Model discrimination via designed experiments: Discriminating between the terminal and penultimate models on the basis of weight average chain length

Simulations have been used to study the application of weight average chain length for discriminating between the terminal and the penultimate copolym erization models. A brief description of the model discrimination method an d of the copolymerization models is given. The problem of parameter observa bility is discussed, showing that weight average chain length on its own le ads to highly correlated parameter estimates. Combining weight average chai n length with triad fractions on the other hand, yields a powerful combinat ion of measurements for model discrimination. In the simulation studies the correct model was selected in each of a variety of different scenarios use d. Compared to using triad fractions alone, including weight average chain length has several advantages, notable among which is the ability to estima te radical reactivity ratios, s(1) and s(2), which are not observable from triad fraction data alone. Also, weight average chain length is more sensit ive to changes in the rate of polymerization.