Nous avons synthétisé des polymères possédant des terminaisons fluorées afin de formuler des nanocapsules comme agents de contraste ultrasonores (ACUs) pour l’imagerie des tumeurs. Ces nanocapsules sont composées d’un cœur de bromure de perfluorooctyle (PFOB), un liquide perfluoré biocompatible et échogène, et d’une coque polymère possédant trois blocs d’affinités différentes. Le bloc hydrophile de polyéthylène glycol (PEG) présent en surface des nanocapsules permet de prolonger leur temps de circulation dans le compartiment sanguin et de favoriser leur accumulation dans les tumeurs par l’effet de perméabilité et de rétention accrue. Le bloc hydrophobe de polylactide (PLA) permet de générer une coque dégradable plus stable que les membranes de lipides ou de tensioactifs qui composent les ACUs utilisés en clinique. Finalement, la terminaison fluorée permet de favoriser l’ancrage du polymère autour de la goutte de liquide perfluoré et d’augmenter l’échogénicité des nanocapsules. Deux stratégies différentes ont été développées pour introduire ce bloc fluoré. La première consistait à synthétiser un PLA terminé par un chaînon fluoré linéaire court (C3F7 à C13F27) et à le mélanger à un polymère dibloc PLA-PEG pour formuler les nanocapsules. Nous avons montré que l’efficacité d’encapsulation du PFOB augmente avec la longueur de chaîne fluorée jusqu’à C8F17. La deuxième stratégie consistait à synthétiser directement un polymère tribloc composé des trois parties PEG, PLA et fluorée sur la même chaîne, la partie fluorée étant constituée de 4 à 15 chaînons C8F17 pendants (structure en peigne). Des mesures de tension interfaciale ont montré que ces polymères triblocs s’adsorbent à l’interface PFOB/solvant organique et encapsulent le PFOB plus efficacement que le PLA-PEG non fluoré. La morphologie des capsules est fortement influencée par le nombre de chaînons fluorés présents dans le polymère et par la quantité de polymère utilisée lors de la formulation. Une masse élevée du polymère contenant 15 chaînons fluorés favorisera ainsi la formation de nanocapsules possédant plusieurs cœurs de PFOB. La diminution de la quantité de polymère fluoré a finalement permis de produire des capsules avec un seul cœur, une coque fine, et de forme légèrement ellipsoïdale. Ces capsules diffusent les ultrasons plus efficacement que les capsules de PLA-PEG non fluoré. Alors que la présence de chaînes de PEG atténue considérablement la réponse acoustique des capsules, l’addition des chaînons fluorés permet de contrebalancer cet effet. Cette amélioration provient de plusieurs paramètres : l’augmentation de la quantité de PFOB encapsulé, l’augmentation de la densité de la capsule, et la diminution de l’épaisseur de la coque des capsules. Par ailleurs, les polymères fluorés et leurs produits de dégradation n’induisent pas de cytotoxicité in vitro comparé à leurs analogues non fluorés. Ces nanocapsules apparaissent donc comme des agents de contraste prometteurs pour permettre de mieux visualiser les tumeurs par échographie. / We have synthesized polymers with fluorinated end chains to formulate nanocapsules as ultrasound contrast agents (UCAs) for tumor imaging. These nanocapsules are composed of a core of perfluorooctyl bromide (PFOB), a biocompatible and echogenic perfluorinated liquid, and a polymeric shell made of three blocks of different affinities. The hydrophilic block of poly(ethylene glycol) (PEG) at the surface of the nanocapsules allows increasing their circulation time in the blood and promoting their accumulation into tumors by the enhanced permeation and retention effect. The hydrophobic block of polylactide (PLA) allows generating a degradable shell with higher stability as compared to the surfactant- and lipid-based membranes of commercialized UCAs. Finally, the fluorinated block favors the wetting of the polymer around the perfluorinated liquid and improves the nanocapsules echogenicity. Two different strategies have been developed to introduce this fluorinated part. The first one consisted in synthesizing a PLA terminated by a short linear fluorinated chain (from C3F7 to C13F27) and mixing it with a PLA-PEG diblock polymer to formulate the nanocapsules. The encapsulation efficiency of PFOB was found to increase with the fluorinated chain length up to C8F17. The second strategy consisted in synthesizing directly a triblock polymer composed of the three parts (PEG, PLA and fluorinated) on the same chain, the fluorinated part consisting of 4 to 15 pendant C8F17 chains (with a comb-like structure). Interfacial tension measurements showed that these triblock polymers adsorb at the PFOB/organic solvent interface and encapsulate PFOB more efficiently than non-fluorinated PLA-PEG. The capsules morphology was strongly influenced by the number of fluorinated chains and the amount of polymer used for formulation. Formulation with a high quantity of the polymer containing 15 fluorinated pendants thus favored the formation of nanocapsules with several PFOB cores. Decreasing the fluorinated polymer quantity then allowed producing capsules with a single core, a thin shell, and a slightly ellipsoidal shape. These capsules were more efficient ultrasound scatterers than non-fluorinated PLA-PEG capsules. While the presence of PEG chains considerably attenuates the capsules acoustic response, addition of fluorinated chains seems to counterbalance this effect. Such improvement arises from several contributions: a higher encapsulated PFOB content, a higher density due to the presence of fluorinated chains, and a lower shell thickness. Furthermore, the fluorinated polymers and their degradation products did not induce any in vitro cytotoxicity as compared to their non-fluorinated analogues. These nanocapsules therefore appear as promising UCAs for tumor imaging.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Aluminium salen and aluminium salan complexes are excellent catalysts for the ring-opening polymerisation of lactide. This thesis studied their efficacy in the polymerisation of novel monomers and their ability to build new macrostructures. Aluminium salen and aluminium salan complexes were tested as catalysts for ring-opening polymerisation of common aliphatic monomers where controlled polymer synthesis has not yet been achieved with similar systems. Excellent control over molecular weight and dispersity was achieved for β-caprolactone polymerisation, with high molecular weights accessible. Immortal polymerisation could also be performed with an extremely high level of chain transfer agent (up to 100 equivalents) and the highest monomer turnover (10000 monomer equivalents) with aluminium salen catalysts to date. Addition of functional groups to the monomer was also studied; the effect of steric bulk in polymerisation of methylsubstituted derivatives was significant. Protected alcohol functionalities can also be introduced into easily synthesised homopolymers and copolymers. The first example of synthesising a polyester with aromatic functionality within the polymer backbone via polymerisation of cyclic ester monomers was studied with an aluminium salen catalyst. 2,3-Dihydro-5H-1,4-benzodioxepin-5-one polymerisation was facile and proceeded under mild conditions. The resulting polymer could be depolymerised back to starting monomer with the same aluminium salen catalyst under dilute conditions. Random, AB diblock and ABA triblock copolymers were readily synthesised with L-lactide and β-butyrolactone as comonomers. Block copolymers with β-butyrolactone could also be selectively depolymerised, to give poly(3-hydroxybutyrate) homopolymers. Attempted polymerisation of a range of other aromatic monomers was unsuccessful due to addition of steric bulk, changing orientation of the monomer ester bond or decreasing the ring size. Synthesis of homopolymer and ABA triblock copolymers with L-lactide and alkyl-substituted β-lactones was investigated. Homopolymerisation of all alkyl-substituted β-lactones resulted in well controlled polymer, with rate decreasing as alkyl-substituent length increased. A sequential addition of monomers method with β-butyrolactone, β-valerolactone and β-heptanolactone was employed for copolymer synthesis. Copolymers synthesised from β-butyrolactone and β-valerolactone resulted in tunable glass transition and melting temperatures. Copolymers synthesised from β-heptanolactone resulted in thermoplastic elastomers exhibiting microphase separation, supported by differential scanning calorimetry and small-angle X-ray scattering. Finally, optimisation of in situ generated carbonylation catalysts was studied. Optimisation of literature complexes allowed for synthesis of β-valerolactone, β- heptanolactone, β-tridecalactone, 4-chloro-β-butyrolactone and β-6-heptenolactone on relatively large scales under much easier experimental protocols. Additionally, tuning of ortho-phenylene bridged salen ligand framework gave to structure-activity relationships. Using this optimised catalyst system, 4-chloro-β-butyrolactone and β- 6-heptenolactone were prepared and used in ring opening polymerisation. Well controlled and efficient polymerisation of 4-chloro-β-butyrolactone was easily achieved with aluminium salen and salan catalysts. Homopolymers and block copolymers with poly(ethylene glycol) and β-6-heptenolactone were readily synthesised.

