Morphological regulation improved electrical conductivity and electromagnetic interference shielding in poly(L-lactide)/poly(ε-caprolactone)/carbon nanotube nanocomposites via constructing stereocomplex crystallites

Morphological control of conductive networks in conductive polymer composites has been demonstrated to efficiently improve their electrical performance. Here, morphological regulation used for the formation of conductive networks occurs in poly(L-lactide)/poly(e-caprolactone) (PLLA/PCL) blends when stereocomplex crystallites (SCs) are formed in the PLLA phase. The SCs formed during the melt-processing increase the viscosity and elasticity of the PLLA phase, which makes the PLLA domains shrink and the PCL phase becomes continuous from the previously dispersed phase. As a result, for PLLA/PCL/multi-walled carbon nanotube (MWCNT) nanocomposites, the MWCNTs prefer to disperse in the PCL phase via morphological regulation. The electrical conductivity and the electromagnetic interference (EMI) shielding effectiveness (SE) of the PLLA/PCL/MWCNT nanocomposites can be abruptly increased and attributed to the simultaneous organization of conductive paths when the continuous PCL phase develops. For example, the electrical conductivity and the EMI SE of the PLLA/PCL/MWCNT nanocomposites increased from 2.1 x 10(-12) S m(-1) and 5.3-8.6 dB to 0.012 S m(-1) and similar to 17 dB, respectively, with 0.8 wt% MWCNTs when adding 20 wt% poly(D-lactide) (PDLA) to the PLLA phase. Furthermore, the percolation threshold of the nanocomposites was reduced from 0.13 to 0.017 vol% by adding 20 wt% poly(D-lactide) (PDLA) to the PLLA phase.