Selective localization of multi-wall carbon nanotubes in homopolymer blends and a diblock copolymer. Rheological orientation studies of the final nanocomposites

Abstract

In this study, pristine as well as polystyrene (PS) and poly(2-vinylpyridine) (P2VP) functionalized multi-wall carbon nanotubes (MWCNTs) were selectively incorporated in homopolymer binary blends of PS/P2VP and diblock copolymer (BCP) of the PS-b-P4VP type [P4VP: poly(4-vinylpyridine)]. Studies on the blends verified the chemical affinity of PS and P2VP grafted MWCNTs to the corresponding phase. Based on the results obtained from the blend systems, MWCNTs were incorporated in a PS-b-P4VP copolymer matrix with lamellar morphology and large amplitude oscillatory shear (LAOS) experiments were performed to achieve orientation of the BCP lamellae. The PS grafted MWCNTs (MWCNT-g-PS) were selectively sequestered in the PS phase and the P2VP grafted MWCNTs (MWCNT-g-P2VP) in the P4VP phase of the diblock copolymer. Unfunctionalized pristine MWCNTs were localized on the PS phase of the blend system and no special preference was observed towards the diblock copolymer PS domains. Small angle X-ray scattering (SAXS) analysis revealed the orientation of the alternating lamellae formed by the diblock copolymer when studied by LAOS. The localization of PS and P2VP grafted MWCNTs on the corresponding blend and BCP phase was also verified by transmission electron microscopy (TEM) studies.