Using QSPR techniques to predict char yield arising from the thermal degradation of polybenzoxazines

Molecular Operating Environment software is used to construct a series of benzoxazine monomers for which a variety of parameters relating to the structures (e.g. water accessible surface area, negative van der Waals surface area, hydrophobic volume and the sum of atomic polarizabilities, etc.) are obtained and quantitative structure property relationships (QSPR) models are formulated. Three QSPR models (formulated using up to 5 descriptors) are first used to make predictions for the initiator data set (n = 9) and compared to published thermal data; in all of the QSPR models there is a high level of agreement between the actual data and the predicted data (within 0.44-0.77% of the entire data set). The water accessible surface area is found to be the most important descriptor in the prediction of char yield. A more complex QSPR model with 15 descriptors (R2 > 0.99) is used to predict char yields for 34 different polybenzoxazines and for this series fine agreement (3.03%) is found.