Sulfur polyacetylene

All conducting polymers have a common feature a long chain of sp2 hybridized carbon atoms, often with nitrogen or sulfur atoms included in the chains. Polyacetylene, the first conducting polymer, is also the simplest, consisting of thousands of —CH=CH -units ... 

Coated materials are evaluated in S-SBR and in 50 50 blends of S-SBR and EPDM rubbers. In blends, the partitioning of fillers and curatives over the phases depends on differences in surface polarity. In S-SBR, polythiophene-modified silica has a strong positive effect on the mechanical properties because of a synergistic reaction of the sulfur-moieties in the polythiophene coating with the sulfur cure system. In S-SBR/EPDM blends, a coating of polyacetylene is most effective because of the chemical similarity of polyacetylene with EPDM. The effect of... 

Polyacetylene-modified sulfur is evaluated as a curative in a 50 50 blend of S-SBR/EPDM. In pure S-SBR, the mechanical properties decrease with the polyacetylene coating due to a reduced release rate of the sulfur out of its shell. The cure and mechanical properties of the S-SBR/EPDM blend are nearly doubled because of improved compatibility. 

PPASs plasma polyacetylene-treated sulfur, PFHSg plasma polyperfluorohexane-... 

Hydrophobicity - After surface modification by plasma polyacetylene, sulfur floats on top of ethylene glycol, whereas the untreated sulfur sinks immediately. The surface energy of uncoated sulfur can therefore be scaled in the range of 47.7-50 mJ/m2 and polyacetylene-encapsulated sulfur in the range of 28.4 17.7 mJ/m2. 

S8 untreated sulfur, PPASg plasma polyacetylene-treated sulfur, PFHSg plasma polyperfluorohexane-treated sulfur, PAASg plasma polyacrylic-acid-treated sulfur n.a. not available... 

Fig. 16 SEM image of cross-section of sulfur that has been plasma-coated with polyacetylene...

Table 12 shows the composition of the S-SBR compound used for these investigations. The sulfur used was either unmodified or one of the four samples of polyacetylene-coated sulfur described in Table 3. 

Fig. 32 Stress-strain properties of carbon-black-reinforced SBR containing different polyacetylene-coated sulfur samples...

For silica in SBR, a polyacetylene coating gives the lowest filler-filler interaction, a good filler-polymer interaction, and the best dispersion compared to untreated and the other plasma-treated samples. However, for the stress-strain properties, the polythiophene-treated sample gives the best results. This shows the importance of sulfur moieties on the surface of the filler, which form a secondary network in the cured materials. In the blend of S-SBR and EPDM rubbers, the situation is less conclusive. The Payne effect, the bound rubber, and... 

A polyacetylene coating applied on sulfur does not negatively influence its activity and speed as curing agent, but it can increase the scorch time. This effect is probably due to a delayed release of the sulfur out of the polymeric shell. In the SBR/EPDM blend, on the other hand, the plasma-treated sulfur results in higher torque values, an indication that the distribution of the plasma-treated sulfur over the different rubber phases is more homogenous, which is the main effect aimed for in the context of this study. 

Polythiophene is a highly crystalline polymer with the chain analog to cis-polyacetylene. The sulfur atoms stabilize the structure and interacts poorly with... 

Fig. 2. A molecular data storage scheme based on an aromatic molecule (naphthalene) bonded to four gold electrodes by sulfur atoms and polyacetylene wires [37). For the surface an insulator has to be chosen to prevent cross-talk between the electrodes. The variables X, Y and Z could either be chemical substituents or, alternatively, connections to further electrodes. Some parts of the molecule, electrodes and variables are drawn in bright colors, which is meant to indicate an active state during a particular read-out. The darker parts are considered to be inactive.

As mentioned in the introduction, the electrical conductivity upon doping is one of the most important physical properties of conjugated polymers. The conductivity ranges from lOOOOOS/cm for iodine-doped polyacetylene [41], 1000 S/cm for doped and stretched polypyrrole [42], to 500 S/cm for doped PPP [43], 150 S/cm for hydrochloric acid doped and stretched polyaniline [44], and 100 S/cm for sulfuric acid doped PPV [45] to 50 S/cm for iodine-doped poly thiophene [46]. The above listed conductivities refer to the unsubstituted polymers other substitution patterns can lead to different film morphologies and thus to a different electrical conductivity for the same class of conjugated polymer in the doped state. 

