Topochemical Polymerization of a Supramolecular Polymer and Prominent Ambipolar Charge-Carrier Mobility

This study reports the topochemical polymerization of a supramolecular polymer of the n-type semiconducting naphthalene-diimide (NDI)-appended diacetylene (DA) building block NDI-DA. It exhibits H-bonding-driven supramolecular polymerization in a nonpolar solvent, producing a fibrillar gel, in which the polymerizable DA units are spatially organized in a manner that facilitates topochemical polymerization. Upon photoirradiation, topochemical polymerization proceeds efficiently, producing the p-type semiconducting polydiacetylene (PDA) backbone with appended n-type NDI chromophores. The resulting polymer (NDI-PDA) was isolated as a red solid and showed a very high molecular weight (Mn) of 232,000 g mol–1 with a narrow dispersity (Đ) of 1.1. The UV/vis spectrum of NDI-PDA, even in a good solvent, showed prominent π-stacking despite the absence of H-bonding among the amide groups, suggesting indeed that the topochemical polymerization had stabilized the NDI stack, as desired. Electron- and hole-transporting pathways along the peripheral NDI array and the PDA backbone, respectively, lead to a significantly high ambipolar charge-carrier mobility of 6.0 × 10–4 cm2 V–1 s–1, estimated by flash photolysis time-resolved microwave conductivity in combination with transient absorption spectroscopy studies.