Construction of the state diagram of polymer blend thin films using differential AC chip calorimetry

The phase separation behavior of polymer blend thin films of 100–150 nm was studied using differential AC Chip calorimetry. By taking advantage of the low sensor and sample mass inherent to chip calorimetry, a new methodology based on temperature jumps was developed. This methodology allowed the construction of the state diagram of polymer blend thin films as evidenced for two model systems (PVME/PS and PVME/Phenoxy) displaying a lower critical solution temperature behavior. ate diagram in thin films was compared to the one obtained in bulk using Modulated Temperature DSC. In comparison with bulk, a lower phase separation temperature and a broadening of the homogeneous glass transition temperatures is observed for both model systems. This might be an indication of a surface induced ‘destabilization’ by composition gradients which are not present in bulk.