Nanostructured thermotropic PBLG-PDMS-PBLG block copolymers

We report on the nano-organization and the thermal behavior of a series of triblock copolymers composed of a central soft polydimethylsiloxane (PDMS) and two polypeptide (poly-γ-benzyl-l-glutamate) blocks. Peptide blocks with varied lengths and therefore different secondary structures (β-sheet or α-helical) were attached to the PDMS central block. These two blocks are incompatible and microphase separate into different morphologies elucidated by polarized optical microscopy (POM), small-angle light scattering (SALS), X-ray spectroscopy (SAXS, WAXS) and atomic force microscopy (AFM). We demonstrate that the relative ratio of PBLG to PDMS direct both the type of nanodomain morphologies formed and also modifies the transition temperature. Each of these block copolymers have shown a reversible transition associated to its thermotropic liquid crystal behavior. At temperatures above the transition, the self-assembled structures are disrupted and prevented the organization at larger scales.