Polymerized acetylene

Tsai et al. have used RAIR extensively in investigations of plasma polymerized acetylene films as primers for rubber-to-metal bonding [12]. Fig. 12 shows RAIR spectra of films having a thickness between about 5.7 and 90.0 nm. A strong band... 

Tsai et al. have also used RAIR to investigate reactions occurring between rubber compounds and plasma polymerized acetylene primers deposited onto steel substrates [12J. Because of the complexities involved in using actual rubber formulations, RAIR was used to examine primed steel substrates after reaction with a model rubber compound consisting of squalene (100 parts per hundred or phr), zinc oxide (10 phr), carbon black (10 phr), sulfur (5 phr), stearic acid (2 phr). 

Polished steel substrates primed with plasma polymerized acetylene films were immersed into a stirred mixture of these materials at a temperature of 155 5°C to simulate the curing of rubber against a primed steel substrate. During the reaction, the mixture was continuously purged with nitrogen to reduce oxidation. At appropriate times between 1 and 100 min, substrates were removed from the mixture, rinsed with hexane ultrasonically for 5 min to remove materials that had not reacted, dried, and examined using RAIR. The RAIR spectra obtained after reaction times of 0, 15, 30, and 45 min are shown in Fig. 13. 

When a plasma polymerized acetylene film on a steel substrate was reacted with the squalene-containing model rubber compound at 155°C for 15 min, a new band assigned to zinc stearate appeared near 1539 cm in the RAIR spectra... 

Fig. 13. RAIR spectra of model rubber compound reacted with plasma polymerized acetylene films on steel substrates for (A) 0, (B) 15, (C) 0 and (D) 45 min. Adapted by permission of Gordon and Breach Science Publishers from Ref. [12].

Many applications of XPS to problems in adhesion science have been reported in the literature. One interesting example is provided by the work of Tsai et al. on the use of XPS to investigate reactions between model rubber compound and plasma polymerized acetylene films that was discussed above [22,23], Consideration of that system permits some interesting comparisons to be made regarding the type of information that can be obtained from RAIR and XPS. 

The XPS survey spectrum of a 75 nm thick film of plasma polymerized acetylene that was deposited onto a polished steel substrate is shown in Fig. 18 [22]. This film consisted mostly of carbon and a small amount of oxygen. Thus, the main peaks in the spectrum were attributed to C(ls) electrons near 284.6 eV and 0(ls) electrons near 533.2 eV. Additional weak peaks due to X-ray-induced O(KVV) and C(KLL) Auger electrons were also observed. High-resolution C(ls) and 0(ls) spectra are shown in Fig. 19. The C(ls) peak was highly symmetric. 

Fig. 18. XPS survey spectrum of a plasma-polymerized acetylene film with a thickness of 75 nm that was deposited onto a polished steel substrate. Reproduced by ptermission of John Wiley and Sons from Ref. [22].

The Auger depth profile obtained from a plasma polymerized acetylene film that was reacted with the same model rubber compound referred to earlier for 65 min is shown in Fig. 39 [45]. The sulfur profile is especially interesting, demonstrating a peak very near the surface, another peak just below the surface, and a third peak near the interface between the primer film and the substrate. Interestingly, the peak at the surface seems to be related to a peak in the zinc concentration while the peak just below the surface seems to be related to a peak in the cobalt concentration. These observations probably indicate the formation of zinc and cobalt complexes that are responsible for the insertion of polysulfidic pendant groups into the model rubber compound and the plasma polymer. Since zinc is located on the surface while cobalt is somewhat below the surface, it is likely that the cobalt complexes were formed first and zinc complexes were mostly formed in the later stages of the reaction, after the cobalt had been consumed. 

Positive SIMS spectra obtained from plasma polymerized acetylene films on polished steel substrates after reaction with the model rubber compound for times between zero and 65 min are shown in Fig. 44. The positive spectrum obtained after zero reaction time was characteristic of an as-deposited film of plasma polymerized acetylene. However, as reaction time increased, new peaks appeared in the positive SIMS spectrum, including m/z = 59, 64, and 182. The peaks at 59 and 64 were attributed to Co+ and Zn, respectively, while the peak at 182 was assigned to NH,J(C6Hn)2, a fragment from the DCBS accelerator. The peak at 59 was much stronger than that at 64 for a reaction time of 15 min. However,... 

Negative SIMS spectra obtained from plasma polymerized acetylene films on polished steel substrates as a function of reaction time with the model rubber compound are shown in Fig. 45. The most important changes observed in the... 

