Construction Of Photonic Crystal Microspheres Based On 3D Confined Assembly Of Block Copolymers

Self-assembly of block copolymers(BCPs)is an important route to construct functional nanomaterials.The ordered structures derived from self-assembly of BCPs have important applications in information storage,controllable drug release and photonic crystals(PCs),etc.Nowadays,it has attracted more and more attentions from scientists.Properties of BCP materials not only depend on their chemical composition,but also relate to the arrangement,order degree and anisotropy of BCPs.Till now,there is still lack of systematic research on BCP PCs.The structures of materials are one-sided and optical properties are difficult to be effectively regulated.Therefore,it is of great significance to design and construct BCP PCs with novel internal ordered structures and morphologies for fundamental researches and optical applications of polymeric optical materials.In this dissertation,the diblock copolymer polystyrene-block-poly(2-vinylpyridine)(PS-b-P2VP)are selected and emulsion-solvent evaporation method is used to study selfassembly behaviors under three dimensional(3D)soft confinement.When the microspheres with periodic nanostructures are obtained,optical properties generated by the periodic structures are discussed.On this basis,varying the 3D confined space and composition of BCPs can effectively regulate the internal ordered structure,and further regulate optical properties and functions of the PC materials.This dissertation mainly includes the following four parts:Firstly,we design and construct a kind of responsive BCP PC microsphere.The PS-bP2 VP can self-assemble into concentric lamellar periodic structure under 3D confinement which can generate photonic bandgap and then endow the microsphere with structural colors.As-prepared microspheres exhibit sensitive responsiveness to specific organic solvents or aqueous p H value in visible light spectrum via structural colors with rotational angleindependence.Meanwhile,we analyze the formation and responsive mechanism of structural colors based on the change of internal structures,and further adjust the responsive range of structural colors by tuning cross-linking degree.Secondly,self-emulsification and 3D confined assembly method are combined to form hollow photonic microcapsules based on diblock copolymer PS-b-P2 VP without any core template.Formation mechanism and the effects of structural parameters on optical properties are demonstrated in detail,and superiority of optical properties for microcapsules compared to solid microspheres are described.On this basis,the structural color variation of the microcapsules are corresponding to various release rates of encapsulated drug,so that drug release capacity of the microcapsule can be visually judged.Thirdly,the inherent spectral properties of PS-b-P2 VP microspheres are successfully regulated by hydrogen-bonding between small molecules 3-pentadecylphenol(PDP)and P2 VP blocks.Range of the spectral regulation covers the whole visible light spectrum.We investigate the effects of PDP and homopolymer h PS addition on periodic structures and optical properties of the microsphere.Meanwhile,the quantitative relationship between periodic amplification and photonic bandgap red-shift is simulated by finite element method,which agree well with the variation of structural colors in experimental results.Fourthly,based on the above results,we replace the building block of BCPs with PStethered gold nanoparticles(GNPs),and study the 3D confined assembly behaviors of this new building block to form hybrid ordered structures with binary GNPs.We systematically study their regular arrangement and prove the universality of core-shell structure template for different polymer-NP building blocks.Besides,the ordered arrangement of binary GNPs can generate controllable photothermal conversion capacity through near-field coupling,potentially useful in photothermal therapy.This dissertation studies the 3D confined self-assembly behaviors of diblock copolymers in emulsion droplets.On this basis,spherical PC materials with novel structures and functions are prepared.The work might enable people to have a deeper understanding of3 D ordered arrangement of BCPs,which somehow providing theoretical and practical basis for the design and preparation of polymeric photonic materials.