[PDF] Synthesis And Self Assembly Of Structurally Well Defined Polyferrocenylsilanes And Their Block Copolymers eBook

Author : Kyoung Taek Kim
Publisher :
Page : 376 pages
File Size : 17,14 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 : David Allen Rider
Publisher :
Page : 598 pages
File Size : 50,87 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 : Hang Zhou
Publisher :
Page : pages
File Size : 38,97 MB
Release : 2018
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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 : Mahboubeh Hadadpour
Publisher :
Page : 370 pages
File Size : 25,97 MB
Release : 2015
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Metal containing polymers (metallopolymers) bring together the synthetic efficiency and versatility of conventional organic polymers with unique redox, responsive, and catalytic properties of inorganic metals. Over the last decade, metallopolymers have gained increased attention because of their unique physical and chemical properties that arise from the incorporation of metal centers into a polymer. Since the first report on a metallocene-based metallopolymer in 1955, there has been growing interest in this class of material. Ferrocene-based metallopolymers represent the vast majority of metallocene containing polymers in the literature. In 1992, the Manners Group established a major milestone in the field of metallopolymers by reporting the ring opening polymerization (ROP) of the strained [1]silaferrocenophane to synthesize polyferrocenylsilane (PFS). The novelty of PFS has attracted attention to incorporate other metallocenes into polymer chains. In comparison to well-studied ferrocene containing polymers, cobaltocene have received far less attention due to the difficulties in preparing its derivatives. In fact, only a few key contributions on this subject have been reported. Cobaltocene with 19 electrons is not stable and is readily oxidized to a cationic 18 electron cobaltocenium. The Tang Group has developed a synthetic methodology to synthesize highly pure cobaltocenium derivatives and incorporated them into well-defined polymers. Alternatively, the Ragogna Group reported the first neutral side-chain?5- cyclopentadienyl-cobalt-?4-cyclobutadiene (CpCoCb) functionalized metallopolymer. This mixed sandwich metallocene is an 18 electron complex, electronically neutral and isoelectronic to ferrocene and cobaltocenium. In this dissertation, the synthesis of welldefined side-chain functionalized CpCoCb containing homo- and block metallopolymers via reversible addition fragmentation transfer (RAFT) polymerization is detailed. Development of a controlled polymerization method to obtain well-defined high molecular weight CpCoCb containing metallopolymers is discussed. Several block copolymers were prepared via sequential RAFT polymerization. Synthesis, characterization, solution and solid-state self-assembly of the metal containing block copolymers is discussed in detail. These materials are used as ink in soft lithography to transfer patterns using a polydimethylsiloxane (PDMS) stamp. Synthesis of a series of CpCoCb monomers where the Cb ring is decorated with different substituents such as ferrocene and thiophene is reported. These highly metalized monomers are used to make metal rich materials with tunable metal content.

Author : Xiaochen Li
Publisher :
Page : 66 pages
File Size : 20,72 MB
Release : 2013
Category : Amphiphiles
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Recently, "shape amphiphiles" has attracted great attention. "Shape amphiphiles" usually refer to molecules possessing differences in the shape of the molecular moieties. It is found that these shape amphiphiles can self-assemble into diverse structure in solution, which is similar as small molecule surfactant and block copolymer, but has distinct molecular designs and topologies. Shape and interactions are two crucial factors to detect the self-assembly of these models. The previous research in our group has revealed that the giant molecular shape amphiphiles based on polystyrene-hydrophilic [60]Fullerene (AC60) conjugates can self-assemble into various structure. In this thesis, a comprehensive study on the synthesis and self-assembly behaviors in solution of a new giant molecular shape amphiphile, namely, the hydrophilic [60]Fullerene (AC60) tethered with polystyrene-b-poly(ethylene oxide) block copolymer (PEO-b-PS-AC60) has been investigated. The synthesis highlighted the Bingel-Hirsch cyclopropanation reaction for C60 surface functionalization and the Huisgen 1,3-dipolar cycloaddition of azide-alkyne, which is also well-known as "click" reaction, between alkyne functionalized AC60 and azide functionalized diblock copolymer PEO-b-PS to give rise to shape amphiphiles with precisely defined surface chemistry and molecular topology. For the block copolymer, the molecular weight of PEO was fixed at 2K/mol, a series of block copolymer PEO45-b-PS[subscript n] with different chain length of PS and narrow molecular weight distribution were synthesized by Atom Transfer Radical Polymerization (ATRP). The chemical structure of all intermediate and final products were fully confirmed and characterized by proton nuclear magnetic resonance(1H-NMR), carbon nuclear magnetic resonance (13C-NMR), Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass, Fourier transform infrared spectroscopy (FTIR) and size-exclusion chromatography (SEC). The self-assembling behaviors of shape amphiphiles as-prepared in solution was investigated by using 1,4-dioxane/DMF mixture as the common solvent and water as the selective solvent. As revealed by transmission electron microscopy (TEM), these shape amphiphilies exhibit versatile self-assembled micellar morphophogies, which can be tuning by changing initial molecular concentration or chain length of PS. Finally, the critical water concentration (CWC) of all shape amphiphiles as-prepared was determined by static light scattering (SLS) experiments. The results indicate that the value of (CWC) is dependent on the chain length of PS.