Polyesters have been realised as a viable replacement for slow or non-degrading petroleum derived polymers. A variety of aliphatic polyesters, e.g. poly(lactic acid), have received a lot of attention because they are produced from renewable feedstocks and have the ability to biodegrade and bioassimilate. Poly(lactic acid)'s broader family, poly(α-hydroxy acid)s, have been produced with a wide variety of properties, that has given polyesters the potential for a more diverse range of applications. However, their synthesis has proven difficult. This thesis investigates a family of 1,3-dioxolan-4-ones as a monomer source to ease difficulties in current synthetic routes. Polymerisation of the parent 1,3-dixoxolan-4-one was tested. The copolymerisation of Llactide and 1,3-dioxolan-4-one was conducted with various monomer feedstocks. Ringopening polymerisation of 1,3-dioxolan-4-one led to the formation of paraformaldehyde as a polymerisation by-product. The copolymerisation was found to be best controlled when using a coordination-insertion type catalyst. 1,3-dioxolan-4-one was also copolymerised with ε-caprolactone and β-butyrolactone to produce copolymers with various compositions. The formation of poly(lactic acid) and poly(mandelic acid) from 5-methyl-1,3-dioxolan- 4-one and 5-phenyl-1,3-dioxolan-4-one was investigated. Poly(lactic acid) and poly(mandelic acid) were synthesised with either isotactic or atactic tacticities. Molecular weights were found to be lower than the expected values. A variety of MeAl(salen) catalysts were explored for the polymerisation of 5-methyl-1,3-dioxolan-4-one and catalysts ligated with tertiary-butyl substituted salens were found to have higher rates of polymerisation and reached high conversions. Altering the diimine bridge in the ligand led to variations in rates of polymerisation and molecular weights. The cause of the decrease in molecular weight was found to be caused by a side reaction. The side reaction was bypassed by polymerising 2,2,5- trimethyl-1,3-dioxolan-4-one and 2,2-dimethyl-5-phenyl-1,3-dioxolan-4-one to form poly(lactic acid) and poly(mandelic acid), respectively, with the expulsion of acetone. The scope of 1,3-dioxolan-4-ones capable of being polymerised to form poly(α-hydroxy acid)s was expanded to include iso-propyl, cyclohexyl, normal-butyl, iso-butyl, propargyl, chloromethyl and benzyloxymethyl substituents at the five position. The glass transition temperatures accessible from this synthetic route was expanded (22-105 °C). Kinetic experiments revealed the impact of the substituents steric bulk on the rate of polymerisation and points toward a coordination-insertion mechanism. Poly(lactic acid-co-glycolic acid) was copolymerised with 5-propargyl-1,3-dioxolan-4-one to incorporate alkynyl functionality and hence Raman spectroscopy showed the polymer had a distinct peak at 2128 cm-1. Following post-polymerisation modification of poly(lactic acid-co-3-chloro-2-hydroxypropanoic acid) copolymers, acrylate functionalised polymers were produced. The copolymers were shown to be capable of crosslinking poly(α-hydroxy acid) and poly(methyl methacrylate).

