Miscible entropically driven

In summary, there are two entropically driven processes for surface concentration of the P[3F-co-BrOx] soft block. 3F repeat units are surface concentrated by virtue of low surface energy, immiscibility, and side chain length that mimics an end-group. BrOx repeat units are miscible with the PTMO domain of the bulk phase and lack an end-group-like architecture. The latter provides a contravening effect that works against surface concentration in the chosen bulk polyurethane. 

While miscibility of the low-MW substances is driven by entropy, in polymer blends it is the enthalpy that dominates the phase behavior. In PE/PE blends the absence of the specific interactions and small entropic effects lead to precarious miscibility. In any PO blend including PEj and PE2, a mixmre is composed mostly of -CH2- groups with few -CH3 end groups. Evidently, the intermolecular interactions between them are weak and immiscibOity dominates the behavior. The PE1/PE2 blends with different type chain structure are usually immiscible. The immiscibility is not limited to the resins with different comonomers. For example, two LLDPEs, both being C2+6 copolymers polymerized using Z-N-type catalyst, but one... 

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