Polymerization Of Acetylene Research Articles

Conjugated Acetylenic Polymers Grafted Cuprous Oxide as an Efficient Z-Scheme Heterojunction for Photoelectrochemical Water Reduction.

As attractive materials for photoeletrochemical hydrogen evolution reaction (PEC HER), conjugated polymers (e.g., conjugated acetylenic polymers [CAPs]) still show poor PEC HER performance due to the associated serious recombination of photogenerated electrons and holes. Herein, taking advantage of the in situ conversion of nanocopper into Cu2 O on copper cellulose paper during catalyzing of the Glaser coupling reaction, a general strategy for the construction of a CAPs/Cu2 O Z-scheme heterojunction for PEC water reduction is demonstrated. The as-fabricated poly(2,5-diethynylthieno[3,2-b]thiophene) (pDET)/Cu2 O Z-scheme heterojunction exhibits a carrier separation efficiency of 16.1% at 0.3V versus reversible hydrogen electrode (RHE), which is 6.7 and 1.4-times higher respectively than those for pDET and Cu2 O under AM 1.5G irradiation (100mW cm-2 ) in the 0.1 m Na2 SO4 aqueous solution. Consequently, the photocurrent of the pDET/Cu2 O Z-scheme heterojunction reaches ≈520 µA cm-2 at 0.3V versus RHE, which is much higher than pDET (≈80 µA cm-2 ), Cu2 O (≈100 µA cm-2 ), and the state-of-the-art cocatalyst-free organic or organic-semiconductor-based heterojunctions/homojunctions photocathodes (1-370 µA cm-2 ). This work advances the design of polymer-based Z-scheme heterojunctions and high-performance organic photoelectrodes.

Emerging Nanomaterials for Light‐Driven Reactions: Past, Present, and Future

Emerging Nanomaterials for Light‐Driven Reactions: Past, Present, and Future

Research of the influence of a hydrocarbon coating on the operational stability of membrane fabric

The effect of the hydrocarbon coating on the operational stability of membrane tissues is investigated. Coating on membrane tissues was obtained by plasma-chemical vapor deposition of the products of polymerization and decomposition of acetylene. As a result, the resulting coating allows to: increase resistance to multi-cycle abrasive impact by 9,9-30,1%, while the resistance of the textile base to light, washing, dry and wet friction does not deteriorate; increase tensile strength by 5,7-13,4%; increase elongation to 11,0-18,4%. The stability of fixation of organosilicon impregnation in the structure of the textile base after modification in a nonequilibrium low-temperature plasma increases to 45,5%.

Thermomechanical Actuator Based on a Molecular-Spring Polymer with a Long Alkyl Side Chain

A disubstituted acetylene polymer, with a molecular-spring main chain and a long alkyl side chain of the octadecyl group (PDMC18SP), was examined as an active material for a thermomechanical actuat...

(Arylimido)niobium(V)–Alkylidenes, Nb(CHSiMe3)(NAr)[OC(CF3)3](PMe3)2, That Enable to Proceed Living Metathesis Polymerization of Internal Alkynes

Living polymerizations of internal alkynes (2-hexyne, 3-hexyne, 4-methyl-2-pentyne, and 1-phenyl-1-propyne) have been demonstrated at 50 °C by (arylimido)niobium(V)–alkylidene complex catalysts, Nb(CHSiMe3)(NAr)[OC(CF3)3](PMe3)2 [Ar = 2,6-Me2C6H3 (4a), 2-MeC6H4 (4c), and 2,6-Cl2C6H3 (4d)], in the presence of PMe3, which plays an essential role to proceed the living polymerization without certain catalyst deactivation. The living nature of 4a was preserved even at 80 °C in the 2-hexyne polymerization under optimized conditions, and 4c and 4d showed higher activity than 4a. The living polymerizations of 4-methyl-2-pentyne by 4c,d and of 3-hexyne by 4c have also been achieved in the presence of PMe3 at 50 °C, and the effect of the internal alkynes toward the activity by 4c is in the order 2-hexyne > 4-methy-2-pentyne > 3-hexyne > 4-octyne ≫ 5-decyne (negligible). The living polymerization of 1-phenyl-1-propyne has also been demonstrated by 4d (at 25 and 50 °C) in the presence of PMe3.

