Properties Of Polyacetylene Research Articles

Electrical properties of dehydrated polyvinyl alcohol

Electrical properties of polyacetylene produced by polyvinyl alcohol dehydration were studied at direct and alternative current measurements. These properties exhibit some a peculiarity at 325 K. It is attributed to two phase coexistence. One of them has a hopping conduction and another one goes from a high-conducting to low-conducting band-type state at 325 K.

Uncatalyzed Synthesis and Properties of Polyacetylene with N-Pentylpyridinium Iodide

Uncatalyzed synthesis of a new ionic conjugated polymer, poly(3-ethynyl-N-pentylpyridinium iodide) [P3EPPI] was performed by the activated polymerization of 3-ethynylpyridine using 1-iodopentane. The polymerization proceeded in homogeneous manner to provide a moderate yield of polymer. The polymer structure was characterized by such instrumental methods as NMR (1H- and 13C-), IR, and UV-visible spectroscopies to have a conjugated polymer backbone system having N-pentyl-3-pyridinium iodide as substituents. The photoluminescence maximum peak of P3EPPI was located at 534 nm, which corresponds to the photon energy of 2.32 eV. The cyclovoltamograms of polymer exhibited the electrochemically stable window at the −1.53∼1.50 V region. The kinetics of the redox process of P3EPPI was found to be mainly controlled by the reactant diffusion process from the experiment of the oxidation current density of polymer versus the scan rate.

Synthesis and Study of the Thermal and Chiro-Optical Properties of Polyacetylenes with Bulky Side Groups: Poly(1-ethynyl-4-biphenyl), Poly(1-ethynyl-4- phenoxybenzene) and Poly(1-ethynyl-4-pentylbenzene)

The monosubstituted acetylenes 1-ethynyl-4-biphenyl, 1-ethynyl-4-phenoxybenzene and 1-ethynyl-4-pentylbenzene were polymerized to the corresponding polyacetylenes with bulky side substituents: PEBIP, PEPHENO and PEPB, respectively, using a Rh(I) complex as polymerization catalyst. The FT-IR and UV-VIS spectra of PEBIP, PEPHENO and PEPB were studied using the corresponding spectra of polyphenylacetylene (PPA), polytolylacetylene (PETOL) and poly(1-ethynyl-naphthalene) PEN as reference. Based on the spectral analysis, high cis-trasoid structures were assigned to PEBIP, PEPHENO and PEPB. The specific optical rotation of PEBIP, PEPHENO and PEPB was measured in the chiral solvent α (-)pinene and, only for PEPB, also in α (+)pinene. It was found that even at low concentration PEBIP, PEPHENO and PEPB cause changes in the specific optical rotation of the chiral medium where they have been dissolved. This phenomenon has not been observed when toluene or atactic polystyrene are dissolved in the same chiral solvent in similar concentration. This suggests that the polyacetylenes with bulky side groups are able to rearrange in a helical configuration (prevalently right-handed or vice-versa, depending on the type of chiral medium used) once hosted in a chiral medium giving a contribution to the chirality of the solvent where they have been dissolved. The thermal stability of PEBIP, PEPHENO and PEPB was studied under N2 flow by thermal analysis (TGA, DTG and DTA) in comparison to reference monosubstituted polyacetylenes PPA, PETOL and PEN. The results show that the thermal stability of monosubstituted polyacetylenes is greatly improved by the presence of bulky substitutents as theoretically expected, and similarly, also the char-forming tendency increases with the bulkiness of the side groups.

Synthesis and properties of polyacetylenes containing bis(4-alkylphenyl)terephthalate as pendant and methyleneoxy as spacer

Monosubstituted polyacetylenes containing lateral pendants of bis(p-alkylphenyl)terephthalate with spacer and alkyl tails [R, where R is H, CH 3 and C 3H 7] were synthesized, and the effects of the backbone structure and alkyl tails on the properties were investigated. The monomer with alkyl tails (p-methyl and p-propyl) formed a smectic mesophase upon heating above the melting temperature, but the other one without tails could not exhibit liquid crystallinity at elevated temperatures. The lower melting temperature and wider mesomorphic temperature range of 2-propargyloxy-bis(p-propylphenyl)terephthalate (k 91.6 SmB 102.6 i) than 2-propargyloxy-bis(p-methylphenyl)terephthalate (k 134.3 SmB 143.7 i) indicated that the long tail in mesogen played an important role in the packing order and stability of their liquid crystalline phase. The polymerization of acetylene monomers were carried out with [Rh(nbd)Cl] 2 as a catalyst in toluene. The structures and properties of the monosubstituted polyacetylenes were characterized by the means of nuclear magnetic resonance, polarized optical microscopy, infrared spectroscopy, ultraviolet spectroscopy, photoluminescence, thermogravimetry and differential scanning calorimetry. The molecular weights of the polymers were measured by gel permeation chromatograph. The polymers could not exhibit liquid crystallinity at elevated temperatures. The steric effect of bulky liquid-crystallinity mesogens prevented the coplanar conformation of the polyene backbone, and thus, led to the lower absorption and emission of the polymers.

