The work reported herein describes efforts to create ring-opening metathesis block copolymers and homopolymers. The block copolymers were studied to gain insight into the local nanoscale environment of a block copolymer thin film. Additionally, perylene containing homopolymers were characterized in light of their possible use as an n-type material. In the first section of the thesis, the synthesis of diblock copolymers consisting of two blocks with very different dynamics is described. The covalent attachment of a molecular rotor which is sensitive to its local environment allowed the study of the dynamics of the polymers in thin films. The emissive intensity as a function of temperature allowed us to see discontinuity in the rates of change, indicating a change in the local environment corresponding to the transition of the polymer from a glassy to rubbery state. The corresponding temperature, to this event, is known as the glass transition temperature, Tg. Additionally, a polymer featuring a covalently bound n-type molecule, perylene diimide, was synthesized. The photophysical properties, including aggregation in dilute solution, are described. The material is expected to demonstrate the ability to efficiently transport negative charge, acting as n-type material in organic electronics.
Since the last ASI in Turkey in Sept. 1995, the olefin metathesis has made remarkable strong developments with an incredible speed in various directions. New catalyst systems have been developed which have resulted in the synthesis of novel materials. Other fascinating developments have been the new catalysts for stereoselective metathesis and catalysts with considerable functional group tolerance. These new catalysts in addition to Ring Opening Metathesis Polymerisation (ROMP) and Acyclic Diene Metathesis (ADMET) are now powerful tools for Ring Closing Metathesis (RCM) and have found many applications in the synthesis of natural products. A lot of information has been established about all aspects of the olefin metathesis and there is a vast literature concerning the process, covering the initiators, mechanistic features and applications of this reaction in organic and polymer synthesis. The NATO ASI on rd th ROMP and Related Chemistry took place in Polanica-Zdroj, Poland during 3 to 15 Sept. 2000, to highlight the developments in this area and to discuss the prospects and visions for the year 2000 and beyond. The aims of the ASI were: to provide a platform for dissemination of knowledge; to promote communication between people who have a serious interest in this field of chemistry; to help establishing international scientific contacts and to provide an opportunity for the scientists with an appropriate scientific background to learn of recent developments in this field of science. There were 15 lecturers and 67 participants in this NATO ASI.
Expanding Monomers: Synthesis, Characterization, and Applications provides a thorough discussion of expanding polymer systems and their potential applications. The scope of the book includes background information on conventional monomers, their polymeric systems, and associated shrinkage problems. Monomers that expand during polymerization are covered in detail, including their synthesis and characterization. Polymerization (homopolymerization and copolymerization) of expanding monomers is discussed, in addition to mechanisms and kinetics of several polymerization processes, such as cationic initiation and free radical ring-opening polymerization. The book also explores various applications in which expanding polymer systems have potential. These applications include coatings, casting and potting materials, composite adhesives, and electrical insulations. Expanding Monomers: Synthesis, Characterization, and Applications will be valuable as a reference for manufacturers, researchers, teachers, and students in polymer and materials science, in addition to industry and university libraries.
This book overviews methods for the synthesis of metal-containing monomers with various types of metal bonds to the organic moiety of the molecule, such as ionic, covalent, donor-acceptor, and others. Published data on homopolymerization, copolymerization, and graft polymerization of these monomers are generalized. Synthesis and Polymerization of Metal-Containing Monomers discusses features typical of the molecular and structural organization of the resulting metal-containing polymers, their properties and the associated major applications, such as catalytical and biological activity, electrophysical characteristics, and thermal resistance.
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 J-aggregation 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 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 J-aggregation 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 [alpha subscript v beta subscript 3] integrin 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 [alpha subscript v beta subscript 3] 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.
A series of well-defined polynorbornenes containing pendent aromatic ether or aliphatic side chains have been prepared. Synthesis of the monomeric materials proceeded via initial cyclopentadienyl iron-mediated nucleophilic aromatic substitution reactions and DCC-mediated condensation reactions, followed by removal of the metal moiety via photolytic demetallation. Structural analysis of both the metallated and nonmetallated compounds was accomplished using homo- and heteronuclear correlation spectroscopic techniques as well as IR, MS and C, H elemental analysis. Subsequent ring-opening metathesis polymerization of these building blocks was achieved in the presence of a ruthenium-based catalyst, namely bis(tricyclohexylphosphine)benzylidene ruthenium (IV) dichloride, which liberated the resulting polymeric materials in high conversion of the monomer to the polymer. Gel permeation chromatography of each of the polymers revealed high molecular weights as well as low to narrow polydispersity indices. Thermal analysis of the aromatic ether functionalized polynorbornenes was accomplished using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). These results showed that when the number of aromatic groups pendent to the polymer chain increased (within each polymer repeat unit), a subsequent increase in the thermal stability was noted. TGA of the aliphatic-bridged systems revealed decreased thermal stability as the length of the aliphatic flexible spacer increased. Changing the spacer from a purely methylene-bridged system to one containing a tri(ethylene glycol) chain was found to increase the overall thermal properties of the resulting polymeric material.
