The phase separation of a thin polymer blend layer undergoing a simultaneou
s transesterification reaction is examined by a variety of experimental tec
hniques [neutron and X-ray reflectivity, optical microscopy, atomic force m
icroscopy (AFM)] to determine morphological features unique to reactive pha
se separation. Neutron reflectivity measurements suggest; that a copolymer
layer reactively forms at the interface between the phase-separating blend
components. Evidence for a copolymer layer is also provided by AFM and opti
cal images which indicate a strong inhibition ("frustration") of droplet co
alescence and a tendency of the droplets to cluster in late-stage phase sep
aration. The influence of the transesterification reaction on phase separat
ion is found to depend strongly on temperature.