Fabrication of carboxyl-functionalized polymer microtubes via RAFT copolymerization of diurea-type xerogel fibers and acrylic acid.

A new diurea-type gelator was synthesized from 2-isocyanoethyl acrylate and 4′-diaminodiphenylmethane, which formed supramolecular gel in acetonitrile driven by hydrogen bonds. The xerogel fibers with a smooth lamellar structure were used as templates and monomer source in fabricating polymer microtubes via reversible addition-fragmentation chain transfer polymerization. Because of a very low solubility of the gelator, the polymerization in toluene gave no insoluble product. As suitable amount of methanol was used together with toluene, the polymerization was conducted successfully to obtain ribbon-like polymer tubes with smooth surface. Based on which, acrylic acid was further used as a co-monomer to form carboxyl-functionalized polymer tubes. The resulting products were characterized by multiple techniques. Compared with the ordinary polymer tubes, the carboxyl-functionalized polymer tubes exhibited much improved adsorption capability for methylene blue (MB) at pH 7 and the absorbed MB molecules could be released in both acidic water and acidic ethanol. [ABSTRACT FROM AUTHOR]