  Kinetics of steady-state copolymerization has been investigated since 1940s.
Irreversible terminal and penultimate models were successfully applied to a
number of comonomer systems, but failed for systems where depropagation is
significant. Although a general mathematical treatment of the terminal model
with depropagation was established in 1980s, penultimate model and higher-order
terminal models with depropagation have not been systematically studied, since
depropagation leads to hierarchically-coupled and unclosed kinetic equations
which are hard to be solved analytically. In this work, we propose a truncation
method to solve the steady-state kinetic equations of any-order terminal models
with depropagation in an unified way, by reducing them into closed steady-state
equations which give the exact solution of the original kinetic equations.
Based on the steady-state equations, we also derive a general thermodynamic
equality in which the Shannon entropy of the copolymer sequence is explicitly
introduced as part of the free energy dissipation of the whole copolymerization
system.
