Phase separation behavior of the Polyurethane(PU)-Polystyrene(PS) interpenetrating polymer networks (IPN's) was investigated by light scattering technique during simultaneous polymerization. Measurements were made as a function of composition, crosslink density and compatibility. The process of the phase separation was developed as a result of the increase in molecular weight from an initial homogeneous mixture of PU prepolymer and styrene monomer. However, it was observed that in spite of the thermodynamic incompatibility of the two polymer, the high degree of interlocking between the constituent networks in IPN hindered phase separation.
For early stage of phase separation in PEG based PU-PS IPN the time (t) dependence of maximum intensity of scattered light,Im, and the domain correlation length,dm, could be represented by power law; $Im \infty t^{\gamma}$ and $dm \infty t^{\phi}$ with γ=2.9, Φ=0.25. Early stage of phase separation in PTMG based PU-PS IPN obey the Cahn's theory and domain growth rate R(km) = $1.41\times10^{-3}sec^{-1}$ for U50%-PS50% IPN (Mc=3200).