Mo2(0R)6 compounds in hydrocarbon solvents rapidly polymerize acetylene to a black metallic-looking form of polyacetylene. Propyne is polymerized to a yellow powder, while but-2-yne yields a gelatinous rubber-like material (45). The detailed nature of these polymers is not yet known and the only molybdenum containing compounds recovered from these polymerization reactions were the Mo2(0R)6 compounds. When the reactions were carried out in the presence of pyridine/hexane solvent mixtures, simple adducts Mo2(0R)6(py)2(ac) were isolated for R = i-Pr and CH2-t-Bu, and ac = HCCH, MeCCH and MeCCMe (45,46). 

Abstract The past two decades have profoundly changed the view that we have of elemental carbon. The discovery of the fullerenes, spherically-shaped carbon molecules, has permanently altered the dogma that carbon can only exist in its two stable natural allotropes, graphite and diamond. The preparation of molecular and polymeric acetylenic carbon allotropes, as well as carbon-rich nanometer-sized structures, has opened up new avenues in fundamental and technological research at the interface of chemistry and the materials sciences. This article outlines some fascinating perspectives for the organic synthesis of carbon allotropes and their chemistry. Cyclo[n]carbons are the first rationally designed molecular carbon allotropes, and... 

In 1958, Natta and co-workers polymerized acetylene for the first time by using a Ti-based catalyst. This polymerization proceeds by the insertion mechanism like the polymerization of olefins. Because of the lack of processability and stability, early studies on polyacetylenes were motivated by only theoretical and spectroscopic interests. Thereafter, the discovery of the metallic conductivity of doped polyacetylene in 1977 stimulated research into the chemistry of polyacetylene, and now poly acetylene is recognized as one of the most important conjugated polymers. Many publications are now available about the chemistry and physics of polyacetylene itself. 

Grubbs second generation complex was found to polymerize acetylene to give mostly /r< / i--polyacetylene whose conductivity was lO S cm after doping. ... 

Many other fuels such as soot, turf, corkmeal, powdered anthracite, woodmeal, carbene (polymerized acetylene), calcium hydride, and spongy aluminum have been tried. Physical and chemical properties of many LOX fuels are given by Howell et al (Ref 3) and O Neil Van Fleet (Ref 5a)... 

Surface modification of silica, another filler used in the rubber industry, has been reported by Nah et al. [36, 37]. The silica surface was modified by plasma polymerization of acetylene. The modified silica was mixed with SBR to study its performance. They observed an increase in reinforcement with the plasma-modified silica and hence better mechanical properties. They also observed an improvement in the dispersion properties for the plasma-coated silica. The authors explained the observed improvement in properties by a mild crosslinking between plasma-polymerized acetylene and the butadiene part of the SBR matrix. 

The plasma polymerization onto silica was carried out after charging 100 g of dried silica Ultrasil VN3 into the reactor, pumping down to 13 Pa and introducing plasma gasses or monomer vapors for further plasma polymerization. The conditions for the preparation of plasma-polymerized acetylene (PA), pyrrole (PPy) and thiophene (PTh) are presented in Table 2. 

Functionalities on the silica surface - The ToF-SIMS spectra were recorded of the untreated and treated silicas. Figure 8 represents an untreated silica sample, and Fig. 9 an acetylene-treated one. They show a complex structure of a plasma-polymerized acetylene film on the silica surface. 

In the spectra of the untreated silica sample, no specific peaks in the low mass region up to 150 amu (atomic mass units) such as from 3+, 10+, and no cluster peaks in the higher mass region are found. The spectra of the acetylene-treated sample do show these specific plasma-polymerized acetylene peaks in the... 

Fig. 7 Water penetration into powder beds of untreated silica and plasma-polymerized acetylene-, pyrrole-, and thiophene-coated silica...

Systematic studies of acetylene polymerization were conducted in the laboratories of the duPont Co and the results are described in numerous papers (see Ref 3). Studies of acetylenic polymers from the point of view of their utilization in solid rocket propeliancs has been conducted by Reaction Motors (see Ref 10). Polymerization under press is described in Ref 4 and some industrial products obtained by polymerizing acetylene are listed in Ref 5... 

One of the most interesting alternatives to the Shirakawa catalyst has been the systems disclosed by Luttinger 22-23) and later elaborated by Lieser et al. 24). The tris(2-cyanoethyl)phosphine complex of nickel chloride reacts with sodium boro-hydride to produce a catalyst system capable of polymerizing acetylene in solutions in either alcohol or, quite remarkably, water. A more efficient catalyst is obtained by replacing the nickel complex with cobalt nitrate. Interest in Luttinger polyacetylene seems to have waned in the last few years. 

Another approach to blending of polyacetylene with tough polymers is to form graft or block copolymers 280,281). Aldissi282) produced block copolymers by polymerizing acetylene at the ends of chains of anionic polyisoprene after conversion of... 

Controlled polymerizations, acetylenes, 11, 574 Conventional heating, and microwaves and ultrasound,... 

Living anionic ring-opening polymerization, strained metallocenophanes, 12, 326 Living polymerization acetylenes... 

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