Design and preparation of glassy molecular precursors by adjusting molecular structures for facile processing of high-performance polymers

Abstract

High-performance polymers in possession of excellent thermal stabilities and mechanical strength have been explored for many years in high-tech fields. However, a big challenge still remains for balance of the processability and performance. Herein, to address this problem, a new design was attempted to conduct the manufacturing process on amorphous micromolecular precursors, rather than traditional crystals, oligomers or polymers. Firstly, a series of crosslinkable precursors were synthesized from commercial aromatic diamines by simple one-step amidation reaction. These molecular materials showed different glass-forming abilities, which were obviously associated with their molecular structures (size, flexibility and symmetry). Owing to the disordered molecular arrangement, amorphous precursors obtained excellent fluidity when the temperature exceeded the glass transition temperatures (T_g, 52–88 °C), allowing for facile processing at low temperatures. The considerable temperature difference between the T_g and reaction temperature (∼200 °C) led to wide processing windows, at which the viscosities could be adjusted by temperature or shear rate within a wide range from 10⁵ to 10⁰ Pa s (|η*|), showing their broad applicability in diverse traditional processing operations for polymers. All the cured resin films prepared by direct molding and subsequent curing exhibited high thermal decomposition temperatures (T_d,5% > 428 °C), high T_g (>234 °C) and robust mechanical strength (storage moduli >1.8 GPa). By taking the advantages of amorphous molecular precursors and BCB crosslinking, the outstanding processability and high performance were well-integrated.