Acetylene oligomers

When alkynes are treated with catalytic amounts of a carbene complex, polymerization instead of metathesis can occur (Figure 3.44) [565,595,597,752-754]. The use of carbene complexes to catalyze alkyne polymerization enables much better control of the reaction than with heterogeneous or multi-component catalysts. Pure acetylene oligomers (n = 3-9) with terminal fcrf-butyl groups have been prepared with the aid of a tungsten carbene complex [755]. 

The compound HBNH is expected to be thermodynamically unstable toward oligomerization. The cyclodimer, (HBNH)2, isoelectronic with cyclobutadiene, is found to be more stable by 63.3 kcal/mol, and the cyclotrimer, (HBNHlj, by 193.8 kcal/mol than 2 or 3 mol of HBNH, respectively (23). The oligomerization energy is due to an increase in the number of (7-bonds at the expense of the relatively weak Tt-bonds. Note that the situation is the same for acetylene. Oligomers like cyclobutadiene, benzene, benzvalene, and cyclooctatetraene are... 

Acetylene hydrogenation is widely practiced and efficient. However, a green-oil which comprises vinyl acetylene oligomers is also produced and in some instances can foul the unit. In large cracking operations, the acetylene may be recovered by absorption processes based on copper salts, which selectively absorb the acetylene. 

In contrast, reaction of alkynes with carbon dioxide in the presence of Ni(COD)2/Ph2P(CH2)4PPh2 in benzene at 120 °C (50 bar carbon dioxide pressure) produces pyrones 21 and acetylenic oligomers... 

In the narrow sense, bis-maleimide resin means the thermosetting resin eom-posed of the bis-maleimide of methylene dianiline (BMI, bis(4-maleimidophenyl)-methane) and methylene dianiline (MDA, bis(4-aminophenyl)methane) (Fig. 1). Beeause of the addition meehanism, the resin is eured without elimination, whieh is a eharacteristic of this resin. Bis-maleimide resin is used as a thermally stable matrix up to 204°C (400 F) whieh typical epoxy resins may not normally be used. However, in spite of having an imide structure, bis-maleimides are classified as being moderately thermally stable resins. The aliphatic structure of the resin is not stable for long periods above 232°C (450°F.) If a highly aromatic thermally stable thermosetting resin is necessary, acetylene end-capped aromatic imide-based oligomers should be used. 

This article summarizes efforts undertaken towards the synthesis of the cyclo[ ]carbons, the first molecular carbon allotropes for which a rational preparative access has been worked out. Subsequently, a diversity of perethynylated molecules will be reviewed together, they compose a large molecular construction kit for acetylenic molecular scaffolding in one, two and three dimensions. Finally, progress in the construction and properties of oligomers and polymers with a poly(triacetylene) backbone, the third linearly conjugated, non-aromatic all-carbon backbone, will be reviewed. 

The goal of this work is to elucidate the relationship between the thermal isomerization and crosslinking reactions occurring in this acetylene terminated polyisoimide oligomer Thermid IP600. The... 

Structure of Thermid IP-600 Acetylene Terminated Isoimide Oligomer. 

Eddy, L. T. R. Lucarelli, A. M. Helminiak, T. Jones, W. Picklesimer, L. F. An Evaluation of An Acetylene Terminated Sulfone Oligomer. Internal Report, A FWAL/MLBC, January 1983. 

Acetylene-terminated oligomers, incorporation of isoimide functionality, 462 Acid functionalities, block copolymers, 258... 

About 1970, research was initiated under Air Force funding on acetylene-terminated imide oligomers (ATI) which could be thermally chain extended through the acetylenic end-groups (33, 34). This effort resulted in the development of HR-600 (Eq. 9) and subsequent commercialization by Gulf Oil Chemicals Company in the form of Ther-mid -600. Neat resin properties of HR-600 are presented in Table IV while preliminary composite properties are given in Table V. 

Although HR-600/Thermid-600 provided promising neat resin and composite properties, major processing problems have plagued these as well as other acetylene-terminated oligomers. Resin flow and wetting is inhibited due to the reaction of the terminal ethynyl groups prior to the formation of a complete melt or soft state. This becomes even more severe due to heat transfer problems as... 

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