Self-assembling supramolecular polymer membranes for highly effective filtration of water-soluble fluorescent dyes

Self-assembling supramolecular polymer membranes (SPMs), a combination of self-complementary multiple hydrogen bonding interactions and a flexible polymer-based material, can be advantageously used to induce and manipulate the self-assembly of polymer chains in the solid state, making it possible to achieve unprecedented structural and chemical diversity as well as novel functions. Herein, we successfully developed a new ureido-cytosine (UrCy)-functionalized supramolecular polymer [poly(UrCy-PPG)] that exhibits many attractive properties, such as excellent thermoreversible behavior, a unique fiber-like self-assembled microstructure and rapid film-forming ability owing to its reversible UrCy-induced physical cross-linking. In addition, when a poly(UrCy-PPG) film was employed as the filtration membrane in a double-layered filtration system that exhibited a remarkable performance in the filtration of aqueous solutions of the fluorescent dye rhodamine 6G (R6G), the resulting spin-coated R6G films demonstrated increased fluorescence efficiency and improved color stability. Surprisingly, the fluorescence intensity of poly(UrCy-PPG)-filtered films was nearly 6 times higher than that of an unfiltered R6G film and films filtered through the support membrane alone. Given its simplicity, ease of processability, multifunctional features and high filtration efficiency, this newly devised SPM system offers a potential route towards the development of high-performance water-based fluorescent films.