan, Behzad Faradizaji, Karl M. Mukeba, Ketki E. Shelar, Maleesha De Silva, Amanda L. Patrick, Bruno Donnadieu, Dennis W. SmithAbstract:
Perfluorocycohexenyl (PFCH) Aromatic Ether polymers were synthesized by step-growth polycondensation of polycyclic Aromatic hydrocarbon (PAH) bisphenols and decafluorocyclohexene (DFCH) affording a new class of unsaturated semi-fluoropolymers containing the rigid PAH linkage. Two acenaphthenequinone and two phenanthrenedione derived PAH bisphenols underwent base-mediated step-growth vinyl addition/elimination polymerization with DFCH to give polymers with well-defined unsaturation, moderate molecular weights, and variable glass transition (Tg) and thermal decomposition (Td) temperatures based on the starting PAH bisphenol monomer. With one exception exhibiting a low degree of crystallinity, PFCH polymers with PAH bisphenols were amorphous with Tg ranging from 184 to 240 °C. The new polymers contain intact unsaturation and reactive PAH moieties amenable for selective post-polymerization functionalization and crosslinking.
Semi-fluorinated Aromatic Ether polymers via step-growth polymerization of fluoroalkenesOpportunities for Fluoropolymers, 2020Co-Authors: Ganesh Narayanan, Behzad Farajidizaji, Dennis W. SmithAbstract:
Abstract Three classes of semi-fluorinated Aromatic Ether polymers, namely: perfluorocyclobutyl (PFCB), perfluorocycloalkenes (PFCA), and fluorinated arylene vinylene Ether (FAVE), which are mostly amorphous have been reported via step-growth polymerization of fluoroalkenes. Unlike traditional fluoropolymers which have higher degree of crystallinity and are plagued by lack of solubility in common organic solvents, these uncured semi-fluorinated polymers are readily soluble in most organic solvents resulting in improved processability. In addition, all three semi-fluorinated polymers are versatile and can be custom-designed and fabricated into linear, telechelic, alternating and segmented-block, and network polymers, facilitating applications in optics, optoelectronic, photonics, proton exchange membranes, sensors, and fuel cells. Major aim of this timely review is to provide account of synthetic opportunities these semi-fluorinated offer in various applications.
Protective action of semi-fluorinated perfluorocyclobutyl polymer coatings against corrosion of mild steelJournal of Materials Science, 2019Co-Authors: Eugene B Caldona, Dennis W. Smith, David O. WipfAbstract:
This study examines perfluorocyclobutyl (PFCB) Aromatic Ether polymers and demonstrates, for the first time, their potential as corrosion-resistant coatings. PFCB polymers are a distinct class of semi-fluorinated polymers that are based on thermal cyclopolymerization of Aromatic trifluorovinyl Ethers. They combine the flexibility and thermal stability of Aromatic Ethers with strong fluorocarbon linkages. Electrochemical impedance spectroscopy and potentiodynamic scans reveal that PFCB coatings display protective barrier properties against corrosion attack nearly equal to that of polyvinylidene fluoride (PVDF) coatings. The PFCBs also show excellent adhesion to metal surfaces and nonstick properties comparable to that of PVDF. Combined with their high thermal resistance, PFCBs may lead to new corrosion-resistant coatings in marine, oil and gas, and other applications.
Jingshuai Yang – One of the best experts on this subject based on the ideXlab platform.
quaternized poly Aromatic Ether sulfone with siloxane crosslinking networks as high temperature proton exchange membranesApplied Surface Science, 2018Co-Authors: Jin Wang, Haoxing Jiang, Jingshuai YangAbstract:
Abstract Novel high temperature proton exchange membranes, quaternized poly(aryl Ether sulfone) (QPAES), were prepared using triethylamine (TEA) as quaternization reagent and (N,N-diethyl-3-aminopropyl) trimethoxysilane (EPMS) as the crosslinking agent, respectively. To improve the mechanical strength and dimensional stability of the membranes, the crosslinked structure of Si O Si network was formed by hydrolyzing siloxane groups of EPMS. Compared with the non-crosslinked membrane, the crosslinked PAES membranes displayed significantly enhanced mechanical properties, improved dimensional stabilities as well as high conductivities. The QPAES-10EPMS-90TEA membrane with a phosphoric acid doping level of 12.1 exhibited a tensile strength of 9.16 MPa at room temperature, and a conductivity of 74.8 mS cm−1 at 180 °C under no humidification conditions.
