Synthesis via RAFT of Amphiphilic Block Copolymers with Liquid-Crystalline Hydrophobic Block and Their Self-Assembly in Water

Two families of amphiphilic diblock copolymers, in which the hydrophobic block was a cholesteryl-based smectic liquid-crystalline polymer and the hydrophilic block was either a neutral polymer with a lower critical solution temperature (LCST), poly(N,N-diethylacrylamide), or a copolymer containing acrylic acid moieties and poly(ethylene oxide) side chains, were successfully synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Nanoassemblies of these amphiphilic species in water or in buffer solution were prepared using the cosolvent method. The morphology of the nanoassemblies clearly depended on the weight fraction and the nature of the hydrophobic block. The amphiphilic liquid-crystal (LC) block copolymers with a hydrophobic/hydrophilic weight ratio of 74/26 or 65135 formed long nanofibers, whereas the non-LC copolymers based on polystyrene of similar ratio formed vesicles or short cylindrical micelles. Such morphologies were assigned to the presence of a smectic order in the hydrophobic domain of the assemblies, as revealed by small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy.