Search results for "Polyacetylene"
showing 6 items of 6 documents
Theoretical Characterization of the Electronic Structure of Poly(Heteroaromatic Vinylenes)
1990
Since the pioneering work of the mid-seventies, the number of organic π-conjugated polymers, that can be made highly conducting upon appropriate chemical treatment, has grown tremendously. Among the most studied of these compounds are those based on fivemembered heteroaromatic rings, such as polythiophene (PT) and polypyrrole (PPy). The attractiveness of these polymers, relative to polyacetylene (PA) and poly(p-phenylene) (PPP), is the high chemical and thermal stability they show.1
Electrolyte-driven electrochemical amplification by poly(thienylacetylene) encapsulated within Zeolite Y
2006
Electrochemical oxidation and reduction of poly(thienylacetylene) encapsulated inside zeolite Y (PTA@Y) exhibit with large anodic and cathodic doping currents with a significant reversibility. Thienyl groups lower the redox potential of polyacetylene chain whereas encapsulation stabilizes the resulting charged radical species blocking undesired post electron-transfer cross-link reactions. Size-exclusion effects associated produces an electrolyte-dependent amplification of currents recorded at PTA@Y-modified electrodes for electrochemical processes involving selected substrates in solution, namely, dinitrobiphenyl and benzidine. Keywords: Poly(thienylacetylene), Zeolite Y, Electrochemistry, …
Quantum Monte Carlo study of the alternating extended Peierls–Hubbard model applied to the trans-polyacetylene
2001
Abstract The one-dimensional alternating Peierls–Hubbard model is especially interesting as nontrivial model for conjugated polymer chains, such as polyacetylene. We study this model for chains of 64 sites using the determinantal method based on Hubbard–Stratonovich transformation. We obtain the first electronic energies and their mean fluctuations at half-filling as a function of the on-site electron–electron interaction (both short and long range U, V coupling are considered). We also study the effect of the electron–electron interaction on the dimerization by investigating some of the important correlation functions, such as spin–spin correlation, on-site charge and the specific heat. Th…
Catalytic one-handed helix-induction and memory of amphiphilic poly(biphenylylacetylene)s in water
2020
Abstract A series of amphiphilic biphenylylacetylene-based homo- and copolymers (PBPAs) carrying chiral and/or achiral oligo(ethylene glycol) pendants at the 4’-position of the biphenyl units were synthesized and the amplification of the macromolecular helicity through noncovalent and/or covalent chiral interactions followed by the memory of the helicity were investigated in both water and organic solvents. The macromolecular helicity was efficiently induced in the homopolymers of achiral monomers through specific encapsulation of a catalytic amount of hydrophobic chiral guests in water and their induced helicities were stably memorized in water after complete removal of the optically-activ…
Quantum Monte-Carlo calculation of correlation functions of undistorted, cis-distorted and trans-distorted polyacene
2003
Abstract We have studied polyacene within the Hubbard model to explore the effect of electrons correlations on the bond–bond correlation as well as spin–spin correlation functions. We employ the determinantal quantum Monte-Carlo to resolve the microscopic Hamiltonian of this system which involves a nearest-neighbor electron hopping matrix element t , an on-site Coulomb repulsion U . The objective of this study is to understand the effect of electron–electron (e–e) correlations on the structural instability in polyacene. We find strong similarities between polyacene and polyacetylene. The system shows no tendency to destroy the imposed bond-alternation pattern. The spin–spin correlations sho…
Spontaneous doping and magnetic properties of polyacetylene and polypropyne synthesized in situ in Ni-exchanged mordenite and mesoporous MCM-41
2001
Upon polymerisation of acetylene and propyne inside the channels of Ni2+-exchanged mordenite and mesoporous MCM-41 spontaneous doping and formation of antiferromagnetic NiO clusters are observed to various extents. The population of polarons present in the final polymer/zeolite composite: (i) is higher for polyacetylene than for polypropyne; (ii) increases with polymerisation temperature in the range 100 to 335 °C; (iii) increases with the C content; and (iv) is higher for mordenite than for MCM-41 under the same conditions. The use of Ni(0),H+-mordenite for polymer formation enhances the polaron population of the resulting polymer by over one order of magnitude. Doped polyacetylene encapsu…