[PDF] New Directions In The Crystallisation Driven Self Assembly Of Polyferrocenylsilane Containing Block Copolymers eBook

Author : Hang Zhou
Publisher :
Page : pages
File Size : 20,43 MB
Release : 2018
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ISBN :

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Polyferrocenylsilane (PFS) di-block copolymers self-assemble in selective solvents to form rod-like micelles, driven be the crystallization of the PFS block in the core. One of the unique features of these rod-like micelles is that the length can be extended upon addition of an extra amount of PFS block copolymers in a good solvent for both blocks. This process, referred to as the living crystallization-driven self-assembly (CDSA), has been utilized to prepare near monodisperse rod-like micelles. To further investigate the potential bio-medication application of these rods, I set out to synthesize new PFS BCPs with water-soluble thermoresponsive corona to prepare uniform nano-rods in polar media, and study their solution behavior. The first part of my thesis describes the synthesis and living CDSA of poly(ferrocenyldimethylsilane-b-N-isopropyl acrylamide) (PFS-b-PNIPAM) by a Cu-catalyzed alkyne/azide coupling reaction to covalently combine the two homopolymers. In self-assembly studies, I found that the growth rate of the rod-like micelles in alcohol solvents decreased dramatically when the number of PNIPAM repeating units was increased. Varies attempts to transfer the micelles to water were accompanied by extensive fragmentation. I attributed the phenomenon to the cononsolvency of PNIPAM corona in alcohol/water mixture. The second part describes the preparation of a photocleavable PFS-hv-poly(2-vinylpyridine) (P2VP) block copolymer bearing an o-nitrobenzyl ester (ONB) group at the junction. I investigated in detail the UV light-induced cleavage of the P2VP corona chains from the rod-like micelles by GPC, TEM and multiangle light scattering. The third part in the thesis describes the formation of rod-like co-micelles with segregated coronas via living CDSA of two mixed unimers of PFS-b-PNIPAM and PFS-hv-P2VP. By controlling the epitaxial growth rate of the two competing species, the morphology of the co-micelles could be varied from patchy to block co-micelles. The fourth part describes the synthesis and living CDSA of PFS-b-poly(oligo(ethylene glycol) methyl ether methacrylate) (PFS-b-POEGMA). I explored the self-assembly condition of this polymer in different alcohol media and found a methanol/ethanol mixture as selective solvent to prepare uniform nano-rods by living CDSA. These nano-rods stayed intact after transfer to water. The thermoresponsiveness of these uniform cylindrical brushes was investigated by multiangle light scattering.

Author : David Allen Rider
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Page : 598 pages
File Size : 49,15 MB
Release : 2007
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ISBN : 9780494527382

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A series of well-defined polystyrene-block-poly(ferrocenylethylmethylsilane) (PS-b-PFEMS) diblock copolymers was synthesized. Both PFEMS and PS- b-PFEMS were shown to be amorphous due to the atactic nature of the PFEMS. As a result, PS- b-PFEMS readily undergo solid-state self-assembly in the bulk producing a spectrum of ordered nanometer sized iron-rich morphologies. When cylinder-forming PS-b-PFEMSs were studied in thin films, well-ordered arrays of hexagonally packed iron-rich cylindrical microdomains oriented either parallel to or normal to the substrate were produced. The orientation was found to depend strongly on the film thickness and/or the conditions of annealing. The etching of these films using (i) reactive plasmas, and (ii) an oxidative chemical wet etch technique were investigated. Using (i), surface-patterned magnetic ceramics were produced as well as a nanotextured silver metal film. The latter was found to dramatically enhance the Raman spectroscopy of an adsorbed analyte molecule. Using (ii), nanoporous polystyrene films were generated by the quantitative elimination of PFEMS domains by exposure to a nucleophilic non-solvent under oxidizing conditions.Thin films of PS-b-PFEMS generated efficient iron nanoparticle catalysts for single-walled carbon nanotube (SWNT) growth via a chemical vapor deposition growth process. The kinetics of the formation of iron catalysts from PS- b-PFEMS and PFEMS were compared. Despite the lower iron content for PS-b -PFEMS films, more active iron sites were produced. Additionally, the tube diameter and density were tunable by adjusting the chain lengths of polyferrocenylsilane- block-polysiloxanes in thin films. Lastly, high-throughput field-effect SWNT transistors have been fabricated with more than 160 individually addressable devices on a chip.The influence of strong 3D confinement on the self-assembly of PS-b-PFEMS was studied. Both silica colloidal crystals and silica inverse colloidal crystals were used for directing the self-assembly. Unusual morphologies, such as concentric shells and branched lamellae, resulted from the interaction of the lamellar-forming PS-b-PFEMS with the high surface area templates. In addition, the control of the 3D confined morphology of cylinder-forming PS-b-PFEMS was demonstrated through mediation of the interfacial interactions within the colloidal crystal.For solution state self-assembly, PS-b -PFEMSs and polystyrene-block-poly(ferrocenylmethylphenylsilanes) (PS-b-PFEMSs) were stoichiometrically oxidized in solution. Due to a redox-induced polarity change for the PFEMS and PFMPS blocks, self-assembly into well-defined spherical micelles occurred. The micelles, composed of a core of partially oxidized PFS segments and a corona of PS, disassembled when treated with a reducing agent and regenerated unassociated free chains.Lastly, the photochemical treatment of metal-containing ferrocenophane monomers with low energy Pyrex-filtered light from a mercury lamp (lambda > 310 nm) or bright sunlight in the presence of an anionic initiator led to living polymerizations in which the conversion and molecular weight of the resulting polymer was controlled by irradiation time. The polymerization proceeded via attack of the initiator or propagating anion on the iron atom of the photoexcited monomer. The formation of functional block copolymer architectures was possible when the light is alternately switched on and off in between the sequential addition of different monomers.

