Synthesis and characterization of negative‐type photosensitive polyimides based on cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride

A series of negative‐type photosensitive polyamic acids (PAAs) with various molecular weights was synthesized from cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride, 2‐(methacryloyloxy)ethyl‐3,5‐diaminobenzoate, and 2‐(methacryloyloxy)ethyl‐4‐aminobenzoate in N‐methyl‐2‐pyrrolidone. We investigated the degree of planarity, transmittance, and thermal stability for the PAAs after the photoirradiation reaction at an exposure dose of 200 mJ/cm². The films prepared from the PAA with the lowest molecular weight (PAA‐1) exhibited a higher degree of planarity and transmittance compared with those of the film prepared from the PAA with the highest molecular weight (PAA‐4). The initial decomposition temperatures of the cured PAAs with different molecular weights were similar and were stable up to around 300°C. Further, the photosensitivity and transmittance of PAA‐1 were investigated in the presence of photoinitiators at 365–400 nm with a high‐pressure mercury lamp. The resolution of the photocured film was about 50 μm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2300–2308, 2005