Linear Polyacetylene Research Articles

Semi-conducting cyclic copolymers of acetylene and propyne

Polyacetylene (PA) exhibits conductivities comparable to metals after doping, yet the extremely low solubility of PA limits its processing and utility. Introducing pendent groups can alter the properties of PA. Copolymerizing acetylene and propyne using Zieglar-Natta type catalysts affords linear poly(acetylene-co-propyne) as free-standing films. However, this process requires grams of catalysts and extensive workup. Cyclic polyacetylene is a unique topological isomer of linear polyacetylene. Herein, we report a facile synthesis of cyclic poly(acetylene-co-propyne) as thin, flexible films with extremely low catalyst loading (milligrams) and easy purification. Altering the feed ratio of acetylene and propyne produces copolymers with different acetylene/propyne incorporations. The films exhibit similar conductivities as linear copolymers after doping. The soluble portions of different cyclic copolymers exhibit low acetylene incorporation. TGA analysis reveals the cyclic copolymers are less thermally stable than cyclic PA, with the stability dependent on the ratio of acetylene and propyne incorporation.

Soluble Polymer Precursors via Ring-Expansion Metathesis Polymerization for the Synthesis of Cyclic Polyacetylene

Cyclic polyacetylene (c-PA) is the cyclic derivative of the semiconducting linear polyacetylene. As with the linear derivative, cyclic polyacetylene is insoluble, making its characterization and processing challenging. Herein, we report the synthesis of c-PA via an indirect approach, employing ring-expansion metathesis polymerization of cyclic alkenes to form soluble polymer precursors. Subsequent retro-Diels–Alder elimination through heating provides c-PA. Dilute solution characterizations of the polymer precursors including 1H nuclear magnetic resonance spectroscopy, gel permeation chromatography, and infrared and Raman spectroscopy confirm their cyclic structure and, by inference, the cyclic topology of the resulting c-PA. Solid-state thermal analyses via thermogravimetric analysis and differential scanning calorimetry reveal the chemical and physical transformations occurring during the retro-Diels–Alder elimination step and concurrent isomerization. Freestanding films are attainable via the soluble precursors, and when doped with I2, the films are semiconducting.

Polyacetylene comes full circle

Many of today’s flexible electronic devices can trace their ancestry back to the first synthesis of linear polyacetylene in 1958. Researchers have now used a highly active catalyst to create cyclic...

Cyclic polyacetylene.

Here we demonstrate the synthesis of cyclic polyacetylene (c-PA), or [∞]annulene, via homogeneous tungsten-catalysed polymerization of acetylene. Unique to the cyclic structure and evidence for its topology, the c-PA contains >99% trans double bonds, even when synthesized at -94 °C. High activity with low catalyst loadings allows for the synthesis of temporarily soluble c-PA, thus opening the opportunity to derivatize the polymer in solution. Absolute evidence for the cyclic topology comes from atomic force microscopy images of bottlebrush derivatives generated from soluble c-PA. Now available in its cyclic form, initial characterization studies are presented to elucidate the topological differences compared with traditionally synthesized linear polyacetylene. One advantage to the synthesis of c-PA is the direct synthesis of the trans-transoid isomer. Low defect concentrations, low soliton concentration, and relatively high conjugation lengths are characteristics of c-PA. Efficient catalysis permits the rapid synthesis of lustrous flexible thin films of c-PA, and when doped with I2, they are highly conductive (398 (±76) Ω-1 cm-1).

Improved oxygen permeation of a multi-stranded network two-dimensional polymer synthesized by three-step polymerizations of a novel monomer bearing three different polymerizable groups followed by photoexfoliation

We synthesized a novel multi-stranded network two-dimensional polymer (2DP) by three-step polymerizations of a new acetylene monomer bearing three different polymerizable groups, two styrenes and one allyl group, followed by photoexfoliation. The starting linear polyacetylene was soluble and fabricated as a good self-supporting membrane, and the following two polymerizations, photo-induced radical addition polymerization and acyclic diene metathesis polycondensation, were carried out in the membrane states. The resulting membranes maintained self-supporting properties. Finally, 2DP was obtained by highly selective photocyclic aromatization (SCAT) of the original polyacetylene backbone. As a result, both of the oxygen permeability and permselectivity increased simultaneously and the performance was placed above the upper bound line.

Petroacetylene, a new polyacetylene from the marine sponge Petrosiasolida that inhibits blastulation of starfish embryos

A new C30 linear polyacetylene compound designated petroacetylene (1) has been isolated from the marine sponge Petrosia solida Hoshino 1981, collected off the coast of Amami-Oshima, Kagoshima Prefecture, Japan. The structure was elucidated on the basis of spectroscopic data and chemical means. Petroacetylene (1) inhibited blastulation of starfish embryos at a concentration of 3.1 μg mL− 1 or greater.

New polyacetylene glucosides from the florets of Carthamus tinctorius and their weak anti-inflammatory activities

Eight new linear polyacetylene glucosides (1–8), containing two C10-, one C13- and five C14-acetylenes, together with three known polyacetylenes (9–11) were isolated from the florets of Carthamus tinctorius L. Their structures were elucidated by means of spectroscopic methods and chemical evidence. The absolute configurations of compounds 3–9 were confirmed by Snatzke and Gerards’s method, observing the induced circular dichroism after addition of dirhodium tetrakis (trifluoroacetate) [Rh2(OCOCF3)4] in CHCl3. All the isolated compounds (1–11) were also tested for inhibitory activities against LPS-induced NO production in murine macrophages and just showed weak activities at concentrations of 1×10−5M.