One-Pot Tandem Ring-Opening and Ring-Closing Metathesis Polymerization of Disubstituted Cyclopentenes Featuring a Terminal Alkyne Functionality

Tandem metathesis polymerization of terminal alkynes with a small functional ring-size cycloalkene remains a challenge. A series of 1-propargyl-1′-carboxylate ester monomers M1–M4 derived from 3-cy...

The Introduction of the Radical Cascade Reaction into Polymer Chemistry: A One-Step Strategy for Synchronized Polymerization and Modification.

SummaryPolymerization and modification play central roles in polymer chemistry and are generally implemented in two steps, which suffer from the time-consuming two-step strategy and present considerable challenge for complete modification. By introducing the radical cascade reaction (RCR) into polymer chemistry, a one-step strategy is demonstrated to achieve synchronized polymerization and complete modification in situ. Attributed to the cascade feature of iron-catalyzed three-component alkene carboazidation RCR exhibiting carbon-carbon bond formation and carbon-azide bond formation with extremely high efficiency and selectivity in one step, radical cascade polymerization therefore enables the in situ synchronized polymerization through continuous carbon-carbon bond formation and complete modification through carbon-azide bond formation simultaneously. This results in a series of α, β, and γ poly(amino acid) precursors. This result not only expands the methodology library of polymerization, but also the possibility for polymer science to achieve functional polymers with tailored chemical functionality from in situ polymerization.

Chiral Reaction Field with Thermally Invertible Helical Sense that Controls the Helicities of Conjugated Polymers.

A chiral reaction field with thermally invertible helical sense enables control of the helicity of the reaction product, which is a central challenge in asymmetric synthesis that has yet to be overcome. A novel chiral compound comprising two types of chiral moieties with opposite helicities and temperature dependences is synthesized; this compound is added as a chiral dopant to a mixture of nematic liquid crystals to prepare a chiral nematic liquid crystal (N*-LC). The N*-LC containing the chiral dopant exhibits thermally invertible helicity to yield left- and right-handed helical senses at low and high temperatures, respectively. Interfacial polymerization of acetylene is achieved in the N*-LC by modulating the temperature. Helical polyacetylenes (H-PAs) that are synthesized at low (-12 °C) and high (28 °C) temperature show right- and left-handedness, respectively, in terms of the fibrils, fibril bundles, and spiral morphology. In addition, the helical sense of H-PA is opposite that of the N*-LC because of the peculiar polymerization mechanism for acetylene in the N*-LC. The current N*-LC is the first chiral reaction field that has not only the thermally invertible helical sense but also the chemical functions and stability needed to serve as the medium for polymer reactions.

Model-based research toward design of innovative materials: molecular weight prediction of bridged polysilsesquioxanes.

Toward the design and manipulation of innovative materials, we propose a new concept called “model-based research (MBR)”. In MBR, measurable physical and chemical properties of materials are mathematically modelled by explanatory parameters obtained by computer simulation from an atomistic point of view. To demonstrate the potential of MBR, we modelled the molecular weights of a series of polysilsesquioxanes with respect to the H2O/silane molar ratio employed for the polymerization of monomers bis(triethoxysilyl)methane, ethane, ethylene, and acetylene (BTES-M, -E1, -E2, and -E3), as an example. The equation y = axn well reproduced the behaviour of the molecular weights of the BTES series, in which a and n were obtained using the calculated molecular parameters for monomers as the explanatory parameters. Detailed understanding and discussion were theoretically possible on the basis of the mathematical model. We predicted the molecular weights of polymers that would be obtained from monomers BTES-P and BTES-Ph with C3H6 and C6H4 as the spacer, respectively, using the mathematical model. Experimental validation of these polymers clearly showed the possibility of qualitative categorization. Our proposed concept, MBR, is a powerful tool to analyse materials science toward innovative materials design.

Retracted Article: Metal-free [2+2+1] cycloaddition polymerization of alkynes, nitriles, and oxygen atoms to functional polyoxazoles.

