Preparation and properties of hydroxylated styrene–butadiene–styrene tri-block copolymer/multi-walled carbon nanotubes nanocomposites via covalent bond

In this study, styrene–butadiene–styrene tri-block copolymer (SBS)/multi-walled carbon nanotubes (MWCNTs) nanocomposites were prepared by means of a solution processing method. To enhance the compatibility between SBS and MWCNTs, the hydroxylated styrene–butadiene–styrene tri-block copolymer (HO-SBS) and the acyl chloride-activated MWCNTs (MWCNTs-COCl) were used to replace SBS and MWCNTs, respectively. The pristine MWCNTs were chemically oxidized by a mixture of H2SO4 and HNO3 and then reacted with thionyl chloride to functionalize them with acyl chloride groups. The resulting nanocomposites have been characterized by the testing of gel fraction and degree of swelling, Raman spectra, FTIR, SEM, TEM, DSC, TGA, and Instron mechanical tester. The results of gel fraction and degree of swelling show that the HO-SBS/MWCNTs nanocomposites have cross-linked structure and exhibit high solvent resistance. The results of Raman spectra and FTIR indicate that there are ester groups on the surface of MWCNTs. The results of SEM, TEM, and DSC show that the well-dispersed MWCNTs not only disturb the microphase-separated structure of HO-SBS but also decrease its order–disorder transition temperature, and the presence of MWCNTs could lead to an increase of glass transition temperatures of PB domains. In addition, mechanical tests reveal that dispersion of MWCNTs-COCl via covalent bond in polymer matrix is a useful method to regulate mechanical properties of the HO-SBS.