Copolycondensation, linear

Alongside the radical distinction of the mechanism of this process from that of chain polymerization, linear polycondensation features a number of specific peculiarities. So, for instance, the theory of copolycondensation does not deal with the problem of the calculation of a copolymer composition which normally coincides with the initial monomer mixture composition. Conversely, unlike chain polymerization, of particular importance for the products of polycondensation processes with the participation of asymmetric monomers is structural isomerism, so that the fractions of the head-to-head and head-to-tail patterns of ar-... 

The first success was achieved when optically active (chiral) monomeric units were combined with a nematic LC polymer 105,123,143,144). The approach was based on the idea that a cholesteric mesophase may actually be realized as a helical nematic structure. Then by chemical binding of chiral and mesogenic units into a chain, accomplished by copolymerization or copolycondensation (in case of linear polymers) of nematogenic and optically active compounds, it was found feasible to twist a nematic mesophase and obtain copolymers of cholesteric type (Table 13). 

In the rich assortment of polyamides an important position is held by aliphatic unsubstituted linear pdyamides, known under the current name of nylons. They are prepared either by polycondensation of aliphatic diadds and diamines or of aliphatic co-amino adds, or by pofyaddition of their lactams. The numera](s) following the term nylon indkate(s) the number of carbon atoms in the monoiiKric unit thus, e the pdymer of pytrolidone is called nylon 4, that of caprolactam is nylon 6, the copolycondensate of hexamethyienedhimine and adipic add is nylon 6,6 and the copolycondensate of hexamethylenediamine and sebadc add is nylon 6,10. 

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