Natural fibers are gaining popularity as reinforcement materials for thermoset resins over the last two decades. Natural fibers are inexpensive, abundant, renewable and environmentally friendly. Kenaf fibers are one of the natural fibers that can potentially be used for reinforcing unsaturated polyester (UPE). As a polymer matrix, UPE enjoys a 40% market share of all the thermoset composites. This widespread application is due to many favorable characteristics including low cost, ease of cure at room temperature, ease of molding, a good balance of mechanical, electrical and chemical properties. One of the barriers for the full utilization of the kenaf fiber reinforced UPE composites, however, is the poor interfacial adhesion between the natural fibers and the UPE resins. The good interfacial adhesion between kenaf fibers and UPE matrix is essential for generating the desired properties of kenaf-UPE composites for most of the end applications. Use of a coupling agent is one of the most effective ways of improving the interfacial adhesion. In this study, six novel effective coupling agents were developed and investigated for kenaf-UPE composites: DIH-HEA, MFA, NMA, AESO-DIH, AESO-MDI, and AESO-PMDI. All the coupling agents were able to improve the interfacial adhesion between kanaf and UPE resins. The coupling agents were found to significantly enhance the flexural properties and water resistance of the kenaf-UPE composites. Fourier transform infrared spectroscopy (FTIR) confirmed all the coupling agents were covalently bonded onto kenaf fibers. Scanning electron microscopy (SEM) images of the composites revealed the improved interfacial adhesion between kanaf fibers and UPE resins. / Graduation date: 2013

