Oxabicyclic alkenes have been the focus of many synthetic studies as they are versatile compounds which act as synthetic intermediates to produce a variety of useful heterocyclic, carbocyclic and acyclic products. The nucleophilic ring opening reaction of oxabenzonorbornadiene was studied. Methanol was the primary nucleophile used throughout the investigation, however various other alcohol nucleophiles were also tested for their efficacy. The effects of substitution were explored, providing ring opened products in yields of up to 81%. The [2+2] cyclodimerization reaction of oxanorbornadienes was also examined providing the first examples of dimers of this kind. The scope was expanded to include other 2,3-diester oxanorbornadienes as well as various C1 substitutions. Changing the ester moiety did not affect the reaction, however the addition of a C1 alkyl substituent did result in lower yields. Moderate yields of up to 66% were obtained. Additionally, a new ruthenium complex was discovered in the process.

Thesis (Ph.D.)--Ohio University, March, 2008. / Abstract only has been uploaded to OhioLINK. Includes bibliographical references (leaves 115-125)

Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2010. / Committee Chair: Weck, Marcus; Committee Member: Breedveld, Victor; Committee Member: Fahrni, Christoph; Committee Member: Kelly, Wendy; Committee Member: Lyon, L. Andrew. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Polysaccharides, one of three types of natural polymer, are used by living organisms for energy storage, structural support, and other vital applications. In particular, acidic polysaccharides such as alginic acid and hyaluronan play important roles in lubrication and water storage. Isolation of polysaccharides is complicated by the difficulty of purification and lack of batch-to-batch consistency. Polysaccharide synthesis has also proved challenging due to their stereochemical complexity and high density of functional groups with similar reactivity. One solution is the synthesis of mimics that possess many of the properties of natural polysaccharides, including a rigid pyranose or furanose backbone and numerous hydroxyl or carboxylic acid groups. Synthesized polysaccharide mimics include polymers with ether linkages not seen in nature, non-ether linked sugar monomers, and polymers created from non-carbohydrate sources. These mimics have been used in various applications, including biolubrication, membrane synthesis, and DNA delivery. As a first approach to a polysaccharide mimic, a polymer with a rigid cyclic backbone and several pendant water-soluble functional groups was sought. High molecular weight ester-functionalized norbornene polymers were synthesized by ring-opening metathesis polymerization of 5-norbornene-2-ethyl ester. The resulting polymers were saponified and hydroxylated along the polymer backbone without a reduction in chain length. The chemical, thermal, and mechanical properties of the various polymers were measured, indicating high thermal stability and strong solid-like character. Even in their saponified and hydroxylated form, the polymers possessed very limited water solubility. Poly-amido-saccharides, a new type of carbohydrate polymer mimetic, were synthesized by the controlled anionic ring opening polymerization of a beta-lactam glucose monomer. The primary alcohol was oxidized to investigate the effects of an ionizable carboxylic acid group, such as those found in natural polysaccharides containing glucuronic acid. Circular dichroism revealed an ordered helical secondary structure in solution that was lost following ring opening. The oxidized poly-amido-saccharides were shown to stabilize lysozyme towards freezing and dehydration stresses better than currently used methods. Glycopolymers containing the poly-amido-saccharides on a poly(acrylamide) backbone were also synthesized and characterized as a model for more complex systems.

This Thesis describes the synthesis and characterisation of new Group 2, Group 3 and lanthanide amide, alkyl, halide, borohydride and alkoxide complexes, and their uses as catalysts for the living ROP and immortal ring-opening polymerisation (iROP) of rac-, L, D- and meso-lactide. <strong>Chapter One</strong> introduces cyclic esters and possible mechanistic pathways leading to polyesters by ROP. Living and immortal ROP, including their kinetic characteristics are discussed. An overview of ROP from an industrial perspective and a literature review are also given. <strong>Chapter Two</strong> describes the synthesis and characterisation of a new series of magnesium and zinc amide, alkyl, halide, borohydride and alkoxide complexes supported by a carbazole-bis(dimethyloxazoline) ligand. Their activities towards the ROP of rac-, L- and meso-lactide are presented. Detailed mechanistic studies using spectroscopic techniques are discussed and a new mechanism is proposed. <strong>Chapter Three</strong> describes the synthesis and characterisation of a new series of calcium, strontium, yttrium, lanthanum and samarium amide, alkyl, halide, borohydride and alkoxide complexes supported by a carbazole-bis(dimethyloxazoline) ligand. Their activities towards the ROP of rac-, L- and meso-lactide are presented. Detailed mechanistic studies using spectroscopic techniques are discussed. <strong>Chapter Four</strong> describes the synthesis and characterisation of a new series of magnesium, calcium, strontium, yttrium, lanthanum and samarium amide, halide and borohydride complexes supported by a chiral carbazole-bis(isopropyloxazoline) ligand. Their activities towards the ROP of rac-, L-, D- and meso-lactide are presented. <strong>Chapter Five</strong> contains experimental details and characterising data for the new complexes reported in this Thesis. <strong>CD Appendix</strong> contains .CIF files for all the new crystallographically-characterised complexes.

