Terephthalic acid polyamide monomers

Furan-2,5-dicarboxylic add also has tremendous industrial potential, because it could replace oil-derived diadds such as adipic or terephthalic acid as monomers for polyesters and polyamides [98, 99]. This diadd can be synthesized by Pt-catalyzed oxidation with 02 of 5-hydroxymethylfurfural the latter is obtained by acid-catalyzed dehydration of D-frudose or frudosans (inulin) the latter, however, are too expensive as starting materials, and yields from glucose-based waste raw materials are no higher than 40%. Therefore, the potential attractive option of furan-2,5-dicarboxylic acid will develop only after an effident generation of 5-hydroxymethylfurfural from forestry waste materials has been developed. The same compound is also the starting material for the synthesis of other interesting chemicals obtained by oxidative processes, such as 5-hydroxymethylfuroic add, 5-formylfuran-2-carboxylic add and the 1,6-dialdehyde. 

When unsymmetrical monomers are used, the normal ability of the polymer to crystallize can be disrupted amorphous (transparent) nylons can then be formed. For example, the polyamide prepared from the condensation of terephthalic acid with a mixture of 2,2,4- and... 

So far we have only discus those substituted polyamides derived from substituted phenylenediamines and isophthalic or terephthalic acids, i.e. from benzene derivatised monomers. Numerous monomers containing several aromatic rings have also been u d in the synthesis of polyamides as shown in Table 6. 

Strong interaction between monomers and the template is a prerequisite for the template process, while in simple polycondensation high temperature and low pressure is applied. However, in mild conditions using the direct polycondensation method it was demonstrated that terephthalic acid connected with poly(4-vinylpyridine) (79), poly(ethylene oxide) (80), poly(vinylp5UTolidinone) (81) and activated by triphenyl phosphite reacts with hexamethylenediamine, giving polyamides with high molecular weight. 

Amorphous Nylons n (l)When unsymmetrical monomers are use to synthesize polyamides (Nylons), the normal ability of the chains to crystallize can be disrupted and amorphous (often transparent) polymers are formed. (2) Transparent aromatic polyamide thermoplastics. Produced by condensation of hexamethylene diamine, isophthalic and terephthalic acid (Sepe MP (1998) Dynamic mechanical analysis. Plastics Design Library, Norwich, New York). 

The third method to create two-step aromatic polyamide networks is chemically similar to the one discussed above in Sect. 3.1.6.2. Here, a fraction of the terephthalic monomer in the reaction solution is replaced by 2,3-cyclobuta-terephthalic acid (619a). Upon polymerization a lyotropic aromatic polyamide is obtained which, when heated to 380 °C or higher, randomly crosslinks along the stiff chains to form a two-step network. Not much else is known at present about this system. 

Linear step-growth polymerizations require exceptionally pure monomers in order to ensure 1 1 stoichiometry for mutually reactive functional groups. For example, the synthesis of high-molecular-weight polyamides requires a 1 1 molar ratio of a dicarboxylic acid and a diamine. In many commercial processes, the polymerization process is designed to ensure perfect functional group stoichiometry. For example, commercial polyesterification processes often utilize dimethyl terephthalate (DMT) in the presence of excess ethylene glycol (EG) to form the stoichiometric precursor bis(hydroxyethyl)terephthalate (BHET) in situ. 

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