Is a Vitrimer with a High Glass Transition Temperature Available? A Case Study on Rigid Polyimides Cross‐Linked with Dynamic Ester Bonds

• Published in: Macromolecular rapid communications. Vol. 45; no. 19; pp. e2400312 - n/a
• Main Authors: Wang, Yueh‐Hsin, Hung, Du‐Yuan, Liu, Ying‐Ling
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-10-2024
• Subjects: Chemical bonds; covalent adaptable network; dynamic bond; Freezing; Glass transition temperature; High pressure; High temperature; Molecular chains; polyimide; Polyimide resins; Polymers; Recyclability; Recycling; Relaxation time; Reprocessing; Rigidity; Side reactions; Stress relaxation; Temperature dependence; Thermal properties; Thermodynamic properties; Thermoplastic resins; Topology; Transition temperatures; vitrimer; Vitrimers
• ISSN: 1022-1336; 1521-3927; 1521-3927
• DOI: 10.1002/marc.202400312

Vitrimers, possessing associative covalent adaptable networks, are cross‐linked polymers exhibiting malleable (glass‐like) feature and recyclable and reprocessable (thermoplastics‐like) properties. The dynamic behaviors of vitrimer are dependent on both chain/molecular mobility (glass transition temperature, Tg) and dynamic bond‐exchanging reaction rate (topology freezing transition temperature, Tv). This work aims on probing the effect of high Tg on the stress relaxation and physical recyclability of vitrimers, employing a polyimide cross‐linked with dynamic ester bonds (Tg: 310 °C) as the example. Due to its high Tg and chain rigidity, the cross‐linked polyimide does not exhibit a high extent of stress relaxation behavior at 320 °C (10 °C above its Tg), even though the temperature is much higher than the hypothetical Tv. While raising the processing temperature to 345 °C, the cross‐linked polyimide exhibits a stress relaxation time of about 3300 s and physical malleability. Nevertheless, side reactions may occur in the recycling and reprocessing process under the harsh condition (high temperature and high pressure) to alter the thermal properties of the recycled sample. The diffusion control plays a critical role on the topography transition of a vitrimer having a high Tg. The Tg ceiling is noticeable for developments of vitrimers.
This work demonstrates the first study on synthesis of aromatic polyimide vitrimers exhibiting a high glass transition temperature (Tg) of about 310 °C. The effect of the high Tg on the bond‐exchanging reaction, stress‐relaxation behavior, and reprocessing property of the polyimide vitrimers is discussed. The restricted chain mobility plays a critical role on the vitrimer‐like behaviors.