Aromatic diacid, polymerization

The diacids are characterized by two carboxyHc acid groups attached to a linear or branched hydrocarbon chain. AUphatic, linear dicarboxyhc acids of the general formula HOOC(CH2) COOH, and branched dicarboxyhc acids are the subject of this article. The more common aUphatic diacids (oxaUc, malonic, succinic, and adipic) as weU as the common unsaturated diacids (maleic acid, fumaric acid), the dimer acids (qv), and the aromatic diacids (phthaUc acids) are not discussed here (see Adipic acid Maleic anhydride, maleic acid, and fumaric acid Malonic acid and derivatives Oxalic acid Phthalic acid and OTHERBENZENE-POLYCARBOXYLIC ACIDS SucciNic ACID AND SUCCINIC ANHYDRIDE). The bihinctionahty of the diacids makes them versatile materials, ideally suited for a variety of condensation polymerization reactions. Several diacids are commercially important chemicals that are produced in multimillion kg quantities and find appHcation in a myriad of uses. 

Aromatic polyesters were efficiently synthesized from aromatic diacid divinyl esters. Lipase CA induced the polymerization of divinyl esters of isoph-thalic acid, terephthalic acid, and p-phenylene diacetic acid with glycols to give polyesters containing aromatic moiety in the main chain. The highest molecular weight (7.2 x 10 ) was attained from a combination of divinyl isophthalate and 1,10-decanediol. Enzymatic polymerization of divinyl esters and aromatic diols also afforded the aromatic polyesters. ... 

Monomer structure can affect the competition between cyclization and linear polymerization. For example, phthalic acid (ortho isomer) is more prone to cyclization than terephthalic acid (para isomer) at the very-low-molecular-weight end, for example, the dimer stage. The ortho structure makes more likely the conformations that are more favorable for cyclization. Stiff linear chains such as those formed in the reaction between an aromatic diamine and aromatic diacid chloride are much less prone to cyclization than the flexible chains formed from the corresponding aliphatic monomers. 

During the polymerization of aromatic diacids and diesters with hydrazine in fuming sulfuric acid, aromatic oxadiazole units are formed first which are subsequently methylated by monomethyl sulfate or its homologues (derived from reaction of the diester with H2SO4) forming an aromatic N-methyl oxadiazolium polymer. This polymer is hydrolyzed during the spinning operation to the fiber polymer, i.e., p-/m-phenylene oxadiazole/N-methyl hydrazide copolymer. 

The same research group using the lipase from Mucor miehei in diphenyl ether (11.1% w/v) studied copolymerizations of an aromatic diacid (terephthalic or isophthalic) and an aliphatic diol (1,4-butane- or 1,6-hexanediol) [50]. Even at temperatures up to 70 °C, polymerizations of these aromatic diacids were unsuccessful. However, using Novozym 435 as catalyst, polymerizations of aromatic diacids were accomplished, with yield ranging 85-93%. For example, while the Novozym 435-catalyzed reaction of isophthalic acid with butanediol yielded oligomers, a similar reaction between the C-6 diol and isopthalic acid at 70 °C yielded a polymer with = 55000. 

Thermoplastics are aromatic polyamide prepared by polymerization of aromatic diamine and aromatic diacid or its derivatives (e.g., anhydride). These plastics are characterized by high heat re-... 

Blends of liquid crystal polymer (LCP) polyester, LCP poly(ester amide) and PAS exhihit a reduced melt viscosity.LCP polyesters are made hy polymerizing aromatic diacids with diols or hy polymerizing aromatic hydroxy acids, e.g. 4-hydroxyhenzoic acid and 6-hydroxy-2-naphthoic acid. In LCP poly(ester amide)s, some of the hydroxyl groups in the monomers are replaced with amino groups. 

Several different classes of catalysts, so-called condensing agents, have been reported in the literature [52-55] for the polycondensation reaction of aromatic diamines with aromatic diacids. This polycondensation is called direct polymerization because unmodified monomers can be used in the reaction. The condensing agents, which are generally derived from phosphorus or sulfur compounds, activate the dicarboxylic acid in situ during the... 

