Analysis of the non-ideal crosslinking process in thiol-X “click” thermosets

Abstract

Thiol-click reactions are widely used in the preparation of thermosets. The network build-up process follows step-wise polymerization behavior, which is commonly analyzed assuming ideal step-wise behavior using well-known expressions such as the Flory-Stockmayer equation for the prediction of the gel point conversion. However, a number of factors contributing to departures from the expected ideal behavior can be identified: a) impurity of the reagents, b) complexity of the reaction mechanism and c) internal cyclization processes. In order to maximize the accuracy of predictions about the expected crosslinking behavior and therefore fine-tune the design of thermosets designed as dual-curing systems or covalent adaptable networks (CANs), it is necessary to take into consideration all these sources of non-ideality. In this work, we aim to describe the effects of such factors on the network build-up process of thiol-click thermosets, making use of the recursive methodology of Miller and Macosko. The contribution of each factor is analyzed separately and their overall combined effect is discussed in relation with real data reported in the literature and experimental results.