Abstract
Hierarchical assembly of macromolecules has been central in creating complex nanostructures. In this work, polystyrene-block-poly (perfluorooctyl ethyl acrylates) (PS-b-PFOA) diblock copolymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and shown to assemble into hierarchical structures in bulk with the interplay of nanophase separation and crystallization. The molecular weights were determined by gel permeation chromatography (GPC) and 1H NMR spectra. The phase-separated nanostructures of these block copolymers were investigated via small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) in reciprocal space and by transmission electron microscopy (TEM) in real space. The results showed that well-ordered lamellar morphologies were formed in the bulk of samples with volume fraction of PFOA (f_PFOA) around 0.390–0.538. Within the PFOA layers, the side chains were found to further crystallize, forming crystalline layers with thicknesses about twice that of the length of fluorinated side-chains. The SAXS patterns from sheared samples further show that the orientation of crystalline layers was perpendicular to the lamellar layers formed by micro-phase separation.