Structure And Properties Of Supramolecular Polymer/Inorganic Nanoparticles Ordered Composites

The properties of nanocomposites depend not only on the individual building blocks,but also on the organization and spatial arrangement of individual blocks within the host.Block copolymer, which can microphase separate into a variety of periodically orderednanostructures, have shown their potential for organizing inorganic nanoparticles inbulk/thin film. Supramolecular block polymers can further provide more versatile routes tocontrol spatial arrangement of the nanoparticles over multiple length scales. Arrangementof nanoparticles to form ordered arrays with single particle precision over macroscopicdistances will not only enable a basic understanding of the physical properties of this newfamily of material, but also pave the way for next-generation nanoparticle-based devices.In this thesis, we systematically investigated the self-assembly behaviors ofsupermolecular polymers and nanoparticles. The purposes of this thesis include predictingthe underlying rules of self-assembled structures with the variation of the content ofindividual blocks within the host, understanding the origin of the formation of the orderednanostructures, elucidating of the mechanism for the morphological transitions betweendifferent structures, and providing guidelines for design and fabrication of novelnanocomposites.Polystyrene-poly(4-vinyl pyridine)(PS20K-b-P4VP17K) and pentadecylphenol (PDP)were dissolved in chloroform to form PS-P4VP(PDP)x(x represents ratio of PDP to P4VP)comb-coil supramolecules. NPs were synthesized and functionalized with a thiol-end PS.Upon addition of PS-coated NPs to the supramolecules, hierarchical structures, whereNPs were selectively incorporated in PS cylindrically confined phases withinP4VP(PDP)1.0matrices were formed. Isolated wormlike micelles with uniformly dispersedgold NPs along the centerline were obtained by removal of small molecule PDP. Thisversatile approach allows us to fine tune interparticle distance and micellar morphology byvarying the content of nanoparticles and/or hydrogen bonding agent in the supramolecularassemblies. Spatial distribution of NPs in micellar core depends on D/R0(D denotes theoverall diameter of PS-coated Au NPs, R0is the root-mean-square end-to-end distance of host block of the block copolymer). And the relationship between translational entropy ofthe particles and polymer conformation entropy were estabilished.The NP loading and the PDP addition effect on the hybrid aggregate morphology withspherical, cylindrical, or nano-sheet morphologies were systematically investigated. Thebalance between the NP loading and the PDP addition maintains the same micellarmorphology while achieves high NP loading. Based on the data above, effect of theamount of PDP and NP loading on the hybrid micellar morphology were summarized in aphase diagram.We describe an effective approach to disperse and orient nanorods (NRs) withincylindrically confined microdomains of block copolymer (BCP)-based supramolecularself-assemblies by tethering two populations of the same homopolymer brushes withdifferent lengths on the surface of the NRs. The mismatch of binary polymer brushes withdifferent lengths on the surface of the NRs was used to effectively improve the dispersionof the NRs within polymer matrix, due to the enhanced wetting of the brushes bysurrounding mismatch polymers. Location and orientation of the NRs can be tailored byvarying the content of NRs, the aspect ratio of the NRs, or the diameter of the cylindricalnano-objects. UV-visible spectroscopy measurements and finite-difference time-domain(FDTD) calculations confirm that our approach provides a simple yet versatile route tocontrol the optical properties of the hybrid nano-objects via the tunable assembly of theNRs.The hydrophilic gold nanorod grafted with a hydrophobic polymer at both ends wasconsidered as ABA triblock copolymer. We reported on a different approach to fabricatelarge-area, free-standing2D,3D superlattice through combining phase separation, stericrepulsion and long range attractive interaction between nanoparticles. The packingbehavior of the metal nanoparticle can be controlled by varying the geometries ofnanoparticles or the ligands on the surface of nanoparticles. The self-assemblymechanisms have been discussed.Finally, we introduce a facile way to fabricate hybrid micelles through interfacialinstabilities of oil-in-water emulsion droplets containing polystyrene-b-poly(ethyleneoxide) and PS-grafted Au nanoparticles. Hybrid micellar morphology can be tuned fromvesicles to wormlike micelles and to spherical micelles via varying the concentration of surfactant sodium dodecyl sulfate. In addition, our experimental technique can beextended to encapsulate fullerene(C60) and polythiophene.These findings will provide an understanding of the nature of the self-assembly ofsupramolecular polymers and nanoparticles, and help engineers to design orderednanostructured functional materials and optimize the fabrication process.