L’étude des assemblages supramoléculaires inspirés du vivant a permis de synthétiser les polyrotaxanes (PRs), dont les molécules cycliques portées par la chaine polymère ne sont pas liées de manière covalente et permet d’envisager de nouveaux biomatériaux. Le but ultime de cette étude est de synthétiser et de caractériser un PR à base de poly(dimethylsiloxane) et de cyclodextrines en faisant varier le nombre de molécules cycliques ainsi que leur taux de modification afin d’envisager des applications dans le domaine ophtalmique.La réalisation de la synthèse de ce nouveau type de PR couplant matériaux organiques et inorganiques a été réalisée en utilisant la chimie de couplage radicalaire mise au point au laboratoire, mais aussi, en utilisant une nouvelle méthode qui utilise une technologie très en vogue et industriellement intéressante, qui est l’alcoolyse assistée par micro-onde. Des caractérisations approfondies ont été réalisées, notamment la technique STD (RMN 600MHz) pour mettre en évidence la présence du polymère dans les macrocycles. Une étude détaillée des spectres de masses obtenus et une optimisation des conditions d’analyse par MALDI-TOF a permis de valider le mécanisme de la réaction de blocage en mettant en évidence pour la première fois les hautes masses de PR. Les voies de purification classiques des polymères ont été testées, démontrant les propriétés et les difficultés d’extraction de cette supramolécule. Les premiers PRs ont été finalement purifiés par chromatographie d’exclusion stérique préparative. La modification chimique des groupements hydroxyles des cyclodextrines des PRs a permis de les purifier et d’aborder l’étude des gels à base de PR. / Supramolecular assemblies’ studies inspired from biological systems permit to synthesize polyrotaxanes (PRs), which cyclic molecules borne by polymer chains are not linked covalently, and pave the way to new biomaterials. Ultimate goal of this study is the synthesis and the characterization of a polydimethylsiloxane and cyclodextrins based PR, modifying the number of cyclic molecules and their modification ratio for ophthalmic applications.The synthesis of this new kind of PR joining organic and inorganic materials was managed using radical course, already used in the laboratory for PR synthesis. A new method has been also used,with an innovating technology and industrially interesting; alcoholysis assisted by microwave. Deep characterizations have been managed using STD protocol (600MHz NMR) in order to evidence polymer presence inside the macrocycles. A detailed study of MALDI-TOF spectra andoptimization of analysis conditions permit to validate the chemical mechanism of the reaction, and evidenced for the first time this newly synthesized high molar mass PR. Classical ways of polymer purification were tested, demonstrating properties and difficulties to extract this supramolecule. First PRs were finally purified by preparative sterical exclusion chromatography. Chemical modification of hydroxyl groups of the cyclodextrins PRs permitted to purify them and approach PR gelation studies.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaf 169). Also available via the Internet.

Polyrotaxanes possess a molecular architecture resembling that of a wheel and axle: linear polymer chains are threaded by cyclic molecules with no covalent bonds linking the two species. One of two methods can be employed for the preparation of polyrotaxanes: a template method to guide threading or an in situ polymerization of monomers in the presence of cyclic molecules. The research described in this dissertation was divided into two distinct sections, which were devoted to each method of polyrotaxane preparation. The first step of synthesizing polyrotaxanes via the in situ polymerization method was to prepare a cyclic molecule. α,Ï -Dihydroxy-PDMS was cyclized and then efficiently purified by an anion-exchange resin to remove uncyclized, yet anionically charged, linear PDMS. The second part of this dissertation included examining polyrotaxanes created by the template-directed threading of α-CD onto polyoctene (PO). End-capped PO, which was unthreadable by α-CD, was synthesized from 1,9-decadiene and a monovinyl bulky compound by acyclic diene metathesis. PO and ecPO each were sonicated in aqueous solutions of α -CD; PO formed a white precipitate indicative of a rotaxanated polymer, but no precipitate formed by the addition of ecPO. These results provided evidence that PO had been included within the cavity of α-CD.

