Polymer blend is two or more polymers or copolymers
combined to form one material.
In polymer blend : combinatorial entropy is very small.
The miscibility can be achieved when the heat of mixing
is negative (-). This means there is specific interaction
between different molecules, such as H-bonding.
Another group of miscible blend is polymers of great
similarity (no specific interaction), such as
polyetheretherketone and polyetherimide.