Filing volume has declined since a 2017 peak of 435 publications, falling to 44 in the most recent partial year, with the 2022 midpoint still at 407. That trajectory points to a maturing field rather than a growing one, though publication lag of roughly 18 months means the very latest year understates real activity. New filings are more likely to succeed in less-crowded application or processing niches than in the core dianhydride-diamine chemistry.

Japanese and Korean specialty-chemical majors such as 钟渴化学工业, UBE, 三井化学 and 日产化学, alongside DuPont, anchor the deepest historical portfolios in this corpus, often filing jointly with affiliated entities. However, recent-year momentum data shows all of these assignees at zero or negative year-over-year filing, meaning their positions were largely built earlier in the tracked window rather than currently expanding.

The IPC composition shows claim density concentrated in core condensation polymerization (C08G) and general polymer compositions (C08L), while application-facing classes like printed-circuit dielectrics, coatings and laminate adhesion sit at a fraction of that volume. Sub-areas such as low-CTE optical copolymer design, aqueous poly(amic acid) routes and solvent-free imidization processing show comparatively thin coverage relative to the base chemistry. That doesn’t guarantee novelty, but it does mean the prior-art thicket is thinner there.