Conformational analysis by IR and birefringence measurements for poly(β-phenylpropyl L-aspartate) exhibiting a helical sense inversion in the solid state

Abstract

Formation of helices with both handedness in poly(L-aspartate) (PLA) indicates that the energy difference between right-handed and left-handed helices is relatively small. The handedness of helices is easily affected by several factors such as the side chain, solvent, pressure and temperature. The helical sense inversion of polymer backbone simultaneously results in the sense inversion of the macroscopic helix of the cholesteric liquid crystal. The uniaxial orientation of the helical axes is maintained on the transition and the transition is a type of homogeneous nucleation. The hexagonal chain packing is identical before and after the transition and so the enthalpy change observed on the transition reflects the energy difference between the helices.