Author : Kyoung Taek Kim
Publisher :
Page : 376 pages
File Size : 28,98 MB
Release : 2007
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ISBN : 9780494217849

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Block copolymers of poly ferrocenylsilanes (PFSs) and polypeptide were synthesized by the ring-opening polymerization of strained [1]-silaferrocenophanes and alpha-amino acid-N-carboxyanhydrides (alpha-NCA). PFS-b-poly(gamma-benzyl-L-glutamate) (PFS- b-PBLG) block copolymers showed thermotropic liquid crystalline phases. The benzyl ester groups of poly(gamma-benzyl-L-glutamate) were deprotected under standard hydrogenation conditions, and the resulting amphiphilic block copolymer, PFS-b-poly(L-glutamic acid), formed micelles in water. Dendronized polyferrocenylsilanes were synthesized by a substitution reaction of reactive poly(chloromethylferrocenylsilane) with monodendrons with a focal hydroxy group. AFM studies of the fractionated high molecular weight PFS samples revealed a spherical cocoon structure for the single chains of the dendronized polymer as well as elongated single chain structures. Thermoreversible gelation of PFS-b-PBLG in toluene was observed. Organogels of PFS-b-PBLG were studied by transmission electron microscopy (TEM), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS). Based on the experimental results, a new mechanism for the self-assembly was proposed to explain the gelation of these PBLG block copolymers. This mechanism is likely to be general for numerous block copolymers based on helical polypeptides. Diblock copolymers, poly isoprene-b-polyferrocenylsilane (PI-b-PFS), were synthesized by living anionic polymerization. The PI block formed in cyclohexane showed a high content of 1,4-cis -microstructure rather than 1,2- or 3,4-microstructure. The micellization behavior of these block copolymers in hexane and decane (selective solvents for the PI block) was studied by TEM, and comparisons were made between polymers with high and low 1,4-cis-microstructure contents. New macromolecular self-assembling building blocks, dendron-helical polypeptide copolymers and dendritic-helical copolypeptides, have been synthesized. These materials possess a well-defined 3-D shape and self-assemble in solution to form nanoribbons via a mechanism proposed in this thesis. The well-defined 3-D structures of these macromolecular building blocks also affect their self-assembly behavior such as a lyotropic liquid crystal formation in organic solvents and micellization in water. Redox-active ferrocene groups were incorporated in conjugated polymer backbones. The resulting polymers with bissilylferrocenyl moieties showed photoluminescence triggered by the oxidation of ferrocene groups in the main chain. The intensity of the luminescence increased with increasing extent of oxidation of ferrocene groups in the polymer backbone. The polymer containing ferrocenyl groups in the backbone showed photovoltaic properties upon illumination.

Author : Yujin Cha
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Page : pages
File Size : 10,72 MB
Release : 2017
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ISBN :

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Self-assembly of Block copolymer (BCP) provides a robust method to construct a variety of micellar morphologies, ranging from spheres to vesicles. Crystallization-Driven Self-assembly (CDSA), one of the methods for the preparation of nano-objects, has attracted a great deal of interest due to its unique ability for dimensional control over 1D, 2D, and 3D nano-objects. Metallopolymers have been utilized in CDSA. I will present CDSA of cobaltocenium-containing block copolymers, poly(caprolactone)-b-poly(cobaltocenium amidoethyl methacrylate) (PCL-b-PCoAEMA), which can form 2D hexagonal platelet structures in protic solvents. By changing the composition of block copolymers, the block copolymers self-assembled into various two-dimensional platelets, from hexagons to diamonds.