Author : Senbin Chen
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Page : 0 pages
File Size : 20,89 MB
Release : 2012
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This work dealt with the preparation and the study of supramolecular block copolymers based on hydrogen-bonding between homocomplementary or heterocomplementary stickers. The synthetic strategy was based on the combination of RAFT-mediated controlled radical polymerization and supramolecular chemistry. In the Chapter 2, we developed a strategy relying on the design of RAFT agents bearing thymine/diaminopyridine (DAP) recognition pairs and capable to grow well-defined miktoarm star supramolecular copolymers. To further extend the scope of H-bonding RAFT agents, in the Chapter 3, we also investigated the preparation of RAFT agents functionalized with motifs exhibiting very high binding constants. The Hamilton/barbiturate couple (log(K)≈4-5) was selected to generate more stable supramolecular block copolymers. Aiming at elaborating original associating macromolecules and at simplifying the strategy of synthesis, we finally explored the preparation ABC triblock supramolecular copolymers based on PA11 oligomers (OPA11) in Chapter 4. Ligation of a relevant dithiobenzoate group on the oligomers afforded oligomeric RAFT agents that allow for the preparation of ABC triblock supramolecular copolymers, where A is semi-crystalline, B in rubbery state and C in glassy state. Studies on the incorporation of such copolymers in epoxy networks are under progress.

Author : Brandon Aubrey Fultz
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Page : 0 pages
File Size : 49,71 MB
Release : 2020
Category : Chemistry
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This dissertation investigates the use of block copolymer self-assembly to create nanostructures with unique domain properties. Precise control over nanoscale feature size and properties of materials has become increasingly more important to keep up the ever-decreasing size of technology. Bottom-up approaches using block copolymers has been progressively more attractive due to their ability to autonomously self-assembly into an array of complex morphologies with features sizes as small as 2-3 nanometers. Modifications of these systems has generally been limited to only one domain as the processes under which modifications are carried out generally result in the disruption or destruction of the underlying morphology. We originally set out to create a block polymer system containing poly(vinylpyridine) (PVP) segments which can undergo several transformations such as protonation, metal coordination, or quaternization. By coupling PVP segments with poly(tert-butyl methacrylate), we believed that a well-ordered charged mosaic containing segregated opposite charges could be created without disruption of the underlying morphology. Thin films of hexagonally packed P4VP cylinders were self-assembled perpendicular to the surface and subsequently treated with bromoethane vapor at various durations to quaternize pyridinyl nitrogens. The PtBMA matrix was then partially hydrolyzed to poly(methacrylic acid), PMAA, through HCl vapor treatment followed by neutralization by brief submersion in KOH solution. Using techniques such as AFM, contact angle testing, and ToF-SIMS, we were able to determine the success of these transformations as well as methodologies in which structural morphology was maintained. An additional exploration into the use of tris(trimethylsilyl)silane (TTMSS) as non-toxic alternative to tin hydrides using only light was investigated as a method to remove reversible addition-fragmentation transfer (RAFT) chain transfer agents. As the end group removal from PVP polymers derived from RAFT has to our knowledge never been reported, we felt that these results would be invaluable to the scientific community due to the ubiquitous use of PVP in many systems. Not only was TTMSS found to be an effective reagent for RAFT removal of PVP polymers, it was also found to be effective for the removal of RAFT end groups from polystyrene which has been generally reported in literature to be difficult due to the stability of the benzyl radical. Reactions were found to be complete for most polymers in less than 2 hours whereas, other reported reagents typically took 24 hours or as much as 1 week.

Author : Victor Ho
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Page : 132 pages
File Size : 17,40 MB
Release : 2014
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Conjugated polymers have been widely studied for their use in lightweight, flexible, and solution-processable electronic devices. However, the optimization of such polymer-based devices has been largely Edisonian in nature due to both a poor understanding of and an inability to control the complex hierarchical structure observed in semicrystalline polymers. In this thesis, we show that simple chemical modifications to commonly-studied conjugated polymers can have a large effect on the observed structure ranging from the unit cell to that on the order of device features. In particular, the self-assembly of block copolymers in which one of the components is optoelectronically-active is presented as a facile method to obtain nanostructured materials. For the work in this thesis, we will focus on poly(3-alkylthiophenes), a widely studied class of conjugated polymers due to their favorable optoelectronic properties, high solubility in organic solvents, and susceptibility to simple chemical modification. Although the synthesis of conjugated block copolymers has been presented in the past, complexities arising from crystallization of the conjugated moiety have dominated the observed solid state morphologies. Specifically, the crystallization of the semicrystalline block dictates the block copolymer microphase separation, a well-known phenomenon in the literature for non-conjugated semicrystalline block copolymers, which has resulted in solid state morphologies that do not differ significantly from that of the semiconducting homopolymer. To address this, we first show that the side chain chemistry controls the thermal transitions and optoelectronic properties in poly(3-alkylthiophenes). Such control over the crystallization kinetics provides an experimentally convenient approach to investigate the importance of the crystalline structure over a wide range of length scales on the optoelectronic properties. Furthermore, the ability to control the thermal transition temperatures can be used to directly manipulate, and thereby balance, the competition between the driving forces for crystallization and self-assembly. As evidence, the nanoscale structure is shown to be directly controlled via synthesis of block copolymers in which one block is the low melting temperature semiconducting polymer, poly(3-(2-ethylhexyl)thiophene). A wide range of morphologies with curved interfaces are observed which, in the past, have been precluded by the crystallization of poly(3-alkylthiophenes) with unbranched aliphatic side chains such as poly(3-hexylthiophene). Importantly, confinement of the conjugated polymer to nanoscale domains is not detrimental to the crystallinity or to charge transport over device-scale dimensions. Additionally, this approach is shown to be effective for a number of different chemistries providing a flexible methodology for obtaining periodic, semiconducting domains on the nanoscale. Together, these simple synthetic strategies can be used to tune the morphology of various length scales of thin film active layers and provide synthetic rules for design of novel semiconducting polymer systems.