Poly disubstituted

Muroga T, Sakaguchi T, Hashimoto T (2012) Synthesis and photoluminescence properties of heterocycle-containing poly(disubstituted acetylene)s. Polymer 53(20) 4380-4387. doi 10. 1016/j.polymer.2012.08.009... 

Sivkova R, Vohlidal J, Blaha M, Svoboda J, Sedlacek J, Zednik J (2012) Poly(disubstituted acetylene)s with pendant naphthalimide-based fluorophore groups. Macromol Chem Phys 213(4) 411 24. doi 10.1002/macp.201100509... 

All the entries above the broken line in Table 2.3 are disubstituted, and those below, with the exception of poly (dimethyl siloxane), are mono-substituted. Those in the former category consistently have larger values of f than the latter. 

The selectivity of the oxidation of 2,6-disubstituted phenols depends on the type of oxidizing agent. For example, with a series of cobalt-containing catalysts of the salcomine type, oxidation of 2,6-dimethylphenol produces three products the poly(phenylene oxide), the diphenoquinone, and... 

Halogen Displacement. Poly(phenylene oxide)s can also be prepared from 4-halo-2,6-disubstituted phenols by displacement of the halogen to form the ether linkage (48). A trace of an oxidizing agent or free radical initiates the displacement reaction. With 4-bromo-2,6-dimethylphenol, the reaction can be represented as in equation 10 ... 

Halophenols without 2,6-disubstitution do not polymerize under oxidative displacement conditions. Oxidative side reactions at the ortho position may consume the initiator or intermpt the propagation step of the chain process. To prepare poly(phenylene oxide)s from unsubstituted 4-halophenols, it is necessary to employ the more drastic conditions of the Ullmaim ether synthesis. A cuprous chloride—pyridine complex in 1,4-dimethoxybenzene at 200°C converts the sodium salt of 4-bromophenol to poly(phenylene oxide) (1) ... 

The 1,1-disubstitution of chlorine atoms causes steric interactions in the polymer, as is evident from the heat of polymeri2ation (see Table 1) (24). When corrected for the heat of fusion, it is significantly less than the theoretical value of —83.7 kJ/mol (—20 kcal/mol) for the process of converting a double bond to two single bonds. The steric strain apparentiy is not important in the addition step, because VDC polymeri2es easily. Nor is it sufficient to favor depolymeri2ation the estimated ceiling temperature for poly (vinyhdene chloride) (PVDC) is about 400°C. 

Various 2,6-di8ubstituted p-benzoquinones have been prepared by oxidation of the corresponding 2,6-disubstituted phenols with potassium nitrosodisulfonate or lead dioxide in formic acid. Oxidative coupling of 2,6-disubstituted phenols to poly-2,6-disubstituted phenylene ethers followed by treatment of the polymers in acetic acid with lead dioxide is reported to give low yields of the corresponding 2,6-disubstituted p-benzoquinones. 

By using a cocatalyst of Pd-Cu, aryl-alkenyl halides couple efficiently widi alkynes to generate die disubstituted alkynes (Scheme 9.6).8 This coupling reaction has been applied to die synthesis of polyphenyleneethynylenes by Yamamoto et al. in 1984 (Scheme 9.7).9a Due to the ready availability of diacetylenes and the mild coupling condition, this strategy has been widely used for die preparation of many poly(aryleneethynylene)s.9... 

L.M. Leung and G.L. Chik, Phase-transfer catalysed synthesis of disubstituted poly(phenylene vinylene), Polymer, 34 5174—5179, 1993. 

However the formation of thin polymer film on the electrode, i.e. passivation of the electrode, resulted in cessation of the polymerization, which restricted the electro-oxidation as a polymerization procedure. The electro-oxidative polymerization as a method of producing poly(phenyleneoxide)s had not been reported except in one old patent, in which a copper-amine complex was added as an electron-mediator during the electrolysis (4). The authors recently found that phenols are electro-oxidatively polymerized to yield poly-(2,6-disubstituted phenyleneoxide)s, by selecting the electrolysis conditions This electro-oxidative polymerization is described in the present paper. 

Electro-oxidative polymerization of 2,6-disubstituted phenols is listed in Table I, with the polymerizations catalyzed by the copper-pyridine complex and oxidized by lead dioxide. 2,6-Dimethylphenol was electro-oxidatively polymerized to yield poly(2,6-dimethylphen-yleneoxide) with a molecular weight of 10000, as was attained by other polymerization methods. The NMR and IR spectra were in complete agreement with those measured for the other polymerization... 

Among other in vitro enzymatic polymerizations that have been studied are the oxidative polymerizations of 2,6-disubstituted phenols to poly(p-phenylene oxide)s (Sec. 2-14b) catalyzed by horseradish peroxidase [Higashimura et al., 2000b] and the polymerization of P-cellobiosyl fluoride to cellulose catalyzed by cellulase [Kobayashi, 1999 Kobayashi et al., 2001],... 

Polymers containing rings incorporated into the main chain (e.g., by double-bond polymerization of a cycloalkene) are also capable of exhibiting stereoisomerism. Such polymers possess two stereocenters—the two atoms at which the polymer chain enters and leaves each ring. Thus the polymerization of cyclopentene to polycyclopentene [IUPAC poly(cyclopen-tane-l,2-diyl)] is considered in the same manner as that of a 1,2-disubstituted ethylene. The... 

Since radical polymerizations are generally carried out at moderately high temperatures, most of the resulting polymers are highly atactic. This does not mean that there is a complete absence of syndiotacticity. There is a considerable difference in the extent of syndiotacticity from one polymer to another. Thus, methyl methacrylate has a much greater tendency toward syndiotactic placement than vinyl chloride. Whereas the poly(vinyl chloride) produced at the usual commerical polymerization temperature ( 60°C) is essential completely atactic, that is, (r) (m) 0.5, this is not the case for poly(methyl methacrylate). The polymerization of MMA, usually carried out at temperatures up to 100°C, yields polymers with appreciable syndiotacticity—(r) is 0.73 at 100°C. The difference is a consequence of the fact that MMA is a 1,1-disubstituted ethylene, leading to greater repulsions between substituents in adjacent monomer units. 

With a few exceptions, 1,2-disubstituted alkenes are not polymerized because of steric hindrance. The exceptions include 1-deuteropropene (Sec. 8-4g) and cydoalkenes. Polymers are obtained from some 1,2-disubstituted alkenes, but the reactions involve isomerization of the monomer to a 1-alkene prior to polymerization, e.g., 2-butene yields poly( 1-butene) [Endo et al., 1979]. There is one report of polymerization of trans-2-butene to poly( ranv-2-butene) using the a-diimine nickel initiators described in Sec. 8-8b [Leatherman and Brookhart,... 

Trimethyl Benzene under Disubstituted and Poly substituted Benzene Hydrocarbons... 

Since only Ta and Nb catalysts, which are not tolerant to polar groups, are available for the polymerization of disubstituted acetylenes, it is generally difficult to synthesize disubstituted acetylene polymers having such a highly polar substituent as a hydroxy group. Recently, synthesis of poly[l-phenyl-2-( -hydroxyphenyl)acetylene] has been achieved by the polymerization of 1-phenyl-2-(p-siloxyphenyl)acetylene and the subsequent acid-catalyzed deprotection reaction. 

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