The metal-free [2+2+1] cycloaddition polymerization of alkynes, nitriles, and O-atoms for the regioselective assembly of highly substituted oxazole compounds has been achieved by the use of iodosobenzene (PhIO) with trifluoromethanesulfonic acid (TfOH). The present reaction could be applied to a facile synthesis of polyoxazoles. In this work, the cycloaddition polymerization of 4-cyano-4′-ethynylbiphenyl and PhIO was developed and modified polyoxazole was prepared. All experimental conditions such as polymerization solvent, temperature, catalyst and time were systematically studied. The structure of the obtained polyoxazole was characterized by GPC and NMR, and its thermal properties were studied by TGA. In addition, the good thermal stability of polyoxazoles with unreacted terminal alkynes and cyano groups makes them potentially useful for modifying resins.

Pure Organic Semiconductor‐Based Photoelectrodes for Water Splitting

Currently, photoelectrochemical water‐splitting research is dominated by inorganic and organic–inorganic hybrid photoelectrodes. Although organic semiconductors have several advantages over their inorganic counterparts, the development of photoelectrodes based on pure organic materials has been lagging for the last decade. Recent improvements in molecular design, synthesis, and processing of organic semiconductors, such as polythiophenes, graphitic carbon nitrides, conjugated acetylenic polymers, alternating donor–acceptor‐conjugated polymers, and N‐containing fused‐ring small molecules, significantly enhance the performance of these photolectrodes without added cocatalysts. Although this research has been conducted over the past few years, this overlooked topic still stays unexplored, with more efficient materials yet to be discovered. Herein, the early development and recent advances of exclusively organic photoelectrodes for water splitting are summarized and brief perspectives for future improvements are provided.

Multicomponent Tandem Polymerization of Aromatic Alkynes, Carbonyl Chloride, and Fischer's Base toward Poly(diene merocyanine)s

Summary of main observation and conclusionMulticomponent polymerization (MCP) is a popular tool to construct polymers with diverse structure, simple operation, and high efficiency, which faces the challenges of limited product structures. Multicomponent tandem polymerization (MCTP), combining two or multiple reactions in a one‐pot fashion, could expand the scope of MCP and enrich the polymer structures. Herein, a one‐pot three‐component tandem polymerization of diynes, carbonyl chloride, and Fischer's base has been developed to afford conjugated poly(diene merocyanine)s with mild condition, satisfactory molecular weights (Mw up to 10900 g/mol) and yields (up to 81%). The polymers enjoy good solubility and high thermal stability. The unique emission behavior of the model compound and polymer show that they are aggregation‐induced emission (AIE)‐active, suggesting that the diene merocyanine moiety is a potential AIEgen. This MCTP shows great potential in the preparation of functional polymer materials, which could build new AIE functional units directly from the polymerization, demonstrating its synthetic simplicity and elegance.

Acetylene polymerization in plasma of direct current

Plasma polymerization is a technique that allows obtaining polymer of any type of hydrocarbon, including the non-polymerizable by standard methods. This because of in the plasma state the activation energy can be reduced for the realization of reactions difficult to be presented under standard experimental conditions. For plasma polymerization only the implementation of different types of discharges in the radio frequency regime has been reported, leaving aside the application of direct current discharges for this process. The acetylene polymer consists of carbon chains with alternation of single and double covalent bonds. The formation of this polymer has been reported using radio frequency discharges in the abnormal regime. The paper reports the formation of polymer from acetylene using the abnormal glow discharge in the direct current regime, a novel process not yet reported in the literature. The deposition of the polymer is carried out at different times on a polycrystalline copper substrate previously treated in a glow discharge of argon and hydrogen. For the generation of this polymer an atmosphere of 60% Ar+35% H2+5% C2H2 at 2 torr pressure and a temperature of 600 °C is used. The structural and morphological analysis of the deposits is carried out by infrared spectroscopy and scanning electron microscopy, respectively.

