Phenyl substituted poly acetylene

The MW of polymers of aliphatic disubstituted acetylenes such as 2-octyne remarkably reduces, when such polymers are irradiated with y-rays in airll7) (Fig. 10). In contrast, polymers of aromatic disubstituted acetylenes like 1-phenyl-1-propyne hardly degrade by y-rays irradiation in air. Thus the degradation behavior of substituted poly acetylenes is greatly dependent on the kind of substituent. The mechanism is essentially the same as that for thermal degradation. 

Figure 10.6 Substituted triphenylphosphine used to solubilize [Rh(nbd)(acac)] (nbd = nor-bornadiene, acac = acetylacetonate) precursor for the synthesis of poly(phenyl acetylene) in scC02...

The azide-alkyne click reactions are useful to attach a number of polar FGs including various azobenzene moieties to the pendants of poly(l-phenyl-5-chloro-l-pentyne), (Eq. (7)) [90]. Nucleophilic substitutions of the same starting polymer result in the formation of an imidazole-functionalized, disubstituted acetylene polymer, (Eq. (8)) [91]. The degree of incorporation of the imidazole moiety is about 65%, and the product polymer exhibits good solubility in ethanol. Hydrolysis reaction of poly[l-(/w-methoxycarbonylphenyl)-l-octyne] yields a carboxy-functionalized disubstituted acetylene polymer poly[l-(/w-carboxyphenyl)-l-octyne], (Eq. 9) [92]. Hydrazine-catalyzed deprotection of poly[l-phenyl-ll-Af-benzimide-l-undecyne] affords the corresponding polyamine, which can be further ionized with hydrobromic acid to give a polyelectrolyte ammonium salt, (Eq. (10)) [93]. 

Two isomeric acetylenic benzothiazole monomers, 2-(3-ethynyl-phenyl)-5-ethynylbenzothiazole (3) and 2-(3-ethynylphenyl)-6-ethynyl-benzothiazole (4) were prepared according to the general reaction scheme shown below. The synthesis of the benzothiazole heterocyclic structure was carried out by the condensation of m-bromobenzoic acid with isomeric bromo-substituted o-aminomercaptobenzenes in poly-phosphoric acid (PPA). The bis-bromobenzothiazoles were converted to the acetylene systems by the reaction with 2-methyl-3-but3m-2-ol and subsequent displacement of acetone with base. The bromo displacement reaction utilized a catalyst composed of triphenylphosphine, (bis-triphenylphosphine)palladium dichloride and cuprous iodide. 

PerfluoroaIkyl-5-substituted-l//-pyrazoles 61 can be obtained in excellent yields by reaction of either perfluoroalkylacetylenes 59 [31] or A -aryl per(poly) fluoroalkyl phenyl acetylenic imines 60 [32] with hydrazine hydrate in EtOH (Scheme 18). The loss of two molecules of hydrogen fluoride in the former case, and arylamine in the latter, led to the final products. As it has been mentioned above, this strategy can be also applied for the preparation of polyfluorinated derivatives (see Scheme 3), by reaction of perfluoro-2-methyl-2-pentene with hydrazones [4] or arylhydrazines [5, 6] in a basic medium. 

Substituted P(Ac)s may be synthesized using a wide variety of methods, primarily condensation polymerizations. Fig. 13-5 shows a sampling of these. Poly(phenyl acetylene) (P(PhAc)), a typical substituted P(Ac), is soluble in its undoped state in common organic solvents [563]. 

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