Integrated Simulation System for Soft Materials.

By using the molecular dynamics engine COGNAC, we can evaluate the glass transition temperature Tg of polymers. Specifically, a system is set to a high temperature, and as the temperature drops at regular intervals (quench), the changes in system volume are evaluated. As a result, when the folding point in the volume change appears, the temperature represents the glass transition temperature.

We have evaluated the glass transition temperature using data from polymers in an amorphous state. Figure 2 shows the specific volume of the temperature changes for a system of polyethylene in an amorphous state. Each change in volume has a temperature which the volume change dramatically varies, these temperatures are used to evaluate as the glass transition point.

The glass transition temperatures for various substances are calculated. The tendency of each substance has been captured by graphing the results of the various substances. There are a few reasons why these Tg evaluations are higher than experimental data values. One is that the quench speeds of the MD calculations are extremely fast. Also, the degree of precision for these calculations is limited. However these calculations can be used to generate sufficient qualitative evaluations.