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Two novel poly(biphenylylacetylene)s (PBPAs) bearing achiral alkylphenyl groups at the 4'-position of the biphenyl pendant through ester linkers with different sequences were synthesized by the rhodium-catalyzed polymerization of the corresponding monomers. The influence of the alkylphenyl pendants and the ester sequences on the macromolecular helicity induction and subsequent static helicity memory was investigated. In addition, the chiral recognition ability as chiral stationary phases for high-performance liquid chromatography of the helicity-memorized PBPAs was also examined. Both polymers formed almost perfect right- and left-handed helical conformations through noncovalent chiral interactions with enantiomeric alcohols, and their induced macromolecular helicities were completely retained ("memorized") after removal of the helix inducer. A PBPA bearing a 4-n-butylphenoxycarbonyl pendant group with a static helicity memory showed a remarkably high chiral recognition ability toward a wide variety of chiral aromatics, including simple point chiral compounds, axially chiral biaryls, a chiral spiro compound, helicenes, and planar chiral cyclophanes, particularly under the reversed-phase conditions., (© 2021 Wiley Periodicals LLC.)

New hyper-cross-linked porous organic polymers (POPs) with a high content of pyridine segments (7.86 mmol pyridine g -1 ), and a micro/mesoporous texture are reported. The networks are achieved by the chain-growth homopolymerization of 2,6- and 3,5-diethynylpyridines. The pyridine segments form links interconnecting the polyacetylene main chains in these networks. The content of pyridine segments in the networks can be tuned by copolymerizing diethynylpyridines with 1,3-diethynylbenzene. The pyridine rings in the networks serve as base and hydrophilic centers for the sorption of CO 2 and water. The homopolymer pyridine networks are highly efficient in the low-pressure adsorption/desorption of CO 2 . This sorption mode is promising for the postcombustion removal of CO 2 from the fuel gas. The poly(3,5-diethynylpyridine) network exhibits high efficiency in capturing and releasing water vapor (determined capacity 376 mg g -1 at 298 K and relative humidity (RH) = 90% is one of the highest values reported for POPs) and is a promising material for the cyclic water harvesting from air. The reported networks are characterized by 13 C cross-polarization magic angle spinning NMR, thermogravimetric analysis, and N 2 adsorption/desorption and their efficiency in CO 2 and H 2 O capturing is discussed in relation to the content and type of incorporated pyridine segments., (© 2021 Wiley-VCH GmbH.)

Synthetic chiral helical polymers have achieved impressive progress in past few decades. Unfortunately, how to construct chiral helical polymer-derived functional materials still remains highly challenging. The present contribution reports an unprecedented, one-step strategy for judiciously combining chiral helical polymer with graphene to construct chiral hybrid foams. Graphene oxide (GO), ascorbic acid (L-AA), Rh catalyst, and an achiral acetylenic monomer bearing phenylboronic acid group are mixed in an aqueous dispersion. Under mild conditions, the monomer underwent polymerization; meanwhile GO transforms into reduced graphene oxide (RGO) which in situ self-assembles to construct a 3D porous structure. Herein, L-AA simultaneously plays double roles: 1) working as a chiral source for the monomer to undergo helix-sense-selective polymerization or transferring its chirality to the polymer chains via forming borate structure; and 2) working as a reducing agent for reducing GO. The preparation strategy combines four processes into one single step: monomer polymerization, chirality transfer, reduction of GO, and RGO's self-assembly. The eventually obtained chiral hybrid foams demonstrate advantages of porous structure, chirality, and reversible borate functional groups. The established preparation strategy promises a potent platform for conveniently constructing advanced chiral polymeric materials and even chiral hybrids starting from achiral monomers., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Recent developments in the synthesis of substituted polyacetylenes have considerably benefitted from advancements in organometallic catalysis; however, most important developments rely on the advent of Rh-catalyzed living polymerizations. The latter not only allow the tailoring of well-defined degrees of polymerization with low and narrow polydispersity but also enable access to stereochemical well-defined cis-transoidal polymers with a helical structure. These novel polymers open new avenues for application in photonics and electronics. Rh-catalyzed living polymerizations are mild and concise metal-catalyzed polymer syntheses that not only allow for the decoration of sidechains with multiple functionalities, including chiral units, but also enable enantioselective induction of helical chirality, memory of chirality, well-defined copolymerization, and end-group functionalization at both termini. This review summarizes recent developments in metal-catalyzed syntheses of substituted polyacetylenes, with a special focus on Rh-catalyzed living polymerizations. [ABSTRACT FROM AUTHOR]

The measurement of anisotropic residual dipolar couplings (RDCs) parameters for the structure elucidation of organic molecules relies on suitable alignment media. Employment of self‐assembled liquid crystalline systems to create anisotropic alignment can be an effective way to realize aligned samples and acquire RDCs. This Mini‐review highlights the recent advances on amino acid‐based helical polymers and supramolecular oligomers forming rigid, rod‐like structures that aggregate into ordered liquid crystalline phases, including amino acid‐based helical polyisocyanides, polyacetylenes, polypeptides, and oligopeptides assembled alignment media. The methodology for the determination of anisotropic liquid crystals is briefly discussed, and a summary of recent research progress in the enantiodifferentiation of helical polymers aligned media is followed. In addition, the self‐assembled mechanism of oligopeptides and their RDCs structural analysis are also described. [ABSTRACT FROM AUTHOR]

