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

Abstract

Polyimide diffractive membrane lens can be used in space optical telescope to reduce the size and mass of an imaging system. However, traditional commercial aromatic polyimide membrane is hard to meet the challenging requirements of dimensional stability and optical homogeneity for optical use. Based on molecular structure design and the optimization of fabrication process, the prepared copolyamide-imide membrane achieved the desired performance of membrane as an optical material. It showed a very low coefficient of thermal expansion (CTE), which is 0.95 ppm/°C over a temperature range of −150–100 °C and relatively low coefficient of moisture expansion (CME), which is only 13.30 ppm/% RH (0~90% RH). For the optical use, the prepared copolyamide-imide membrane (φ200 mm) achieved good thickness uniformity with wave-front error smaller than λ/30 (λ = 632 nm) in RMS (root mean square). Besides, it simultaneously meets the optical, thermal, and mechanical requirements for space telescope use. Copolyamide-imide membranes in this research with good comprehensive performance can be used as large aperture membrane optical system architectures.

Fabrication of a Composite Film Optic with High Transmittance in Vis and IR Regions for an Optical System

“…Polyimide film (PI) was prepared referring to the previous method [29]. The synthesis details are as follows: 5.8844 g 3,3 ,4,4 -Biphenyltetracarboxylic Dianhydride (BPDA, 98%, TCI) and 4.5452 g Diamine 4,4 -Diaminobenzanilide (DABA, 98%, TCI) (Tokyo Chemical Industry Co., Ltd., Tokyo, Japan) (n DABA :n BPDA = 1:1) were dissolved in 117.542 g N-Methyl-2-Pyrrolidinone (NMP, 99.5%, Aladdin reagents) (Shanghai Aladdin Bio-Chem Technology Co., Ltd, Shanghai, China) in a dry three-neck flask equipped with a mechanical stirrer and nitrogen flow at room temperature.…”

Preparation and Properties of Low Internal Stress Polyimide-b-Polysiloxane with a Hyperbranched Structure

“…In addition, many studies have been devoted to reducing internal stress by minimizing the discrepancy between the coefficients of thermal expansion of PI and the substrate, ,, decreasing the modulus of PI, ,, and introducing stress reliving domains into the polymer matrix . Among all of these methods, hyperbranched polyimides have attracted many researchers’ attention and are expected to have unique properties. − Liu.…”

“…6−10 To overcome the drawbacks of rigid rod-like PI, a variety of poly(ester imide)s (PEsIs) were prepared by Hasegawa, and the PI films tend to be flexible with a considerably low CTE of 9.9 ppm/K, which was caused by the highly oriented PI main chains. 7,11,12 In addition, many studies have been devoted to reducing internal stress by minimizing the discrepancy between the coefficients of thermal expansion of PI and the substrate, 2,13,14 decreasing the modulus of PI, 1,12,15 and introducing stress reliving domains into the polymer matrix. 1 Among all of these methods, hyperbranched polyimides have attracted many researchers' attention and are expected to have unique properties.…”

Highly Transparent Aromatic Polyamides from Unsymmetrical Diamine with Trifluoromethyl Groups

“…Aromatic polyamides (PAs) are another representative class of high performance polymeric materials and they are well known for high thermal resistance and transition temperature comparable to PIs. Their outstanding properties arise from strong and highly directional interchain hydrogen bonds which grant high cohesive energy between the polymer chains [ 19 , 20 ]. However, the application of PAs in the form of films or membranes often get frustrated because of the rigid aromatic chains interacting strongly with multiple hydrogen bonds which make them intractable and insoluble in organic solvents.…”