New anhydrous proton exchange membranes based on fluoropolymers blend imidazolium poly (Aromatic Ether ketone)s for high temperature polymer electrolyte fuel cellsInternational Journal of Hydrogen Energy, 2018Co-Authors: Jingshuai Yang, Wang Yihan, Guohao Yang, Sifan ZhanAbstract:
Abstract The blend polymer membranes were synthesized from the methylimidazolium poly (Aromatic Ether ketone) (MeIm-PAEK) and fluoropolymers (PVDF and PVDF-HFP) with excellent thermal stability and improved dimensional stabilities for high-temperature polymer electrolyte fuel cells. The MeIm-PAEK exhibited good compatibility with PVDF or PVDF-HFP without phase separation. High phosphoric acid doping contents of the blend membranes were achieved at elevated temperatures with acceptable swellings. The acid doped blend membranes displayed lower dimensional swellings and higher mechanical strength compared to the MeIm-PAEK membrane, which allowed the blend membranes to obtain higher acid doping contents and proton conductivities. The MeIm-PAEK/10%PVDF membrane with a phosphoric acid doping content of 700 wt% showed a proton conductivity as high as 0.192 S cm−1 at 180 °C under the non-humidified condition and a tensile strength of 4.3 MPa at room temperature.
Zhixue Zhu – One of the best experts on this subject based on the ideXlab platform.
induced fit binding of π electron donor substrates to macrocyclic Aromatic Ether imide sulfones a versatile approach to molecular assemblyChemistry: A European Journal, 2010Co-Authors: Howard M. Colquhoun, David J. Williams, Zhixue Zhu, Michael G B Drew, Christine J Cardin, Yu Gan, Andrew G Crawford, Todd B MarderAbstract:
Novel macrocyclic receptors that bind electron-donor Aromatic substrates through pi-stacking donor-acceptor interactions are obtained by cycloimidisation of an amine-functionalised aryl Ether sulfone with pyromellitic and 1,4,5,8-naphthalenetetracarboxylic dianhydrides. These macrocycles can form complexes with a wide variety of pi-donor substrates, including tetrathiafulvalene, naphthalene, anthracene, pyrene, perylene and functional derivatives of these polycyclic hydrocarbons. The resulting supramolecular assemblies range from simple 1:1 complexes to - and pseudorotaxanes and even (as a result of crystallographic disorder) an apparent polyrotaxane. Direct five-component self-assembly of a metal-centred pseudorotaxane is also observed on complexation of a macrocyclic Ether imide with 8-hydroxyquinoline in the presence of palladium(II) ions. Binding studies in solution were carried out by using (1)H NMR and UV/Vis spectroscopy, and the stoichiometries of binding were confirmed by Job plots based on the charge-transfer absorption bands. The highest association constants were found for strong pi-donor guests with large surface areas, notably perylene and 1-hydroxypyrene, for which K(a) values of 1.4×10(3) and 2.3×10(3) M(-1), respectively, were found. Single-crystal X-ray analyses of the receptors and their derived complexes reveal large induced-fit distortions of the macrocyclic frameworks as a result of complexation. These structures provide compelling evidence for the existence of strong attractive forces between the electronically complementary Aromatic pi systems of host and guest.
macrocyclic Aromatic Ether imide sulfones versatile supramolecular receptors with extreme thermochemical and oxidative stabilityJournal of the American Chemical Society, 2002Co-Authors: Howard M. Colquhoun, David J. Williams, Zhixue ZhuAbstract:
Macrocyclic receptors having extreme thermo-oxidative stability, and which bind a wide range of electron-donor substrates via π-stacking donor−acceptor interactions, are accessible by cycloimidization of an amine-functionalized aryl Ether-sulfone with pyromellitic dianhydride or 1,4,5,8-naphthalenetetracarboxylic dianhydride. The potential of these receptors in supramolecular chemistry is illustrated, for example, by the spontaneous self-assembly and crystallization of a five-component pseudorotaxane from a solution of its constituents.
Synthesis and ring-expanding oligomerization of an extremely strained macrocyclic Aromatic Ether-sulfone.Organic Letters, 2001Co-Authors: Howard M. Colquhoun, Zhixue Zhu, David J. WilliamsAbstract:
[reaction: see text] An extremely strained, 5-ring, macrocyclic Aromatic Ether-sulfone, [-1,4-C(6)H(4)SO(2)-1,4-C(6)H(4)O-1,3-C(6)H(4)O-1,4-C(6)H(4)SO(2)-1,4-C(6)H(4)-], synthesized by nickel-catalyzed intramolecular coupling of a bis-chlorophenylene-terminated precursor, undergoes fluoride-promoted ring expansion in dilute solution, giving a series of higher macrocyclic oligomers including cyclic dimer, trimer, and tetramer. The latter contains 20 Aromatic residues in a 92-atom ring and is one of the largest synthetic organic macrocycles to be crystallographically characterized. The synthesis, structure, and ring expansion of a related macrocyclic Ether-ketone are also reported.