Helical polymers have attracted a great deal of attention and been extensively investigated due to their various applications. One of the most important applications of helical polymers is chiral recognition and resolution of enantiomers for the reason that a pair of enantiomers is commonly with different physiological and toxicological behaviors in biological systems. Helical polymers usually present unexpected high chiral recognition ability to a variety of racemic compounds. What's more, the chiral recognition and resolution abilities of the system are dependent on the highly ordered helical structures of the helical polymers. This mini review mainly focuses on the recent progress in chiral recognition and resolution based on helical polymers. The synthetic methodology for helical polymers is firstly discussed briefly. Then recent advances of chiral recognition and resolution systems based on helical polymers, especially polyacetylenes and polyisocyanides, are described. We hope this mini review will inspire more interest in developing helical polymers and encourage further advances in chiral-related disciplines. [ABSTRACT FROM AUTHOR]

Artemdubosides A-E (1–5), the first examples of natural polyacetylenes substituted by 6'- O -crotonyl β- glucopyranoside, and artemdubosides F-G (6–7) that were two unusual polyacetylenes featuring a 6'- O -acetyl β- glucopyranoside moiety, were isolated from Artemisia dubia var. subdigitata. Their structures were elucidated based on the spectral data including HRESIMS, UV, IR, 1D and 2D NMR, and ECD calculations. Antihepatoma assay suggested that compound 1 exhibited activity against HepG2, Huh7, and SK-Hep-1 cells with inhibitory ratios of 77.1%, 90.8%, and 73.1% at 200.0 μM, respectively. [Display omitted] • Artemdubosides A-G (1 – 7) were isolated from Artemisia dubia var. subdigitata. • Compounds 1 – 5 represented the first examples of natural polyacetylenes substituted by 6′-O-crotonyl β-glucopyranoside. • Compounds 6 – 7 represented the first examples of natural polyacetylenes substituted by 6′- O -acetyl β-glucopyranoside. • Compound 1 showed activity against HepG2, Huh7, and SK-Hep-1 cells at 200.0 μM. [ABSTRACT FROM AUTHOR]

Conductive organic polymers are most commonly generated from the oxidation or reduction of conjugated polymers. Although such conjugated polymers are typically viewed as modern materials, the earliest examples of these polymers date back to the early 19th century. The modern era of conjugated polymers began with the first reports of their conductive nature in the early 1960s. However, it was advances in the 1970s that brought particular focus to these materials with the first example of conductivity values in the metallic regime, for which the 2000 Nobel Prize in Chemistry was awarded to Hideki Shirakawa, Alan MacDiarmid, and Alan Heeger. Unfortunately, the historical narrative of these polymers is currently quite muddled in the primary literature, with various inaccuracies commonly propagated. In an effort to present a more accurate account as a resource for the field, the present report will review the first 150 years of the four primary parent polymers-polyaniline, polypyrrole, polyacetylene, and polythiophene, from their early origins in 1834 to their rapid development in the mid-1980s. [ABSTRACT FROM AUTHOR]

The longitudinal polarizability, αxx, and second hyperpolarizability, γxxxx, of polyacetylene are evaluated by using the coupled perturbed Hartree-Fock/Kohn-Sham (HF/KS) scheme as implemented in the periodic CRYSTAL code and a split valence type basis set. Four different density functionals, namely local density approximation (LDA) (pure local), Perdew-Becke-Ernzerhof (PBE) (gradient corrected), PBE0, and B3LYP (hybrid), and the Hartree-Fock Hamiltonian are compared. It is shown that very tight computational conditions must be used to obtain well converged results, especially for γxxxx, that is, very sensitive to the number of kvector points in reciprocal space when the band gap is small (as for LDA and PBE), and to the extension of summations of the exact exchange series (HF and hybrids). The band gap in LDA is only 0.01 eV: at least 300 kvector points are required to obtain well converged total energy and equilibrium geometry, and 1200 for well converged optical properties. Also, the exchange series convergence is related to the band gap. The PBE0 band gap is as small as 1.4 eV and the exchange summation must extend to about 130 Å from the origin cell. Total energy, band gap, equilibrium geometry, polarizability, and second hyperpolarizability of oligomers -(C2H2)m-, with m up to 50 (202 atoms), and of the polymer have been compared. It turns out that oligomers of that length provide an extremely poor representation of the infinite chain polarizability and hyperpolarizability when the gap is smaller than 0.2 eV (that is, for LDA and PBE). Huge differences are observed on αxx and γxxxx of the polymer when different functionals are used, that is in connection to the well-known density functional theory (DFT) overshoot, reported in the literature about short oligomers: for the infinite model the ratio between LDA (or PBE) and HF becomes even more dramatic (about 500 for αxx and 1010 for γxxxx). On the basis of previous systematic comparisons of results obtained with various approaches including DFT, HF, Moller-Plesset (MP2) and coupled cluster for finite chains, we can argue that, for the infinite chain, the present HF results are the most reliable. [ABSTRACT FROM AUTHOR]

