Copolyamide-Imide Membrane with Low CTE and CME for Potential Space Optical Applications

Area of Science:

• Materials Science
• Optical Engineering
• Space Technology

Background:

• Traditional aromatic polyimide membranes lack the dimensional stability and optical homogeneity required for space optics.
• Reducing the size and mass of space optical telescopes is crucial for mission feasibility and cost-effectiveness.

Purpose of the Study:

• To design and fabricate a copolyamide-imide membrane with enhanced optical, thermal, and mechanical properties for space telescope applications.
• To overcome the limitations of conventional polyimide membranes in demanding space environments.

Main Methods:

• Molecular structure design of copolyamide-imide.
• Optimization of the membrane fabrication process.
• Characterization of thermal expansion (CTE), moisture expansion (CME), thickness uniformity, and wavefront error.

Main Results:

• Achieved a very low coefficient of thermal expansion (CTE) of 0.95 ppm/°C (-150-100 °C).
• Demonstrated a low coefficient of moisture expansion (CME) of 13.30 ppm/% RH (0-90% RH).
• Prepared a 200 mm diameter membrane with thickness uniformity resulting in a wavefront error < λ/30 RMS (λ = 632 nm).

Conclusions:

• The developed copolyamide-imide membrane meets stringent optical, thermal, and mechanical requirements for space telescope use.
• This material is suitable for large-aperture membrane optical system architectures in space applications.
• The enhanced performance enables the development of more compact and lightweight space imaging systems.