Chiang Mai Journal of Science

Molecular mechanics, semiempirical and density functional theory were used to calculate the heats of  polymerization for a series of  lactones of  different ring sizes. The change in the internal energy upon polymerization was calculated from the difference in the minimized energy between the 5- and 4-mers and the monomer. The best trend for the calculated heats of polymerization was obtained from the AM1 method. Although the direct correlations between the calculated properties (bond angles, distance, and charge) and the experimental ↑/↓H_p values have not been found, a clear correlation between the bond angle strain energy of C-O2-[C1=O1] ( ) and O2-[C1=O1]-C( ) and the experimental ↑/↓H_p values has been observed and can be applied to the prediction of  polymerizability.