Synthesis and properties of polyacetylenes having pendent phenylethynylcarbazolyl groups

Novel acetylene monomers substituted with phenylethynylcarbazolyl groups, 3-[(4-octylphenyl)ethynyl]-9-propargylcarbazole (1), 3,6-bis[(4-octylphenyl)ethynyl]-9-propargylcarbazole (2), 9-(4-ethynylphenyl)-3-[(4-octylphenyl)ethynyl]carbazole (3), and 9-(4-ethynylphenyl)-3,6-bis[(4-octylphenyl)ethynyl]carbazole (4) were synthesized, and polymerized with Rh+(nbd)[η6–C6H5B−(C6H5)3] and WCl6–n-Bu4Sn catalysts. The corresponding polyacetylenes with number-average molecular weights ranging from 9200 to 94 000 were obtained in 20–98% yields. The IR spectra of the polymers revealed that acetylene polymerization took place at the terminal ethynyl group, while the ethynylene group remained intact. The UV–vis absorption band edge wavelengths of W-based poly(3) and poly(4) were longer than those of the other polymers. W-Based poly(4) emitted fluorescence with the highest quantum yield (41%). Poly(1) exhibited excimer-based fluorescence in dilute solution.

Synthesis and Properties of Polyacetylene and Polynorbornene Derivatives Carrying 2,2,5,5-Tetramethyl-1-pyrrolidinyloxy Moieties

PROXYL-containing propargyl ester HC⋮CCH2OCO-3-PROXYL (1), N-propargylamide HC⋮CCH2NHCO-3-PROXYL (2), 1-pentyne-4,4-dimethyl ester HC⋮CCH2C(CH3)(CH2OCO-3-PROXYL)2 (3), and norbornene diester monomers NB-2,3-exo,exo-(CH2OCO-3-PROXYL)2 (4), NB-2,3-endo,endo-(CH2OCO-3-PROXYL)2 (5), and NB-2,2-(CH2OCO-3-PROXYL)2 (6) (NB = norbornene, PROXYL = 2,2,5,5-tetramethyl-1-pyrrolidinyoxy) were polymerized to afford novel polymers containing the PROXYL radical at high densities. While 1 and 2 provided polymers with number-average molecular weights of 3300−29 800 in 60−65% yields in the presence of a Rh catalyst, monomers 4−6 gave polymers with number-average molecular weights up to 209 000−272 000 in 90−94% yields with a Ru catalyst. The formed polymers were thermally stable up to ca. 220 °C according to TGA and soluble in common organic solvents including toluene, CHCl3, and THF. Poly(1), poly(2), and poly(4)−poly(6) hardly exhibited absorption above 400 nm, which corresponds with their very light color. The oxidation...

Synthesis and properties of polyacetylenes with directly attached bis(4‐alkoxyphenyl)terephthalate mesogens as pendants

AbstractLiquid‐crystalline, monosubstituted polyacetylenes containing lateral pendants of bis(4‐alkoxyphenyl)terephthalate with no flexible spacers and alkoxy tails {RO, where R is CH3 [P(1)] or C6H13 [P(6)]} were synthesized, and the effects of the backbone structure and alkoxy tails on the properties of the polymers were investigated. The polymerizations of acetylene monomers were carried out with chloronorbornadiene rhodium(I) dimer as a 1,2‐insertion catalyst in toluene. The structures and properties of the monosubstituted polyacetylenes were characterized and evaluated with nuclear magnetic resonance, infrared spectroscopy, thermogravimetry, differential scanning calorimetry, polarized optical microscopy, ultraviolet spectroscopy, and photoluminescence analyses. The molecular weights of the polymers were measured by gel permeation chromatography. The polymer with long tails (p‐hexyloxy), that is, P(6), formed a smectic mesophase upon heating above the melting temperature, but the other one with short tails (p‐methoxy), that is, P(1), could not exhibit liquid crystallinity at elevated temperatures. The steric effect of bulky, liquid‐crystalline mesogens and a direct connection with the main chain prevented the planar conformation of the polyene backbone and, therefore, led to the lower absorption and emission wavelength of the polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2499–2509, 2006

