Molecular Design And Preparation Of Polymer-Carbon Nanotube-based Multifunctional Nanomaterials

Carbon nanotubes （CNTs）, owing to their light weight, high strength as well asexcellent electric, optical, and thermal properties, have been considered as idealnanofillers for preparation of multifunctional polymer-based nanomaterials.Magnetic-fluorescent polymer, owing to its unique properties, can be widely applied inmany promising high-tech fields such as biology, pharmacology, and military. Thecombination of CNTs and magnetic-fluorescent polymer is highly possible to providemore excellent properties and wider application fields. In this work, we adopt thebottom-up methodology to molecularly design and synthesize a novelmagnetic-fluorescent bifunctional polymer. It is then covalently grafted onto thesurface of CNTs, providing a new way to prepare polymer-CNT-based multifunctionalnanomaterials.In previous study, we proposed a new strategy to fabricate magnetic-fluorescentpolymer by combining magnetic unit and fluorescent unit into one singlemacromolecular chain, in which the fluorescence and magnetic responses are providedby pyrene-containing unit and complex of Fe³⁺with imidazole group, respectively. Atypical bifunctional polymer is described as Poly[vinylimidazole-co-（1-pyrene） methyl2-methyl-2-propenoate] butyl tetrachloro-ferrate, Poly（VI-co-PyMMP）Bu[FeCl₄]. Inthis study, to covalently graft such bifunctional polymer onto the CNT surface, a thirdunit terminated with-OH is further introduced into the polymer chain so as to providethe reactive sites for its covalent bonding with CNTs. With this in mind, we havesynthesized a series of fluorescent tercopolymers of Poly（VI-PyBMM-PEGMA）BuClwith various monomer unit ratios. The corresponding complex with FeCl3can emitblue fluorescence under UV irradiation （365nm） and display superparamagnetism at 300K. When the monomer feed ratio of VIBuCl/PyBMM/PEGMA is96/3/1,fluorescence emission and magnetism of the resultant material reaches an optimalbalance. Finally, a tercopolymer of Poly（VI-PyBMM-PEGMA） was synthesized on thebase of such optimal result and subsequently attached covalently onto the CNT surfacethrough an esterification reaction.Another important content of this study is to molecularly design and synthesize amagnetic-fluorescent bifunctional polymer with long side chains. It has been provedpreviously that the introduction of Fe³⁺could not only endow with magnetic responseof resultant product, but also result in fluorescence quenching. One of the reasons maybe that the arrangement of FeCl3and pyrene units is so compact that the stronginteractions between them led to high-probability strong electric and/or energy transferand hence cause fluorescence quenching. In this work, a long side chain structure isthus introduced in order to enlarge effectively the distance between pyrene unit andFe³⁺center. The magnetic and fluorescent responses of resultant product aresubsequently explored and correlated. The obtained primary results may supply somehelpful information for our further investigation.