Phase separation behavior of the polybutadiene (PND)-polystyrene(PS) linear blend and semi-interpenetrating polymer networks(semi-INS's) was investigated by the light scattering technique during the polymerization of styrene in PBD-styrene monomer mixture. Transmitted light intensity and scattered light intensity during the reaction were recorded with time. The effects on the phase separation behavior were analyzed with composition, synthesis temperature and the PS crosslink density.
As the polymerization proceeds, the styrene solution, which is a ternary system of the solvent (styrene monomer) and PS and PBD polymers, separated into two phases. One phase is the PS-styrene monomer solution and the other is the PBD-styrene monomer solution. The phase separation resulted from the decrease of compaibility between the PBD and PS by the conversion of styrene monomer into polystyrene during the polymerization. However it was observed that in spite of the thermodynamic incompatibility of the two polymers, the high degree of interlocking in semi-IPN's hindered the phase separation. It was also observed that the rate of phase separation was a function of the diffusion rate controlled by the viscosity.
For the early stage of phase separation the time dependence of the maximum intensity of the scattered light, Im, could be represented by a power law and the time dependence of the domain correlation length, dm, could be represented by a power law in the later stage of the phase separation.
