Polymerization Friedel-Crafts

In fact, the Eriedel-Crafts polymerization is a polycondensation, however, the term polymerization is more common. The Friedel-Crafts polymerization is notorious in producing an intractable reaction product, which is difficult to remove from the reaction vessel and to purify. Further, polymers with undesirably low molecular weights or poor thermal stahihty are obtained, if the reaction conditions are not appropriately chosen.  

In Friedel-Crafts reactions, ortho substitution of the polymer is more likely to occur if the reaction is conducted at elevated temperatures and for a relatively long reaction time. To overcome these problems, it has been proposed to use a boron trifluoride catalyst in anhydrous hydrogen fluoride. Another procedure uses lithium chloride and aluminum chloride to polymerize p-phenoxybenzoyl chloride as the ketone monomer and p-phenoxybenzenesulfonyl chloride as the sulfone monomer.  

High-molecular-weight poly(ketone)s and poly(ketone sulfone)s can be prepared by reacting dicarboxylic acids with aromatic compounds in the presence of trifluoromethanesulfonic acid and phosphorus pentoxide for water binding. 

The polymerization occurs as water is formed by the elimination of a hydroxyl group from the carboxylic acid, and hydrogen from an aromatic ring. In this way, the polymer chain becomes linked together between 

The electrophilic polymerization of this type is often referred to as Friedel-Crafts polymerization. Examples are polymers obtained from near equimolar feeds of terephthalic acid as dicarboxylic acid and 4-phenoxy-phenyl sulfone, or 4-biphenylyl sulfone, respectively. Usage of 4,4 -di-phenoxybenzophenone yields a poly (ketone). 

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Cationic polymerization of coal-tar fractions has been commercially achieved through the use of strong protic acids, as well as various Lewis acids. Sulfuric acid was the first polymerization catalyst (11). More recent technology has focused on the Friedel-Crafts polymerization of coal fractions to yield resins with higher softening points and better color. Typical Lewis acid catalysts used in these processes are aluminum chloride, boron trifluoride, and various boron trifluoride complexes (12). Cmde feedstocks typically contain 25—75% reactive components and may be refined prior to polymerization (eg, acid or alkali treatment) to remove sulfur and other undesired components. Table 1 illustrates the typical components found in coal-tar fractions and their corresponding properties. 

Thermoplastic resins produced from pure monomers such as styrene, alkyl-substituted styrenes, and isobutylene are produced commercially. An advantage of these resins is the fact that they are typically lighter in color than Gardner 1 (water-white) without being hydrogenated. Among the earliest resins in this category were those made from styrene and sold as Piccolastic. Styrene and alkyl-substituted styrenes such as a-methylstyrene are very reactive toward Friedel-Crafts polymerization catalysts. 

Symposium on Friedel-Crafts Polymerization, Proc. Roy. Dublin Soc., 1950, 25, 131. 

The current work on Friedel-Crafts polymerization of cyclic ethers may be considered to date from about 1940 when Meerwein and his associates prepared a series of tertiary oxonium salts and applied them to the polymerization of tetrahydrofuran. These salts, of the general form R30+... M X4i, are easily prepared from the corresponding metal halide in a reaction with an epoxide (preferably epichlorohydrin) in ether solution. According to Meerwein et al. (3) this reaction takes place in the following steps ... 

The boron fluoride catalysed polymerization of epoxides, in spite of its complexity, or perhaps because of it, reveals a great deal about the mechanisms of these Friedel Crafts polymerizations and therefore must be dealt with here in some detail. When boron fluoride is added to a solution of ethylene oxide in ethylene dichloride containing a little water, polymerization sets in and the molecules grow slowly and steadily... 

Friedel-Crafts polymerization of desulfurized C4 refinery streams. Although the feed is a mixed butylenes stream, the polybutene product is essentially a polymer of isobutylene, with a few n-butene units occurring in the polymer chain. The optimum isobutylene concentration in the feed stream is reported to be in the 20-25 percent range. The polymerization reaction yields products with a molecular weight range of 300-3000. 

PEKs that are subsequently end capped with nitrile functions have been prepared by Friedel-Crafts polymerization. For example, m-hexaphenyl ether are reacted with p-cyanobenzoyl chloride with AICI3 as catalyst in dry 1,2-dichloroethane to form a nitrile end capped oligomer. In another study, 5-cyanoisophthaloyl chloride was used as a nitrile-containing comonomer for the Friedel-Crafts polymerization. ... 

In the Friedel-Crafts polymerization, the nitrile compound need not necessarily bear a chlorine function, if another aromatic chlorine compound is present. Actually, a Friedel-Crafts polymerization using 2,6-di-phenoxybenzonitrile as the nitrile compound with the comonomers shown in Figure 8.5 has been used. ... 

The aromatic polyketones can be synthesized [333] when conducting the Friedel-Craft polymerization with acylation by means of the interaction of 2,2 bis(arylphenoxy)bisphenyls with chlorides of arylenebicar-bonic acids in the presence of AICI3. The polyketones obtained using the most efficient 2,2 bis(4-bezoylphenoxy) bisphenyl are well soluble in organic solvents and possess high heat resistance. 

In fact, the Friedel-Crafts polymerization is a polycondensation, however, the term polymerization is more common. The Friedel-Crafts polymerization is... 

It has been recognized lately that, in addition to the aluminum and cobalt compounds, a substance, such as water (Sinn et al., 1961 Gippin, 1962 Cooper, 1963), may be an effective part of the catalyst system when added or present adventitiously in trace amounts. This realization of the role of a trace substance is strikingly similar to what happened years ago in the investigations of Friedel-Crafts polymerizations (Olah, 1963). At first, due to unknown impurities, reactions were observed to go, but later, as the systems were more highly purified, the reactions did not go or go as well until another catalyst component was added. 

One of the early and well-documented methods for producing poly-arylethersulfones involves use of an electrophilic Friedel-Crafts polymerization process. First applied to PES, this synthesis route involved reacting bis(4-chlorosulfonylphenyl)ether in a 1 1 molar ratio with diphenylether [5—7]. Alternatively, a single-monomer Friedel-Crafts synthesis can be employed starting with 4-chlorosulfonyldiphenyl ether as the sole monomer. The Friedel-Crafts route to the production of sulfone polymers was used briefly on a commercial basis in the 1960s but was quickly abandoned due to a number of limitations. In addition to being operationally complex, this sjmthesis route yields polymers that are not always linear or para-linked. 

Method 5. Friedel-Crafts Polymerizations The aluminum chloride-catalyzed condensation of methylene chloride with benzene yields several products (79). 

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