Grafting of maleic anhydride onto styrene–butadiene–styrene triblock copolymer using supercritical CO₂ as a swelling agent

Abstract

Grafting of maleic anhydride (MA) onto styrene-butadiene-styrene triblock copolymer (SBS) was carried out by free radical polymerization using supercritical carbon dioxide (SC CO 2 ) as a solvent of MA and swelling agent of SBS. The effect of various factors such as monomer concentration, initiator concentration, SC CO 2 pressure, and reaction time on grafting ratio was studied. SBS and the product (SBS-g-MA) were characterized by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). GPC data showed that the molecular weight of SBS-g-MA is bigger than that of SBS. DSC testing indicated that the glass transition temperature (T g ) of SBS-g-MA is higher than that of SBS. By SEM photo, we can observe that some particles which contain more oxygen atom grew out from the surface of SBS-g-MA when grafting ratio reached at 5.6%, and the amount and diameter of particles increased with increasing of grafting ratio