Exploring Structure–Property Relationships in Aromatic Polybenzoxazines Through Molecular Simulation

A series of commercial difunctional benzoxazine monomers are characterised using thermal and thermo-mechanical techniques before constructing representative polymer networks using molecular simulation techniques. Good agreement is obtained between replicate analyses and for the kinetic parameters obtained from differential scanning calorimetry data (and determined using the methods of Kissinger and Ozawa). Activation energies range from 85-108 kJ/mol (Kissinger) and 89-110 kJ/mol (Ozawa) for the uncatalysed thermal polymerisation reactions, which achieve conversions of 85-97 %. Glass transition temperatures determined from differential scanning calorimetry and dynamic mechanical thermal analysis are comparable, ranging from the polymer containing the bisphenol A moiety (151 °C, crosslink density 3.6 x 10-3 mol cm-3) to the polymer, based on a phenolphthalein bridge (239-256 °C, crosslink density 5.5-18.4 x 10-3 mol cm-3, depending on formulation). Molecular dynamics simulations of the polybenzoxazines generally agree well with empirical data, indicating that representative networks have been modelled.