Tunable mechanical properties of layer-by-layer self-assembled carbon nanotube/polymer nanocomposite membranes for M/NEMS

This paper presents layer-by-layer (LbL) self-assembly of single-walled carbon nanotube (SWNT)/polymer membranes with a well-dispersed wide-range tunable volume fraction of functionalized SWNTs. The surface morphology of the SWNT/polymer membranes shows a high strength, dense and random network structures. The quartz crystal microbalance (QCM) characterization illustrates that the deposition thickness and the SWNT loading fraction in SWNT nanocomposites can be controlled in a large range based on LbL sequential deposition process. The Young's modulus of the self-assembled SWNT/polymer composite membranes is characterized by a combinative approach of piezoelectric excitation and laser vibrometer measurement. The Young's modulus of SWNT/polymer nanocomposites is tunable from hundreds to tens of GPa, as a function of the SWNT volume fraction. Such significant enhancement of LbL self-assembled SWNTs offers a way in which the embedded SWNTs can realize the true potential to strengthen SWNT/polymer nanocomposites. Conventional mixture models such as rule-of-mixture model and Halpin–Tsai model fail to explain the structure–property regime in nanoscale at a high SWNT fraction ratio. This observed tunability can serve as a benchmark to tailor the design of nanocomposite thin films for potential applications to MEMS and NEMS devices.