This study investigates the synthesis and properties of polyimides with linear backbone structures incorporating ester groups and ether bonds. These polyimides exhibit low dielectric loss (Df) values of 0.0015–0.0024 at 10 GHz, maintaining these values even under high humidity and temperature conditions. The research highlights the importance of high orientation and crystallinity in reducing Df. The study compares various polyimide series, including polyetherimide (PEI), polyimide (PI), and poly-ester-ether imide (PEIS), and finds that PEISs with a combination of rigid and flexible segments, such as ester groups and ether bonds, show superior thermal stability, dielectric properties, and water absorption resistance. The low Df values of PEISs are attributed to their high orientation and dense packing, which restrict dipole moment rotation and enhance relaxation time. Additionally, PEISs exhibit low moisture absorption, ensuring their stability in humid environments. The study also explores the thermal, mechanical, and electrical properties of PEISs, demonstrating their potential for applications in high-frequency communication devices.This study investigates the synthesis and properties of polyimides with linear backbone structures incorporating ester groups and ether bonds. These polyimides exhibit low dielectric loss (Df) values of 0.0015–0.0024 at 10 GHz, maintaining these values even under high humidity and temperature conditions. The research highlights the importance of high orientation and crystallinity in reducing Df. The study compares various polyimide series, including polyetherimide (PEI), polyimide (PI), and poly-ester-ether imide (PEIS), and finds that PEISs with a combination of rigid and flexible segments, such as ester groups and ether bonds, show superior thermal stability, dielectric properties, and water absorption resistance. The low Df values of PEISs are attributed to their high orientation and dense packing, which restrict dipole moment rotation and enhance relaxation time. Additionally, PEISs exhibit low moisture absorption, ensuring their stability in humid environments. The study also explores the thermal, mechanical, and electrical properties of PEISs, demonstrating their potential for applications in high-frequency communication devices.