Thermal mismatch strains in sidewall functionalized carbon nanotube/polystyrene nanocomposites

We present an unusual temperature dependence of thermal strains in 4-(10-hydroxy)decyl benzoate (HDB) modified SWNT/PS (SWNT-single wall carbon nanotube, PS-polystyrene) nanocomposites. The strain transfer from the matrix to nanotubes in these nanocomposites, inferred from the frequency change of the Raman active tangential modes of the nanotubes, is enhanced strongly below 300 K, whereas it is vanishingly small at higher temperatures. The increased strain transfer is suggestive of reinforcement of the HDB-SWNT/PS nanocomposites at low temperatures. On the other hand, the pristine SWNTs couple weakly to the PS matrix over the entire temperature range of 4.5-410 K. We argue that the strain transfer in HDB-SWNT/PS is determined by the thermomechanical properties of the interface region composed of polystyrene plasticized by the tethered alkanelike modifier.