Carbon structures obtained from acetylene in a continuous current abnormal glow

Carbon is the great constituent of all organic matter and a key element of the compounds that make up the enormous and very complex discipline of organic chemistry. It was already known in antiquity to be obtained as a by-product of the incomplete combustion of organic materials. At present the properties of this atom constitutes a potential source for research due to its promising application in nanotechnology and new materials because of its unique mechanical, electrical and optical properties. Carbon has several structural configurations that are known as allotropes, these allotropes have the same basic component, but its molecular conformation is different. Other elements of the fourth column of the periodic table such as silicon, germanium and tin have characteristics similar to those of carbon, however, this is unique in the variety of its allotropes. The different allotropes of carbon can be produced, among other methods, by the chemical vapor deposition method, however, the energy cost of this type of growth is relatively high. Another technique that would allow to obtain deposits of carbon in the laboratory is the plasma of the glow discharge of direct current in abnormal regime, which also offers a wide range of applications in plasmo-chemistry and in the thermochemical treatment of materials. The application of the abnormal glow discharge in the deposition of synthetic materials is a recent technique that represents a decrease in the time and in the energy consumption of the process, because the heating is carried out directly by the bombardment of the ions and neutral atoms on the surface of the cathode where the sample is usually located. The technique of abnormal glow discharge was used in this work with the objective of studying the possibility of formation of carbon deposits, in a copper substrate, from an atmosphere of argon, hydrogen and acetylene. Thus, in the temperature of 600 °C, deposits of graphite, graphene and an acetylene polymer compound were obtained. These were identified by infra-red spectrometry and Raman spectrometry.

Study of the composition of a hydrophobic coating obtained by a plasma chemical deposition from the gas phase on the surface of textile material

In this work, a hydrophobic non-continuous granular coating with a thickness of no more than 1-3 microns, obtained by modifying textile materials with nonequilibrium low temperature plasma (NLTP) in argon-acetylene medium (70:30), was investigated. As a result, the obtained coating is a mixture of hydrocarbons, mainly paraffins, as well as unsaturated hydrocarbons formed during the polymerization and decomposition of acetylene in the presence of copper, such as alkenes, polyacetylene isomers and others, which contribute to an increase in waterproofing properties.

Carbon-Bridged Oligo(phenylene vinylene)s: A de Novo Designed, Flat, Rigid, and Stable π-Conjugated System.

The modern history of conducting organic systems started with a fortuitous error in 1967 on acetylene polymerization, followed by a rational discovery in 1976 on the effects of doping that generates a polaron and, hence, dramatically increases conductivity. Not unexpectedly, however, the prototypical polyacetylene suffers many problems, including C-C single bond rotation, short effective conjugation length, radiationless deactivation, and instability of the polarons. Several strategies have been put in place to solve these problems. An early approach relied on partial rigidification of the polyene structure by conversion into polymers with thiophene, pyrrole, and benzene linkages. An oligo(phenylene vinylene) (OPV) is an all-carbon analogue of polyacetylene, where every other diene unit in the polyene chain is converted to a benzene unit, still leaving many C-C single bonds freely rotating in the molecule. We considered adding additional carbon bridges to rigidify the OPV skeleton entirely to create a carbon-bridged OPV (COPV). Making such a compound was an obvious challenge. This Account describes the authors' efforts to design and synthesize a series of COPV molecules, where the benzene rings in OPV are bridged by sp3 carbon atoms to form a bicyclo[3.3.0]octatriene framework bearing a tetrasubstituted olefin at the ring fusion. This olefinic bond is so strained that it resists further deformation or conversion to sp3 centers, and hence, it is chemically stable despite the strain. The sp3 carbon bridges can bear organic side chains that hinder intermolecular interactions, rendering the excited states stable and long-lived even in the solid state. They also increase solubility, a common problem among rigid molecular systems. With these structural features, the COPV molecules were found to be well behaved both at a single-molecule level and as a bulk material. We reported in 2009 a method for the synthesis of COPVs and have, since then, reported their structures and physicochemical properties, including basic photophysical properties of neutral and charged derivatives, thermal and photostability, and fast electron transfer. These properties have rendered the COPV molecules useful for electronic and photonic research, for example, lasers, solar cells, and molecular wire applications. Noteworthy discoveries in the area connecting chemistry and physics include inelastic tunneling and long-range resonance tunneling at ambient temperature, which were previously observed only for organic molecular wires placed under cryogenic conditions. Given the ready availability of the COPV skeleton bearing a wide variety of substituents, this class of molecules will serve as versatile building blocks for fundamental and applied research on physicochemical and materials chemistry.

Ionic Polymerization in Cold Plasmas of Acetylene with Ar and He.