If their thermal conductivity can be lowered, polyacetylene (PA) and polyaniline (PANI) offer examples of electrically conducting polymers that can have potential use as thermoelectrics. Thermal transport in such polymers is primarily influenced by bonded interactions and chain orientations relative to the direction of heat transfer. We employ molecular dynamics simulations to investigate two mechanisms to control the phonon thermal transport in PANI and PA, namely, (1) mechanical strain and (2) polymer combinations. The molecular configurations of PA and PANI have a significant influence on their thermal transport characteristics. The axial thermal conductivity increases when a polymer is axially stretched but decreases under transverse tension. Since the strain dependence of the thermal conductivity is related to the phonon scattering among neighboring polymer chains, this behavior is examined through Herman's orientation factor that quantifies the degree of chain alignment in a given direction. The conductivity is enhanced as adjacent chains become more aligned along the direction of heat conduction but diminishes when they are orthogonally oriented to it. Physically combining these polymers reduces the thermal conductivity, which reaches a minimum value for a 2:3 PANI/PA chain ratio. [ABSTRACT FROM AUTHOR]

The static longitudinal linear polarizability (α) and second order hyperpolarizability (γ) for neutral and charged, closed- and open-shell trans-polyacetylene (PA) chains C2nH2n+2, C2n-1H2n+1, C2n-1H2n+1+, C2nH2n+2+, and C2nH2n+22+ are systematically investigated and compared. The polarizabilities are calculated within the Pariser-Parr-Pople model, and the electron correlation effect is included through density matrix renormalization group. It turns out that for both α, and γ, two neutral PA chains C2nH2n+2 and C2n-1H2n+1 give similar values, while both singly charged and doubly charged systems present significantly larger magnitude of α and γ values than the two neutral chains. The two singly charged PA chains C2n-1H2n+1+ and C2nH2n+2+ give more apparent nonlinear optical responses than doubly charged case C2nH2n+22+ and both present negative second order hyperpolarizabilities for short to medium sized oligomers. The sign inversion of γ values in singly charged PA molecules is anticipated to take place at the much longer length than ever observed due to the significant effects of electron correlation and geometry. [ABSTRACT FROM AUTHOR]

We have performed periodic restricted Hartree-Fock/6-31G** and B3LYP/6-31G** density functional theory calculations on Li-doped trans-polyacetylene at various dopant concentrations, using C2mH2mLi2 unit cells (m=7-14). Except for maintaining P1 rod symmetry the geometry was completely optimized for both uniform and nonuniform doping structures. In addition to geometry we obtain atomic charges, along with soliton formation and dopant binding energies, as well as band structures and densities of states. A thorough analysis of the band structure and density of states, as a function of dopant concentration, is presented. We also characterize the complex nature of the binding interaction between Li and the polyacetylene chain. [ABSTRACT FROM AUTHOR]

Since its discovery in 1977, a number of quantum chemical calculations have been attempted to simulate the metallic state of highly doped trans-polyacetylene. These simulations have focused on the possible closure of the band gap at high doping level due to a charge-induced elimination of Peierls distortion; however, conclusive demonstration of a metallic state has not been achieved. The present study presents density functional theory calculations of the band structure of highly doped trans-polyacetylene with explicit inclusion of the metal atoms in a one-dimensional periodic structure. The results indicate (i) small lattice dimerization, i.e., remnant of Peierls distortion exists even in the heavily doped trans-polyacetylene sample, (ii) charge induced closure of the Peierls gap is not a necessary condition to arrive at a metallic state in such systems, and (iii) electronic correlation, as described at the density functional theory level, with a charge induced small Peierls distortion is sufficient to achieve metallic state of highly doped n-type trans-polyacetylene even in one dimension. Furthermore, comparison of functionals that include differing degrees of electron correlation suggest that correlation promotes formation of the metallic state. [ABSTRACT FROM AUTHOR]

The calculation of the bond-length alternation (BLA) in trans-polyacetylene has been chosen as benchmark to emphasize the effect of the self-interaction error within density-functional theory (DFT). In particular, the BLA of increasingly long acetylene oligomers has been computed using the Mo\ller-Plesset wave-function method truncated at the second order and several DFT models. While local-density approximation (LDA) or generalized gradient corrected (GGA) functionals strongly underestimate the BLA, approaches including self-interaction corrections (SIC) provide significant improvements. Indeed, the simple averaged-density SIC scheme (ADSIC), recently proposed by Legrand et al. [J. Phys. B 35, 1115 (2002)], provides better results for the structure of large oligomers than the more complex approach of Krieger et al. [Phys. Rev. A 45, 101 (1992)]. The ADSIC method is particularly promising since both the exchange-correlation energy and potential are improved with respect to standard LDA/GGA using a physically appealing correction, through a different route than the more popular approach through the Hartree-Fock exchange inclusion within the hybrid functionals. [ABSTRACT FROM AUTHOR]

