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Bitumen emulsions have often been modified by styrene-butadiene rubber latex. The modified bitumen can have excellent low-temperature cracking resistance, but rutting resistance at high temperature still remains poor. In the current work, for the first time, a stable poly(styrene-b-isoprene-b-styrene) (SIS) triblock copolymer latex is synthesized by reversible addition-fragmentation transfer (RAFT) emulsion polymerization. Based on this, a simple heterocoagulation process is developed to prepare the bitumen emulsions modified by SIS. The heterocoagulation results in hybrid particles of SIS shell and bitumen core. With addition of 5 wt % SIS, a continuous polymer-rich phase could be formed in the modified bitumen once the modified emulsion was broken down. The bitumen modified by 5 wt % SIS shows a significant increase in complex modulus at high temperature and a significant decrease in loss tangent, suggesting excellent resistance to rutting at high temperature, which is consistent with the significant increase in softening point from 41 8C for the base bitumen up to 64 8C. Meanwhile, the ductility at 5 8C of the modified bitumen is also dramatically increased from 1.4 cm for the base bitumen to 40 cm, indicating the low-temperature cracking resistance should also be much enhanced.