Tunable Phase Behavior of Polystyrene-Polypeptoid Block Copolymers

Block copolymers with tunable compositions offer the ability to directly control the interaction strength between the two blocks and therefore polymer properties. The miscibility of an A B block copolymer can be increased by introducing B or B-like comonomers into the A block, and literature has shown that both the amount and the distribution of these comonomers affect the compatibility of the two blocks. Sequence-defined block copolymers in which one can exactly control the composition and comonomer distribution provide a unique opportunity to control the overall strength of segregation. Here, sequence-defined block copolymers have been synthesized via azide-alkyne coupling using polystyrene and sequence-specific polypeptoids (N-substituted glycines) with 2-methoxyethyl side chains. These polystyrene-polypeptoid block copolymers readily self-assemble into hexagonally packed and lamellar morphologies. N-(2-phenylethyl)glycine residues, which have a styrene-like side chain, were introduced throughout the polypeptoid block to increase the compatibility with the polystyrene block. As the compatibility increased, the strength of segregation and therefore the block copolymer order disorder transitions decreased. The polystyrene polypeptoid block copolymers provide a tunable platform for further studies on the effect of composition and sequence design on self-assembly and block copolymer properties.