Preparation and Characterization of Epoxidized Styrene—Isoprene—Styrene Tri-block Copolymer Using Formic Acid—Hydrogen Peroxide

The epoxidized styrene—isoprene—styrene tri-block copolymer (ESIS) is prepared with performic acid generated in situ from hydrogen peroxide and formic acid. The effects of reaction temperature, reaction time, and the amounts of hydrogen peroxide, formic acid, and polyethylene glycol are studied on the mass fraction of epoxide groups. The structure of ESIS is characterized by GPC, FTIR, and 1H NMR. The oil resistance of ESIS is characterized by swelling ratio. The results show that when mol (HCOOH)/mol (C=C) and mol (H2O2)/mol (C=C) are 0.3 and 0.6, respectively, reaction temperature is 65°C, reaction time is 2.5 h, mass fraction of epoxide groups reach 15.3%. A small amount of PEG-400 is favorable to the epoxidation of styrene—isoprene—styrene. GPC analysis confirms that the molecular weight of ESIS has an increasing tendency and molecular distribution widens with the increase of mass fraction of epoxide groups. FTIR and 1H NMR results reveal that the order of reactivity of double bonds in polyisoprene block toward epoxidation is: cis-1,4-structure> trans-1,4-structure>3,4-structure. The oil resistance of ESIS increases markedly with increasing mass fraction of epoxide groups.