Mechanically strong polyimide / carbon nanotube composite aerogels with controllable porous structure

Abstract

Developing aerogels with controllable pores, outstanding mechanical properties and excellent thermal stability still remains a key challenge in evolution of aerogels. In the present work, polyimide (PI) composite aerogels with controllable porous structures and tunable multi-functions have been fabricated with the addition of carbon nanotubes (CNTs) with different functional groups and aspect ratio via an eco-friendly freeze-drying method followed by a thermal imidization process. The interactions between PI chains and CNTs can form crosslinking points through physical or chemical bonding, which could overcome the expansive force in the ice crystal growth process and the capillary force during ice sublimation, thus forming a three-dimensional porous structure. Through increasing the content of functional groups on CNTs, the PI/CNT composite aerogels show enhanced structural stability with a less shrinkage (<20%) during processing, further resulting in improved mechanical properties. As a result, the PI composite aerogels exhibit low density (∼0.1 g cm−3), improved compression modulus (33.5 MPa), and high thermal stability (above 580 °C), showing great potential for application as lightweight and high-performance materials. Additionally, this work develops a new strategy to realize the controllable preparation and tunable properties of polymer aerogels by utilizing nanofillers as an effective crosslinking agent.