Phase separation in polystyrene/poly (vinyl methyl ether) blend revealed by two-dimensional correlation resonance light scattering spectroscopy

Two-dimensional (2D) correlation resonance light scattering (RLS) spectroscopy has been successfully applied to investigate phase separation of polystyrene (PS)/poly (vinyl methyl ether) (PVME) film by using a conventional spectrofluorimeter. 2D synchronous correlation RLS spectrum indicates that the RLS peak intensity drastically increases with a rise in temperature due to aggregation of chromophores (i.e. phenyl rings) in PS particles in the course of phase separation. In addition, as concluded by 2D asynchronous correlation RLS spectrum, RLS has higher sensitivity than conventional light scattering. For RLS, the closer to the absorption band, the more sensitive it is to the aggregation during phase separation. By means of moving-window two-dimensional (MW2D) correlation spectrum based on autocorrelation calculations, the cloud point (370 K) was determined, which is in good agreement with the literature. On the other hand, time evolution of RLS intensity at various temperatures distinctly shows that phase separation of PS/PVME film involves two mechanisms, i.e. spinodal decomposition (SD) and nucleation and growth (NG). Accordingly, 2D correlation RLS proves to be a very simple and sensitive method to monitor phase separation in polymer blends and might supplement the existing characterization tools.