Oxidation polymerization reactions

Oxidative Polymerization Reactions. Clays can initiate polymerization of unsaturated compounds through free radical mechanisms. A free radical R", which may be formed by loss of a proton and electron transfer from the organic compound to the Lewis acid site of the clay or, alternatively, a free radical cation, R+, which may be formed by electron transfer of an electron from the organic compound to the Lewis acid site of the clay, can attack a double bond or an aromatic ring in the same manner as an electrophile. The intermediate formed is relatively stable because of resonance, but can react with another aromatic ring to form a larger, but chemically very similar, species. Repetition of the process can produce oligomers (dimers, trimers) and, eventually, polymers. 

The oxidative polymerization reaction is rapid at room temperature. Oxidation of 2.6-dimethylphenol readily gives high polymer with only a minor amount of the diphenoquinone (VIII R=R1=CH3). This polymer is now being produced commercially. In general when the substituents are small (Table 4) the polymer is formed preferentially (35). If one of the substituents is as large as tert-butyl or both as large as isopropyl then the diphenoquinone is preferentially formed. 

Cationic-oxidative polymerization reactions have been developed to synthesize PPS under less severe conditions. For example, PPS has been obtained by a cationic-oxidative polymerization of thiophenol or diphenyl disulfide at room temperature. However, the resulting PPS has a low molecular weight due to premature precipitation. The cationic-oxidative polymerization reaction has been performed electrolytically [109] [Eq. (24)], with Lewis acids [110] [Eq. (25)], with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) [111] [Eq. (26)], and with O2 in the presence of a catalytic amount of VO(acac)2 [112] [Eq. (27)]. 

SAFETY PROFILE A human poison by an unspecified route. Poison experimentally by inhalation. An eye, mucous membrane, and systemic irritant by inhalation. Mutation data reported. A common air contaminant. Difficult to ignite. Explosion hazard when exposed to flame or in a fire. NH3 + air in a fire can detonate. Potentially violent or explosive reactions on contact with interhalogens (e.g., bromine pentafluoride, chlorine trifluoride), 1,2-dichloroethane (with liquid NH3), boron halides, chloroformamideium nitrate, ethylene oxide (polymerization reaction), magnesium... 

In recent studies of styrene oxide polymerization reactions we found the phenyl substituent to have a significant Influence on the course of the polymerization process, too. In our particular case, however, the influence is due not only to steric factors, but also to the inductive effects of the phenyl ring, which Influences directly the course of the oxirane ring-opening reaction. 

Linear perfluoroalkylene ether dicarboxylic acids, HOOC-(CF2CF2OCF2CF2)nCOOH, are reported to have been prepared by UV-catalyzed coupling reactions (6) and oxidative polymerization reactions (11). Although these structures are considered to represent the preferred chain segments, the synthesis methods apparently have not been developed enough for commercial availability. 

Materials produced from natural oils by oxidative polymerization reactions, e.g. binding agents in linoleum mats, will under the effects of moisture produce and emit degradation products such as fatty acids, higher aldehydes, and alcohols. 

Figure 29.5 The conventional synthesis of polyaniline and its morphology, (a, b) The oxidative polymerization reaction of aniline is typically carried out in an acidic solution (e.g., 1 M HCl) [45].

P. Liu and K. Gong, Synthesis of polyaniline-intercalated graphite oxide by an in situ oxidative polymerization reaction. Carbon, 37, 706-707 (1999). 

We have demonstrated that oxidative polymerization reactions leading to conducting polymers can be carried out within the channel systems of zeolites. Acidic zeolite forms are required to synthesize intrazeolite polyaniline by analogy to the oxidative coupling of aniline in acidic solutions. The presence of intrazeolite oxidants such as Cu(II) and Fe(III) ions is fundamental for the polymerization of pyrrole, thiophene and 3-methylthiophene. The degree of polymer chain oxidation and probably the chain lengths are influenced by the dimension ity of the zeolite channels. 

Autoxidation inhibitors n. Chemical agents, which inhibit the autoxidation (or oxidative polymerization) reactions, i.e., phenol and arylamines. Bart J (2005) Additives in polymers industrial analysis and applications. John WUey and Sons, New York. Zaiko GE (ed) (1995) Degradation and stabilization of polymers. Nova Science Publishers Inc., New York. 

The formation of poly (2,6-dimethyl-1,4-phenylene oxide) 2, later called PPO resin, represented a new method of polymerization which was termed polymerization by oxidative coupling. PPO was commercialized in 1964 and two year later blends of PPO with polystyrene, NORYL resins that are miscible blends of PPO and polystyrene, were commercially introduced. The scope and mechanism of the oxidative polymerization reaction and the historical development of PPO and its blends have been extensively reviewed previously... 

The oxidative polymerization reaction was found to be a general reaction and linear high molecular weight polymers and diphenoquinones were prepared from other 2,6-dialkylphenols. If the substituents are bulky, e.g. a t-butyl group, only the diphenoquinone is formed. We were also able to synthesize high molecular weight poly (2,6-diphenyl-1,4-phenylene oxide) (P3O, 5) from 2,6-diphenylphenol 4. (Scheme 2)... 

One of the early challenges was an understanding of the mechanism of the oxidative polymerization reaction. It was studied intensively by workers at GE and at AKU in the Netherlands where a joint company, NV Polychemie AKU-GE, was formed in 1963 to develop PPO in Europe. The mechanism has been discussed in detail in several reviews. Some of the key points of the reaction are discussed below. Endres and Kwiatek first showed that the reaction behaved like a step growth polymerization reaction. Cooper et demonstrated that in the initial stages of the... 

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