Linear polyamides

AH commercial linear polyamides that melt at or below 280°C are melt- rather than solution-spun into fiber because melt spinning is more economical. 

Polymerization of /3-lactams to yield linear polyamides could have industrial applications if the cost of the starting materials can be reduced sufficiently to make the process economically attractive (75S547 p. 58l). 

Of the many possible methods for preparing linear polyamides five are of commercial importance ... 

Proteins are linear polyamides formed from a-amino acids. An a-amino acid is one in which carboxylic acid and the amino group reside on the same carbon atom (1.7). 

These are now known to have been linear polyamides, probably of high molecular weight. 

Many hydrogenation and polymerization reactions in the chemical industry are carried out with liquid-phase reactants. An example is the hydrogenation of aliphatic dinitriles to produce diamines (108,109), which are subsequently converted with adipic acid in solution and polymerized to produce linear polyamides, including nylon 6,6. Recently, the development of wet-environmental transmission electron microscopy (wet-ETEM) for direct nanoscale probing of... 

Which protein would be more apt to be present in a helical conformation (a) a linear polyamide with small pendant groups or (b) a linear polyamide with bulky pendant groups ... 

Munoz-Guerra and Galbis et al. have initiated in the past decade a systematic study of a series of sugar-based AABB linear polyamides. These polyamides are derived... 

Long-chain a,o)-dicarboxylic acids have been condensed with diamino-isohexides, forming linear polyamides suitable for producing fibers having a silklike texture and higher moisture-absorption properties than nylon-like polymers.206... 

Macrocyclic lactams.1 These lactams have generally been prepared by reaction of dicarboxylic acid chlorides and diamines under high dilution. Yields are generally mediocre because linear polyamides are also formed. Actually, free dicarboxylic acids, when activated by diphenylphosphoryl azide, can condense with diamines to... 

The products (5) were isolated as the hexafluorophosphates. IR and NMR data confirmed the linear polyamide structures. However, viscometric and vapor pressure osmometric investigations on the polymers were found to be inconclusive because of polydissociation in solvents. 

Although the initial calibration is actually in terms of the relation between [rjl and Mw or M , as described, Eq. (3-44) can only be used to estimate My, for unknown polymers. It cannot be employed to estimate M , (or as the case may be) for such samples unle.ss the unknown is also a fraction with a molecular weight distribution very similar to those of the calibration samples. An important class of polymers which constitutes an exception to this restriction consists of linear polyamides and polyesters polymerized under equilibrium conditions (Chapter 5). In these cases the molecular weight distributions are always random (Section 5.4.3) and the relation... 

The influence of a surface on the course of a polymerization reaction was discussed by Carothers (69) in 1936. He pointed out that in bulk solution the amino acids or their esters polymerize mainly to the cyclic dimers, the diketopiperazines. In living cells, however, these cyclic compounds are evidently not formed reaction is exclusively intermolecu-lar leading to the formation of linear polyamides. Carothers suggested that adsorption at a fat-water interface may well be responsible for this, since here the reactant monomer molecules will be oriented to lie flat in the plane of the surface. As an example, the molecule NH2 CH2-CO-NH-CHs COOH is anchored to the interface through the polar groups at each end and in the middle of the molecule. Under these conditions the difficulty of bending may prevent cyclization. 

Many condensation polymers are formed by the interaction of bifunctional inter- mediates with the elimination of a small by-product molecule at each point of combination. A well-known example is the commercial preparation of 6-6 nylon. For this preparation, a diamine and a diacid are combined to form a polymeric salt, which then is subjected to heat and later to heat and vacuum water is eliminated and a linear polyamide is formed. 

Patent of FRG No 1903244. Method of synthetic linear polyamide dyeing in mass (1978) (in Russian). 

Direct polycondensations of aromatic diamines with dicarboxylic acids have generally been described as a poor route to high molecular linear polyamides. Recently, high molecular weight polyamides have been obtained with limited success by a melt polymerization of 4,4 -diaminodiphenylmethane (MDA) with aliphatic dicarboxylic acids14. ... 

Linear polyamide resins are prepared by the reaction of dimer fatty acid and diamine compounds. The resulting resin has frequent inner molecular ring structures and a repeating amino amide structure. 

Whang and Wu [3] have described the liquid crystalline state of polyimide precursors and shown that certain polyamic acids derived from pyromellitic anhydride exhibit lyotropic behaviour. Liquid crystal phases have also been observed by Wenzel et al. [4] in polyimides derived from pyromellitic anhydride and 2,5-di-n-alkoxy-1,4-phenyl ene diisocyanate. Dezern [5] has disclosed a synthesis for linear polyamide-imides derived from benzophenone dianhydride but the occurrence or otherwise of mesophases is not mentioned. 

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