Di acetylenes

The extensive studies of the behavior of mixed monolayers or bilayers of di-acetylenic lipids and other amphiphiles parallel to some degree the studies of dienoyl-substituted amphiphiles. Since the dienoyl lipids do not contain a rigid diacetylenic group in the middle of the hydrophobic chains, they tend to be miscible with other lipids over a wide range of temperatures and compositions. In order to decrease the lipid miscibility of certain dienoyl amphiphiles, Ringsdorf and coworkers utilized the well-known insolubility of hydrocarbons and fluorocarbons. Thus two amphiphiles were prepared, one with hydrocarbon chains and the other with fluorocarbon chains, in order to reduce their ability to mix with one another in the bilayer. Of course it is necessary to demonstrate that the lipids form a mixed lipid bilayer rather than independent structures. Elbert et al. used freeze fracture electron microscopy to demonstrate that a molar mixture of 95% DM PC and 5% of a fluorinated amphiphile formed phase-separated mixed bilayers [39]. Electron micrographs showed extensive regions of the ripple phase (Pb phase) of the DM PC and occasional smooth patches that were attributed to the fluorinated lipid. In some instances it is possible to... 

Branched phenylacetylene monomers can be used to construct dendrimers on supports. This was accomplished using a triazene tether as a focal point, the reaction triad outlined above, and an AB2 monomer, as seen in Scheme 7.16 As in similar solution-phase convergent dendrimer syntheses, the first step was to prime the periphery of the dendrimer with t-butyl groups by di-coupling of a triazene-tethered dibromoaryl monomer with (di-f-butyl-phenyl)acetylene. In this and all subsequent coupling steps, an excess amount of the monodendron acetylene was used to drive the reaction to completion. The reagents and catalysts were washed away and the excess monodendron was recovered. At the end of the first step, the tri-aryl dendron I-M3-(t-Bu)4 was cleaved from the support (M represents the dendritic monomer unit). Two equivalents of this product were then coupled with the triazene-tethered di-acetylene ary] monomer to produce the heptaaryl dendron I-M7-(r-Bu)8. 

Electrocracking A general name for processes that decompose organic liquids or gases by passage through an electric arc. Thus methane is converted to acetylene and di-acetylene. Developed in Russia in the early 20th century, but probably never commercialized. 

From Di-phenyl Di-acetylene.—The proof that the two isatin or indole residues are linked together by the carbons is in the synthesis of indigo from di-phenyl di-acetylene, CeHs—C = C—C = C—CeHs. This compound by conversion into the di- (ortho-nitro) product, and treatment with sulphuric acid and reduction with ammonium sulphide, yields indigo. This indicates that the chain of carbon linkings remains as in the above compound. 

Compounds such as (12.227a) can be used in emulsion polymerisation of polystyrene [65]. Di-acetylenic phospholipids such as (12.227b) will form hollow open-ended cylindrical tubes 0.5 mm diameter and up to 300 mm long. Subsequent polymerisation to increase stability can be effected with UV radiation [66,67]. 

Fig. 13 Top CD spectra of tubules of various mixtures of the two enantiomers of di-acetylenic phospholipid 22 (inset variation of the molar ellipticity as a function of enantiomeric excess) prepared from methanol/water. Bottom CD spectra of tubules of diacetylenic phospholipid 22 solid /me), of an achiral analogue dotted line), and of a mixture of the achiral analogue with 6.1% of 22 dashed line). Reprinted with permission from [34] and [102]. Copyrights 1998 American Chemical Society and 2003 National Academy of Sciences (USA)...

Eisenbach C D, Hofmann J and MacKnight W J (1994) Dynamic-mechanical and spectroscopic study of ionomer blends based on carboxylated or sulfonated flexible polystyrene and rigid poly(di-acetylenes) with functional side groups. Macromolecules 27 3162-3165. 

Currently, there is widespread interest in the process of solid-state polymerization in single crystals of di-acetylene compounds. Much of this is centred round the question of whether or not lattice defects play any role in this process. 

In common with other surfactants containing the diacetylene group, diacetylene containing phosphatidylcholines only polymerise in the solid state, in this case when they are cooled below Tc. 2) Polymerisation occurs either when the lipid is dispersed in water in the form of liposomes or compressed in KBr discs. That di acetylene containing phosphatidylcholines dispersed in water do form closed... 

The picolinyl ester of a mono-acetylenic fatty acid gave a spectrum which resembled that from its monoethylenic analogue except that there was a gap of 24 amu for fragmentations on either side of the triple bond [172], A series of di-acetylenic fatty acids gave spectra which were rather complex, but the terminal triple bond generally exhibited a fragmentation with a gap of 24 amu [174],... 

Some of the first third order NLO studies of CPs were carried out on the poly(di-acetylenes) (P(DiAc)). One of the first such studies, on P(DiAc)-toluene sulfonate (PTS) single crystals, carried out by Sauteret et al. [502], revealed third order bulk NLO susceptibilities x fzzzz) polymer chain axis) of 1.6 X 10 ° esu at 2.62 pm and 8.5 X 10 ° esu at 1.89 pm. These values have as yet been exceeded only by one study, that of Drury on oriented Durham P(Ac) [503], in which a value for x zzzz> (Z= polymer chain axis) of 10 esu at 1.9 pm. However, this value of the susceptibility was inferred from THG data somewhat indirectly. Dennis et al. [504] reported off-resonant x xyyx values of 7 X 10 esu for solutions of various P(DiAc), extrapolated to pure substance and determined via DFWM at 532 nm. 

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