The ionic polymerization of acetylene in cold plasmas of C2H2/He and C2H2/Ar has been experimentally studied and modeled in radio frequency (rf) discharges with conditions selected to avoid particle formation. Steady-state distributions of positive and negative ions were measured with mass spectrometry. All the measured distributions are dominated by ions with an even number of carbon atoms, reflecting the characteristic polyyne structures typical for the polymerization of acetylene. The distributions show a monotonic decrease in intensity from ions with two carbon atoms until the highest number of atoms detected. For cations, the distributions extend until 12 carbon atoms. The anion distributions extend further, and negative ions with 20 C atoms are observed in the C2H2/Ar plasma. From the measured mass spectra it is not possible to decide on the possible presence of aromatic species in ions with more than six carbon atoms. A simple model assuming a homogeneous discharge was used to describe the plasma kinetics and could account for the measured ion distributions with reasonable values of charge density and electron temperature. The results of this work stress the important role of the vinylidene anion and indicate that Ar and He do not have much influence on the carbon chemistry.

Ethynylation of Formaldehyde over Binary Cu-Based Catalysts: Study on Synergistic Effect between Cu+ Species and Acid/Base Sites.

Most studies on the Cu-based catalysts in the ethynylation of formaldehyde are merely focused on the tuning of electronic configuration and dispersion of the Cu+ species. So far, little attention has been paid to the synergy between Cu species and promoters. Herein, binary nano-CuO-MOx catalysts (M = Si, Al, and Mg) were synthesized and the effects of the promoter on the surface basicity/acidity were systematically studied as well as the ethynylation performance of the nano-CuO-based catalysts. The results show that the introduction of MgO provided a large number of basic sites, which could coordinate with the active Cu+ species and facilitate the dissociation of acetylene as HC≡Cδ− and Hδ+. The strongly nucleophilic acetylenic carbon (HC≡Cδ−) is favorable to the attack at the electropositive carbonyl Cδ+ of formaldehyde. The MgO-promoted CuO catalyst showed the highest yield of BD (94%) and the highest stability (the BD yield decreased only from 94% to 82% after eight reaction cycles). SiO2 effectively dispersed Cu species, which improved catalytic activity and stability. However, the introduction of Al2O3 resulted in a large number of acidic sites on the catalyst’s surface. This led to the polymerization of acetylene, which covered the active sites and decreased the catalyst’s activity.

Molecular Engineering of Conjugated Acetylenic Polymers for Efficient Cocatalyst‐free Photoelectrochemical Water Reduction

AbstractConjugated polymers featuring tunable band gaps/positions and tailored active centers, are attractive photoelectrode materials for water splitting. However, their exploration falls far behind their inorganic counterparts. Herein, we demonstrate a molecular engineering strategy for the tailoring aromatic units of conjugated acetylenic polymers from benzene‐ to thiophene‐based. The polarized thiophene‐based monomers of conjugated acetylenic polymers can largely extend the light absorption and promote charge separation/transport. The C≡C bonds are activated for catalyzing water reduction. Using on‐surface Glaser polycondensation, as‐fabricated poly(2,5‐diethynylthieno[3,2‐b]thiophene) on commercial Cu foam exhibits a record H2‐evolution photocurrent density of 370 μA cm−2 at 0.3 V vs. reversible hydrogen electrode among current cocatalyst‐free organic photocathodes (1–100 μA cm−2). This approach to modulate the optical, charge transfer, and catalytic properties of conjugated polymers paves a critical way toward high‐activity organic photoelectrodes.

Molecular Engineering of Conjugated Acetylenic Polymers for Efficient Cocatalyst-free Photoelectrochemical Water Reduction.

Conjugated polymers featuring tunable band gaps/positions and tailored active centers, are attractive photoelectrode materials for water splitting. However, their exploration falls far behind their inorganic counterparts. Herein, we demonstrate a molecular engineering strategy for the tailoring aromatic units of conjugated acetylenic polymers from benzene- to thiophene-based. The polarized thiophene-based monomers of conjugated acetylenic polymers can largely extend the light absorption and promote charge separation/transport. The C≡C bonds are activated for catalyzing water reduction. Using on-surface Glaser polycondensation, as-fabricated poly(2,5-diethynylthieno[3,2-b]thiophene) on commercial Cu foam exhibits a record H2 -evolution photocurrent density of 370 μA cm-2 at 0.3 V vs. reversible hydrogen electrode among current cocatalyst-free organic photocathodes (1-100 μA cm-2 ). This approach to modulate the optical, charge transfer, and catalytic properties of conjugated polymers paves a critical way toward high-activity organic photoelectrodes.