Polyacetylenes disubstituted

It seems quite obvious that the thiophenes are related to the polyacetylenes which they accompany. This viewpoint has recently been illustrated by the formation of thiophenes from polyacetylenes and hydrogen sulfide under almost biological conditions. In a recent lecture summary, the preparation of terthienyl, junipal, and (241) from 1,4-disubstituted butadiynes and hydrogen sulfide is claimed. A large number of bithienyls have been prepared and their nemato-dicidal activity investigated. All the compounds with strong activity were found to be derivatives of 2,2 -bithienyl. ... 

S.V. Frolov, A. Fujii, D. Chinn, M. Hirohata, R. Hidayat, M. Taraguchi, T. Masuda, K. Yoshino, and Z.V. Vardeny, Microlasers and micro-LEDs from disubstituted polyacetylene, Adv. Mater., 10 869-872, 1998 and references therein. 

R. Hidayat, S. Tatsuhara, D.W. Kim, M. Ozaki, K. Yoshino, M. Teraguchi, and T. Masuda, Time-resolved study of luminescence in highly luminescent disubstituted polyacetylene and its blend with poorly luminescent monosubstituted polyacetylene, Phys. Rev. B, 61 10167-10173, 2000 and references therein. 

As discussed earlier, substitution onto the polyacetylene chain invariably has a deleterious effect on dopability and conduction properties. At the same time the stability tends to improve. Masuda et al.583) studied a large range of substituted polyacetylenes and found that stability increased with the number and bulkiness of the substituents, so that the polymers of aromatic disubstituted acetylenes were very stable, showing no reaction with air after 20 h at 160 °C. Unfortunately, none of these polymers is conducting. Deitz et al.584) studied copolymers of acetylene and phenylacetylene they found that poly(phenylacetylene) degrades even more rapidly than does polyacetylene and that the behaviour of copolymers is intermediate. Encapsulation of the iodine-doped polymers had little effect on the degradation, which is presumably at least in part due to iodination of the chain. 

In Table 19 are collected typical monomers that polymerize with group 5 and 6 transition metal catalysts to produce high-molecular-weight (Mw > 1 x 10s) polyacetylenes. Among them, tert-butylacetylene and 3-(trimethylsilyl)-l-octyne are monosubstituted acetylenes, while the others are disubstituted ones. It is noteworthy that all of these monomers are considerably sterically crowded. By judicious choice of polymerization conditions, the polymer yield becomes fair to quantitative in every case. The Rtw s of the polymers reach ca. 3 x 10s 2 x 106. 

The polymers whose geometric structures have been quantitatively evaluated are polyacetylene 89), poly(ferf-butylacetylene)19), poly(isopropylacetylene)14), and poly-(phenylacetylene)88). In the case of polymers from aromatic monosubstituted acetylenes, qualitative evaluation of geometric structure is possible by means of IR spectroscopy, differential thermal analysis, and X-ray diffraction 66,90). In contrast, no information has been obtained on the geometric structure of disubstituted acetylene polymers. This is due to the fact that their main chain comprises fully substituted ethylene units, the difference between cis and trans structures being small. 

The instability of polyacetylene is notorious, that is, it is easily oxidized in air at room temperature. On the other hand, the substituted polyacetylenes shown in Table 27 are much more stable96. In general, the stability of substituted polyacetylenes increases with increasing number and/or bulkiness of substituents -f-CH = C(n-alkyl)- < -fCH=CPh, -f CMe=C( -alkyl)+n < CH=C(t-Bu), -f-CMe= CfSiMes)- < -j-C(n-alkyl) = CPh-, -(-CC CPh. Especially, the polymers of aromatic disubstituted acetylenes (e.g., (CMe=CPh, -fCCl=CPh ) are extreme-... 

Optically active polyacetylene derivatives 97 were synthesized through ring-opening polymerization of the corresponding cyclooctatetraene derivatives.25 A twisted conformation of the main chain was proposed on the basis of CD and UV absorptions. Various optically active polyacetylenes have also been prepared from chiral monomers.24,25,263,177-183 The examples include a phenylacetylene derivative (98),26a alkylacetylenes 99,24 propionic esters such as 100,177,178 a Si-containing monomer (101),179 and disubstituted monomers such as 102.180 Poly-(A)-98 synthesized using a [RhCl(norbornadiene)]2 catalyst shows intense CD bands in the UV—vis region, probably based on a predominant helical sense of the main chain.263 This polymer effectively resolves several racemic... 

