The aim of this research was to prepare high performance and fully biodegradable polymer nanocomposites. The most representative polymers classified as biodegradable are poly(!-caprolactone) (PCL) (issued from petrochemistry) and polylactide (PLA) (issued from renewable bio-resources). Biodegradable nanoparticles purposely extracted from biomass were selected, namely Cellulose NanoWhiskers (CNW) and Starch NanoCrystals (SNC). CNW are rod-like nanoparticles with 2 nanometric dimensions while SNC consists in nanosheets, thus with 1 nanometric dimension. A 3 nanometric-dimension particle often considered as “silica- type nanocage” was selected to complete this study, namely Polyhedral Oligomeric Silsesquioxane (POSS). The addition of such nanoparticles was expected to enhance several properties of the filled polymer matrix, especially thermo-mechanical performances and extent of crystallinity. In this field, the quality of the nanoparticle dispersion throughout the matrix is an essential parameter to produce nanocomposite materials with largely improved properties. One of the most cited techniques to overcome nanofiller aggregation and even agglomeration relies upon the creation of strong chemical bonds between the nanoparticle and the polymer matrix, leading to the preparation of so-called nanohybrids. For that purpose, the surface of the nanoparticles was first modified by chemical grafting and polymerization reactions. The ring-opening polymerization (ROP) of e-caprolactone and L,L-lactide catalyzed by tin(II) 2- ethylhexanoate (tin octoate, Sn(Oct)2) was initiated from functional groups available on the nanoparticle surface. The grafting efficiency was demonstrated for the three investigated nanofiller/polyester systems. Different characterization techniques were approached depending on the nanofiller nature. In a second step, the so-formed nanohybrids were used as “masterbatches” and dispersed in their corresponding commercial polyester matrices, i.e. PCL and PLA, by melt-compounding using a mini-lab twin screw extruder. The nanocomposite materials were fully characterized, correlating morphological observations with thermal, mechanical and rheological properties. To highlight the beneficial effect of the surface covalent grafting, simple melt-blends, i.e., containing unmodified nanofillers and polyester matrices (PCL or PLA) were prepared. The level of property improvement was most of the time directly related to the degree of nanofiller dispersion, and proved systematically better in case of masterbatch-based materials. Keeping in mind the effect of the nanoparticle geometry, as well as its mechanical modulus, crystallinity or extent of dispersion within the polyester matrix, the rod-like 2D-nanofiller, namely cellulose nanowhiskers extracted from ramie, appeared as the most efficient candidate for polyester reinforcement. The incorporation of PCL chains surface-grafted onto CNW contributed to substantially increasing the overall thermo- mechanical properties, most likely due to the formation of a strong physical chain network between surface- grafted chains and chains composing the matrix. Additionally, CNW-based nanohybrids revealed their potential as both nucleating sites dramatically increasing the crystallization rate of PLA matrix and compatibilizing PCL/PLA immiscible blends.

Aluminum complexes, [O3PMe]AlR(R = OtBu, OPh), containing tris-(3,5-di-tert-butyl-2-hydroxy-phenyl)phosphine ([O3P]H3) which is a novel tridentate ligand have been synthesized and characterized by NMR, X-ray diffraction and elemental analysis. Theses complexes were used as catalysts for ring-opening polymerization of £`-caprolactone. We suggested that the stereo effect of catalysts is the main factor in the ring-opening polymerization and compared the mechanism with DFT. In additional, we studied the electronic states and electronic chemistry of [O3PMe]AlR by DFT, UV and PLE. The novel ligand, bis(3,5-tert-butyl-2-phenoxy) tert-butylphosphine ([tBuOPO]H2), reacted with alkali metals such as n-BuLi, NaH and KH to form a series metal complexes, [tBuOPO]M2(Solvent)x (M = Li, Na, K). These metal complexes are all dimeric molecules characterized by X-ray diffraction, NMR and elemental analysis. Moreover, we reacted {[tBuOPO]Li2(DME)}2 with metal complexes of group 4, TiCl3 and MCl4(THF)2 (M = Ti, Zr, Hf), and we received [tBuOPO]2M and [tBuOPO]MCl2(THF) (M = Ti, Zr, Hf). We also synthesized alkoxide complexes of the series metal complexes and studied the catalytic reactivity for ring-opening polymerizations. Furthermore, tantalum complexes, [tBuOPO]2TaX (X = F, Cl) and [tBuOPO]TaCl3, have been synthesized and characterized. Especially synthesizing [tBuOPO]TaCl3 should be carefully controlled by lowering the concentration of TaCl5.

