Aggregation-Dependent Chromism and Photopolymerization of Aminoanthraquinone-Substituted Diacetylenes

Polydiacetylenes have attracted significant interest for their unique chromatic properties and applications in sensing, imaging, and optics. Here, it is demonstrated that aminoanthraquinone-substituted diacetylenes exhibit distinct aggregation-dependent chromatic properties, affected by the alignment of both the aminoanthraquinone headgroups and diacetylene sidechains. Specifically, it is shown that aminoanthraquinone-diacetylene monomers adopt different film organizations depending upon the polarity of the solvent employed for predissolution. In particular, a yellow aminoanthraquinone-diacetylene phase, which undergoes photopolymerization upon ultraviolet irradiation, is produced upon dissolution in polar organic solvents prior to deposition and drying on solid substrates. In contrast, a red phase that can not be polymerized is observed when the monomers are predissolved in apolar solvents. Microscopic and spectroscopic analyses indicate that the optical properties of the films are determined by the degree of overlap between the aminoanthraquinone headgroups as well as the alignment of the diacetylene sidechains; both factors are intimately affected by interactions of the monomers with solvent molecules. It is shown that the aggregation-dependent diacetylene films exhibit remarkable solvochromic, thermochromic, and mechanochromic properties. The aminoanthraquinone-substituted diacetylenes may facilitate chromatic tuning of polydiacetylene systems in the solid state, determined by solvent- and intermolecular interactions and concomitant self-assembly of the pendant sidechains and aromatic headgroups.