The molecular influence on glass transition temperature (T-g) of select model polyamides was investigated by atomistic modeling. These include nylon 6,6, nylon 6,12, a cycloaliphatic polyamide consisting of 4,4'-methylene-bis(cyclohexylamine) and dodecanedioic acid, as well as a corresponding aromatic counterpart consisting of 4,4'-methylenedianiline and dodecanedioic acid. For each model system, all-atom atomistic molecular dynamics simulations were used to discern and differentiate parameters such as free volume, hydrogen bonding, and chain rigidity. Simulations were able to predict the correct trend in T-g, where the model cycloaliphatic polyamide was shown to have the highest Tg followed by the aromatic polyamide. This is presumably due to the greater chain rigidity exhibited by the cycloaliphatic polyamide around the cyclohexyl ring, which was revealed through a calculation of the dihedral rotation free energy barrier associated with the methylene moiety between either the bis-cyclohexyl or bis-phenyl rings, despite the former having a higher extent of free volume. Published by Elsevier Ltd.