A tridentate diphenolate phosphine ligand H2[OPO] (bis(3,5-di-tert-butyl-2-hydroxyphenyl)phenylphosphine) has been synthesized in high yield. Treatment of H2[OPO] with Ti(OEt)4 in toluene at room temperature produced reddish orange crystalline Ti[OPO]2. The bis-ligand complex Ti[OPO]2 also be obtained from the in situ lithiation of H2[OPO] in THF or toluene followed by addition of TiCl4(THF)2. The reactions of MCl2[N(SiMe3)2]2 (M = Zr, Hf) with H2[OPO] in pentane at room temperature generated cleanly [OPO]2Zr(H2O) and [OPO]2Hf(H2O), respectively, in high yield. Treatment of TiCl4(THF)2 with Ti[OPO]2 in toluene afforded [OPO]TiCl2(THF). The solution and solid-state structures of Ti[OPO]2, [OPO]TiCl2(THF), [OPO]2Zr(H2O) and [OPO]2Hf(H2O) were studied by multinuclear NMR spectroscopy and X-ray crystallography. lithiation of H2[OPO] with n-BuLi in DME solution afforded [OPO]Li2(DME)2. The metathetical reactions of H2[OPO] with NaH or KH in DME solutions, respectively, produced the corresponding complexes [OPO]Na2(DME)2 and {[OPO]K2(DME)2}2. Both [OPO]Li2(DME)2 and [OPO]Na2(DME)2 are highly active catalysts for ring-opening polymerization of caprolactone. A series of tetravalent tin complexes [OPO]SnX2 (X = Cl, Me, n-Bu) also be obtained from the in situ lithiation of H2[OPO] in THF followed by addition of SnCl2X2. A divalent tin complexe [OPO]Sn also be obtained by analogous way from the in situ lithiation of H2[OPO] in pentane followed by addition of SnCl2.

Thesis (Ph. D.)--University of Nevada, Reno, 2007. / "December, 2007." Includes bibliographical references. Online version available on the World Wide Web.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 190-197).

Undergraduate honors paper--Mount Holyoke College, 2005. Dept. of Chemistry. / Includes bibliographical references (leaves 62-65).

Thesis (Ph.D.) - University of St Andrews, January 2009. / Thesis and abstract restricted until 7th January 2014.

In the first Chapter, Polyhomologation, a powerful technique to synthesize well-defined, perfectly linear, polyethylenes with controllable molecular weight, topology and low polydispersity, is presented in the first Chapter. In this Chapter is also discussed the combination of polyhomologation with other polymerization techniques such as Ring Opening Polymerization, ROP, Atom Transfer Radical Polymerization, ATRP, as well as with chlorosilane linking chemistry towards well-defined polyethylene-based macromolecular architectures. In the second Chapter, α,ω-dihydroxy-polyethylene was synthesized by the polyhomologation of dimethylsulfoxonium methylide with 9-thexyl-9-BBN (9-BNN: 9-borabicyclo[3.3.1]nonane), a novel difunctional initiator produced from 9-BBN and 2,3-dimethylbut-2-ene with two active and one blocked sites, followed by hydrolysis/oxidation. The terminal hydroxy groups were used either directly as initiators, in the presence of 1-tertbutyl-2,2,4,4,4-pentakis(dimethylamino)-2λ5,4λ5-catenadi(phosphazene) (t-BuP2), for the ring opening polymerization of ε-caprolactone, ε-CL, in order to afford polycaprolactone-b-polyethylene-b-polycaprolactone (PCL-b-PE-b-PCL) or after transformation to ATRP initiating sites in order to polymerize styrene and produce polystyrene-b-polyethylene-b-polystyrene (PSt-b-PE-b-PSt) triblock copolymers. Molecular characterization by 11B, 13C and 1H NMR as well as FTIR, and high-temperature GPC (HT-GPC) confirmed the well-defined nature of the synthesized new difunctional initiator and triblock copolymers. Differential scanning calorimetry was used to determine the melting points and degree of crystallinity of PE and PCL. In the third Chapter, a novel triallylborane initiator was synthesized and used to afford α-allyl-ω-hydroxy-polyethylene by polyhomologation of dimethylsulfoxonium methylide. The α-allyl-ω-hydroxy-polyethylene was then used as a macroinitiator (OH group) for the ROP of ε-CL and LLA to afford well-defined triblock terpolymer of polylactide-b-polyethylene-b-polycaprolactone (PLLA-b-PE-b-PCL). The characterization of all intermediate and final products by 1H NMR, FTIR, and HT-GPC, verified the well-defined nature of the triblock terpolymer. In the fourth Chapter, polyethylene (PE)-based 3- and 4-miktoarm star [PE(PCL)2, PE(PCL)3], as well as H-type [(PCL)2PE(PCL)2] block copolymers (PCL: polycaprolactone), were synthesized by combining polyhomologation, chlorosilane chemistry, and Ring Opening Polymerization (ROP). For the synthesis of miktoarm stars, a hydroxyl-terminated PE-OH, prepared by polyhomologation of dimethylsulfoxonium methylide with a monofunctional boron initiator, reacted with either chloromethyl(methyl)dimethoxysilane or chloromethyltrimethoxysilane. After the hydrolysis of the methoxysilane groups, the produced difunctional or trifunctional macroinitiators were used for the ROP of ε-caprolactone, in the presence of 1-tert-butyl-2,2,4,4,4-pentakis(dimethylamino)-2λ5,4λ5-catenadi(phosphazene)(t-BuP2). The H-type block copolymers were synthesized using the same strategy but with a difunctional polyhomologation initiator. All intermediates and final products were characterized by HT-GPC, 1H NMR, and FTIR analysis. The thermal properties of the PE precursors and final products were studied by DSC and TGA. In the fifth Chapter, the self-assembly properties of the amphiphilic linear block copolymer PE-b-PCL and 3-miktoarm star copolymers (PE-b-PCL2) were studied in THF, a selective solvent for PCL, by Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM) and Atomic Force Microscope (AFM). All the above findings presented in this dissertation emphasize the utility of polyhomologation for the synthesis of well-defined polyethylene-based complex macromolecular architectures, which is practically impossible through another kind of polymerization, including the catalytic polymerization of ethylene. In the sixth Chapter, the summary of the thesis and some consideration on the subjects of future work are given.

