Molecular-weight and cooling-rate dependence of polymer thermodynamics in molecular dynamics simulation

Min-Hsueh Chiu

Abstract:

Molecular dynamics (MD) simulations are conducted to systematically benchmark the effects of molecular weight, chain
number, and cooling rate on the glass transition temperature (Tg) and coefficient of thermal expansion (CTE) of poly
(ethylene oxide) (PEO). Hyperbolic regression as an objective identified method is used to extract Tg and CTE. The results
show that for a cooling rate higher than 5 × 1013 K/min, Tg and CTE are both strongly affected by rapid quenching. For a
cooling rate lower than 5 × 1013 K/min, Tg and CTE in the high-temperature domain still slightly depend on the cooling rate.
Eventually, to eliminate the finite size effect of the model, a threshold molecular weight of 11,240 g/mol should be satisfied
in the system. In addition, the chain number must be more than 10, at least for an oligomer system (50 monomers).