Dicyclopentadiene (DCPD), a tricyclic olefin, is available from the C5 fraction of petroleum feedstocks. Owing to its high reactivity (due to the presence of a strained alkene), low cost, and lack of other commercial uses, DCPD has been extensively pursued as a monomer for use in ring-opening metathesis polymerization processes. The olefin metathesis reaction, for which Yves Chauvin, Robert H. Grubbs, and Richard R. Schrock received the 2005 Nobel prize, is among the most attractive approaches to polymerize olefins, allowing production of high-molecular weight polymers including linear macromolecules, block copolymers, and crosslinked materials. Polydicyclopentadiene (PDCPD), which can be produced using a variety of early- and late-transition metal catalysts, is a thermoset polymer with a highly crosslinked structure. PDCPD has excellent impact strength, high storage modulus, good chemical resistance, wide service temperature range, and low density. As a result, it has found broad commercial utility in industrial manufacturing. Additionally, the reaction injecting molding (RIM) process used for DCPD polymerization makes it possible to precisely control the shape and dimensions of PDCPD products. Owing to its lack of chemical functionality, however, polydicyclopentadiene has many limitations. Previously, our research group developed a modified dicyclopentadiene monomer by adding an electron withdrawing group – a methyl ester functional group – on the pendent cyclopentene ring of the monomer. Polymerization of this functionalized monomer led to a novel thermoset material – methyl ester functionalized polydicyclopentadiene (fPDCPD) – that exhibits tunable surface hydrophobicity. In experiments described in this dissertation, my collaborators and I confirmed the thermal crosslinking mechanism of fPDCPD using a combination of solution-state and solid-state NMR, FTIR, and Raman spectroscopy. We also explored the surface chemistry of our novel material, by harnessing the embedded functional group in order to exert finer control over hydrophobicity, and to control interactions with biological organisms through the conjugation of biologically relevant functional groups. To further extend the utility of our functionalized dicyclopentadiene monomer, we synthesized a series of statistical polymers: fPDCPD-stat-PDCPD. Once again, we used a wide range of characterization methods, and showed that we can both tune the surface hydrophobicity of the copolymers and manipulate the mechanical properties by adjusting the molar fractions of functionalized and non-functionalized monomers. Chemical structures of these copolymers were interrogated by NMR, FTIR, and Raman spectroscopy. Frontal ring-opening metathesis polymerization was applied in an effort to study the kinetics of (co)polymerization. Finally, to lay the groundwork for future fPDCPD manufacturing, we successfully optimized the production of fDCPD monomers to half-kilo scale and fPDCPD polymers at 20-gram scale, while developing a reaction-injection molding process that permitted the production of dimensionally controlled fPDCPD objects. This in turn allowed us to conduct a rigorous assessment of the mechanical properties of our fDCPD through dynamic mechanical analysis (DMA), which established for the first time that our functionalized material has a comparable storage modulus to that of the parent (unmodified) PDCPD. The development of fPDCPD is approaching a new stage where it is ready to be commercialized and mass produced. We hope that our novel fPDCPD material will soon play a crucial role in replacing traditional metallic components in vehicle design and engineering material manufacturing. / Graduate / 2021-12-14

Presented diploma thesis deals with the study of ring-opening polymerization (ROP) of caprolactone catalyzed by novel organic and organometallic compounds. In the theoretical part of the thesis a summary of polymerization strategies and catalytic/initiators systems for ROP of polyesters is overviewed on the basis of reported background research. In experimental part a series of caprolactone polymerization runs with the view of polymerization conditions (solution/monomer ratio, catalyst/initiator ratio, monomer/initiator ratio and monomer concentration) at the temperature range of 25-70 °C was carried out. The experimental study was focused on catalytic precursors based on organic carbenes (tBuNCH=CHN+tBu)CH Cl- (NHC-tBu) in tetrahydrofuran solution and complex of aluminium{O,O’-[4,5-P(O)Ph2tz]-AlMe2} Ph = phenyl, tz = triazole, (OAlMe2) in chlorobenzene solution. Obtained polymers were precisely characterized by means of 1H NMR spectroscopy (Bruker Avance), Differential scanning calorimetry (TA Instruments Q 2000) and Gel permeation chromatography (Agilent Technologies 1100 series) methods. The microbial degradability of synthesized polymer sample having Mn = 12 kg/mol, Mw/Mn = 2.5 and crystallinity degree of 53 % was examined. The polymer in the form of melt-pressed films and powder form was bacterially aged in Bacillus subtilis (BS) strain inoculated mineral and nutrient media for 42 days. Scanning electron microscopy (SEM) and Confocal laser scanning microscopy (CLSM) confirmed the crack development on the surface of films as the consequence of microbial attack in comparison with unchanged control samples. Moreover, the pink coloration of polymer suspension was observed as the consequence of bacterial activity.

No description available.