Polylactides (PLA) are thermoplastic materials known for their biodegradability and biocompatibility, and therefore mostly utilized in biomedical applications. PLA-containing block copolymers further expand their application to include commodity materials and even advanced nanoporous materials. This research part of the thesis focuses on the synthesis and characterization of PLA-containing block copolymers, as well as their corresponding stereocomplexes formed by mixing block copolymers containing PLLA and PDLA segments. This work is divided into three parts. First, by using “living” anionic polymerization of styrene (St) and 2-vinylpyridine (2VP) followed by subsequent ethylene-oxide (EO) termination, well-defined hydroxyl-terminated polystyrene (PS) and poly(2-vinylpyridine) (P2VP) were synthesized. The resulting homopolymers were characterized by 1H nuclear magnetic resonance (NMR), size-exclusion chromatography (SEC), and infrared (IR) spectroscopy. The molecular weights were determined by SEC to be 6,200 and 5,500 g.mol-1 for PS and P2VP, respectively. In the second part, the two homopolymers, PS-OH and P2VP-OH were used as the macroinitiators for the ring-opening polymerization (ROP) of D- and L-lactides (D/L-LA) to obtain PS-b-PDLA and P2VP-b-PLLA, respectively. The targeted molecular weights of PLA blocks were varied to be 5,000, 7,000, and 10,000 g.mol-1 In the final part, quantitative stereocomplex formation was achieved by mixing PS-b-PDLA and P2VP-b-PLLA having equimolar PLAs segments. The physical and chemical properties of the diblockcopolymers and their corresponding stereocomplex, as well as the influence of varying the molecular weights of PLA blocks, were investigated by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), and circular dichroism (CD) spectroscopy.

Interest in macrocyclic monomers can be dated back to the 1960's. The recent surge of research activities in this area is prompted by two facts: the encouraging discovery of high yield synthesis and facile ring-opening polymerization of cyclic polycarbonate; the need for a technique to solve the tough processibility problem of high performance polymers. This work was intended to address the following aspects in the cyclic poly(ether ketone) or sulfone system. The first goal was to understand the structure-property relationship of this type of macrocycles. A large number of macrocycles were synthesized by nucleophilic aromatic substitution cyclization reactions under pseudo-high dilution conditions. Pure individual macrocycles as well as cyclic mixtures were characterized by NMR, HPLC, GPC, FABMS, MALDI-TOF-MS, DSC and TGA. Comparison study suggests that the cyclic distribution is kinetically controlled. Several factors determine the melting points of individual macrocycles. The first factor is the ring size. A series of cyclic monomers for poly(ether ether ketone)s were synthesized and isolated. The melting point decreases as ring size increases. Single crystal X-ray structural results suggest that this phenomenon is related to the increased flexibility of the larger sized macrocycles. The second factor is the functional groups of the macrocycles. X-ray structural and GPC experiments reveal that the sulfone group is more rigid than the ketone group, than ether group. The effect of functional groups on melting point is in the order sulfone>ketone>ether. A third factor is the symmetry of the macrocycles. Breaking the symmetry of macrocycle through comacrocyclization dramatically decreases the melting point of individual macrocycles as well as the cyclic mixture as a whole. Based on these findings, a novel two step method was developed to control the ring size distribution, which effectively reduced the amount of the small sized macrocycle and decreased the melting point. In addition to the nucleophilic aromatic substitution cyclization, it was also demonstrated in this work that macrocycles can be synthesized by Friedel-Crafts acylation cyclization. However, this method is limited by the solubility problem. The ring-opening polymerization of macrocyclic monomers was systematically studied. Several factors were considered in this study: the nature and amount of catalyst, temperature and time. CsF; metallic phenolate and Na2S are good initiators. Conversion to near 100 % is possible under the controlled polymerization conditions. It was found that crosslinking is an inherent phenomenon. The molecular weight of the soluble fraction near complete conversion is almost independent of initiator and polymerization temperature. It is limited by the crosslinking reaction. It is demonstrated for the first time that the macrocyclic monomer techniques can be applied to more valuable semicrystalline systems. Tough polymers such as high performance poly(ether ether ketone)s were produced through ring-opening polymerization. The last chapter is devoted to the challenging synthesis of monodisperse poly(ether ether ketone)s. A convergent strategy was devised. A monofluoroaryl compound was synthesized by Friedel-crafts acylation reaction. The final monodisperse linear oligomers were generated by reacting the monofunctional compound with a bisphenol through a quantitative reaction. / Ph. D.