High Optical Transparency in the Alicyclic Poly(Ether‐b‐amide) Copolymer Induced by Multiscale Structure via Weak Microphase Separation

Abstract

ABSTRACT Developing transparent materials combining superior optical and mechanical properties with robust service stability remains a significant challenge. Herein, an amorphous alicyclic poly(ether‐b‐amide) (PEBA) copolymer is synthesized by incorporating bis(4‐aminocyclohexyl) methane (PACM) into the hard segment (HS) to suppress crystallization, combined with low‐molecular‐weight poly(tetramethylene ether glycol) (PTMEG) as the soft segment (SS) to enhance segmental compatibility. Such molecular design results in a weakly microphase‐separated structure with diffused boundaries between the nanometer microdomains. This “interface‐erasing” strategy yields a hot‐pressed film with a miscible‐dominated morphology with phase regions ranging from 50 to 100 nm, significantly smaller than visible‐light wavelengths. Finite element analysis (FEA) simulations further demonstrate that these small phase regions, together with the miscible phase acting as a refractive index (RI) buffer, collectively reduce off‐axis scattering, achieving excellent optical clarity (91.1% transmittance, 5.80% haze). The material also shows robust mechanical properties (>30 MPa, >1000% elongation), low‐temperature impact resistance, service reliability, solvent resistance, and damping performance. By integrating multiscale characterization and theoretical modeling, this work provides a simple yet effective molecular design strategy and a multiscale mechanistic insight for transparent high performance elastomers, promising for applications as transparent protective layers.