Twenty five years after the first report on catalytic polymerization of acetylene by Shirikawa, McDiarmid and Heeger [130], the Nobel prize has been awarded to these researchers for their contribution to the field of conducting polymers. Indeed, such polymers have promising applications such as low weight/high charge density batteries, polymer-modified electrodes, or capacitors to name only a few. Driven by these applications, different classes of polyacetylenes have been synthesized, starting from acetylene itself and from mono- or disubstituted acetylene derivatives. 

Yanovskaya, L.A., Stepanova, R.N., and Kucherov, V.F., Chemistry of polyene and polyacetylenic compounds. Part 23. Synthesis of some unsymmetrically a.CO-disubstituted polyenes, kv. Akad. Nauk SSSR, Ser. Khim., 1334, 1967 Bull. Acad. Sci. USSR. Div. Chem. Sci. (Engl. Transl.). 1282, 1967. 

Polyacetylene is black in the powdery state and shows a metallic luster in the filmy state. On the other hand, substituted polyacetylenes are variously colored depending on the number and kind of substituents (Table 10). Or/Zzo-substituted poly(phenylacetylenes) have deep colors, i.e. brown to purple. The color of poly(phenylacetylene) depends on the catalysts, and it is auburn with W catalysts. Polymers from aromatic disubstituted... 

While polyacetylene is an electrical semiconductor, substituted polyacetylenes are virtually insulators (Table 13). Among them, the aliphatic polymers possess specific conductivities as low as 10 S cm" while aromatic monosubstituted acetylene polymers have values in the order of ca 10 S cm"h The low conductivities of substituted polyacetylenes are attributable to their twisted main-chain conformation induced by the bulky substituents. The unpaired-electron densities of most disubstituted acetylene polymers are below a detection limit of 1 x 10 spin In contrast, poly(phenylacetylene)... 

In contrast to simple mono- and disubstituted polyacetylenes, in which the coplanarity is generally hindered by the bulky substituents adjacent to the polymer backbone, the presence of a cyclic ring in the cyclopolymer of nonconjugated diynes tends to make the conjugated polymer backbone more coplanar. ... 

By analogy with classical systems, the new systems allow the possibility of topochemical reaction (Fig. 5). But their functional groups also permit them to take part in other reactions such as oxidative coupling (chem. or electrochem.) or as dienophiles in addition reactions with dienes, e.g. polyacetylenes and condensed hydrocarbons such as perylene (mono- or disubstituted) ... 

Trusov A, Legkov S, van den Broeke LJR Goetheer E, Khotimsky V, Volkov A. Gas/liquid membrane contactors based on disubstituted polyacetylene for CO absorption liquid regeneration at high pressure and temperature. J Membr Sci 2011 383(l-2) 241-249. 

B.A. San Jose, S. Matsushita, Y. Moroishi, K. Akagi, Disubstituted liquid crystalline polyacetylene derivatives that exhibit linearly polarized blue and green emissions. Macromolecules 44, 6288-6302 (2011)... 

Kwak, G., Fukao, S., Fujiki, M., Sakaguchi, T., Masuda, T. Nanoporous, honeycomb-structured network fibers spun from semiflexible, ultrahigh molecular weight, disubstituted aromatic polyacetylenes superhierarchical structure and unique optical anisotropy. Chem. Mater. 18, 5537-5542 (2006)... 

The primary photoexcitation dynamics in PDPA solutions and films in the fs to ps time domain using transient PM spectroscopy were extensively studied [182]. The PDPA polymer used was a disubstituted biphenyl derivative of frans-polyacetylene, where one of the hydrogen-substituted phenyl groups was attached to a butyl group, which is referred to as PDPA-mBu (Figure 22.25 inset) [181]. The polymer films were cast on sapphire substrates from a toluene solution the same solution was used for measuring the photoexcitation dynamics in a PDPA-mBu solution. 

FIGURE 47.19. Examples of EL polyacetylenes, (a) Monosubstituted (b) disubstituted. Reprinted with permission from Synth Met 1997 91 283. 1997 Elsevier Science. 

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