COMPARISON BETWEEN THE GLASS-TRANSITION TEMPERATURES OF THE 2 PMMA TACTICITIES - A MOLECULAR-DYNAMICS SIMULATION POINT-OF-VIEW

The difference in the glass transition temperatures, T-g of the iso- a nd syndiotactic forms of PMMA has been investigated through molecular dynamics simulations of short duration (110 ps) using an accurate forc e field, pcff: To correlate with the Gibbs-DiMarzio theory, which spec ifies that conformational energy is a primary factor in determining T- g, an energetic analysis has been carried out. It is found that syndio tactic PMMA possesses lower intramolecular energy where the governing contribution is brought by the angle bending term; whereas the isotact ic PMMA exhibits lower intermolecular energy. Such a behavior suggests that the chain packing greatly determines the difference in the T-g.