A sterically encumbered m‐terphenyl oxacyclophane substituted with two aryl iodide substituents has been prepared as a versatile monomer for the preparation of π‐conjugated polymers. The monomer has been used to prepare a poly(p‐phenylene ethynylene) derivative (P1) incorporating oxacyclophane units as canopies that shield one side of the π‐system from inter‐chain interactions. The photophysical properties of P1 in dilute solution compare well to those of a poly(p‐phenylene ethynylene) derivative (P2) that lacks the canopy. The presence of the steric canopy leads to a diminished inter‐chain interaction in the solid state and enhances the kinetic response of P1 to vapors of nitro‐organics such as TNT, presumably by increasing the permeability of P1 to these analytes over that of P2.