Poly(butylene succinate) (PBSu), poly(2-methyl-1,3-propylene succinate) (PMPSu), and their two novel poly(butylene succinate-co-2-methyl-1,3-propylene succinate)s (PBMPSu 95/05 and PBMPSu 90/10) were synthesized by a two-stage esterification reaction. PBMPSu 95/05 and PBMPSu 90/10 were characterized as having 6.5 and 10.8 mol% 2-methyl-1,3-propylene succinate (MPS) units, respectively, by 1H NMR. These copolymers were characterized to be random from the 13C NMR spectra. In this study, the nonisothermal crystallization and thermal degradation behaviors of the polyesters were investigated via different approaches. A differential scanning calorimeter (DSC) and a polarized light microscope (PLM) were employed to investigate the nonisothermal crystallization of these copolyesters and neat PBSu. Morphology and the isothermal growth rates of spherulites under PLM experiments at three cooling rates of 1, 2.5 and 5 ¢XC/min were monitored and obtained by curve-fitting. These continuous rate data were analyzed with the Lauritzen-Hoffman equation. A transition of regime II ¡÷ III was found at 96.2, 83.5, and 77.9 ¢XC for PBSu, PBMPSu 95/05, and PBMPSu 90/10, respectively. DSC exothermic curves at five cooling rates of 1, 2.5, 5, 10 and 20 ¢XC/min show that almost all of the nonisothermal crystallization occurred in regime III. DSC data were analyzed using modified Avrami, Tobin, Ozawa, Mo, Friedman and Vyazovkin equations. All the results of PLM and DSC measurements reveal that incorporation of minor MPS units into PBSu markedly inhibits the crystallization of the resulting polymer. The nonisothermal crystallization behavior of these polyesters was also investigated using a Fourier-transform infrared spectrometer (FTIR) with an attenuated total reflection (ATR). The absorbance peaks of crystals for the £\ form (918, 955, and 1045 cm-1) of PBSu and PBMPSu copolyesters were observed by ATR-FTIR under nonisothermal crystallization. When these semicrystalline polyesters started to be solidified from the melt state, these characteristic absorption bands for PBSu and its copolyesters crystals have been detected. In this study, the thermal degradation mechanisms of PBSu, PMPSu, PBMPSu 95/05, and PBMPSu 90/10 were investigated using a thermogravimetric analyzer combined Fourier-transform infrared spectrometer (TGA-FTIR) and a pyrolysis-gas chromatography¡Vmass spectrometry (Py-GC-MS). The volatile products evolved from the thermal degradation of these two copolyesters were identified to be anhydride, ether, ester, alcohol, alkene, aldehyde, and CO2. FTIR spectra displayed that the main degradation products for these four polymers were anhydrides. Moreover, PBSu-rich PBMPSu copolymers exhibited the same thermal degradation mechanism as that of PBSu at lower thermal degradation temperatures (< 403 ºC) and as that of PMPSu at higher thermal degradation temperatures (> 403 ºC) by the TGA-FTIR analysis. The results of the TGA-FTIR analysis clearly demonstrates that the influence of MPS units on the thermal degradation process is gradually increased as the temperature increases for PBMPSu copolymers. The degradation mechanism of PBMPSu at lower thermal degradation temperatures and PBSu mainly follows the £]-hydrogen bond scission mechanism and the back-biting process from the polymer chains. Moreover, the degradation mechanism of PBMPSu at higher thermal degradation temperatures and PMPSu occurred mainly through the £]-hydrogen bond scission and secondarily through £\-hydrogen bond scission. Finally, the thermal stability and degradation kinetics of these polyesters were investigated using a TGA at heating rates of 1, 3, 5, and 10 ºC/min under dynamic nitrogen. The activation energies of thermal degradation in elective conversions were estimated using the Friedman and Ozawa methods. The results clearly demonstrated that the thermal stabilities of these PBMPSu copolyesters were slightly reduced with the incorporation of minor MPS units into PBSu. Two model-fitting methods of nth-order and autocatalysis nth-order reaction mechanisms were adopted to determine the mass loss function f(£\), the activation energy and the associated degradation parameters. The results revealed that the mechanism of autocatalysis nth-order fitted the experimental data much more closely than did the nth-order mechanism for PBSu, PMPSu and PBMPSu copolymers.

Thèse doctorat : Matériaux Polymères et Composites : Villeurbanne, INSA : 2004. / Titre provenant de l'écran-titre. Bibliogr. p. 185-193.

The aim of the dissertation is to investigate the dependencies of the structure of polyester multifilament yarn fabrics and their permeability to air on the fabric structure factors and to develop methods for designing air permeable fabrics.

Thesis (M.S.)--Rochester Institute of Technology, 1989. / Includes bibliographical references (leaves 131-133).

Thesis--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 235-246).