Carbon nanotubes (CNTs) can enhance properties such as tensile strength and electrical conductivity when incorporated into polymer composites. When these polymer nanocomposites enter the environment post-consumer their fate and persistence will be intimately dependent upon their interactions with microorganisms present in landfills, soils, and surface waters. To study the initial interactions of microbial populations with nanocomposites surfaces we have investigated how CNT loading in a polyvinyl alcohol matrix impacts the initial viability of Pseudomonas aeruginosa. CNT-polyvinyl alcohol composites were prepared with CNT loadings relevant to those used in products (0.1-10 wt.%) and were characterized using X-ray photoelectron spectroscopy, attenuated total reflectance IR, and SEM imaging. Nanocomposites were then inoculated under static conditions and treated with fluorescent stains to assess cell viability.  For both oxidized multi-walled and single-walled CNTs, an increase in CNT loading caused a systematic increase in the nanocomposite's cytotoxicity although SWNTs were found to be more cytotoxicity at an equivalent weight loading. However, the cytotoxicity of CNTs requires direct contact between the CNTs and microbes and was therefore restricted to initial microbial interactions, with biofilm formation being observed for more prolonged microbial exposures. To assess the longer term interactions of CNT nanocomposites with microbial populations, the biodegradable polymer, polycaprolactone (PCL), and its respective CNT composites were prepared. The CNT loading was varied in the polymer matrix and mass loss studies were carried out in P. aeruginosa cultures shaken at 30�C and 125 rpm. Results indicated that the extent of nanocomposite biodegradation decreased significantly as the CNT loading increased. Indeed, CNT loadings of 4% were sufficient to create nanocomposites containing biodegradable polymer matrices that were essentially inert to biodegradation. In summary, we have found that an increase in CNT loading within a nanocomposite will cause an increase in initial cytotoxicity and longer term persistence of the material.

Interactions of carbon nanotube polymer nanocomposites with microorganisms

247th National Meeting (2014)

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