ქიმიის ტერმინთა განმარტებითი ლექსიკონი

Straight line parallel to the direction of chain extension, connecting the centres of mass of successive blocks of chain units, each of which is contained within an identity period.

Fig.  Side view (above) and end view (below) of the macromolecule of isotactic  poly[1-(1-naphthyl)ethane-1,2-diyl] in the crystalline state. The helix symbol is s(2*4/1). The chain axis is shown by the dashed line, and c is the chain identity period. Hydrogen atoms are omitted. [From P. Corradini and P. Ganis. Nuovo Cimento, Suppl. 15, 96 (1960)].