Polythiophene (PT) 20 can be regarded as a hybrid structure of cis-polyacetylene and sulfur, where the incorporation of the heteroatom leads to a much higher environmental stability of PT compared with that of PA [131], The outstanding physical and bulk properties make PT a desirable material for device applications like sensors, energy storage, solar cells, LEDs, NLO devices, and more [132], Due to the large number of possible technical applications, much effort has been made to tailor the properties of PT by synthesis. 

Polymers with unsaturated carbon chain backbone form another important class of macromolecules, many of the compounds from this class having properties of elastomers. The most common polymers from this class are obtained from 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene) and their derivatives. Natural rubber, which is poly(c/s-isoprene), as well as the natural polymers gutta-percha and balata also have an unsaturated carbon chain backbone. For many practical applications, the polymers from this class are subject to a process known as vulcanization, which consists of a reaction with sulfur or S2CI2, and leads to the formation of bridges between the molecular chains of the polymer. This process significantly improves certain physical properties of practical interest. A separate subclass of polymers with unsaturated carbon chain backbone is formed by polyacetylene. 

The blend of EPDM and polyacetylene was crosslinked using sulfur monochloride in a toluene solution. It should be noted that the crosslinked blend could not be doped with iodine. 

Samples containing more than 2% of sulfur did not pick up any iodine even after a 72-hour period. The completely saturated EPDM portions of the blend seem to prevent any iodine molecules from permeating into the polyacetylene moieties. In order to circumvent this problem, we have doped the blend with iodine prior to the crosslinking procedure. Subsequently, the doped material having a conductivity of 60 ft-1 cm-1 was reacted with sulfur monochloride in a toluene solution for 10 minutes. The color of the solution turned from pale yellow to dark red while the polymer film remained insoluble in the toluene solution. 

IODINE (7553-56-2) A powerful oxidizer. Material or vapors react violently with reducing agents, combustible materials, alkali metals, acetylene, acetaldehyde, antimony, boron, bromine pentafluoride, bromine trifluoride, calcium hydride, cesium, cesium oxide, chlorine trifluoride, copper hydride, dipropylmercury, fluoride, francium, lithium, metal acetylides, metal carbides, nickel monoxide, nitryl fluoride, perchloryl perchlorate, polyacetylene, powdered metals, rubidium, phosphorus, sodium, sodium phosphinate, sulfur, sulfur trioxide, tetraamine, trioxygen difluoride. Forms heat- or shock-sensitive compounds with ammonia, silver azide, potassium, sodium, oxygen difluoride. Incompatible with aluminum-titanium alloy, barium acetylide, ethanol, formamide, halogens, mercmic oxide, mercurous chloride, oxygen, pyridine, pyrogallic acid, salicylic acid sodium hydride, sodium salicylate, sulfides, and other materials. 

About seven hundred polyacetylenes have been isolated so far mainly from plants belonging to the family of Asteraceae, Umbelliferae and Campanulaceae [11]. Polyacetylenes occur principally as straight chain polyines, allenes, phenyl, thiophenyl, thioether and spiroketal-enoether derivatives in a quite high yield. Thiophenes and related sulfur compounds are usually grouped together with die polyacetylenes because of their common biosynthetic pathways [11]. Few plant-derived lactones, butenolides and phospholipids show antiviral activity. The antiviral activities of thiophenes, polyacetylenes, lactones, butenolides and phospholipids from plant origin are reported in table 8. 

About the same time, Alan Mac-Diarmid at the University of Pennsylvania was working with an inorganic polymer of sulfur nitride (SN)jj that also looked like a metal and raised questions about the conductivity of polymers, MacDiarmid and Shirakawa met by chance at a seminar in Tokyo, and a collaboration was begun. Because Shirakawa knew that the optical properties of a polymer change on oxidation, they oxidized polyacetylene with iodine vapor. The product was double bond had transferred to the iodine (to give I3). The result was that elec-... 

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