Digital Image Analysis of Phase Separation Structures in Spinodal Decomposition of a Polymer Blend

Digital image analysis was applied to characterize structure growth in the phase separation of a poly(carbonate)/poly (methyl methacrylate) blend of a critical composition at various temperatures. Two-dimensional Fourier transformation was obtained from photographs of phase-separation structures. It was shown that the phase separation occurred in two stages. The first stage was characterized by a steady average domain distance during phase separation, and the second stage by the existence of a scaling law for structure growth. The fractal dimensionality and boundary length of the interfacial structures were also obtained during the second stage of the separation. The fractal dimensionality decreased with time, suggesting that the interface became smooth as the phase separation proceeded. The interfacial length obtained at various temperatures revealed a similar time-dependence which was approximated by a simple power law.