Hydrogen-Bonding Driven Polymerization Induced Self-Assembly And Stimuli-Responsive Pore-Switchable Nanotubes

Polymerization-Induced Self-Assembly(PISA)has emerged as the robust and efficient technique to fabricate nanomaterials by combining controlled/living radical polymerization and large-scale solution self-assembly.Aqueous PISAs have attracted increasing attention in this decade.Most of those are driven by hydrophobic association undergoing sphere-to-worm-to-vesicle transition.Inspired by aqueous insoluble cellulose due to hydrogen bonding(HB),this thesis reports a novel HB-driven PISA(HB-PISA)formulation,which undergoes unprecedented film/silk-to-ribbon-to-vesicle transition.Nano-object pure phases,including vesicles and nanotubes,are achieved simply by slight electrostatic repulsion perturbation.Pore-switchable nano-objects and high media-sensitivity of tubular membranes as compared to vesicular counterparts have been demonstrated.Hydrophilic macromolecular chain transfer agent(PHPMA30 macro-CTA)was first synthesized and chain-extended with hydrophilic H-donator/acceptor-containing diacetone acrylamide(DAAM)via visible light mediated RAFT aqueous dispersion polymerization at 25 ?,leading to an aqueous PISA.Unprecedented film/silk-to-ribbon-to-vesicle transition occurrs over a wide range of solids contents,entirely different from conventional sphere-to-worm-to-vesicle transition.Nanometer-scale films(without stirring)and silks(under stirring)are achieved even at low DP of core-forming block over 25-38%w/w solids content in free-flowing aqueous solution.Moreover,PDAAM oligomers are aqueous insoluble over 5-85 ?,due to inter/intra-chain interactions.1H NMR and FTIR spectroscopy confirmed significant HB interactions of core-forming block.Therefore,film/silk-to-ribbon-to-vesicle transition attributes to inter/intramolecular HB association.To explore pure phase,in situ electrostatic repulsion perturbation of HB association was studied by introduction of minor cationic AEAM monomer into the core-forming block.The results demonstrate that pure phase of nanotubes or vesicles can be achieved by disturbation over 2-8%AEAM monomer fraction.It undergoes nanofilm/silk-to-ribbon-to-vesicle-to-nanotube transition.Furthermore,above-synthesized nanotubes and vesicles exhibit evident pore-switchable behavior in response to ionic strength and solution pH.Tubular membranes are more sensitive than those of vesicular counterparts.In short,the HB-PIS A undergoes film/silk-to-ribbon-to-vesicle transition.Electrostatic repulsion effectively perturbs the association and hence leads to the formation of pure phase of nanotubes or vesicles.These nano-objects exhibit media-responsive properties in terms of their switchable membrane porosity.Intrinically,tubular membranes are more sensitive than vesicular counterparts in responsive to aqueous surroundings.This strategy provides a robust approach to large-scale production of advanced nanomaterials,e.g.flexible nanofilms,pore-switchable nanotubes and vesicles.Their media-responsive behavior and reactivity of ketone and primary amine moieties pave an avenue for green efficient synthesis of advanced functional nanomaterials.