INFLUENCE OF BACKBONE RIGIDITY ON THE LIQUID CRYSTALLINITY OF MESOGEN-CONTAINING POLYACETYLENES

Two acetylene polymers containing cyanobiphenyl-based mesogens,poly { 10-[ （（4’- cyano-4-biphenylyl ） oxy ） carbonyl] - 1 -decyne } （PA8CN ）, which has a relativelyfiexible polyalkyne backbone, and poly {[4-（（（12-（（4’-cyano-4-biphenylyl）oxy）dodecyl）oxy）carbonyl） phenyl]-acetylene} （PB12CN）, which has a fairly rigid poly （phenylacetylene ）backbone, were synthesized using respectively WCl6 and [Rh（nbd）Cl]2 as the catalysts.PA8CN exhibits enantiotropic interdigitated smectic A phase (SAd) over a temperaturerange as wide as ca. 100℃, whereas PB12CN is non-mesomorphic, demonstrating thatthe backbone rigidity plays an important role in determining the liquid crystallinity of thepolyacetylenes.

SYNTHESIS AND PROPERTIES OF POLYACETYLENES CONTAINING CARBAZOLE AND AMINO ACID MOIETIES

Novel 9-proparylcarbazole monomers containing amino acid moieties,2-N(tert-butoxycarbonyl)-L-alanine- 9-proparylcarbazole ester(1),2-N-(tert-butoxycarbonyl)-L-O-cyclohexyl-L-glutamic acid-9-proparylcarbazole ester(2) and 2-N-(tert-butoxycarbonyl)-L-phenylalanine-9-proparylcarbazole ester(3) were synthesized and polymerized with (nbd)Rh^+[η~6-C_6H_5B^-(C_6H_5)_3]to give the corresponding polymers with number-average molecular weights ranging from 7050 to 10500 in 70%-86%yields.The polymers were completely...

POLYMER DIODES MADE OF ION IMPLANTED POLYACETYLENE FILMS

Polyacetylene films were doped with FeCl3 and implanted with 30 k’eV K+ ions. Physical changes to the films were examined by a series of measurements, which include the four-probe test, infrared ray absorption and 2 MeV He+ particle elastic recoil dettection and Rutherford backscattering. The chemical dopants (Fe+++ and Cl-) were redistributed after the implantation and the different species (K+. Fe+++ and Cl-ions) formed p - n junctions at the implantation depths. The implanted films exhibited desirable Ⅰ-Ⅴ characteristics, with current densities as high as 600 mA/cm- at 3V and back - to - forward ratio of current over 300. The polymer diodes kept their behavior for over 60 days. Discussions on the results were given in detail.

Effects of Various Dopants on Solitons in Polyacetylene

The effects of various dopants on solitons in polyacetylene were studied by using CNDO/2 level semiempirical quantum chemical method. The width of solitons is reduced when dopant is present, and the charge density wave(CDW) is further gathered on the carbon atom in soliton center. The effects of p-type of dopants are greater than those of n-type of ones. The charge transfer in doped polyacetylene can be achieved by the propagation of CDW along the chain. The conductivity of doped polyacetylene is proportional to the quantity of charge transfer between dopant and polyacetylene chain.

Accurate theoretical evaluation of strain energy of all-carboatomic ring(cyclo[2n]carbon),boron nitride ring,and cyclic polyacetylene

