in polymers
The ratio of the mean-square end-to-end distance, \(< r^{2} >_{0}\), of a @L03556@ chain in a theta state to \(N\cdot L^{2}\), 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. \[L^{2}=\sum _{i}\frac{L_{i}^{\bar{2}}}{N}\] In simple single-strand chains, the bonds are taken as the rigid sections. The recommended symbol is: \(C_{N}\) (\(C_{\infty }\) when \(N\rightarrow \infty \)).
Purple Book, 1st ed., p. 49 [Terms] [Book]