During the past few years, in polymer science, great efforts have been made on a new generation of functional polymeric materials by design at the molecular level. Polypeptoids that combine the advantages of sequence-specific proteins and traditional synthetic polymers, perhaps provide the most convenient platform for achievement of precise architectures. We studied a series of chemically-defined diblock copolypeptoids containing a poly-N-2-(2-(2-methoxyethoxy)ethoxy)ethylglycine (pNte) block in combination with both a crystalline poly-N-decylglycine block (pNdc), and an amorphous poly-N-2-ethylhexylglycine block (pNeh)(Figure 1). A fixed length composition scan was performed for each diblock, where the main chain polymer length was fixed at 36 monomers, and the volume fraction of each block was systematically varied. Both block copolymers formed lamellar structures over an unexpectedly wide range of compositions. In the case of the pNdc-containing diblocks, the lamellar structure is driven by the crystallization of the pNdc block. Interestingly, the crystalline pNte-b-pNdc diblock copolymer consists of two crystalline lamellar phases, even though the pNte homopolymer is amorphous. In contrast, the same pNte block is amorphous in the pNte-b-pNhe diblock copolymer. We believe that in the crystalline diblock copolymer, the preorganization of the pNdc chains induces crystallization of pNte chains due to the nearly identical molecular volumes of the side chains. This study enhances our understanding of block copolymer phase behavior and crystallization, and demonstrates that sequence-specific polypeptoid materials are excellent candidates for studies on the effect of composition and sequence design on physical properties and self-assembly of block copolymers.

Self-assembly and crystallization in sequence-specific peptoid diblock copolymers

248th National Meeting (2014)

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