Poly-2-octyne

The radiation degradation of poly(2-octyne) occurs only in the presence of oxygen. Its degradation products contain carbonyl and hydroxyl groups, and so dissolve in polar solvents (e.g., acetone). Such solubility change is essential to resist materials. The Gs value (number of main-chain scission per 100 eV of absorbed dose) of poly(2-octyne) is ca. 12. It is noteworthy that this value is higher than that of poly-(methyl methacrylate) (Gs ca. 2)118) which is being used as electron-beam resists. 

The polymerization procedure is the same as that of poly(2-octyne) catalyst MoClj—EtjSiH. 

The study of the chain conformation in solution of PPA and poly(2-octyne) is of interest for two reasons. First, these two polymers differ as the PPA solution is red while the poly(2-octyne) solution is transparent, so that if it exists, any relation between the chain stiffness and the n electron delocalization may be expected to have a statistical length larger for PPA than for the poly(2-octyiie). The second reason is that PPA and polystyrene have almost identical monomer unit structures, the unique difference being the conjugated backbone structure of the PPA. 

The scattering function at large q of the poly(2-(octyne) sample (Figure 5.8) differs markedly from the... 

Figure 5.8. q g(q,c) plots of the scattering function of poly(2-octyne). The continuous line corresponds to the same fit as the one displayed in Figure 5.7. (Reprinted with permission from ref 41)...

With regards to the mechanical properties of substituted polyacetylenes, aromatic polymers like poly(diphenylacetylene) derivatives are generally hard and brittle, whereas aliphatic polymers with long alkyl chains like poly(2-octyne) are soft and ductile.Considerations of mechanical properties are especially important when polymer membranes or fibers are required for the specific application. 

Other hyperbranched polymers showed similar absorption and luminescence properties. Upon photoexcitation, the hb-PA solutions emitted deep-blue to blue-green lights, whose intensities were higher than that of poly(l-phenyl-l-octyne), a well-known highly emissive polyene. The PL efficiencies of the polymers varied with their molecular structures. Polymers hb-P(38-VI), hfo-P(45-V), hb-P(48-VI), M>-P(50-VI), fcfo-P(50-VII) and hb-P(59-VI) exhibited (P values higher than 70%, with hfc-P(50-VII) giving the highest value of 98%. 

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. 

The general formula of metal halide-based living polymerization catalysts is expressed as MO,jCl ,-co-catalyst-ROH (M = Mo or W, = 0 or 1, m = 5 or 4). The most important feature of these catalysts is ease of preparation, but their initiation efficiency is low. A typical living polymerization by metal halide-based catalysts has been achieved with 1-chloro-l-octyne as monomer and using MoOCl -w-Bu Sn-EtOH (1 in Table 15.2) as catalyst [41]. Specifically, poly(l-chloro-l-octyne) with a narrow MWD < 1.2) is obtained, and the... 

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]. 

---