Optimization of foaming process using triblock polyimides with thermally labile blocks

Fabrication of Ordered Porous Polyimide Films Templated by (AB)m Type of Diblock Copolymer

Ordered porous polyimide films were fabricated from (AB)_m type of diblock copolymer polyimide-b-polystyrene (PI-b-PS). An increase in PS volume fraction (f ^V_PS) is beneficial to decrease the relative dielectric constants and water contact angles of the obtained porous PI films: the relative dielectric constant decreases to 1.89 and water contact angle decreases to 43° when f ^V_PS is 0.36, indicating porous PI films can be used as low-κ material and have good wettability. The solvent uptake of the porous PI films increases with increasing f ^V_PS. A net-like morphology appears when f ^V_PS reaches 0.36. The net-like porous PI film reaches equilibrium uptake of water within approximately 2.5 h, with a final equilibrium uptake ratio of 17.5%, and reaches equilibrium uptake of toluene within approximately 8 h, with a final equilibrium uptake ratio of 15.4%, displaying the highest and fastest solvent uptake compared with other microstructured porous PI films, which is ascribed to the specific characteristic of the interconnecting porous channels derived from the self-assembly of PI-b-PS with f ^V_PS 0.36. Introducing thermally degradable segments to PI-based block copolymer is an effective method to prepare porous PI films and can enhance some of their properties.