Abstract:

Group additive property（GAP） method considers that the property of polymer can be calculated from the contribution of the groups that make up the main and side chains of the repeating unit. The glass transition temperature（T_g） and melting point et al. for polymer can be calculated by GAP. Aromatic polyimides are high-performance polymers obtained by dehydration condensation between dianhydride and diamine. Quantitatively predicting the glass transition temperature of polyimide from the chemical structure is helpful to optimize and prescreen the monomer molecular structure， but it remains a challenge. The T_g values of 74 polyimides were calculated by known group contributions offered by van Krevelen， the predicted T_g values are in good agreement with the experimental ones， with the standard deviation（s） of 21 K and R² of 0.88， but there is still a large systematic error due to the deviation of the fitted curve slope（0.78） from 1. Therefore， the T_g values of these 74 polyimides were recalculated after the contribution values of the groups contained in these polyimides were corrected. The results showed a good correlation（R²=0.88， s=18 K） with experimental values， and the slope of the fitted curve（0.94） was close to 1， which means the systematic error is effectively eliminated. The corrected group contribution values were used in following calculations. A method to assign the group contribution values to unknown groups was proposed. Then the Y_g values of 7 unknown dianhydrides and 6 unknown groups contained in dianhydrides or diamines were calculated by using this assignment method. The reliability of the contribution values of the 13 groups was verified by using the data of a training set（82 polyimides） and a test set（35 polyimides）. This correction method and the assignment method presented in this work can also be used to other heteroaromatic polymers.

Key words: Group additive property, Polyimide, Glass transition temperature, Group contribution