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

Grafting of maleic anhydride (MA) onto styrene–butadiene–styrene triblock copolymer (SBS) was carried out by free radical polymerization using supercritical carbon dioxide (SC CO₂) as a solvent of MA and swelling agent of SBS. The effect of various factors such as monomer concentration, initiator concentration, SC CO₂ 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. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4425–4429, 2006