THERMODYNAMIC INTERACTIONS IN BLENDS OF POLYDIENES

Thermodynamic interactions and phase behavior in binary blends of model mixed microstructure polybutadienes with model 1,4-polyisoprene were studied using small angle neutron scattering and differential scanning calorimetry (DSC). Themicrostructureof the polybutadiene ranged from8% 1,2(92% 1,4)1090% 1,2(10% l,4)units,while thepolyisoprcne contained 93% 1,4 and 7% 3,4 units. The blends of protonalcd polybutadienes (HPB) with deuterated 1,4 polyisoprene (DPI) exhibited lower critical solution temperature (LCST) behavior when the polybutadiene contained 38 mol % or more of 1,2 units. Below this 1,2 content of the polybutadiene, all HPB/DPI blends were found to be phase separated at all temperatures above 25 °C. The DSC measurements revealed that other than a blend containing 8% 1,2-polybutadiene and (protonated) 1,4 polyisoprene, all other blends were single phase at room temperature. These results are understood in the context of previous work performed by Han and coworkers on deulerated polybutadiene-protonated poiyisoprene blends.