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Synthesis of Single Wall Carbon Nanotube-Polymer Composites by a Novel Two Steps Approach

Pu Zhang, Chemical & Biological Engineering, University of Missouri-Rolla, 143 Schrenk Hall, Rolla, MO 65401 and David Henthorn, Chemical Engineering, University of Missouri-Rolla, 143 Schrenk Hall, Rolla, MO 65401.

One of the most promising applications for carbon nanotubes is as a support material for different applications. In this work, we successfully developed a new “graft from” strategy to functionalize the surface of carbon nanotubes. In the first step, the carbon nanotubes were functionalized by initiator, providing active sites for subsequent polymer attachment. Depending on the application, polymer chains can be grown from the nanotubes surface either by ultraviolet light initiated polymerization or slow thermal reactions. For bio-oriented application, an ultraviolet light initiated “graft from” polymerization method was used to fabricate single wall carbon nanotube-polymer composites with pendant chains of various functionalities. Grafted polymer molecules with pendent PEG side chains were used to boost aqueous dispersibility while glycidyl methacrylate (GMA) monomer provided reactive epoxy functional groups for protein immobilization. A model enzyme, alkaline phosphatase, was used to study the loading efficiency as well as the retention of enzymatic activity. Samples with various ratios of the two monomers poly(ethylene glycol) methyl ether methacrylate (PEGMA) and GMA (PEGMA: GMA=4:1, 1:1, 1:4, 1:10) were fabricated to optimize their use in aqueous environments, and an optimum formula (1:1) of the composition was developed.

Polymer nanotubes composites rich in the GMA monomer was dispersed in epoxy resin and cured. An epoxy composite containing 0.5 wt% functionalized multiwall carbon nanotube (MWNT) was produced. With the addition of 0.5 wt% of functionalized MWNT, the reinforced epoxy exhibited a 48% enhancement in Young's modulus and 33% enhancement in ultimate strength.