Fig. 7. (a) Gel fraction of PI4, PI4-G5 and PI4-G7versus exposure dose (75 mW cm⁻², λ < 400 nm, N₂) as obtained from FT-IR measurements. (b) Confocal micrograph of positive-tone relief structures (100 and 50 μm lines and spaces) inscribed into PI4-G5 by photolithography after the development in tetrahydrofuran.