# High-Performance Polyimides with Enhanced Solubility and Thermal Stability for Biomimetic Structures in Extreme Environment

## TL;DR

This paper introduces a new type of polyimide with improved solubility and thermal stability for use in biomimetic structures under extreme conditions.

## Contribution

A novel silicon–alkyne-functionalized diamine-based polyimide design that balances processability and thermal stability.

## Key findings

- The polyimides show high decomposition temperature (Td5% = 560 °C) and char yield (72.0% at 800 °C).
- The rigid fluorene core and bulky siloxy groups enhance chain stiffness and solubility in polar solvents.
- DFT calculations confirm twisted geometries and favorable noncovalent interactions that improve performance.

## Abstract

Designing the high-performance polyimides (PIs) for the biomimetic structures, which are used in extreme conditions, remains greatly challenging, due to the conflict between processability and thermal stability. Here, we report a series of silicon–alkyne-functionalized diamine-based polyimides that exhibit remarkable processability and thermal stability. The incorporation of bulky siloxy groups disrupts chain packing and increases free volume, enabling excellent solubility in polar solvents, while the rigid fluorene core enhances chain stiffness. DFT calculations confirm twisted molecular geometries (Si bond angle ≈ 103°, dihedral angle ≈ 89°) which weak π–π stacking, while heterogeneous electrostatic potentials enable favorable noncovalent interactions (e.g., C–F···H–C), promoting solvent diffusion. After thermal curing, the obtained product shows a high decomposition temperature (Td5% = 560 °C), char yield of 72.0% at 800 °C, and glass transition temperature (Tg) of 354.6 °C. Meanwhile, locally planar fluorene units retain inherent thermal stabilization benefits through constrained rotational mobility. These results demonstrate a spatially decoupled siloxy–alkyne design that synergistically enhances molecular flexibility, disorder, and electronic stability, offering a molecular strategy for tailoring PI-based matrices to meet the demands of emerging biomimetic architectures and other high-performance composites operating under severe thermal loads.