Efficient and Robust Reactions for Polyethylene Covalently Grafted Carbon Nanotubes

Surface modification of carbon nanotubes (CNTs) with long polymer chains has attracted great attention since it promises high performance nanomaterials. However, due to the chemical inertness of both polyethylene (PE) and CNT, it still remains a challenge to covalently conjugate CNT with PE in a facile manner. In this report, trimethoxysilane terminated PE (TMS-PE) and trimethoxysilane modified multiwall carbon nanotube (TMS-MWNT) is prepared through radical mediated thiol-ene addition reaction between (3-mercaptopropyl)trimethoxysilane and vinyl terminated PE or pristine carbon nanotube, respectively. Subsequently, organotin-catalyzed hydrolytic co-condensation of TMS-PE and TMS-MWNT lead to PE covalently grafted mutliwall CNT (PE-Si-MWNT) with high graft ratio (17.5 wt%). Such reactions are robust and efficient and the reaction conditions are mild. In addition, the authors provide the very first evidence that end-grafted PE chains in PE-Si-MWNT, which are clearly observed in TEM images, can render high compatibility and good interfacial interactions between CNT and low density PE (LDPE) matrix and thus promote homogeneous dispersion of CNT into LDPE matrix as shown by scanning electron microscopy (SEM) characterization of brittle fracture surfaces of LDPE/PE-Si-MWNT nanocomposites.