Cyclocarbon fully consists of sp-hybridized carbon atoms,which shows quite unusual electronic and geometric structures compared to common molecules.In this work,we systematically studied strain energy(SE)of cyclocarbons of different sizes using regression analysis method based on electronic energies evaluated at the very accurate DLPNO-CCSD(T)/ccp VTZ theoretical level.In addition,ring strain of two systems closely related to cyclocarbon,boron nitride(BN)ring,and cyclic polyacetylene(c-PA),is also explored.Very ideal relationships between SE and number of repeat units(n)are built for cyclo[2n]carbon,B_(n)N_(n),and[2n]c-PA as SE=555.0·n^(-1),145.1·n^(-1),and 629.8·n^(-1)kcal·mol^(-1),respectively,and the underlying reasons of the difference and similarity in their SEs are discussed from electronic structure perspective.In addition,force constant of harmonic potential of C-C-C angles in cyclocarbon is derived based on SE values,the result is found to be 56.23 kcal·mol^(-1)·rad^(-2).The possibility of constructing homodesmotic reactions to calculate SEs of cyclocarbons is also explored in this work,although this method is far less rigorous than the regression analysis method,its result is qualitatively correct and has the advantage of much lower computational cost.In addition,comparisons show thatωB97XD/def2-TZVP is a good inexpensive alternative to the DLPNO-CCSD(T)/cc-p VTZ for evaluating energies used in deriving SE,while the popular and very cheap B3LYP/6-31G(d)level should be used with caution for systems with global electron conjugation such as c-PA.

MECHANICAL PERTURBATION INDUCED MOLECULAR ALIGNMENTS IN A SIDE-CHAIN LIQUID CRYSTALLINE POLYACETYLENE, POLY{10-[4-(4'-METHOXYPHENOXY-CARBOML)PHENOXYCARBONYL]-1-DECYNE}

A new liquid crystalline polyacetylene containing a phenyl benzoate mesogen （5） is synthesized,whose mesomorphic properties are found to be easily "tunab1e" by simple mechanical perturbation. Thepolymerization of 10- [ 4 - （4’ -methoxyphenoxycarbonyl ）phenoxycarbonyl] - 1 -decyne （4 ） in itiated by theWCl6-Ph4Sn/dioxane complex yields polymer 5 with a Mw of 28400. The molecular structure of 5 ischaracterized by NMR, IR, and UV spectroscopy and its liquid crystalline behavior is investigated by DSC,POM, and XRD analysis. Upon mechanical perturbation, 5 exhibits unusual agitation-induced high-strengthdisclinations, shear-induced inversion walls, and solidification-induced banded textures. Such phenomenahave been observed in the main-chain liquid crystalline polymers with rigid backbones, but have seldom beenreported for the side-chain liquid crystalline polymers with flexible backbones, suggesting that the rigidpolyacetylene backbone of 5 plays a constructive role in inducing the novel molecular alignments.

A Viscidane Diterpene and Polyacetylenes from Cultures of Hypsizygus marmoreus

Investigation on the cultures of Hypsizygus marmoreus resulted in the isolation of a new viscidane diterpene,8-oxoviscida-3,11(18)-diene-13,14,15,19-tetraol(1)and two new polyacetylenes,(E)-10-(1,1-dimethyl-2-propenyloxy)-2-decene-4,6,8-triyn-1-ol(2)and 10-(1,1-dimethyl-2-propenyloxy)deca-4,6,8-triyn-1-ol(3),together with two known polyacetylenes,(E)-2-decen-4,6,8-triyn-1-ol(4)and 4,6,8-decatriyn-1-ol(5).Their structures were elucidated on the basis of extensive spectroscopic studies.Compound 1 is the first finding of viscidane diterpene in mushrooms.Compounds 1,3 and 5 were tested for cytotoxicity against human tumor cell lines HL-60,SMMC-7721,A-549,MCF-7 and SW-480.None of the compounds showed cytotoxic activity(IC50[40 lM).

Preparation of Polyacetylene with a High Conductivity

A new type free-standing long-chain stable polyacetylene film was polymerized by modifying Narrmann’s method. The conductivity of this film was over 104 s/cm after doping with iodine,The most interesting point is that the conductivity increased stepwisely upon iodine doping concent ratton.

