Phase Behavior of Solutions of Polymers with Multiply Aggregating Groups

Abstract

We have theoretically investigated phase diagrams of solutions of aggregating polymers. In our model all polymer chains in the solution carry a certain number of aggregating groups (“stickers”), capable of the formation of thermoreversible aggregates, each assumed to consist of exactly m stickers. The treatment of aggregation corresponds to the Flory-like theory of gelation. We have studied the dependence of the phase diagram on the parameters of aggregation, such as its strength (fraction of monomeric units carrying stickers and aggregation constant) and cooperativity (aggregation number). In the considered system of homopolymer chains the stickers have been found to always promote phase separation. The value of aggregation number m is crucial for the topology of the phase diagram: for m ≥ 5 the triple point may appear in the phase diagram. Conditions on the properties of the system ensuring the appearance of this feature have been obtained. The interrelation between gelation and phase separation for different values of parameters is elucidated.