Innocuous solvent-based, low-temperature curable, and highly transparent photosensitive polyimides developed using soluble polyimides containing bio-based magnolol moieties

Traditional photosensitive polyimide (PSPI) materials require a high curing temperature and exhibit low transparency, limiting their applications in thermally sensitive optical devices. To overcome this challenge, soluble photosensitive polyimide resins were synthesized based on the structural design of a bio-based magnolol monomer. It is noteworthy that the PI photoresist, developed by using the as-prepared polyimides and non-toxic solvents (2-acetoxy-1-methoxypropane, PGEMA) and other additives, demonstrated an impressive low-temperature curing performance (180 °C). Furthermore, the solvent residue in the cured film prepared using PGEMA as solvent was markedly decreased compared to that prepared using <i>N</i>-methyl pyrrolidone (NMP). In addition, the C-PI-3 films cured by photoinitiated thiol-ene radical reactions exhibited high transparency with an average visible light transmittance of 87.8%, as well as excellent thermal stability, dielectric and breakdown properties, and photo-patterning capabilities. This partially bio-based and innocuous solvent-based PSPI with low-temperature curability and high transparency properties could be a pioneering example to resolve the challenges of energy efficiency and environmental sustainability and is expected to be used in the field of color filters.