Fabrication of melamine/Tb3+-intercalated polydiacetylene nanosheets and their thermochromic reversibility

Polydiacetylene (PDA) is one kind of the conjugated polymer with layered structure, which can serve as a host to accommodate the guest components through intercalation. In these intercalated PDAs, some of them were reported to have a nearly perfect organized structure and perform completely reversible thermochromism. Till now, these reported intercalated PDAs were made by only introducing a single component for intercalation. Here, we chose 10,12-pentacosadiynoic acid (PCDA) as the monomer, of which the carboxyl-terminal groups can interact with either Tb3+ ions or melamines (MAs). When the feeding molar ratio of PCDA, MA, and Tb3+ ion was 3:267:1, only Tb3+ ions were intercalated though excess MAs existed. Such Tb3+-intercalated poly-PCDA exhibited completely reversible thermochromism, where almost all the carboxyl groups interacted with Tb3+ ions to form the nearly perfect structure. When the feeding molar ratio of PCDA, MA, and Tb3+ ion was 3:267:0.6, both Tb3+ ions and MAs were intercalated. There existed some defects in the imperfect MA-intercalated domains and at the domain boundaries. The MA/Tb3+-intercalated poly-PCDA exhibits partially reversible thermochromism, where the backbones near the defects are hard to return the initial conformation, while the rest, those at nearly perfect organized domains, are still able to restore the initial conformation.