Synthesis and Characterization of Copolymer Poly(propylene-co-styrene) Grafted-Multiple-walled Carbon Nanotubes by Nitroxide-mediated Living Radical Polymerization and Solution Intercalation Method

Chemical modification of commercial and industrial copolymers and polymers such as polypropylene (PP) is one of the challenges of polymer chemistry. In this research work, a polypropylene nanocomposite modified with polystyrene (PSt) and carbon nanotube was synthesized by new methods, including living free radical polymerization (LFRP).

Maleic anhydride was grafted onto polypropylene (PP) followed by opening of the anhydride ring with ethanolamine to produce hydroxylated polypropylene (PP-OH). Hydroxyl groups were esterified using α-phenyl chloroacetyl chloride to obtain PP-Cl. Then 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) was immobilized onto the PP backbone using a nucleophilic substitution reaction to produce PP-TEMPO macroinitiator. Afterward, the monomer (St) was grafted onto the backbone (PP) through “grafting onto” technique to afford (PP-TEMPO)-g-PSt. The chloride-end-caped PP-g-PSt copolymer was then attached to the oxidized MWCNTs in the presence of DMF as solvent to produce the MWCNTs-g-(PP-g-PSt) nanocomposite by solution intercalation method. Also, the present study confirmed that PP-g-MA was efficient to promote the dispersion of MWCNTs in the PP matrix, which solved the problem of CNTs aggregation and limited compatibility between nanotubes and polymer matrices. In another study nanotubes-polypropylene nanocomposities were prepared through esterification process.

The chemical structures of all samples were identified using Fourier transform infrared spectroscopy. Chemical bonding (PP-TEMPO)-g-PSt to MWCNTs was confirmed by thermogravimetric analysis and differential scanning calorimetry results. In addition, morphology studies were investigated using TEM and SEM images. A synthesized MWCNTs-g-(PP-g-PSt) nanocomposite can be used as a reinforcement for polymer (nano-) composites due to the superior features of MWCNTs as well as their compatibility with polymer materials after functionalization processes.