Controlled Synthesize Of Carbon Nanotubes/Polymer Composites Via ATRP Method

It is well know that there exists excellently properties of carbon nanotubes (CNTs), in addition, CNTs is a kind of reinforcement for polymer nanocomposites. However, the full potential of employing CNTs as reinforcements has been severely limited because of the difficulties associated with dispersion of entangled CNT during processing and poor interfacial interaction between CNTs and polymer matrix. The nature of dispersion problem for CNTs is rather different from other conventional fillers, such as spherical particles and carbon fibers, because CNTs are characteristic of small diameter in nanometer scale with high aspect ratio (>1000) and thus extremely large surface area. In addition, the commercialized CNTs are supplied in the form of heavily entangled bundles, resulting in inherent difficulties in dispersion. The performance of a CNT/polymer nanocomposite depends on the dispersion of CNTs in the matrix and interfacial interactions between the CNTs and the polymer. The problems can be improved by functionalizing the surface of CNTs, there are some methods to functionalized CNTs, and these methods can be conveniently divided into chemical functionalization and physical methods based on the interactions between the active molecules and carbon atoms on the CNTs. Chemical functionalization is based on the covalent linkage of functional entities onto carbon scaffold of CNTs. It can be performed at the termini of the tubes or at their sidewalls, and the chemical reactivity of CNTs improved with functionalized groups introduces, results in the enhance of the interaction between CNTs and polymer. Physical functionalization is based on the non-covalent bond of organic molecule onto the surface of CNTs by encapsulation or winding. Compared with chemical functionalization and physical functionalization, the interaction obtained by chemical functionalizaton is more stronger than physical functionzation.In the chapter one, the structure, properties, applications and functionalization methods of CNTs have been introduced briefly. The several methods of living polymerization for CNTs were described in detail, with emphasis on the mechanism, relevant research and a series of optimizations of atom transfer radical polymerization (ATRP) for CNTs.In the chapter two, firstly, the amorphous carbon and impurity in MWCNTs were removed by pretreated with concentrated nitric acid, and the activity groups of hydroxyl groups (—OH) and carboxyl groups (—COOH) were introduced to the surfaces of MWCNTs. The MWCNTs-Br based ATRP initiator were obtained by acyl chloride reaction, ethylene glycol reaction and isopropyl bromide butyryl bromine reaction on the surfaces of MWCNTs. The MWCNTs/PMMA nanocomposites were then obtained by the ATRP living polymerization of methyl methacrylate monomers which was initiated by the ATRP initiator. The dispersing performance of MWCNTs and MWCNTs/PMMA nanocomposites in chloroform were investigated.In the chapter three, the MWCNTs/PS nanocomposites was obtained by the living polymerization of vinyl benzene monomers which was initiated by ATRP initiator, and the MWCNTs-Br based ATRP initiator were obtained by the carboxyl reaction, acyl chloride reaction, hydroxyl reaction and a-bromoisobutyric acid tert-butyl ester reaction step by step. The structure of MWCNTs/PS nanocomposites were investigated by FTIR, NMR and TGA, and the dispersity and mechanical properties of MWCNTs/PS nanocomposites were also research. The results shows that the miscibility of MWCNTs in organic solvent improved with grafted PS on MWCNTs. The strength of MWCNTs/PS nanocomposites improved as MWCNTs added to polymer matrix.In the chapter four, the thermoresponsive polymer PNIPAM with hydrophilic character and the biodegradable polymer PCL with hydrophobic character were grafted to the surface of MWCNTs, the MWCNTs/PCL-b-PNIPAM nanocomposites were fabricated by open-ring polymerization and ATRP. The structure of MWCNTs/PCL-b-PNIAM nanocomposites were investigated by FTIR, RM, TGA, H’NMR and TEM, the crystallization of MWCNTs/PCL-b-PNIAM nanocomposites was researched by XRD. The results indicated that PCL-b-PNIPAM copolymer has grafted on the surface of MWCNTs successfully, the crystallization of MWCNTs/PCL-b-PNIPAM is similar to PCL-b-PNIPAM copolymer, and the miscibility of MWCNTs in organic solvent improved with grafted polymers on MWCNTs.