Main-chain chiral copoly(2-oxazoline)s

Abstract

(Chiral) poly(2-oxazoline)s are regarded as pseudo-polypeptides, however, not much is known about their secondary structure formation. Recently we reported that chiral homopolymers based on R- and S-2-butyl-4-ethyl-2-oxazoline (BuEtOx) monomers form flexible dynamic helices in solution (Soft Matter, 2010, 6, 994–1003) and a chiral crystalline structure in the solid state (Macromolecules, 2010, 43, 4654–4659). In the current work we addressed the chiral structure formation of main-chain chiral copoly(2-oxazoline)s with controlled ratio of S-BuEtOx and R-BuEtOx. No chiral amplification was found in solution or in the solid state, clearly indicating that the polymers adopt a dynamic helical structure that is easily disrupted by incorporation of the second monomer. Nonetheless, the properties of these main-chain chiral copoly(2-oxazoline)s, such as the optical rotation, solubility and crystallinity, can be tuned by controlling the enantiomeric excess (ee).