Surface modification of halloysite nanotube with an amine terminated block copolymer

The surface modification of the halloysite nanotube (HNT) can make it a prospering vehicle for cancer drug delivery. In the present study, the surface of HNT clay was modified with a copolymer of polyacrylic acid (PAA) and polyaniline (PANI). The copolymer was decorated on the HNT surface via grafting from strategy. To fulfill this, the surface was firstly modified with an organosilane component, and then with a chain transfer agent (CTA). Later, the copolymer was grown on the surface via subsequent stages of reversible addition-fragmentation chain transfer (RAFT) and oxidative polymerizations. The successful formation of copolymer on the HNT surface was corroborated by spectroscopic analyses, including FTIR and 1 HNMR. The morphology of the polymer-grafted HNTs was studied using electron microscopes, SEM and TEM, and the results revealed that nanostructures with respective mean diameter and length of 40 and 100 nm possessing polymer coating on the interior and exterior surfaces were obtained. The structural analysis with XRD verified the crystalline structure of HNTs was almost preserved in the presence of copolymer graft, and only the interlayer distances were increased. The thermal study via DSC confirmed that the copolymer-grafted HNTs possessed glass transition, melting, and degradation peaks. TGA analysis unveiled that HNTs grafted with copolymer represented higher thermal stability than those grafted with pristine PAA. Moreover, quantitative results of TGA substantiated that more than 59% copolymer was grafted onto the HNT surface.