We have investigated the geometries as well as the longitudinal dipole moment (μ), polarizability (α), and first hyperpolarizability (β) of polymethineimine oligomers using different approaches [Hartree–Fock (HF), second-order Møller–Plesset (MP2), and hybrid density functional theory (DFT) methods (B3LYP and PBE0)] for evaluating the geometries and the nonlinear optical properties. It turns out that (i) HF and the selected DFT methods provide the incorrect sign for β of short and medium size oligomers. (ii) The B3LYP and PBE0 electron correlation correction are too small for μ, too large for α, and for some oligomer lengths, they are in the wrong direction for β. (iii) On the contrary to polyacetylene, the hybrid-DFT geometries are in poor agreement with MP2 geometries; the former showing much smaller bond length alternations. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The formation of biexcitons in conjugated polymers is examined within the Pariser-Parr-Pople (PPP) model of polyacetylene. The calculations are done using a scattering formalism that provides a size-consistent description of excited states containing both single and double electron-hole pair excitations. The excited-state absorption spectrum from the 1 [SUP1]B[SUBu] exciton state was calculated and examined for signatures of biexciton formation. Calculations were performed on polyenes with up to 9 unit cells, and on long chains using periodic boundary conditions. While polyenes with 7 to 31 unit cells exhibit states with some of the features expected for biexcitons, such states are not seen in the limit of long chains. This suggests that, within the two-band model considered here, exciton-exciton interactions are not of sufficient strength to lead to biexciton formation in the limit of long chains, and that their presence in shorter chains is due to confinement effects. In the long-chain limit, transitions are found to states consisting of overlapping electron-hole pairs, but these states have energies above that required to make two free excitons. These states may result from scattering resonances between excitons. [ABSTRACT FROM AUTHOR]

We present first-principles simulations of cis-polyacetylene fragments under tensile stress. The barrier of a cis-trans isomerization of conjugated carbon–carbon double bonds is lowered by tensile stress. However, it does not seem likely that the barrier can be sufficiently reduced to achieve a cis-trans isomerization in an atomic force microscopy experiment. In particular, the transition state of the reaction cannot be converted into a stable or metastable minimum by mechanical stress. We devise a general model for the calculation of bond rupture probabilities. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents the formalism for the correction of the band structure for correlation effects of polymers in the framework of a localized orbital approximation using a quasiparticle model. Use of an ab initio framework Moller-Plesset perturbation theory in second order; Water stack; Hydrogen bonded water chain; Polyacetylene.

Nonlinear optical properties of the linear polyenes C4H6 through C30H32 are calculated at frequencies below the first resonance using ab initio time-dependent Hartree–Fock theory. The results are used to determine accurate values for the infinite polymer, polyacetylene, by means of a new extrapolation method. Dispersion coefficients describing the low frequency behavior are obtained for the largest oligomer. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

It is shown that the low frequency collective modes of quasilinear polymers can contribute to the vibrational polarizability and hyperpolarizability despite the fact that their infrared or Raman intensity vanishes in the infinite chain limit. The most significant of these modes are characterized and the dynamic vibrational nonlinear optical (NLO) properties are obtained, at the doubly harmonic Hartree–Fock level of approximation, from static field calculations on polyacetylene as well as polyyne, polysilane, and polyethylene. Comparison is made to a pair of unit cell modes, one Raman-active and the other infrared-active, that are expected to generate a large vibrational hyperpolarizability. The combined effect of the collective and unit cell vibrations is potentially of considerable importance for the enhancement of NLO properties. Further studies are suggested to exploit this potential. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Ab initio restricted Hartree–Fock 6-31G calculations are reported for the static longitudinal hyperpolarizability of the linear polyenes C4H6 through C44H46. Using a new extrapolation technique the infinite chain value in polyacetylene is determined with an accuracy similar to that achieved for small molecules. This is the first in a series of articles leading to a comprehensive ab initio treatment for the nonlinear optical properties of conjugated polymers. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Quantum chemical calculations are performed to theoretically study the interaction between low work function metal atoms and trans-tetradecaheptaene, an extended model molecule for π-conjugated polymers. We present characterizations of metal/polyene complexes obtained by the local spin density method. The results show that charge transfer reactions occur for Na and Ca and the formation of a covalent bond for Al. Mg atoms, however, are found not to react significantly with π-conjugated systems. Differences in the bonding mechanism between the metals are discussed and the theoretical density of valence states are compared to experimental photoelectron spectroscopy (UPS) data. The results demonstrate that the local spin density method can be successfully used to interpret valence UPS spectra from early stages of metal/π-conjugated interface formation. [ABSTRACT FROM AUTHOR]

