The Quenched Instationary Polymerization System, 5. The Peak Broadness as an Invariant Quantity of the Number,Molar Mass and Hyper Distributions

The total number, molar mass and hyper distributions generated by quenched instationary polymerization techniques are dominated by the radical chain length distribution (RCLD) whereas the contribution from the polymer chain length distribution (PCLD) is in most cases negligible. For the determination of the rate constant of propagation (k_p) the location of different extraordinary points of the distribution curves is determined by the use of the first and second derivatives. For the number, molar mass and hyper distributions these points are related in an unambiguous way to k_p[M]t_x and can be used to extract k_p. The choice of t_x (duration of the dark period, or an initiation period, or the sum of different periods) depends on the experimental conditions (δ‐pulse, incomplete pre‐effect, combination of periods differing in initiation extent) and is essential for the proper determination of k_p. The broadness of appearing peaks (introduced as the difference between two successive points of inflections) turned out to remain the same irrespective which type of distribution curve was analyzed. Analytical expressions for the peak broadness were derived for different types of quenched instationary polymerization conditions. For δ‐pulse initiation the broadness of the Poisson peak depends simply on the number of propagation steps that occurred whereas for non‐δ‐pulse initiation conditions the peak broadness is governed by the corresponding duration of the initiation period.