The kth radius of gyration for a polycondensation reaction with identical structural units A_aB_b

For a polycondensation reaction with identical structural units A_aB_b (i.e. each unit has a functional groups of type A and b of type B) the kth radius of gyration \documentclass{article}\pagestyle{empty}\begin{document}$ \begin{array}{*{20}c} {\left\langle {R^2 } \right\rangle _k = \sum\limits_n {n^k \cdot \left\langle {R_n^2 } \right\rangle P_n } } & {({\rm sum over all }n{\rm - mers; see Eqs}{\rm . (11) and (17))}{\rm }} \\ \end{array} $\end{document} is investigated. By means of a differential method, a recursion formula that holds true for both the pre‐gel and the post‐gel state is obtained for the evaluation of the kth radius.