The Influence of One Block vs. Two Block Polydispersity on Phase Separation of Diblock Copolymers*

Polymer composition (f) and segregation strength (χN) are two key parameters that determine the microphase separation behavior of block copolymer. However, recent findings show that block polydispersity can also influence block copolymer phase separation. The published studies thus far have been mainly focused on the phase behavior of asymmetric systems where at least one of the blocks is monodisperse. With the recent advances in polymer synthesis, living free radical polymerization condition can be modified to achieve block copolymer with controlled polydispersity. We prepared a series of poly(styrene)-b-poly(methyl methacrylate) diblock copolymers where either one block is polydisperse or both blocks are polydisperse. The phase separation and microdomain morphology of these diblocks were then examined and compared to illustrate the importance of controlling polydispersity on block copolymer phase behavior.