Mean Field Theory and Intramolecular Repulsion Concepts

5 Mean Field Theory and Intramolecular Repulsion Concepts 

A procedure for mapping the miscibility space of homopolymer-copolymer or copolymer-copolymer blends referred to as the mean field binary interaction model has proven to be quite useful. This approach was developed and pubhshed independently by three different laboratories [171-173].A number of papers [174—178] employing this approach have demonstrated excellent agreement of prediction with experiment. 

For the case of homopolymer(l)-copolymer(2) blends with homopolymer repeat unit a and copolymer repeat units of b and c, the following expression for Bu is employed. 

This analysis reveals that polymer blends can be designed to exhibit negative values of xn or Bi2 if the value of Bi,c meets the following requirement  

In essence, if the units of the copolymer are highly immiscible with each other relative to their respective interactions with the homopolymer, miscibility can be achieved. This has been referred to as specific rejection or intramolecular repulsion and appears to be another mode of achieving miscibility as contrasted to the more apparent specific interaction approach. 

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