The interactions between aluminum atoms and model molecules representing trans-polyacetylene are studied quantum chemically by a local density functional method. We focus on the chemical and electronic structure of the organoaluminum complexes. Special emphasis is put on a comparison between results at the local spin density approximation and ab initio Hartree–Fock levels. In unmetallized polyenes, the density functional method provides a very good description of the carbon–carbon bond lengths of conjugated systems; in the case of hexatriene, it reproduces the bond dimerization in very good agreement with experimental measurements. Upon metallization, a strong covalent interaction between aluminum and carbon is found. The Al–C bond formation induces an interruption of the bond alternation pattern and reduces the π-conjugation in the oligomer, in qualitative agreement with photoelectron spectroscopy data and previous theoretical results at the Hartree–Fock level. Notably, the π-electron levels in the organoaluminum complexes maintain delocalization. In contrast to Hartree–Fock results where an aluminum atom binds to a single carbon, the interactions calculated with the local spin density approximation lead to (i) formation of multicenter aluminum–carbon bonding; (ii) near planarity of the polyene molecule; and (iii) a lower degree of charge transfer from the metal atom to the polymer. [ABSTRACT FROM AUTHOR]

Much of the theoretical effort to understand the mechanism of optical nonlinearity in π-conjugated polymers has been focused towards explaining the early observation of only two resonances in the third harmonic generation spectrum of trans-polyacetylene. A recent theory of third order optical nonlinearity predicts three, instead of two, resonances, with their intensities decreasing with increasing frequencies. This is a fundamental difference between the band and the exciton pictures of π-conjugated polymers. Very recent experimental results obtained with cis-polyacetylene, as well as earlier experiments on two blue forms of polydiacetylenes, are in complete agreement with this prediction. An isolated single strand of cis-polyacetylene should exhibit exciton behavior. We briefly discuss the latest experimental results for trans-polyacetylene. [ABSTRACT FROM AUTHOR]

We report the results of initial measurements on two derivatives of poly(1,6-heptadiyne): a di-ketone (PHDK) and a di-ester (PHDE). Both polymers have the degenerate ground state of poly(1,6-heptadiyne); both are soluble in common organic solvents. Electron spin resonance (ESR) measurements on pristine samples place an upper limit of 10-4 spins per monomer for both polymers. At low doping levels, we observe a single doping-induced absorption band at an energy of approximately half the π-π* gap, Eg/2; the doping-induced spectral features were fully reversible. In situ ESR and absorption measurements during doping show that charge is stored predominantly in spinless charge carriers. Because of the inequivalent carbons on the conjugated backbone, the results are discussed in terms of the (A=B)n polymer. Both PHDK and PHDE are relatively stable in air; the strength of the π-π* absorption band is nearly constant over a period of a week in air, decreasing to 80% of the initial value. [ABSTRACT FROM AUTHOR]

A Herzberg–Teller expansion for π electrons in the ground state of conjugated polymers identifies quadratic electron–phonon (e–ph) contributions and suggests a σ+π reference force field F0 based on butadiene. Linear response theory then fixes linear e–ph coupling constants for the Raman shifts in polyacetylene (PA) due to π-electron fluctuations. The same coupling constants and the known isotopic dependences of the reference accurately give the Raman frequencies of (CD)x and (13CH)x; with a different susceptibility, F0 and the coupling constants also account for Raman modes of polyenes and for photo- or dopant-induced infrared modes of PA and its isotopes. We develop a general phenomenological approach for identifying modes coupled to π-electron fluctuations and show that both CCC and CCH bends are weakly active in PA. Linear and quadratic e–ph coupling constants and various susceptibilities are related to π-electron Hamiltonians, primarily to Hückel models and to Coulomb interactions in the Pariser–Parr–Pople model. We also relate our approach to previous PA models with linear e–ph coupling or modified force fields. [ABSTRACT FROM AUTHOR]

Discusses a study that fabricated the first solid-state heterojunction device involving two conducting organic polymers from polyacetylene and p-doped poly(N-methylpyrrole) (PNP). Modification of the electronic properties of the interface in a solid-state device; Polymerization of poly(N-methylpyrrole), (PNP), carried out electrochemically under argon; Photoresponse of device III under irradiation of a tungsten lamp.

Results from a set of minimum energy calculations performed for the Su Schrieffer Heeger Hamiltonian for trans-polyacetylene are presented. We fix the occupation numbers of the electronic states and look for the bond geometry which minimizes the total energy. The usual nonlinear solutions (polarons, solitons) are recovered for appropriate sets of occupation numbers of the electronic states. We study the spectrum of excited states and the properties of the model in the case of arbitrary doping. The situation where the original SSH Hamiltonian is modified in such a way as to account for the intrinsic periodicity of the monomeric units of conjugated polymers without a degenerate ground state is also examined. [ABSTRACT FROM AUTHOR]

Conformational disorder plays an important role in determining the electronic properties of conjugated polymers. To obtain a better theoretical description of the role and extent of conformational disorder, we derive the π electron correlation length and the bond correlation length in terms of the effective torsional potential and geometry of the conjugated polymer chains. These quantites are related to the conjugation lengths and persistence lengths of the chain, which are computed for polyacetylene, polydiacetylene, polythiophene, and polypyrrole. In spite of uncertainties in the torsional potential parameters for these materials, good qualitative agreement is found between experiment and theory. [ABSTRACT FROM AUTHOR]

