Influence of Carbon Nanotubes on the Morphology and Properties of Styrene-Butadiene Based Block Copolymers

Structure property correlations in a styrene-butadiene star block copolymer melt mixed with varying amounts of multiwalled carbon nanotubes (MWCNTs) were evaluated. The MWCNTs are well dispersed within the matrix and do not significantly impact the star block copolymer morphology or the glass transition temperature. The electrical percolation threshold was found to be at similar to 1 wt% of MWCNT concentration. A distinct increase in Young's modulus could be observed at a nanofiller content of 0.1 wt% while maintaining the elastomeric matrix property profile, an observation in tune with the rule-of-mixture prediction. Additionally the existence of double yielding was detected in these nanocomposites with a pronounced first yield point indicating a significant enhancement of stiffness in composites with low MWCNT content. Analysis of elastic moduli using Halpin-Tsai and two-phase Takayanagi model revealed a matrix-controlled elastic response without any interfacial contribution due to MWCNT incorporation.