The study of phase behavior in SBS triblock copolymer polybutadiene methyl isobutyl ketone ternary system

The phase separation behavior of a ternary system consisted with SBS, PBD, and MIK was studied. The cloud point (T-p) was determined by turbidimetry and binodal curves were drawn by the data obtained from the H-1-NMR analysis for those components of the phases obtained from the phase separation experiments. The cloud point test yielded that there was no turbidity generated in the polymer concentration range 0 to 4 wt% of the solution of polymer mixture. No turbidity was observed in the polymer concentration range 5 to 9 wt% as well where the weight fraction of SBS to PBD varies from 0.7 to 1.0. The ternary system shows a lowering trend of T-p as the amounts of SBS added increased in the lower limit of concentration range of polymer mixture, but at higher concentration range the T(p)s are found to be elevated to the temperature range of 7.5 similar to 16 degrees C. The phase diagram obtained by the phase separation experiment reveals that the stable region is expanded as the temperature is elevated. The steep slope of the tie line inclined to the PBD/MIK axes implies that the two polymers used have different affinities to the solvent. The polymer-polymer interaction parameter chi(23)(t) found by Einaga equation lies in the range of 0.8 to 1.3, which indicates SBS and PBD are incompatible.