Electronic Gas-Phase Spectra of Larger Polyacetylene Cations

The origin bands of the A 2Pi-X 2Pi electronic transition for three new linear polyacetylene cation chains, HC12H+, HC14H+, and HC16H+, have been recorded in the gas phase at approximately 30 K, located at 924.7, 1034.6, and 1144.0 nm. The absorption spectra were observed using a two-color two-photon ion-photodissociation experiment that utilizes the cooling capabilities of a 22-pole ion trap. Such spectra allow a direct comparison between laboratory and astrophysical data; however, no matches were found between the experimentally determined origin bands and the known diffuse interstellar bands.

Photochemical polymerization of acetylene in water suspension. A study of the resulting photopolymer in comparison with thermally aged linear polyacetylene

Saturated solutions of acetylene in water were irradiated for several hours by a 125 W u.v. lamp. Photopolymerization has been followed with u.v.-vis spectroscopy and different polymerization pathways involving diacetylene, vinylacetylene and cumulene formation have been discussed. Solvent evaporation from the resulting milky-white solution of photopolymer in water resulted in isolation of a cream coloured powder of acetylene photopolymer which is insoluble in common solvents. This photopolymer was characterized by means of elemental analysis, Ft-i.r. and u.v. spectroscopy and found to incorporate about 18% of oxygen (probably taken from water) in the form of ketonic, carboxylic, hydroxylic and ether derivatives. Ft-i.r. spectroscopy reveals the structural similarity between the acetylene photopolymer to that of linear polyacetylene, oxidized in air at 150–160°. The thermal oxidation of a linear polyacetylene has been studied by Ft-i.r. and it is also discussed.

Polymerization of acetylene and 1-alkynes by rare-earth coordination catalysts

Polyacetylene has been shown to be an electrical conductor in the metallic range when doped with various agents; hence, considerable attention has been focused on this macromolecule in both industrial and academic laboratories. A natural extension of these studies is the investigation of the polymerization of substituted alkynes. Only a few transition metal catalysts are known to produce high molecular weight polyacetylenes: e.g., ti(OC 4H 9) 4/ Al(C 2H 5) 3 for acetylene, Fe(acac) 3/Al(i-C 4H 9) 3 for alkylacetylenes, and WCl 6 and MoCl 5 for phenylacetylene and other 1-alkynes. This study reports the first example of a systematic investigation of rare earth compounds as catalysts for the polymerization o acetylene and 1-alkynes. The polymerization of acetylene, which was carried out at −16 to −100 °C at an optimum AlR 3/Ln (Ln = rare earth compound) mol ration in the 3 - 9 1 range, yielded crystalline, high cis, metallic lustrous films. The polymers were characterized by infrared spectrophotometry, differential scanning and transmission electron micrography, and electrical resistivity measurements. The nature, yield, and other properties of the polyacetylene obtained in the reactions depends somewhat on the nature of the counterion of the lanthanide ion, the alkyl group on aluminum, the solvent, and donor additives to the solvent, the results of which will be presented. The polymerization of phenylacetylene was catalyzed by rare-earth naphthenates in combination with triethylaluminum in chlorobenzene at 50 °C. Moderate molecular weight, atactic polyphenylacetylene was obtained in all cases in relatively low yield, and all polymers, showed the presence of both cis and trans double bonds in the chain. The polymers exhibited a low degree (∼28%) of crystallinity, although the neodymium system produced a crystalline (45%) cis-cisoid polymer. An interesting, but as yet unexplained, correlation exists between activity of the catalyst, as indicated by the yield of the polymer obtained, and the number of f electron on the metal. The polymers were characterized by vapor-osmometry, infrared and nuclear magnetic resonance spectrometry, and X-ray diffraction, the results of which will be presented. The polymerization of alkyl-substituted, terminal acetylene, as well as phenylacetylene, was carried out at 20 °C, using rare earth naphthenates with triisobutylaluminum or triethylaluminum as the catalyst. The monomers 1-hexyne, 1-pentyne, 3-methyl-1-pentyne, 4-methyl-1-pentyne, and isopropylacetylene gave light yellow, occasionally elastomeric polymers in very high yields in some cases. Membrane osmometric measurements revealed that the molecular weights for the polymers obtained are in the 80,000−170,000 range, which is extremely high for polymers of substituted acetylenes. These polymers were studied by ultraviolet, infrared and NMR spectrometry. The ultraviolet spectra show absorption at much lower wavelengths than those expected for a polyconjugated structure. However, NMR data show aliphatic to olefinic intensity ratios very close to those calculated for the linear polyacetylene ( e.c., for poly-1-hexyne, the calculated and observed integrated intensity ratios are 9:1, aliphatic:olefinic). The UV spectra are very similar to those found previously for poly-1-hexyne and poly-4-methyl-1-hexyne, and the presence of low wavelength absorption is explained by the presence of large pendant groups on the main chain. These groups, through steric interaction, apparently cause the chain to be twisted somewhat from planarity, thus effectively negating the molecular orbital overlap that should result from polyconjugation. The net effect is that the polymers appears to be made up of blocks of conjugation of two or three units.

Bioactive marine metabolites III. A novel polyacetylene alcohol, inhibitor of cell division in fertilized sea urchin eggs, from the marine sponge tetrosia sp.

A new C 30 linear polyacetylene alcohol, triaconta-4,15,26-triene-1,12,18,29-tetrayne-3,14,17,28-tetraol, has been isolated from the sponge Tetrosia sp. The compound inhibits mitotic cell division in sea urchin eggs.