Polyamides, chain type orientation

These data show that the dissociation energy of the urethane-type bonds is lower than that of -C-C- bonds from polyethylene or polypropylene. It is also two times lower than the dissociation energy of the bond from the polyamide chain. In this last case, the energetic barrier that must be overtaken in order as a elementary craek to appear is higher due to the supplementary orientation of the amorphous domains of fibres, realised by forced orientation during stretching. 

Besides polymerization, another type of polyreaction can be used for stabilizing model membrane systems. Recently, Fukuda et al.28) described polyamide formation via polycondensation in monolayers at the gas/water interface (definition of mono-layers see Sect. 3.2). Long-chain esters of glycine and alanine were polycondensed to yield non-oriented polyamide films of polyglycine and polyalanine. 

These theoretical considerations have led to the following view on a nematic solution, in particular of a solution of a para-aromatic polyamide in sulfuric acid [38]. In a quiescent solution of a lyotropic polymer the chains are more or less aligned parallel inside domains of microscopic size, see Fig. 3. The degree of orientation inside the domain, as represented by the order parameter (Pj), is determined by the concentration and temperature. The excluded volume entropy term leads to the formation of oriented blobs with a size of the order of Lp, the persistence length. These blobs line up due to their anisotropic polarizability, which implies that the formation of the anisotropic phase is governed by a dipole-dipole type of interaction, immediately leading to the Maier-Saupe mean-field potential. The entropy or excluded volume interaction merely tells us... 

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