He et al. measured the spinodal decomposition (SD) kinetics of a blend of poly(butyl methacrylate) with a polystyrene modified with 1.5 mol% of a hydroxy-containing comonomer that exhibited intermolecular hydrogen bonding, who studied blends. For small excursions into the spinodal region, multiple structures developed in the blend, which suggested that multiple mechanisms may be involved in the phase separation process. For most cases, however, the kinetics of phase separation followed Cahn-Hilliard theory in the early stage of spinodal decomposition and a self-similar mechanism in the later stages, similar to non-associating polymer blends such as PS/PVME. The failure to observe an effect of a specific intermolecular interaction on SD kinetics may be a consequence of the low concentration of hydroxyl groups on the polystyrene, ca. five per chain, and the weakening of the hydrogen bond at the elevated temperatures used to study phase separation where the crosslink effect of hydrogen bonding may not be significant. At elevated temperatures, the association-dissociation equilibrium shifts towards non-associated hydroxyl and ester groups. An objective of the present study was to use a polymer blend having a relatively higher degree of intermolecular association at the phase separation temperature and to investigate how physical crosslinks affect the phase separation kinetics accompanying spinodal decomposition