Studies On Novel Stimuli-responsive Polymeric Assemblies

Stimuli-responsive block copolymer self-assemblies have been extensively studied both experimentally and theoretically for their unique properties and promising applications during the past decade. Conventional stimuli such as pH, temperature, light were used as the trigger in most cases. Recent research has been focused on novel stimuli responsive polymeric nanoparticles. In this paper, we delicately designed two stimuli responsive polymeric nanoparticles and will introduce them in two chapters.In the first chapter, we studied a shear responsive polymeric nanoparticle system. We prepared kinetically stabilized Large Compound Micelles (LCMs) based on glutathione end-capped poly(4-vinylpyridine). Under continues shearing, the LCMs underwent LCMs-thick wall vesicles-drum-like vesicles-branched nanofibers transformation. To the best of our knowledge, drum-like vesicle was observed for the first time. We studied the morphological transformation mechanism and the intrinsic flexibility of the polymeric aggregate under the experiment conditions.In the second chapter, we studied an enzyme responsive polymeric nanoparticle system. The nanoparticles prepared with polymers based on GP4VP75dissociated and re-assembled when exposed to Glutathione S-Transferase, which is an enzyme abundant in livers. As GSH is the substrate of GST, it could be anchored onto GST with hydrogen bonding. When the50kDa GST is bonded to the GSH on the polymer chain in the LCMs by enzyme-substrate specific interaction, the hydrophilicity of that chain increased significantly, leading to its dissociation from the LCM. Subsequently, the new formed GST-GP4VP75"block copolymers" self-assemble into morphologies such as micelles and vesicles.