Well-defined arrays of porphyrins attached to a rigid polyisocyanide backbone have been synthesized and their physical and optical properties studied. The helical polymers are rigidified by an inter-side chain hydrogen-bonded network and have an average mass of 1.1×106 Daltons and a polydispersity index of 1.3. Each of the polymer strands contains four columns of around 200 stacked porphyrins and has an overall length of 87 nm. The chromophores are arranged in a left-handed helical fashion along the polymer backbone. Photophysical studies show that at least 25 porphyrins within one column are excitationally coupled.