Synthesis and properties of polyacetylenes containing carbazolylmethyl groups

Novel acetylene monomers containing carbazolymethyl groups, 3,5-bis[(3,6-di-t-butyl)carbazolylmethyl]-1-ethynylbenzene (1), 3-(3,6-di-t-butyl)carbazolylmethyl-1-ethynylbenzene (2), and 4-(3,6-di-t-butyl)carbazolylmethyl-1-ethynylbenzene (3) were synthesized, and polymerized with [(nbd)RhCl]2–Et3N, Rh+(nbd)[η6-C6H5B−(C6H5)3], and WCl6-n-Bu4Sn catalysts. The corresponding polyacetylenes with number-average molecular weights ranging from 1600 to 115,000 were obtained in 18%-quantitative yields. The UV–vis absorption band edge wavelengths of the polymers obtained with W catalyst were longer than those of the Rh-based polymers. The photoluminescence quantum yields of the W-based polymers were 1.1–3.1%, while those of the Rh-based ones were 0.18–4.1%.

Charge Transport in Conducting Polymers: Polyacetylene Nanofibres

The preparation of individual polyacetylene nanofibres has allowed a more probing investigation of the properties of polyacetylene. A significant discovery is that at low temperatures, polyacetylene nanofibres show temperature-independent Zener-type tunnelling, that we suggest is tunnelling of the conjugated-bond pattern along single polyacetylene chains. At higher temperatures, the current shows a strong increase with temperature and the nonlinearity of the current-voltage characteristics decreases. We make a comparison with similar behaviour found in single-wall carbon nanotube networks, and show that the decrease in nonlinearity is consistent with our generic calculations for fluctuation-assisted tunnelling and thermal excitation. There is no evidence for superconductivity in resistance measurements on polyacetylene. The thermoelectric power of polyacetylene and other bulk organic conducting polymers indicates the absence of significant superconductivity arising from the conventional electron-phonon mechanism.

Synthesis and properties of polyacetylenes with salicylideneaniline groups

AbstractAcetylenes containing salicylideneaniline groups—N‐salicylidene‐3‐ethynylaniline (1), N‐(3‐t‐butylsalicylidene)‐3‐ethynylaniline (2), and N‐(3‐t‐butylsalicylidene)‐4‐ethynylaniline (3)—polymerized smoothly and gave yellow to red polymers in excellent yields when a rhodium catalyst was employed. Polymers with alkyl substituents on the aromatic rings [poly(2) and poly(3)] were soluble in CHCl3, tetrahydrofuran, and so forth, whereas the polymer without alkyl substituents [poly(1)] was insoluble in any solvent. N‐(3‐t‐Butylsalicylidene)propargylamine did not provide any polymer. Thermogravimetric analyses of the resultant polymers exhibited good thermal stability (To, onset temperature of weight loss > 300 °C). The ultraviolet–visible spectra of the polymers showed absorption maxima and cutoff wavelengths around 360 and 520 nm, respectively. The polymers exhibited largely Stokes‐shifted fluorescence (emission wavelength ≃ 550 nm) upon photoexcitation at 350 nm, which resulted from the photoinduced intramolecular proton transfer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2458–2463, 2002

Influence of organoiron compounds on properties of polyacetylenes prepared by phase-transfer dehydrochlorination of polyvinyl chloride

The influence of ferrocene and iron acetylacetonate additives on the chemical, magnetic, and electrophysical properties of thermolyzed and nonthermolyzed polyacetylenes prepared by phase-transfer dehydrochlorination of polyvinyl chloride was studied.

Synthesis and properties of polyacetylenes with adamantyl groups

Synthesis and properties of polyacetylenes with adamantyl groups

Synthesis and properties of polyacetylenes with adamantyl groups

Three disubstituted acetylenes with an adamantyl group—1-(p-adamantylphenyl)-2-chloroacetylene (ClpAdPA), 1-(p-adamantylphenyl)-1-propyne (pAdPP), and 1-(p-adamantylphenyl)-2-phenylacetylene (pAdDPA)—polymerized in good yields in the presence of MoCl5- or TaCl5-based catalysts. The highest weight-average molecular weights of poly(ClpAdPA), poly(pAdPP), and poly(pAdDPA) reached 3.6 × 105, 1.1 × 106, and 6.0 × 106, respectively. The polymers were yellow to white solids and completely soluble in toluene, chloroform, and so forth. These polymers thermally were fairly stable, and the onset temperatures of weight loss in air were over 360 °C. Poly(pAdPP) and poly(pAdDPA) provided free-standing films by solution casting, and their oxygen permeability coefficients (PO2) at 25 °C were 8.6 and 55 barrers [1 barrer = 1 × 10−10 cm3 · (STP) · cm/(cm2 · s · cm Hg)], respectively, which are relatively small compared to those of other substituted polyacetylenes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4546–4553, 1999