Ring opening metathesis polymerization (ROMP) is established as one of the efficient controlled living polymerization methods which have various applications in polymer science and technology fields. The research presented in this dissertation addresses several applications of multifunctional well-defined norbornene-based block copolymers synthesized by ROMP using ruthenium-based Grubbs catalysts. These novel block copolymers were applied to stabilize maghemite nanoparticles, creating the superparamagnetic polymeric nanocomposites. The Jaggregation properties of the porphyrin dyes were improved via self-assembly with a customized norbornene polymer. Novel multimodal copolymer probes were synthesized for two-photon fluorescence integrin-targeted bioimaging. In Chapter 1 a brief overview of ROMP along with ruthenium metal catalysts and selected applications of the polymers related to this research is presented. Superparamagnetic maghemite nanoparticles are important in biotechnology fields, such as enhanced magnetic resonance imaging (MRI), magnetically controlled drug delivery, and biomimetics. However, cluster formation and eventual loss of nano-dimensions is a major obstacle for these materials. Chapter 2 presents a solution to this problem through nanoparticles stabiulized in a polymer matrix. The synthesis and chracterization of novel diblock copolymers, consisting of epoxy pendant anchoring groups to chelate maghemite nanoparticles and steric stabilizing groups, as well as generation of nanocomposites and their characterization, including surface morphologies and iv magnetic properties, is discussed in Chapter 2. In Chapter 3, further improvement of the nanocomposites by ligand modification and the synthesis of pyrazole-templated diblock copolymers and their impact to stabilize the maghemite nanocomposite are presented. Additionally, the organic soluble magnetic nanocomposites with high magnetizations were encapsulated in an amphiphilic copolymer and dispersed in water to assess their water stability by TEM. To gain a preliminary measure of biocopatibility of the micelle-encapsulated polymeric magnetic nanocomposites, cell-viability was determined. In Chapter 4, aggregation behaviors of two porphyrin-based dyes were investigated. A new amphiphilic homopolymer containing secondary amine moieties was synthesized and characterized. In low pH, the polymer became water soluble and initiated the stable Jaggregation of the porphyrin. Spectroscopic data supported the aggregation behavior. Two photon fluorescence microscopy (2PFM) has become a powerful technique in bioimaging for non-invasive imaging and potential diagnosis and treatment of a number of diseases via excitation in the near-infrared (NIR) region. The fluorescence emission upon two-photon absorption (2PA) is quadratically dependent with the intensity of excitation light (compared to the linear dependence in the case of one-photon absoprtion), offering several advantages for biological applications over the conventional one-photon absorption (1PA) due to the high 3D spatial resolution that is confined near the focal point along with less photodamage and interference from the biological tissues at longer wavelength (~700-900 nm). Hence, efficient 2PA absorbing fluorophores conjugated with specific targeting moieties provides an even better bioimaging probe to diagnose desired cellular processes or areas of interest The αVβ3 integrin v adhesive protein plays a significant role in regulating angiogenesis and is over-expressed in uncontrolled neovascularization during tumor growth, invasion, and metastasis. Cyclic-RGD peptides are well-known antagonists of αVβ3 integrin which suppress the angiogenesis process, thus preventing tumor growth. In Chapter 5 the synthesis, photophysical studies and bioimaging is reported for a versatile norbornene-based block copolymer multifunctional scaffold containing biocompatible (PEG), two-photon fluorescent (fluorenyl), and targeting (cyclic RGD peptide) moieties. This water-soluble polymeric multi scaffold probe with negligible cytotoxicity exhibited much stronger fluorescence and high localization in U87MG cells (that overexpress integrin) compared to control MCF7 cells. The norbornene-based polymers and copolymers have quite remarkable versatility for the creation of advanced functional magnetic, photonic, and biophotonic materials.

Yes / In this work we report a facile method to prepare a fluorescence active self-healable hydrogel via incorporation of fluorescence responsive ionic block copolymers (BCPs). Ionic block copolymers were prepared via a combined effect of ring opening polymerization (ROP) of ε-caprolactone and xanthate mediated reversible addition–fragmentation chain transfer (RAFT) polymerization. Here polycaprolactone (PCL) was modified with xanthate to prepare a PCL based macro-RAFT agent and then it was utilized to prepare block copolymers with cationic poly(2-(methacryloyloxy)ethyltrimethyl ammonium chloride) (PCL-b-PMTAC) and anionic poly(sodium 4-vinylbenzenesulfonate) (PCL-b-PSS). During the block formation, the cationic segments were randomly copolymerized with a trace amount of fluorescein O-acrylate (FA) (acceptor) whereas the anionic segments were randomly copolymerized with a trace amount of 9-anthryl methylmethacrylate (AMMA) (donor) to make both the segments fluorescent. The block copolymers form micelles in a DMF : water mixture (1 : 4 volume ratio). The ionic interaction of two BCPs was monitored via Förster resonance energy transfer (FRET) and zeta potential measurements. The oppositely charged BCPs were incorporated into a polyacrylamide (PAAm) based hydrogel that demonstrated self-healing behavior and is also highly fluorescent. / IIT Kharagpur and MRC (MR/N501888/2)