Effect of functionalized multiwalled carbon nanotubes on thermal stability of poly (L-LACTIDE) biodegradable polymer

The thermal stability of Poly (L-lactide) PLLA biocompatible and biodegradable polymer reinforced with functionalized Multiwalled carbon nanotubes (MWCNTs) was investigated. For improvement of MWCNTs, the pristine MWCNTs (pMWCNTs) were functionalized, at first, by Friedel Crafts acylation, which introduced the aromatic amine groups on the side wall of MWCNTs (MWCNT- NH2) without shortening or cutting of pMWCNTs. Then, the PLLA chains were covalently grafted from the sidewall of MWCNT- NH2 by in situ ring-opening polymerization of L-lactide oligomers (LA), using stannous octanoate as the initiating system (MWCNT-g-PLLA). The FT-IR and XPS spectra revealed that the PLLA chains grafted strongly from the sidewall of MWCNTs. The thermo-gravimetric analysis of prepared composites with various concentrations of MWCNT-g-PLLAs shows a significant increment in the thermal stability of composites, by increasing the concentration of MWCNT-g-PLLAs in composites. The XRD analysis revealed that the MWCNT-g-PLLAs increased the crystallinity of PLLA, indicating that the composites with PLLA grafted MWCNTs were more thermally stable than those of neat PLLA.