Interface-assisted Polymerization-induced Self-assembly Of The Alternating Copolymers

Multi-level structures are widely existed in nature,and they not only form the material basis,but also play important roles in the function of living organisms.Therefore,the construction of artificial hierarchical structures has become a focus in the field of biomimetic materials.Polymeric self-assembly in solution is regarded as a powerful bottom-up method to construct ordered structures.Recently,utilizing this strategy to prepare superstructures with hierarchical complexity has become a hotspot.However,there are still some problems remaining to be resolved: first,the synthesis and purification of polymers are tedious and complicated;second,the entire assembly process is divided into multiple steps,and human interventions between different steps are essential to trigger the following stages;third,the self-assembly process is usually performed at high-diluted polymeric solutions,which hinder the scalable preparation of the products.The emergence of polymerization-induced self-assembly(PISA)has greatly improved the yields at high solid contents but the traditional PISA suffers the inability to construct complex multi-level structures.Moreover,most reported works on PISA were confined to block copolymers(BCPs)obtained through living radical polymerizations.To resolve these problems,we integrated click polymerization into PISA system and further created a variety of interfaces as places for reaction and assembly.Owing to the combined advantages of click chemistry,PISA and interfacial reactions,various alternating copolymer(ACP)-based hierarchical aggregates was successfully prepared on a large scale.The main results are shown below:1.Oil-in-water emulsion-assisted polymerization-induced self-assembly of sea urchin-like hierarchical assemblies on a large-scaleThe oil-in-water emulsion was firstly constructed using hydrophobic1,4-butanedithiol(BDT)-n-hexane mixture as the oil phase.Then the hydrophilic 1,3-butadiene diepoxide(BDE)was added into the water.Thus,click polymerization at the water-oil interface took place between the epoxy group in BDE and the thiol group in the BDT,leading to the formation of the amphiphilic alternating copolymer P(DHB-a-BDT),which would self-assemble into nanotubes in situ.Due to the interfacial tension,the initially formed nanotubes will wrap around the surface of the oil droplet,forming a rattan-ball-like capsule(RBC).After that,the click reaction continued throughout the pores on the RBC,and the newly formed nanotubes stretched outwards radially.In this way,the sea urchin-like hierarchical assembly was formed.The structure and formation mechanism of this aggregate,as well as its application on protein caption and self-propelling micromotors were studied.2.Water-in-oil emulsion-assisted polymerization-induced self-assembly of cytoskeleton-like hierarchical assembliesA water-in-oil emulsion was constructed using n-hexane as the oil phase and the 1,3-butadiene diepoxide(BDE)aqueous solution as the water phase.The hydrophobic 1,4-butanedithiol(BDT)was then added into the n-hexane.Thus,click polymerization took place between BDE and BDT at the water-oil interface,lead to the formation of P(DHB-a-BDT)s.If the interfacial tension is relatively low,these amphiphilic alternating copolymers would self-assemble into nanotubes in situ.Since the n-hexane could not dissolve the polymer,these nanotubes tended to grow inwards to the water droplets,arranging as a centripetal array to form a cytoskeleton-like hierarchical aggregate.However,if the interfacial tension is high,the resulted polymers would deposit onto the surface of water droplets to form micron-sized capsules.We extensively studied the morphologies of these two kinds of assemblies and further explore their formation mechanisms.3.L-phenylalanine colloid-assisted polymerization-induced self-assembly of hydrangea-like hierarchical assembliesThe L-phenylalanine was firstly dispersed in water as globules to form the colloid.Then the hydrophilic 1,3-butadiene diepoxide(BDE)was added to induce the click polymerization between the amino groups in L-phenylalanine and the epoxy groups in BDE at the surface of the globules to form the alternating polymer P(DHB-a-PHE).Driven by a variety of interactions,the newly-formed polymer firstly self-assembled into sheets with ultra-thin lamellar phase.Then the sheets stacked with each other to form thicker micro-flakes.These in-situ generated flakes would stack on the surface of the globules to form a hierarchical core,and then the shell.Consequently,a hydrangea-like hierarchical assembly formed.We call this unique self-assembly process “blooming-like polymerization-induced self-assembly mechanism”(BPISA).The assemblies have a unique hierarchical structure,naming alternating polymer chains,thin sheets,micro-flakes,and hydrangea-like assemblies respectively in a bottom-up sequence.