Glass Transition Temperature Evaluation

Full-Atomistic Molecular Dynamics (FAMD) was used to evaluate the glass transition temperature (Tg) of polymers. Cooling operations (quenching) were performed by lowering temperature stepwise from high temperature, and Tg was determined from the inflection point of specific volume changes. Multiple polymers were tested and compared with experimental values.

Use Cases Highlights

Analysis of specific volume changes by quench calculations
Evaluation of glass transition temperature from the inflection point of specific volume change
Comparison with experimental Tg values for each substance

Creation of amorphous structures

Amorphous structures of polymers created using a United Atom model with J-OCTA’s amorphous structure builder are shown. Temperature is changed stepwise for continuous calculations.

Amorphous structure of polycarbonate

Evaluation of glass transition temperature from the inflection point of specific volume change

As an example, changes in the specific volume (inverse of density) of polyethylene with temperature are shown. A distinct inflection point appears on the graph, and the temperature at this point is evaluated as the glass transition temperature.

Specific volume change of polyethylene

Comparison with experimental Tg values for each substance

The Tg values of polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), and polycarbonate (PC) were calculated and compared with experimental values. Although Tg was overestimated due to high quench rate, the material-dependent trends matched experiments, enabling qualitative evaluation.