Neutron reflection studies of phase separation and transesterification in thin film polymer blends

Neutron reflection is used to investigate the evolution of structure and surface segregation in thin films of a binary polymer blend, deuterated polymethamethacrylate (dPMMA) and polycarbonate (PC). This blend film simultaneously undergoes phase separation and reaction by trans-esterification. A large increase of the critical scattering length density in the first few minutes of annealing at 200°C reflected the rapid layering of the dPMMA at the silicon surface. Further annealing progressively smeared out the specular peak in favor of the off-specular signal in the form of a butterfly pattern reflecting the in-plane anisotropy of the thin film phase separation.