Direct polyamidation

An optically active PAI was prepared by the direct polyamidation of the chiral diacid with azo diamine under green condition using molten tetra- -butylammonium bromide. 

Monomers derived from trimellitic anhydride, mainly V-carboxyphenyltrimel-litimides and V-(co-carboxyalkylene)trimellitimides have been also used many times as starting materials for the synthesis of poly (amide imide)s. These poly (amide imide)s have been traditionally prepared by low temperature solution polycondensation, from diamines and imide-diacid chlorides [182], but they have been also successfully synthesized by the phosphorylation method of direct polyamidation [184], from diamines and imide-diacids [185-188] as depicted in Scheme (36). Trimellitic acid imide (4-carboxyphthal-imide) has also been used for the preparation of poly(amide imide)s, by reaction with aliphatic and aromatic diamines in solution at moderate temperatures [189]. 

A new type of polycondensation by means of phosphoms compounds in mild conditions was described by Higashi and co-workers and template effects were observed. The synthesis of polyamidation of polyamides by direct polyamidation of terephthalic acid with 4,4 -diaminodiphenylmethan was examined. P2VP, P4VP, poly(vinylpyrrolidone), and PEO were used as templates. For example, it was found that poly (terephthalamides) prepared from p-phenylenediamine and 4,4 -diaminodiphenylsulfone in the presence of PVP have much higher molecular weight than the same polymer obtained by a direct polycondensation reaction. 

Amide interchange reactions of the type represented by reaction 3 in Table 5.4 are known to occur more slowly than direct amidation nevertheless, reactions between high and low molecular weight polyamides result in a polymer of intermediate molecular weight. The polymer is initially a block copolymer of the two starting materials, but randomization is eventually produced. 

In 1954 the surface fluorination of polyethylene sheets by using a soHd CO2 cooled heat sink was patented (44). Later patents covered the fluorination of PVC (45) and polyethylene bottles (46). Studies of surface fluorination of polymer films have been reported (47). The fluorination of polyethylene powder was described (48) as a fiery intense reaction, which was finally controlled by dilution with an inert gas at reduced pressures. Direct fluorination of polymers was achieved in 1970 (8,49). More recently, surface fluorinations of poly(vinyl fluoride), polycarbonates, polystyrene, and poly(methyl methacrylate), and the surface fluorination of containers have been described (50,51). Partially fluorinated poly(ethylene terephthalate) and polyamides such as nylon have excellent soil release properties as well as high wettabiUty (52,53). The most advanced direct fluorination technology in the area of single-compound synthesis and synthesis of high performance fluids is currently practiced by 3M Co. of St. Paul, Minnesota, and by Exfluor Research Corp. of Austin, Texas. 

Direct Amidation. The direct reaction of amino acids to form Type AB polyamides (eq. 1) and diacids and diamines to form type AABB polyamides (eq. 2) ate two of the most commonly used methods to produce polyamides. The... 

Direct amidation is generally carried out ia the melt, although it can be done ia an iaert solvent starting from the dry salt (46). Because most aUphatic polyamides melt ia the range of 200—300°C and aromatic-containing polyamides at even higher temperatures, the reactants and products must be thermally stable to be polymerized via this method. 

An all aromatic polyetherimide is made by Du Pont from reaction of pyromelUtic dianhydride and 4,4 -oxydianiline and is sold as Kapton. It possesses excellent thermal stabiUty, mechanical characteristics, and electrical properties, as indicated in Table 3. The high heat-deflection temperature of the resin limits its processibiUty. Kapton is available as general-purpose film and used in appHcations such as washers and gaskets. Often the resin is not used directly rather, the more tractable polyamide acid intermediate is appHed in solution to a surface and then is thermally imidi2ed as the solvent evaporates. 

Monofunctional, cyclohexylamine is used as a polyamide polymerization chain terminator to control polymer molecular weight. 3,3,5-Trimethylcyclohexylamines ate usehil fuel additives, corrosion inhibitors, and biocides (50). Dicyclohexylamine has direct uses as a solvent for cephalosporin antibiotic production, as a corrosion inhibitor, and as a fuel oil additive, in addition to serving as an organic intermediate. Cycloahphatic tertiary amines are used as urethane catalysts (72). Dimethylcyclohexylarnine (DMCHA) is marketed by Air Products as POLYCAT 8 for pour-in-place rigid insulating foam. Methyldicyclohexylamine is POLYCAT 12 used for flexible slabstock and molded foam. DM CHA is also sold as a fuel oil additive, which acts as an antioxidant. StericaHy hindered secondary cycloahphatic amines, specifically dicyclohexylamine, effectively catalyze polycarbonate polymerization (73). 

Direct Dyes. These are defined as anionic dyes, again containing sulfonic acid groups, with substantivity for ceUulosic fibers. They are usually a2o dyes (qv) and can be mono-, dis-, or polya2o, and are ia general planar stmctures. They are appHed to ceUulosic fibers from neutral dyebaths, ie, they have direct substantivity without the need of other agents. Salt is used to enhance dyebath exhaustion. Some direct dyes can be appHed to wool and polyamides under acidic conditions, but these are the exception. 

Direct Dyes. A few selected direct dyes are used to complement the acid dyes ia printing of polyamide. Printing of ceUulosic fibers with direct dyes, as with acid dyes, has lost its importance owiag to iasufficient wetfastness properties of these dyes on ceUulosic fibers, and cumbersome fixation and scouting procedures. 

In recent years there has been considerable interest in aromatic polyamide fibres, better known as aramid fibres. These are defined by the US Federal Trade Commission as a manufactured fibre in which the fibre-forming substance is a long chain synthetic polyamide in which at least 85% of the amide linkages are attached directly to two aromatic rings. ... 

There are two great families of synthetic polymers, those made by addition methods (notably, polyethylene and other polyolefines), in which successive monomers simply become attached to a long chain, and those made by condensation reactions (polyesters, polyamides, etc.) in which a monomer becomes attached to the end of a chain with the generation of a small by-product molecule, such as water. The first sustained programme of research directed specifically to finding new synthetic macromolecules involved mostly condensation reactions and was master-... 

Therefore it is possible to determine absorption spectra directly on the TLC plate by comparison with a substance-free portion of the layer. The wavelengths usually correspond to the spectra of the same substances in solution. However, adsorbents (silanols, amino and polyamide groups) and solvent traces (pH differences) can cause either bathochromic (ketones, aldehydes [60, 61], dyestuffs [62]) or hypsochromic (phenols, aniline derivatives [63]) shifts (Fig. 23). 

SOLUTION (a) Amide groups are present in the backbone, and so the polymer is a polyamide. Because the amide groups face in opposite directions, there are two different monomers, one with two acid groups and the other with two amine groups. We split each amide group apart and add a molecule of water to each amide link. 

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