M -1 in chloroform, Fig. ) is favoured over UPy homodimerization by a 20:1 ratio and we considered this promising as a supramolecular synthon to assemble the first visible light responsive AB type hydrogen-bonded supramolecular polymer. In this initial study, an AB type rather than AA + BB type system was prioritised given the later presents the additional challenge of stoichiometry control, whilst the former represents a single component system that could be readily compared with I and II. Syntheses of I-III including notes on different routes we explored together with experimental procedures and characterisation for final compounds and all intermediates are described in the supporting information.