Block copolymers of poly(pentafluorostyrene) (PFS) and poly(methyl methacrylate) (PMMA) (PFS‐b‐PMMA) have been synthesized using atom transfer radical polymerization (ATRP). Then, nanoporous fluoropolymer films have been prepared via selective UV decomposition of the PMMA blocks in the PFS‐b‐PMMA copolymer films. The chemical composition and structure of the PFS homopolymers and copolymers have been characterized using nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary‐ion mass spectrometry (ToF‐SIMS), and molecular‐weight measurements. The cross‐sectional and surface morphologies of the PFS‐b‐PMMA copolymer films before and after selective UV decomposition of the PMMA blocks have been studied using field‐emission scanning electron microscopy (FESEM). The nanoporous fluoropolymer films with pore sizes in the range 30–50 nm and porosity in the range 15–40 % have been obtained from the PFS‐b‐PMMA copolymers of different PMMA content. Dielectric constants approaching 1.8 have been achieved in the nanoporous fluoropolymer films which contain almost completely decomposed PMMA blocks.

Thermally‐initiated living radical graft polymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA) with ozone‐pretreated poly[N,N′‐(1,4‐phenylene)‐3,3′,4,4′‐benzophenonetetra‐carboxylic amic acid] (PAmA) via a reversible addition–fragmentation chain‐transfer (RAFT)‐mediated process was carried out. The chemical compositions and structures of the copolymers were characterized by nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), and molecular weight measurements. The “living” character of the grafted PEGMA side chains was ascertained in the subsequent extension of the PEGMA side chains. Nanoporous low‐dielectric‐constant (low‐κ) polyimide (PI) films were prepared by thermal imidization of the PAmA graft copolymers under reduced argon pressure, followed by thermal decomposition of the side chains in air. The nanoporous PI films obtained from the RAFT‐mediated graft copolymers had well‐preserved PI backbones, porosity in the range of 5–17 %, and pore size in the range of 30–50 nm. The pores were smaller and the pore‐size distribution more uniform than those of the corresponding nanoporous PI films obtained via graft copolymers from conventional free‐radical processes. Dielectric constants approaching 2 were obtained for the nanoporous PI films prepared from the RAFT‐mediated graft copolymers.

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