The relationship between the reduced viscosity and concentation of sulfonated styrene-isoprene- styrene triblock copolymer（SSIS） and its ionomers in toluene and toluene/methanol solutions were studied. The intrinsic viscosity \ was calculated. The results show that SSIS tends to form an intra-molecular chain interaction and form more enclosed molecular chain with a lower reduced viscosity and intrinsic viscosity when the sulfonation degree x（SO3H） decreased. A change of interaction from intra- to inter-molecular chain was observed, and the intrinsic viscosity improved from 0.641 dL/g to 0.656 dL/g by increasing the sulfonation degree from 3.95% to 7.36% due to the chain combination. This also make the size of molecular chain of SSIS larger than SIS . Although be a precipitant for SIS , a few amounts of methanol can change the solubility of SSIS in toluene by destroying the combination of molecular chain. Lanthanum ionomers showed a lower reduced viscosity as compared with sodium and zinc ionomers.
