Poly( o ‐xylylene)s via Cobalt‐Catalyzed Reductive Polymerization †

Summary of main observation and conclusion Poly( p ‐xylylene)s (PPX) have found wide applications in various fields owing to their chemical robustness, low gas permeability and excellent dielectric properties. As a structural isomer of PPX, poly( o ‐xylylene)s (POX), possessing a distinct main‐chain connectivity, are excellent candidates to pursue high‐performance materials; however, the investigation of POX is hampered by the lack of efficient synthetic methods. Herein, we report a straightforward way to access POXs through a cobalt‐catalyzed reductive polymerization. This method not only allows the direct preparation of electronically unmodified POXs, but also enables the copolymerization between o ‐xylylene dibromides bearing different aryl or benzylic substituents. The glass transition temperatures of the copolymers can be finely tuned by varying the ratio between comonomers. The obtained POXs are solvent processible and amenable for thin‐film fabrication. As aryl bromide moiety remains untouched during the polymerization, post‐polymerization functionalization is easily achieved through Suzuki‐Miyaura coupling reaction. The chemistry also enables the copolymerization of xylylene dibromide regioisomers, thereby leading to diversified non‐conjugated polymers, whose backbones are rich in arylene moieties. Moreover, the use of the polymerization strategy to synthesize structurally novel porous polymers is demonstrated.