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Molecular model setup. (a) Initial atomic structure of the PMMA matrix containing 2 wt. % THF. (b) Distribution of THF within the PMMA matrix for the 2. wt. % case. (c) PMMA matrix containing 20 wt. % THF. (d) Distribution of THF within the PMMA matrix for 20 wt. % case.
Tg Prediction data at various wt. % THF. The glass transition is a second order transition that leads to a change in slope of the MSD as a function of temperature. The intersection of the slopes is predictive of Tg (a) prediction curve for 0 wt. % THF. Predicted Tg = 397 K, average Tg = 395.7 K. (b) Tg prediction curve for 5 wt. % THF. Predicted Tg = 378 K, average Tg = 375.3 K. (c) Tg prediction curve for 10 wt. % THF. Predicted Tg = 342 K, average Tg = 347.3 K. (d) Tg prediction curve for 20 wt. % THF. Predicted Tg = 342 K, Average Tg = 312 K. As the wt. % of THF is increased, there is a steady decrease in the predicted Tg values.
Kelley-Bueche equation comparison with predicted Tg values. The KB equation with a modified alpha value demonstrates a good approximation of the data with an r2 value of 0.92, compared to using the WLF alpha value, which showed an r2 value of 0.56. The best fit curve achieves an r2 value of 0.99 with an as value of 0.001025, compared to the value calculated from simulation of 0.00126.
Parameters for KB theory obtained from MD simulations for theoretical Tg scaling.
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