https://doi.org/10.1351/goldbook.C00982
The ratio of the mean-square end-to-end distance, <r2>0, of a
linear polymer
chain in a theta state to NL2, where N is the number of rigid sections in the main chain, each of length L; if all of the rigid sections are not of equal length, the mean-square value of L is used, i.e. L2=iLi2¯N In simple single-strand chains, the bonds are taken as the rigid sections. The recommended symbol is: CN (C when N).
Source:
Purple Book, 1st ed., p. 49 [Terms] [Book]