Catalytic Arene–Norbornene Annulation (CANAL) Polymerization for the Synthesis of Rigid Ladder Polymers

Abstract

Rigid and contorted ladder polymers are an intriguing class of polymer architecture expected to have many unusual properties, although their synthetic access is rather limited, with only a few methods reported. In this chapter, we describe a catalytic method, termed Catalytic Arene–Norbornene Annulation (CANAL) polymerization, for the synthesis of rigid ladder polymers using norbornadiene and aromatic dibromides as building blocks. CANAL ladder polymers consist of frequent, approximately 120° backbone contortions from the norbornyl benzocyclobutene repeat units with the bridge carbon of norbornyl units oriented randomly. CANAL ladder polymers exhibit high thermal stability without detectable T g and abundant microporosity, representing a new type of polymer with intrinsic microporosity (PIM). Tuning ladder backbone contortions resulted in membranes with unprecedented performance in several gas separations, achieving both high permeability and high selectivity.