Samples of trans-polyacetylene, (CH)x, were doped with the magnetic ion, FeCl-4, by immersion in nitromethane solutions of FeCl3. The resulting dopant levels ranged over two orders of magnitude. ESR spectra and spin–lattice relaxation times, T1, were measured for the undoped polymer and lightly doped polymer over the temperature range 1.5–120 K. The ESR spectra of trans-(CH)x lightly doped (<1 mol % Fe-4 ) with FeCl-4 exhibit a narrow (ΔH≊5–10 G at 4.2 K) g=2.003 signal which decreases in relative amplitude with increasing dopant level, and broad signals at g=2 (ΔH≊500 G), which increases with increasing dopant level, and at g=4.3 (ΔH≊200 G). The narrow signal is the intrinsic trans-(CH)x signal; the broad signals are attributable to iron. T1 for the narrow signal is approximately one-half of the value of undoped trans-(CH)x at 4.2 K. dc susceptibilities for all of the doped samples were measured over the temperature range of 1.5–300 K. The magnetically doped samples all exhibit Curie law behavior, and an analysis of the magnetization data yields an effective moment, Jeff, equal to 2.77, close to the value 5/2 expected for Fe(III). [ABSTRACT FROM AUTHOR]

The local space approximation (LSA) is applied to neutral and positive solitons, S0 and S+, in polyacetylene. In the treatment presented here a solitonic fragment is embedded between two finite polyene side chains. On the basis of INDO model calculations we conclude that electronic structure properties of the infinite system can be represented with chemical accuracy by a C9 solitonic fragment bonded to C4 or C6 side chains in S0 and C10 side chains in S+. The local space for each bond is defined by a C6H4 interaction complex augmented, for S+, with the π orbital of one additional carbon on the solitonic fragment and three additional carbons on the side chain. These results establish the feasibility of using the LSA method to carry out accurate ab initio Hartree–Fock and CI calculations based on a finite chain model for the soliton. [ABSTRACT FROM AUTHOR]

For different chains of trans-polyacetylene with various substituents the equations of motion of the coupled electron–phonon system are integrated within the Su–Schrieffer–Heeger model. NH+, N, and O+ as isoelectronic substitutions for a CH group as well as the effect of an NH and a CO group are investigated. The calculations for the time evolution of an end-generated kink show that neutral solitons can pass a nitrogen atom and an oxygen ion, but not an NH+, NH, or CO group. The negatively charged soliton is not able to pass any of the investigated substitutions. The CO unit, which is of special interest in the light of recent experimental results for acetylene–CO–copolymers with similar properties as trans-polyacetylene, represents a trap for both neutral and negatively charged kinks and a repulsive barrier for a positively charged kink. The limitations of the soliton model are discussed. [ABSTRACT FROM AUTHOR]

ABSTRACT: Two novel fluorene functionalized polyacetylenes with different conjugation bridge architectures (stilbene and azobenzene), poly[2‐[4‐vinyl‐4′‐(N‐methyl, N‐ethyl‐yl propargyloxy) phenyl azo]‐9,9‐dioctylfluorene] (PC1), poly[2‐[4‐vinyl‐4′‐(N‐methyl, N‐ethyl‐yl propargyl group) stilbene ethenyl]‐9,9‐dioctylfluorene] (PC2), were designed and prepared through using [Rh(nbd)Cl]2‐Et3N as the catalysts, respectively. These polymers are soluble in common organic solvents, such as toluene, chloroform, 1,2‐dichloromethane, and tetrahydrofuran, which their structures and properties were systematically characterized by means of Fourier transform infrared spectroscopy, nuclear magnetic resonance, elemental analyses, UV–vis, photoluminescence, thermogravimetric analysis, gel permeation chromatography, and Z‐scan technique. The optical limiting properties were investigated at 780 nm with 450 fs laser pulses. Remarkably, it is expected that, by incorporation of fluorene into functional polyacetylene has endowed the resultant polymers with well optical limiting properties and thermal stability. Additionally, the nonlinear optical properties of functionalized polyacetylenes were significantly affected by different molecular structure of conjugated bridge of substituted group. The polyacetylenes with azobenzene (PC2) conjugated bridge displaying well two‐photon absorption cross‐sections of 3950 cm/GM (2010 cm/GM for PC1 containing stilbene), owning to stronger π‐conjugated chromophores of objective polymer and intramolecular charge transfer effect. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46100. [ABSTRACT FROM AUTHOR]

