Segregative: Two neutral polymers or a polymer and a salt, despite having a favorable mixing entropy (i.e., the increase in total entropy or degree of randomness that occurs when multiple separate systems of different compositions are mixed; usually, favorable mixing entropy results in interaction), do not interact because of repulsive interactions between them. They are consequently divided into two phases, each of which is enriched in one solutes. Examples: Polyethylene Glycol/Dextran. 2) Associative: Formation of a dense polymer-rich phase and a dilute (polymer-poor) supernatant phase upon mixing of oppositely charged polyelectrolytes, resulting in associative phase separation due to ion-pairing interactions. Due to attractive interactions (mostly charge-charge, but also other non-covalent interactions) between them, two or more polymers or polyions eventually reside in the same phase. A specific case is the "complex" coacervate, where there are only two mixed species.