Aliphatic Polybenzimidazoles: Synthesis, Characterization and High-Temperature Shape-Memory Performance

Area of Science:

• Polymer Science
• Materials Science

Background:

• Aliphatic polybenzimidazoles (PBIs) are advanced polymers with potential for high-performance applications.
• Understanding the structure-property relationships in PBIs is crucial for optimizing their performance.
• The incorporation of methylene groups of varying lengths offers a route to tune PBI properties.

Purpose of the Study:

• To synthesize a series of aliphatic polybenzimidazoles (PBIs) with varying methylene chain lengths.
• To investigate the influence of methylene chain length on the thermal, mechanical, and shape-memory properties of PBIs.
• To identify optimal PBI formulations for high-temperature applications.

Main Methods:

• High-temperature polycondensation of 3,3'-diaminobenzidine (DAB) and aliphatic dicarboxylic acids in Eaton's reagent.
• Characterization using solution viscometry, thermogravimetric analysis (TGA), mechanical testing, and dynamic mechanical analysis (DMA).
• Evaluation of shape-memory effect, shape-fixity, and shape-recovery ratios.

Main Results:

• All synthesized aliphatic PBIs demonstrated high mechanical strength (up to 129.3 ± 7.1 MPa), glass transition temperatures (≥200 °C), and thermal decomposition temperatures (≥460 °C).
• The presence of soft aliphatic segments, rigid bis-benzimidazole groups, and hydrogen bonds facilitated a shape-memory effect.
• The PBI derived from DAB and dodecanedioic acid exhibited superior shape-fixity (99.6%) and shape-recovery (95.6%).

Conclusions:

• Aliphatic PBIs with varying methylene chain lengths possess excellent mechanical and thermal properties.
• These PBIs exhibit a significant shape-memory effect, making them suitable for advanced applications.
• The developed aliphatic PBIs hold great potential as high-temperature materials in demanding fields like aerospace.