Acetylenic Polymers: Syntheses, Structures, and Functions

Liu, Jianzhao; Lam, Jacky W. Y.; Tang, Ben Zhong

doi:10.1021/cr900149d

Cited by 1,159 publications

(726 citation statements)

References 544 publications

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“…Although synthesis of this new family of carbon allotropes can be challenging, the H-0 allotrope could be synthetized in a layer by layer fashion using monofunctionalized carbon chains of atoms in the alkyne or alkynide groups [32]. Those groups can be coordinated perpendicularly to a surface, in a way as to allow epitaxial polymerization in the form of a monolayer of oriented chains [33]. Once the first layer is grown, the exposed functional groups can be replaced with a new layer of functionalized chains perpendicular to the first one [34].…”

mentioning

confidence: 99%

Line of Dirac Nodes in Hyperhoneycomb Lattices

Mullen¹,

Uchoa²,

Glatzhofer³

2015

Phys. Rev. Lett.

304

140

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We propose a family of structures that have "Dirac loops", closed lines of Dirac nodes in momentum space, on which the density of states vanishes linearly with energy. Those lattices all possess the planar trigonal connectivity present in graphene, but are three dimensional. We show that their highly anisotropic and multiply-connected Fermi surface leads to quantized Hall conductivities in three dimensions for magnetic fields with toroidal geometry. In the presence of spin-orbit coupling, we show that those structures have topological surface states. We discuss the feasibility of realizing the structures as new allotropes of carbon.Introduction.− In honeycomb lattices, the existence of the Dirac point results from the planar trigonal connectivity of the sites and its sub-lattice symmetry [1]. Less well known are "Dirac loops", three dimensional (3D) closed lines of Dirac nodes in momentum space, on which the energy vanishes linearly with the perpendicular components of momentum [2]. To date there are no experimental observations of Dirac loops, and they were predicted to exist only in topological superconductors [3] and 3D Dirac semimetals [4] in which the parameters such as interactions and magnetic field are finely tuned [2].Theoretically, graphene is not the only possible lattice realization with planar trigonally connected atoms [5]. It is therefore natural to ask if there are variations on the honeycomb geometry that might produce exotic Fermi surfaces with Dirac-like excitations and topologically non-trivial states. In this Letter, we propose a family of trigonally connected 3D lattices that admit simple tight-binding Hamiltonians having Dirac loops, without requiring any tuning or spin-orbit coupling. Some of these structures lie in the family of harmonic honeycomb lattices, which have been studied in the context of the Kitaev model [7][8][9][10][11], and experimentally realized in honeycomb iridates [12]. The simplest example is the hyper-honeycomb lattice, shown in Fig. 1a.We derive the low energy Hamiltonian of this family of systems, and analyze the quantization of the conductivity and possible surface states. Even though these systems are 3D semimetals, their Fermi surface is multiply connected, with the shape of a torus, and highly anisotropic. When a magnetic field with toroidal geometry is applied, we find that the Hall conductivity is quantized in 3D at sufficiently large field. Additional spin-orbit coupling effects can create topologically protected surface states in these crystals. We claim that in the presence of spin-orbit coupling, these structures conceptually correspond to a new family of strong 3D topological insulators [13,14]. We finally discuss the experimental feasibility of realizing those structures as new allotropic forms of carbon.Tight-binding lattice.− Our discussion starts with the simplest structure, the hyper-honeycomb lattice (see Fig.

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mentioning

confidence: 99%

Line of Dirac Nodes in Hyperhoneycomb Lattices

Mullen¹,

Uchoa²,

Glatzhofer³

2015

Phys. Rev. Lett.

304

140

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“…p4´2xq{p3`2xq " rC olefinic {C aliphatic s experimental (1) p2´xq{p3`xq " rC olefinic {C aliphatic s experimental (2) Polymers 2015, 7, page-page…”

Section: Polymerization Reactionsmentioning

confidence: 99%

“…Among them, metathesis polymerization of alkynes [1][2][3] and ring opening metathesis polymerization (ROMP) of cycloolefins [4][5][6] yield unsaturated polymeric materials and are considered as two of the most important tools in polymer chemistry, leading to the synthesis of novel materials (Scheme 1). The properties of these polymers sensitively depend on their microstructure.…”

Section: Introductionmentioning

confidence: 99%

Metathesis Polymerization Reactions Induced by the Bimetallic Complex (Ph4P)2[W2(μ-Br)3Br6]

et al. 2015

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Abstract:The reactivity of the bimetallic complex (Ph 4 P) 2 [W 2 (µ-Br) 3 Br 6 ] ({W 2.5 W} 7+ , a 12 e 3 ) towards ring opening metathesis polymerization (ROMP) of norbornene (NBE) and some of its derivatives, as well as the mechanistically related metathesis polymerization of phenylacetylene (PA), is presented. Our results show that addition of a silver salt (AgBF 4 ) is necessary for the activation of the ditungsten complex. Polymerization of PA proceeds smoothly in tetrahydrofuran (THF) producing polyphenylacetylene (PPA) in high yields. On the other hand, the ROMP of NBE and its derivatives is more efficient in CH 2 Cl 2 , providing high yields of polymers. 13 C Cross Polarization Magic Angle Spinning (CPMAS) spectra of insoluble polynorbornadiene (PNBD) and polydicyclopentadiene (PDCPD) revealed the operation of two mechanisms (metathetic and radical) for cross-linking, with the metathesis pathway prevailing.

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“…Homocoupling of alkynes for obtaining di-and polyacetylenic compounds, electronrich compounds that play different roles in biological systems and in industry [1], are reactions of considerable interest in organic synthesis [2]. The reaction can be catalyzed by a variety of metal-based catalytic systems [3].…”

Section: Introductionmentioning

confidence: 99%

Electrochemical monitoring of the oxidative coupling of alkynes catalyzed by triphenylphosphine gold complexes

Doménech

Leyva‐Pérez

Al‐Resayes

et al. 2012

Electrochemistry Communications

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Abstract. Electrochemical monitoring of the oxidative coupling of alkynes in the homogeneous phase through catalytic cycles involving triphenylphosphine gold complexes and selectfluor as oxidant reveals that at least two gold species in +3 and +1 oxidation states are implicated. Electrochemically driven homocoupling of terminal alkynes using molecular oxygen as the oxidant can be performed using such catalysts.

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Acetylenic Polymers: Syntheses, Structures, and Functions

Cited by 1,159 publications

References 544 publications

Line of Dirac Nodes in Hyperhoneycomb Lattices

Line of Dirac Nodes in Hyperhoneycomb Lattices

Metathesis Polymerization Reactions Induced by the Bimetallic Complex (Ph4P)2[W2(μ-Br)3Br6]

Electrochemical monitoring of the oxidative coupling of alkynes catalyzed by triphenylphosphine gold complexes

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