Spectroscopic properties of polyacetylene segments in copolymers

In this paper we present an extensive study of the optical properties of polyacetylene [$(\mathrm{CH}{)}_{x}$ and $(\mathrm{CD}{)}_{x}$] segments in copolymers by means of several spectroscopic techniques. They include UV-visible absorption, resonant Raman scattering, and photoinduced infrared absorption. A large variety of samples in either diblock or triblock copolymers, in general in the solid state, but also, in one particular case, in solution, are investigated. We show that the optical properties of these copolymers are strongly dependent on the distribution of conjugation lengths of segments in the different samples. A consistent model based on the vibrational and electronic properties of the polyacetylene conjugated segments and on a bimodal distribution is used to reproduce the band shapes observed in the UV-visible absorption, resonance Raman scattering, and photoinduced infrared-absorption spectra. The calculated structured shapes of the bands, and in particular the features in the low-frequency region of the photoinduced infrared absorption band in the different samples, are in very good agreement with the experimental data.

Influence of Molecular Structure and Morphology on the Transport Properties of Polyacetylene Studied by ESR

Influence of Molecular Structure and Morphology on the Transport Properties of Polyacetylene Studied by ESR

EPR in strongly irradiated polyacetylene

The influence of γ-irradiation on the paramagnetic properties of polyacetylene has been studied. The samples were exposed to γ-irradiation up to a dose of 3 MGy.

The Nonlinear Optical Properties of Polyacetylene within the Intermediate Exciton Formalism

ABSTRACTWithin the Singles-CI approximation, the perturbation theory expression for γ (the non-resonant third-order nonlinear optical susceptibility) contains a class of terms which correspond to (i) the creation of an s-type exciton (ii) a transition to a p-type exciton, and (iii) a return to the ground state through an s-type exciton. The contribution of these terms to γ is considered in the limit of an infinite chain of polyacetylene. The infinite chain limit is obtained by considering a ring of polyacetylene and allowing the ring size to go to infinity. The limit is approached using three methods, each of which reveals a different characteristic length of the system. The form of the excitons is found to be independent of ring size for rings which are larger than the size of the exciton.

Synthesis and properties of polyacetylenes with electron donor substituents

New anthracene- and carbazole-containing diacetylenes have been synthesized and subjected to solid phase polymerization, leading to corresponding polydiacetylenes having a polymer chain of ene-ine structure. Doping of the polydiacetylene with iodine depends on its degree of ordering and also on the nature of the electron donor substituent. It is established that there is a maximum on the excitation spectra for the photoconductivity of polyacetylene, located beyond the edge of the optical absorption fundamental. The “internal” doping of polyacetylene with iodine is described: on polymerization of the iodine-containing diacetylene, partial separation of iodine occurs, which results in doping of the polymer formed. The maximum on the excitation spectra for photoconductivity of polyacetylene, located in the region of the absorption of electron donor groups, is associated with “sensitized” photoconductivity, consisting in electron transfer from an excited electron donor substituent into the conductivity zone of the polydiacetylene chain.

Bipolar absorption of light in polyarylenephthalides

The idea of self-localized states in polymers, which are created in the polymers by introducing nor p-type impurities [i, 2], turned out to be very fruitful for explaining the properties of polyacetylene. The case of trans-polyacetylene with a degenerate ground state is, however, still unique, since most of the currently known conducting macromolecules do not have a degenerate ground state, for example, cis-polyacetylene, polyphenylene, polypyrrole, etc. Self-localized states of the polar type are realized in such polymers [3]; these states are accompanied by interesting physical phenomena: generation of local levels in the gap, photoluminescence with anomalous Stokes shift, absence of spin on the charge carriers, photostimulated absorption, etc. In polyaromatic systems the polarons are electrons or holes, surrounded by the deformed part of the polymer chain (quinoid structure). According to existing calculations the number of deformed rings ranges from four for a bipolaron to six for a polaron [4]. Such a polaron structure does not have anything in common with the structure of self-localized states in existing inorganic crystals. The most efficient methods for studying polaron states in polymers experimentally are optical and electrophysical methods.

Synthesis and Properties of Polyacetylene

Abstract This paper presents an introductory review on synthesis and properties of polyacetylene, a typical semiconducting and conducting organic polymer. Electrical conductivity of polyacetylene can be tailored by an appropriate chemical and/or electrochemical doping with electron accepting or electron donating reagents, spanning the range of insulators (10−12 S/cm) and metals (105 S/cm).