| The self-assembly of amphiphilic block copolymers plays a significant role in developing soft materials-based smart nanodevices,and has great application potential in drug delivery,organic photonics,nanoreactors,etc.To regulate the structure and performance of nanodevices,traditional self-assembly focuses on the modification of copolymer properties,e.g.,introducing functional groups(hydrogen bonds,?bonds)or complicating molecular architectures(star,dendrimer).However,the synthesis of complex copolymers has strict requirements on experimental techniques and conditions,as the intra-molecular bonding limits the inter-molecular recognization and combination which delays the development of novel nanoobjects.Despite high molecular recognition and binding properties and low synthesis difficulty,the copolymer assembly technique remains to be developed,which is needed for the preparation of nanoassemblies with special functionality,novel structure and wide applicability,and is of large theoretical and industrial application values.In this work,we orient to prepare hierarchical and complex micro-structures in copolymer nanoassemblies with practical application.Dissipative particle dynamics technique is used to develop the cooperative assembly of multiple block copolymer mixed solution.Copolymers are introduced into a nanoassembly and the cooperative mechanism is revealed by modifying molecular configurations and functional groups.Three types of copolymer composites with controllable noncovalent molecular interactions are constructed.For multi-geometry micelles,a strategy is proposed to design the composite structure by matching different singular assemblies.First,the self-assembly of single diblock copolymer is studied.The relation between morphology and volume fraction of hydrophilic blocks(f A)is established and as follows:multi-compartment f A<0.25,vesicle/lamellae 0.25?f A<0.5,cylinder/fiber 0.5?f A<0.7,and sphere f A?0.7.Then,the co-assembly of binary copolymer blends is performed to explore the combination of different single assemblies.Lots of multi-geometry nanoparticles including Janus,microcapsule,surface helix,satellite,edge serrated disc,etc.,are obtained at specific intermolecular incompatibility a BC(equals to 45).Decreasing the incompatibility a BC to 25 or increasing solvent affinity a AW to 35 has largely affected the morphologies of composite nanoassemblies due to the varation of inter-molecular or micelle/solvent interactions,and some structures have been fused and reassembled.In extended ternary systems,the strategy is assessed to be effective.The micro-interaction mechanism is revealed by analyzing molecular interactions.The relation of“molecular parameter-combination scheme-structure and morphology”is obtained by a systematic study of copolymer physicochemical properties.Results provide a theoretical guidance for the design of multi-geometry nanobjects in experiments.For multi-compartment micelles with many sub-domains,a strategy is proposed to tune the internal and surface morphologies of the micelles by the combination of discrete and layered structures.First,the solvent selective parameter a AW is determined to be 33 and the copolymer self-stretching degree a AB is determined to be 37/60,for the formation of pure multi-compartment micelles.Then,results are used to design the solution parameters in specific binary and ternary systems.The parameter ranges of specific multi-compartment nanocomposites are defined clearly.Particular focus has been put on the spherical(?AB=20%)and cylindrical(?AB=30%)micelles.The tuning mechanisms for surface and internal micro-structures are revealed from inter-molecular interactions.The self-stretching and incompatibility of different block copolymers are the key factors of determining the morphological regulation of nanoassemblies under external stimuli.The nanocomposites have the ability to transpose their“inner-outer”structures under control.Results extend the strategy to design multi-compartment nanodevices in experiments.For block copolymer membranes with bilayer structure,a strategy is proposed to design controlled particle transport pathways on the membranes based on copolymer co-assembly.A block copolymer that can form stable bilayer is used to build the membrane matrix.The other block copolymer with large complexity in block sequence and rigidity is added to the membrane as a dopant.The dopants reassemble around pore edges under membrane stretching(energy minimization),and their equilibrium morphologies depend on their single self-assemblies.At f A<0.5,dopants form semi-circular clusters,while at f A=0.55 or 0.65 dopants form bridged,dotted,and porous morphologies around pores.The increase of a BCfrom 30 to 45 leads to the transition of interface interactions at pores from spreaded binding mode to pointed binding mode,which effectively controls the phase separation behavior.Pore structures obtained by this strategy are stable,and can be repeatedly opened/closed under periodic stretching/shrinking.Results extend the strategy for the design of combined membrane nanodevices with special particle transport pathways. |
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