Effects of substitution and terminal groups for liquid-crystallinity enhanced luminescence of disubstituted polyacetylenes carrying chromophoric terphenyl pendants

Liquid-crystalline and light-emitting poly(2-alkyne)s containing terphenyl cores with hexamethyleneoxy spacers,and cyano or n-propoxy tails -[CH3C=C(CH2)6O-terphenyl-R]n-,where R=CN,CH3PA6CN,R=OCH2CH2CH3,CH3PA6OPr,were synthesized.The effects of the substitution and terminal groups on the properties,especially the mesomorphic and optical properties of the polymers,were investigated.The disubstituted acetylene monomers (CH3A6CN,CH3A6OPr) were pre- pared through multistep reaction routes and were polymerized by WCl6-Ph4Sn in good yields (up to 82%).All the monomers and CH3PA6CN exhibited the enantiotropic SmA phase with a monolayer arrangement at elevated temperatures,whereas CH3PA6OPr formed a bilayer SmAd packing arrangement.Upon excitation at 330 nm,strong UV and blue emission peaks at 362 and 411 nm were observed in CH3PA6OPr and CH3PA6CN,respectively.The luminescent properties of CH3PA6CN and CH3PA6OPr have been improved by introducing the methyl substituted group,and the quantum yield of the polymer with cyano tail CH3PA6CN (φ= 74%) was found to be higher than that of CH3PA6OPr (φ= 60%).Compared to polyacety- lene parents,both CH3PA6OPr and CH3PA6CN showed a narrower energy gap.This demonstrated that the electrical con- ductivities of polyacetylenes could be enhanced by attaching appropriate pendants to the conjugated polyene backbones.

Antidiabetic Properties of Bidens pilosa and Its Polyacetylenic Compounds for Management of Diabetes: Systematic Review

Bidens pilosa is a member of the Asteraceae family that is widely distributed across the tropics. It has been utilized by different communities both as food and medicinal herb. This plant and its polyacetylenic compounds hold potential as a natural antidiabetic intervention that can be used to combat this global public health problem. Bioactive compounds found in this plant constitute promising interventions for combating obesity which is a major risk factor for the development of type 2 diabetes. These phytocompounds can work independently or synergistically to modulate appetite, lipase activity, adipogenesis and adipocyte apoptosis. However, the efficacy, mode of action and scope of management of diabetes by these compounds remains elusive. The current review aims to summarize data on efficacy in the management of diabetes, an antidiabetic candidate polyacetylenic compound and possible biological activities as an antidiabetic agent from the available literature. Much emphasis has been directed to cytopiloyne as a representative of polyacetylenic compounds extracted from Bidens pilosa and its activity on diabetic animal models. The majority of the studies conducted on animal models described antidiabetic mechanisms that range from hypoglycemic to secretagogue activity of cytopiloyne in a dose-dependent manner. A clinical trial pilot indicated improved glycemic control of Bidens pilosa formulation among diabetic patients in the study. Bidens pilosa and its compounds are highly potent antidiabetic agent(s) that should be graduated to an intervention for management of diabetes through pre-clinical and clinical trials to elucidate its efficacy and safety.

THE INFLUENCE OF THE 3d ORBITS OF SULFUR ATOMS ON THE ELECTRONIC PROPERTIES OF POLYACETYLENE SULFIDE

Ⅰ. INTRODUCTIONA problem needing urgent resolution in the world at present is the study of the polyacetylene (PA) conductive material which is stable in the air. We produce the polyacetylene-like sulfide (SLPA) which is stable in the air from polyvinyl chloride, and characterize its structure and property, and make studies on the influence of sulfidation on PA’s electronic property by means of the quantum method.

