Chemical initiation mechanism of maleic anhydride grafted onto styrene-butadiene-styrene block copolymer

The mechanism of grafting styrene-butadiene-styrene (SBS) tri-block copolymer with maleic anhydride (MAH) initiated by benzoperoxide (BPO) or 2,2'-azo-bis-isobutyronitrile (AIBN) was studied by FTIR and H-1 NMR spectroscopies. The variation of C=C (double bond) content in SBS-g-MAH was used to verify the different graft mechanisms of BPO and AIBN, indicating that the chemical initiation mechanisms of MAH grafted onto SBS of AIBN is different from that of BPO. The graft reaction occurs by addition on C=C for AIBN, while by removal of an allylic hydrogen atom from SBS and by addition on C=C at the same time for BPO. The graft efficiency of AIBN is higher than that of BPO in this system. (C) 2003 Elsevier Science Ltd. All rights reserved.