The electronic transport properties of the carbon atomic chain in combination with a stand-up attached polyacetylene (C $$_n$$ H $$_n$$ + 1) molecule sandwiched between two zigzag graphene nanoribbon electrodes, were investigated based on the density-function theory and the nonequilibrium Green's functions approach. Our calculation shows that the transport behavior is sensitive to the number of carbon atoms on the C $$_n$$ H $$_n$$ + 1 chains. Specifically, we demonstrate that the transport properties of even- n C $$_n$$ H $$_n$$ + 1 devices behave much stronger than the odd ones; in addition, the odd- n C $$_n$$ H $$_n$$ + 1 devices provide well-matched resonance transport channels between the transverse carbon chain and stand-up attached C $$_n$$ H $$_n$$ + 1 chains, which induces the isolated transmission peak at the Fermi level. So an abnormal even-odd oscillation in conductance in terms of the number of carbon atoms on C $$_n$$ H $$_n$$ + 1 chains can be found. On the other hand, the striking negative differential resistance behaviors appear in the proposed devices. The mechanisms are analyzed and revealed by the local density of states around the Fermi level at zero bias, with the evolution of the molecular projected self-consistent Hamiltonian associated with the transmission spectrum under different applied bias. [ABSTRACT FROM AUTHOR]

Six undescribed polyacetylenes Atracetylenes A-F (1 – 6) and three known ones (7 – 9) were isolated from the rhizomes of Atractylodes macrocephala Koidz.. The comprehensive interpretation of NMR, HR-ESI-MS, DP4+ calculations, and electronic circular dichroism (ECD) calculations resulted in the elucidation of their structures and absolute configurations. The anti-colon cancer activities of (1 – 9) were evaluated by assaying the cytotoxicity and apoptosis on CT-26 cell lines. Notably, 5 (IC 50 17.51 ± 1.41 μM) and 7 (IC 50 18.58 ± 1.37 μM) exhibited significant cytotoxicity, and polyacetylenes 3 – 6 showed excellent abilities to promote apoptosis of CT-26 cell lines by Annexin V-FITC/PI assay. The results demonstrated that the polyacetylenes in A. macrocephala may be prospective for the treatment of colorectal cancer. [Display omitted] [ABSTRACT FROM AUTHOR]

We report complete vibrational spectra, including IR and Raman intensities of C22H24, C21H+23, and C12H+14 +, as models for pure and doped polyacetylene. The results provide definitive evidence for charged solitonic rather than bipolaronic defects. [ABSTRACT FROM AUTHOR]

This perspective briefly introduces the status quo of various aspects of research on substituted polyacetylenes along with representative references. The research field of substituted polyacetylenes includes polymer design, polymer synthesis, polymer structure and properties, and polymer functions. Developments of well-defined catalysts and unique precision structures of polymers are challenging subjects in polymer design and synthesis. Elucidation of unique properties of substituted polyacetylenes has long drawn much attention and is closely related to their optoelectronic and stimuli-responsive functions under intensive research. This special issue features relatively short review articles of the cutting-edge research of substituted polyacetylenes by experts of the fields. [ABSTRACT FROM AUTHOR]

ABSTRACT A new trapezoidal functional polyacetylene with broadband absorption from the visible to the near infrared and excellent thermal stability was effectively prepared by molecular design and a controllable strategy. It is completely soluble in common organic solvents because the 6-ethynyl-2-methylquinoline copolymerized with phenylacetylene. The absorption spectrum can be effectively adjusted by controlling the ratio of semi-squaraine and squaraine in the process of preparation. Interestingly, it was found that the improvement of thermal stability of the target product may originate from the synergy of the shielding effect of the quinoline ring to the main chain and the strong interactions between squaraine groups. The formation mechanism of the broadband absorbance properties was studied through an online spectrum tracking method. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44096. [ABSTRACT FROM AUTHOR]

Chiral columns formed by a helical cis-polyphenylacetylene (PPA) derivative P1 are reversibly switched during a phase transition between two chiral columnar phases: the frustrated Φh3D-SL phase containing four chains at low temperature and a hexagonal columnar phase Φh at high temperature, accompanied by a simultaneous conformational change. The helix-helix transition along the PPA backbone during the Φh3D-SL-Φh transition makes the uniaxially oriented P1 capable of reversibly and reproducibly elongating (132 %) upon heating and contracting upon cooling, exhibiting the behavior of a two-way shape actuator. [ABSTRACT FROM AUTHOR]

An ionic polyacetylene was prepared via the non-catalyst polymerization of 2-ethynylpyridine using 1,6-dibromohexane. The polymerization proceeded in homogeneous manner to give a high yield of polymer (88%). The polymer structure was characterized by such instrumental methods as IR, NMR, and UV-visible spectroscopies to have the conjugated polymer backbone with the designed bromohexylpyridinium substituents. The absorption spectrum exhibits several absorption peaks such as 289, 330, 387, and 489 nm and band gap was 2.44 eV. The photoluminescence spectrum of polymer showed the maximum peak at 550 nm. Overall redox current shape and values were very stable in the range of −1.5 V to 1.5 V under up to 50 cylcles. Oxidation and reduction were started at 0.35 and −0.6 V. [ABSTRACT FROM AUTHOR]