Vapor-phase polymerization has been described in the patent literature as an alternative route to aromatic polyamides from aromatic diamines and aromatic diacid chlorides [81]. The reaction is carried out in the gas phase by mixing vapors of the two monomers in the presence of an inert gas. The temperature at the reaction zone has to be higher than the glass transition temperature of the polymer to achieve segmental mobility of the growing polymer chain. 

In this section we discuss not only wholly aromatic polyamides, but also some mixed polyamides, prepared from aromatic diacids and aliphatic diamines, or vice versa. One such material was already described in Section 6.3.2. Another one, called Nylon 6T, is formed by interfacial polymerization of terephthaloyl chloride and hexamethylenediamine ... 

An aramid polymer can be crosslinked in the presence of polymers from acrylic acid or methacrylic acid [48]. The crosslinked polymer is obtained by polymerizing a monomeric aromatic diamine with a monomeric aromatic diacid in the presence of poly(meth) acrylic acid, followed by a curing step. The curing step is simply a thermal curing. The crosslinked aramid polymer is then crosslinked via its amide bonds. Here it is not necessary to modify the aramid backbone with other monomers. 

The first low-temperature solution polymerization of PAs from acid chlorides was carried out in halo-genated hydrocarbons. Some of the first polymers were based on piperazines and aliphatic or aromatic diacid. Tertiary amines were used as acid acceptors. Low-temperature solution polycondensation is considered a convenient method for the synthesis of PAs (Scheme 4.1). It involves low-temperature reaction... 

Aliphatic polyesters and polyesters formed from aromatic diacids and aliphatic diols eg, poly(ethylene terephthalate) and poly(butylene terephthalate) (3) cannot decompose by reversion of the polymerization, because the water, or alcohol, eliminated in the synthesis is no longer available. They initially decompose by /3-C—H transfer reactions via a six-membered transition state ... 

Solution Poiymerization. Most of the examples in the patent literatnre utilize solution polymerization. In this techniqne, an aromatic diamine is dissolved in an amide solvent and a stoichiometric quantity of an aromatic diacid chloride is added to the diamine solution while stirring vigorously. Important factors inclnde monomer stoichiometry, ingredient and solvent purity, anhydrous conditions, diamine concentration (and therefore polymer concentration), and temperatnre of the starting diamine solution. 

A 1965 book (21) discusses low temperature solution polycondensation at length, although it does not deal with the reaction of aromatic diamines with aromatic diacid chlorides by this method. The book also discusses interfacial polymerization. 

The direct condensation polymerization of aromatic diacids and diphenols has not been demonstrated to be a feasible route for obtaining high molecular weight polyarylates. However, three monomer variations have been shown to yield acceptable high molecular weight products. These variations include the acid chloride process in which the aromatic diacid is first reacted to form the acid chloride (e.g. phosgene) followed by condensation with the diphenol. The second route involves the preparation of the diphenyl ester of the aromatic diacid followed by reaction with the diphenol. The third process involves preparation of the diacetate of the diphenol followed by reaction with the aromatic diacid. The historical background of these reaction schemes will be discussed. 

A number of methods are available for the preparation of aromatic polymers. The majority of these methods involve the formation of a chemical bond between a carbon atom and a heteroatom. Typical of these are, for example, aromatic polycarbonates the latter are prepared by the reaction of a dihydric phenol with phosgene or derivative thereof.The polymerization proceeds via formation of a carbon-oxygen bond. A similar situation is encountered with the class of polyarylates — the polyesters from dihydric phenols and aromatic diacids. " ... 

The dibasic acid can also be converted into diacid chloride and then condensed with diol. There are basically two methods the first one is interfacial polymerization either at low or high temperature. The aromatic diol is converted to phenolate ion in aqueous alkali solution phase. In organic medium aromatic diacid chloride is taken. Under high stirring the reaction takes place at the interface between phenolate and acid chloride [39]. Phase transfer catalyst can also be used for carrying out the reaction in organic solvent. The reaction rate is much faster than the first method. 

Aramids are formed through step growth polymerization of aromatic diacid chlorides with aromatic diamines in a polar aprotic solvent such as N, -dimethylformamide pMF) to a DP of 100-250. The meta- and para-substi-tuted benzene dicarboxylic acid chlorides and diamines are characteristically used for aramid fibers presently in production, but other fully aromatic ring systems are possible future sources of aramid polymers for fi bers ... 

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