Access to Self-Assembled Poly(2-Oxazoline)s through Cationic Ring Opening Polymerization-Induced Self-Assembly...

Self-assembled block copolymers provide wide range of opportunities in encapsulation and release of active compounds in aqueous and nonaqueous systems. However, developing new polymeric systems that have the precise ratio of blocks and backbone structure has been a challenge where every single methyl group has an enormous effect on the final self-assembled structure. Herein, we present a synthetic route to access sphere, worm, and vesicle shaped self-assembled nanostructures via cationic ring opening polymerization-induced self-assembly (CROPISA) method in nonaqueous media using 2-alkyl-2-oxazolines. This study successfully produced a broad range of nanostructures through careful manipulation of the solvophobicity of the core-forming block. Therefore, poly-(isostearyl-2-oxazoline) was selected as the soluble stabilizing block and CROPISA was conducted at 20 wt % solids content in n-heptane. Although initial attempts using PEtOx as the core-forming block yielded only spherical micelles, switching to a lower T _g and more solvophilic poly-(2-propyl-2-oxazoline) core-forming block allowed access to higher-order structures such as worms and vesicles for the first time. Finally, the thermoresponsive properties of the resulting worm organogel further demonstrated the potential for stimuli-responsive poly-(2-oxazoline) based materials in nonaqueous applications.