Thermophysical and mechanical properties of two conjugated polymers, poly( p-phenylene vinylene) (PPV) and polyacetylene (PA), are predicted using molecular dynamics simulations and compared with results obtained from differential scanning calorimetry, nanoindentation, and dynamic mechanical analysis experiments. Glass transition temperature ( Tg) is calculated from the changes in the slopes of the specific volume versus temperature and cohesive energy density versus temperature plots, obtained from constant pressure and constant temperature simulations (NPT ensemble). The effects of temperature on the torsion angle distributions and characteristic ratio are analyzed. PPV is found to have a Tg of 416 ± 8 K. PA does not exhibit a glass transition in the temperature range of 120 to 500 K. Using the static deformation method, the values of Young's modulus are calculated to be 1.81 ± 0.34 GPa for PA and 9.20 ± 0.57 GPa for PPV at 298 K. These values are in good agreement with the experimental measurements, validating the suitability of these techniques in the prediction of the polymer properties. [ABSTRACT FROM AUTHOR]

Functional materials derived from synthetic helical polymers are attracting increasing interest. Helically substituted polyacetylenes (HSPAs) are especially interesting as typical artificial helical polymers. In recent years, we designed and prepared a series of functional materials based on HSPAs and inorganic materials. The target is to establish some novel hybrid materials that combine the superior properties of both. The examined inorganic materials include silica, graphene, and magnetic Fe3O4 nanoparticles. Such new functional materials hold great promise and are expected to find practical applications, for instance, as chiral absorbents, chiral sensors, chiral selectors for inducing enantioselective crystallization, chiral catalysts towards asymmetric catalysis, and chiral carriers for enantioselective release. The Personal Account summarizes our major achievements in preparing optically active hybrid materials. We hope it will speed up progress in chiral-related research areas. [ABSTRACT FROM AUTHOR]

A novel boron-containing carbon precursor with high yield and crystallisation (i.e., boron-containing arylacetylene polymers (PBAs)) was synthesised by the polycondensation reaction between arylethynyl Grignard reagent and boron trichloride-pyridine complexes. The precursor structures, curing behaviour and carbonisation were investigated. An aromatic ring is formed by polymerisation of a triple bond during the curing reaction of PBAs, which resulted in a significantly higher char yield (i.e., as high as nearly 80%) at 900 °C for the cured PBAs. The boron is chemically bonded to carbons of the PBAs precursor, which reduces the activation energy of the dissociation and rearrangement of the carbon–carbon bonds and promotes the change in the hybridisation of carbon atoms from sp 3 to sp 2 . [ABSTRACT FROM AUTHOR]

Copolymerization of propargylether having antipyrine group (PT) and N-( tert-butoxycarbonyl)- l-valine- N-propargylamide (LA) was conducted with (nbd)Rh+[ η6-C6H5B−(C6H5)3] as a catalyst to obtain novel antipyrine-functionalized chiral copolymer. The controllable secondary structure of the copolymers by different unit ratio or solvent environment led to a controlled fluorescence of the side-chain antipyrine. Poly(LA88- co-PT12) exhibited a large specific rotation and a circular dichroism (CD) signal, while it emitted very stronger fluorescence. From CD and ultraviolet-visible spectra, the regular structure of poly(LA88- co-PT12) was destroyed, and the random coil was formed with temperature increase. The helical conformation of poly(LA75- co-PT25) disappeared by the addition of MeOH to CHCl3 solution, while the fluorescence signal also became weaker than in CHCl3 solution. It is suggested that the copolymer conformation much influenced the performance of chromophores. In the present study, the helix conformation could induce fluorescence enhancement. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We report the recent progress in the preparation of functional poly(disubstituted acetylene)s ( PDSAs) through post-polymerization modification routes. The metathesis polymerization of disubstituted acetylene monomers activated by Mo/ W- Sn complex catalysts, which do not tolerate highly polar functionalities, was assumed to be a key step in the polymer synthetic procedures. We and other groups have explored several approaches to prepare PDSAs with latent reactive functionalities, which are inactive to Mo/ W- Sn complex catalysts but can be used as highly reactive sites for post-polymerization modification. Click chemistry, Michael-type addition reactions, the use of activated esters and other strategies are demonstrated by recently published examples. These works indicate that post-polymerization modification is an efficient route to the synthesis of various functional PDSAs. [ABSTRACT FROM AUTHOR]

ABSTRACT Metathesis polytricyclononenes were synthesized via ROMP polymerization in the presence of the 1-st generation Grubbs catalyst and their gas-transport properties were studied for the first time. The aim of this work was to evaluate the influence of Me3E-groups (E = C, Si, Ge) on gas permeation parameters of ROMP materials. New metathesis poly(3- tert-butyltricyclononene-7) and poly(3-trimethylgermyltricyclononene-7) were obtained with high yields (up to 95%) and high-molecular weights ( Mw∼3-7×105 g mol−1). The glass transition temperatures of the ROMP polytricyclononenes with Me3E-groups decreased when E was changed from C to Si and then to Ge. It was shown that the polytricyclononene containing Me3Si-groups has the highest gas permeability while the polytricyclononene containing Me3C-substituents has the lowest gas permeability. In addition, the gas permeation parameters were estimated for ROMP Me3Si- and Me3Ge-substituted polytricyclonona-3,7-dienes. So the influence of the second double bond in the monomer units on the permeability of the polymers obtained was studied. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41395. [ABSTRACT FROM AUTHOR]