From n-alkane to polyacetylene on Cu(110):Linkage modulation in chain growth

Direct coupling or transformation of inert alkanes based on the selective C-H activation is of great importance for both chemistry and chemical engineering.Here,we report the coupling of polyenes that are transformed from n-dotriacontane(n-C_(22)H_(66))through on-surface cascade dehydrogenation on Cu(110)surface,leading to the formation of polyacetylene(PA).Three distinct linkages have been resolved by scanning tunneling microscope(STM)and noncontact atomic force microscope(nc-AFM).Apart from the α-type linkage which is the stemless coupling of the terminal C-C double bond in trans-configuration,β-and γ-type linkages appear as knots or defects which are,in fact,the C-C couplings in cis-configurations.Interestingly,the“defects”can be effectively suppressed by adjusting the surface coverage,thus making it of general interest for uniform structure modulation.

A theoretical description for solitons in polyacetylene

The bond-alternation domain walls or the solitons in the dimerized polyacetylene are analyzed theoretically. The width of the soliton is many times the period of the chain, so that the soliton can be reasonably well described by a continuum model. Because of the existence of the bond-alternation domain walls, the electron density is different definitely. Thus the electron density can be used to describe the formation of the domain walls, and a self-trapped potential is discussed and introduced in the Hamiltonian. It is shown that the envelope of the wave functions of the chain is governed by the nonlinear Schr?dinger equation which has soliton solutions. Then the shape of the soliton is determined analytically which is in accordance with the numerical calculations by Su, Schrieffer and Heeger. This implies that the bond-alternation domain wall or the soliton is observed as the envelope of the wave function.

Cytotoxic polyacetylenes isolated from the roots and rhizomes of Notopterygium incisum

Phytochemical investigation on the roots and rhizomes of Notopterygium incisum led to the isolation of a new polyacetylene, notopolyenol A (1), along with thirteen known analogues (2-14). Their structures were elucidated by extensive analyses of NMR and HRMS data, and the absolute configuration of 1 was unambiguously determined as 3 R by comparison of its retention time and ECD curve with those of synthetic enantiomers (-)-1 and (+)-1, whose absolute configurations were established by using the modified Mosher's method. Subsequent activity screening revealed that (3 S)-1 exhibited the most significant cytotoxicity against MCF-7, H1299, and HepG2 cancer cells with IC_(50) values of 1.3 μmol/L,0.6μmol/L and 1.4μmol/L, respectively.

STUDIES ON ION IMPLANTATION AND ELECTRICAL PROPERTIES OF POLYACETYLENE FILMS

The effects of ion implantation on ployacetylene films PA have been studied with Ar^+, Fe^+, C1^+, I^+, Na^+ and K^+ ions in the energy range of 15—30 keV. The changes of PA films in the electrical conductivity, due to chemical doping and ion implantation in relation to their structure and depth profiles of impurities, were measured through infrared (ATR/FTIK), Rutherford backscattering spectrometry (RBS) and the four probe technique. In all cases, ion implantation of active ions exhibits the same effects as chemical doping. The formation of p-n junction is observed at the interface of implanted region and chemical doped PA substrate. The mechanism of interaction process between ion beam and polymer is also discussed.

Anticancer Properties of Lobetyolin,an Essential Component of Radix Codonopsis(Dangshen)

Lobetyolin(LBT)is a polyacetylene glycoside found in diverse medicinal plants but mainly isolated from the roots of Codo-nopsis pilosula,known as Radix Codonopsis or Dangshen.Twelve traditional Chinese medicinal preparations containing Radix Codonopsis were identified;they are generally used to tonify spleen and lung Qi and occasionally to treat cancer.Here we have reviewed the anticancer properties of Codonopsis extracts,LBT and structural analogs.Lobetyolin and lobetyolinin are the mono-and bis-glucosylated forms of the polyacetylenic compound lobetyol.Lobetyol and LBT have shown activi-ties against several types of cancer(notably gastric cancer)and we examined the molecular basis of their activity.A down-regulation of glutamine metabolism by LBT has been evidenced,contributing to drug-induced apoptosis and tumor growth inhibition.LBT markedly reduces both mRNA and protein expression of the amino acid transporter Alanine-Serine-Cysteine Transporter 2(ASCT2).Other potential targets are proposed here,based on the structural analogy with other anticancer compounds.LBT and related polyacetylene glycosides should be further considered as potential anticancer agents,but more work is needed to evaluate their efficacy,toxicity,and risk-benefit ratio.

