Penultimate unit effects on sequence length distribution

The penultimate unit effects on sequence length distribution was studied for free-radical polymerizations using probability considerations. The approach adopted in this paper has been taken from the general treatment where equations for depropagation by triad endgroups were considered in a general kinetic scheme. The procedure utilized 16 rate constants for the eight forward propagation steps and the corresponding backward steps, which can be considered equal to zero for the present problem. The equations treat all the reactions as pseudo first order thereby allowing omission of monomer concentration terms and are only strictly correct for equimolar mixtures of reactants. This simplifies the procedure and reduces the number of terms in the equations.