Polyamides polar groups

Permeability of aromatic polyamide membranes have been improved by modification of aromatic rings with pendant polar groups, for examples sulfonic, carboxylic, carboxamide, and sulfonamide groups, in addition to the before-mentioned methoxy group. 

As described above, the modification of the polyamide membrane with pendant polar groups effectively improved their permeation characteristics. 

Application of Eq. (11.14) to these polymers (as a first orientation) yields values for the mean dipole moment of the structural units varying from 0 debye units for hydrocarbon polymers to about 1 debye unit for polyamides. The measured values are low compared with the dipole moments of the polar groups in liquids. 

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. 

In polymers having polar groups, intermolecular electrostatic attractions exert strong influence on chain conformation in their crystals. In polyamides, hydrogen bonds form between the carbonyls and NH groups of neighboring chains (Fig. 2.11) and influence the crystallization of the polymer in the form of sheets, with the macromolecules themselves packed in planar zigzag conformations [see Fig. 2.11(b)]. 

In polymers having polar groups, intermolecular electrostatic attractions exert strong influence on chain conformation in their crystals. In polyamides, hydrogen bonds form between the carbonyls and NH groups of neighboring chains (Fig. 

Chaudhuri et al. [22a] in their study of the thermostability of wholly aromatic polyamides have introduced various polar groups onto the polymer, e.g. NO2, COOH, OH, SO3H, etc. Compared to methylated or chlorinated polymers, the stability of polyamides 16 is lower, and decreases in the following order NO2 > COOH, OH > SO3H... 

Suter et al. synthesized the polyamide 45 having a pyrimidine moiety [62] and polyamide 46 containing a triazine ring was made by Yuki et al. [63]. These heterocycles have polar groups imparting an additional dipole moment to the molecules, and hence they could interact with each other and alter the properties of the polymers containing these groups. 

There are a number of polymers, notably hydrogenated castor oil and its derivatives, polyamides (Chapter 15) and polyamide-oil or polya-mide-alkyd reaction products, which can be used to impart non-Newtonian viscosity. The thickening mechanisms of polymeric additives are not fully established, but the resins have in common the following features borderline solubility in the paints in which they are used and chemical structures involving polar groups, e.g. -OH, -CONH- and -COOH. 

Platonia insignis, 70 Plexaura homoalla, 1 Pneumococcus, 35 Podocarpus nagi, 5 Polar groups in lipids, 321 Polar lipids in fish, 131 Polarizability, 355 Polishing, 191 Pollen, 5 Polyamides, 473... 

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