LINEAR AND HYPERBRANCHED POLYMERS WITH HIGH THERMAL STABILITY AND LUMINESCENCE EFFICIENCY

New acetylene monomers, 6-{[(1-naphthylethynyl-4-phenyl)carbonyl]oxy}-l-phenyl-l-hexyne (1), 2,5-diethynylthiophene (3), and 4,4′-diethynylbiphenyl (6) were synthesized. Homopolymerization of 1 and copolycyclotrimerizations of 3and 6 with 1-heptyne and l-octyne have been achieved with WCI6- and TaC15-Ph4Sn catalysts, respectively, giving soluble linear disubstituted polyacetylene (2) and hyperbranched polyarylenes (5 and 8) with high molecular weights (up to 1.2 ×105) in high yields (upto 98%). The structures and properties of the polymers are characterized and evaluated by IR, NMR,TGA, UV, photoluminescence (PL), and electroluminescence (EL) analyses. All the polymers possess high thermal stability and emit strong blue light upon photoexcitation. The intensity of the emitted light is greater than that of poly(1-phenyl-1-octyne), a well-known highly luminescent disubstituted polyacetylene. Little aggregation-induced red shift in the PL was observed in the thin films of the polymers. By constructing a multi-layer EL device, high EL quantum yield (0.18%) has been achieved in 2, which are the best results for substituted polyacetylenes attainable so far.

SYNTHESIS,CHARACTERIZATION AND OPTICAL PROPERTIES OF THE COPOLYMERS OF C_(60) AND 1-PHENYL-1-PROPYNE

While WCl6-Ph4Sn fails to polymerize 1-phenyl-1-propyne （PP） at room temperature, highmolecular weight （Mw up to 410×103） polymers are obtained in high yields （up to 80%） when thepolymerizations of PP are carried out in the presence of C60 using the W catalyst under the same conditions.The polymers are soluble in common organic solvents such as THF, chloroform, and toluene. Molecularstructures of the polymers are characterized by FT-IR, UV, NMR, GPC and XRD, and it is found that C60 iscopolymerized with PP. Thus C60 plays the dual roles of comonomer and cocatalyst in the polymerizationreaction. C60 contents of the copolymers can be easily changed by varying the C60 amounts in the feedmixtures. The copolymers effectively limit strong 532 nm laser pulses, whose limiting performance issuperior to that of parent C60.

SYNTHESIS AND OPTICAL PROPERTIES OF POLY (THIENYLACETYLENES)

3 -Ethynyl-4-（trimethylsilyl）thiophene （1a） and 3 -ethynyl-4-bromothiophene （1 b ） selectivelyundergo acetylene polymerizations in the presence of the MoCl5- and WCl6-Ph3SiH catalysts to give soluble,high-molecular-weight poly（thienylacetylenes） （2） （Mw up to 602000） in high yields （up to 100%）. Lighttransmission spectra of THF solutions of 2 continuously red-shift with increasing concentration. Theconcentratochromism shows a logarithmic concentration dependence; that is, the optical transitions of 2 arepredictably tunable by simply changing their concentrations.

Synthesis and optical limiting in copolymers of C_(60) and 1-phenyl-1-butyne

While WC16-Ph4Sn is a poor catalyst for the polymerization of l-phenyl-butyne （PB） at room temperature, it effectively polymerizes PB in the presence of C60, giving high molecular weight polymers in high yields. The polymer is soluble in THF and chloroform and spectroscopic analysis reveals that Coo has copolymerized with PB. Thus, C60 plays dual roles of comonomer and cocatalyst in the acetylene polymerization. The copolymers strongly attenuate 532-nm laser pulses, whose limiting performance is superior to that of parent