Multicomponent polymer systems comprised of two or more chemically different polymer moieties provide an effective way to attain the desired properties from a limited palette of commodity polymers. Variations in macromolecular topologies often result in unique and unusual properties leading to novel applications. This dissertation addresses the effect of topology on properties of two multicomponent polymers systems: blends and polyrotaxanes. Blends of cyclic and linear polymers were compared to their topological counterparts, polyrotaxanes, in which cyclic components are threaded onto the linear polymer chains. The first part of the dissertation focuses on the synthesis and purification of cyclic polymers derived from linear (polyoxyethylene) (POE). Cyclic POEs of different cycle sizes were synthesized and then purified from their linear byproducts by inclusion complexation with alpha-cyclodextrin. Polystyrene was threaded through the resulting cycles by in situ free radical polymerization of styrene monomer in the presence of an excess of POE cycles. A bulky free radical initiator was utilized to endcap the polystyrene molecule at the two ends to prevent dethreading of cyclic moieties. In the second part of the dissertation, phase behavior, morphology and dynamics of cyclic POE and polystyrene blends were compared to linear POE and polystyrene blends. Advanced solid-state NMR techniques and differential scanning calorimetry were employed for this purpose. Cyclic POE was found to be much more miscible with polystyrene when compared to linear POE, resulting in nanometer-sized domains and significantly reduced mobilities of the cyclic POE components in the blends. The unusual behavior of cyclic POE in the blends was attributed to topological as well as end-group effects with the topological effects being predominant. Polyrotaxanes composed of polystyrene and cyclic POE components exhibited cyclic POE domain sizes similar to that of physical blends. Cyclic POE dynamics in polyrotaxanes were considerably hindered, however, due to the threaded architecture. Surface segregation studies of cyclic POE/polystyrene blends and polyrotaxanes did not show segregation of POE to the surface because of the improved miscibility and the topological constraints present in these systems.

Polyrotaxanes are new polymers. Macrocyclic molecules, such as crown ethers, are threaded by linear or branched polymer chains. There is no covalent bond between the crown ethers and the polymer backbone. After the crown ethers are threaded onto the polymer backbone, both ends of the polymer can be blocked by large end groups. Polyrotaxanes are the topological isomers of blends of crown ethers and polymers. This architectural modification will produce interesting chemical and physical property changes in the polymer such as T_g and T_m, solubility, tensile strength, flexibility of the polymer. The study include crown ethers, blocking groups, poly(azomethine)s A and B, poly(azomethine)rotaxanes A and B synthesis, characterization, and property research. Crown ethers, 21-crown-7, 30-crown-10, 42-crown-14, and 60-crown-20, were synthesized from oligo(ethylene glycol)s and oligo(ethylene glycol) ditosylates with 22-40% yield. The high temperature synthetic method was developed so that the percentage yield of large crown and the small crowns in the same reaction could be controlled. A new purification method, low temperature recrystallization method was developed. The crown ethers properties included melting points, decomposition temperature, chemical shift on NMR spectra were studied. A series of blocking groups were synthesized and characterized. Several synthetic routes were studied, and the best route was the Grignard synthesis. The purification method was improved by recrystallization in cyclohexane or carbon tetrachloride. A by-product, bis(p-t-butylphenyl)methanol, was obtained. The new compounds, p-tri(p-t-butylphenyl)methylaniline and p-tri{(p-t-butylphenyl)methylphenol, were identified by ¹H NMR, FTIR, and elemental analysis. Poly(azomethine)s A and B are liquid crystalline polymers. They are rigid and strong. They have high T_m's and do not dissolve in general solvents. To check the reported information, the synthesis and characterization of these polymers were repeated. They precipitated from the reaction solution when their degree of polymerization reached 3-5. They were not thermally stable and were easily hydrolyzed in strong acids and in GPC column. In order to establish the effectiveness of the blocking groups, a monomeric rotaxane, a di(azomethine)rotaxane, was designed and synthesized. The compound was successfully isolated by multiple reprecipitations and recrystallizations. A 12% yield of this compound was obtained. The largest crown ether that the blocking group could block was 42-crown-14. / Master of Science

No description available.

Part I: Single sized, pure arylene ether macrocycles ranging from 30 to 60 atom ring sizes were synthesized in good yields (up to 83%) by the two component method under high dilution conditions. These macrocycles have unsymmetric structures containing sulfone/ketone or sulfone/phosphine oxide functional groups and have relatively low melting points. The melt ROP of the single sized macrocycles to form poly(arylene ether)s exhibits two stage characteristics: the first stage is very fast, driven by the large entropy difference between cyclics and linears; the second stage is very slow and is diffusion controlled due to the high viscosity created in the first stage reaction. The latter stage leads to incomplete polymerization at the low initiator concentrations (1-3 mol%). At high initiator concentrations (5-7 mol%), 100% conversion is reached due to improved initiator distribution in macrocycles; however, this reduces molecular weights of the polymers. The molecular weight is found to build up very rapidly, independent of conversion, reaction time and type of initiator. The ROP is initiated by CsF and alkali phenoxides. The efficiency of the alkali counterion is generally in the order of Cs+>K+>Na+, while a phenoxide initiator is more efficient than a fluoride initiator. It is also found that the Cs counterion leads to highest degree of crosslinking. The ROP of cyclic oligomeric mixtures is also reported for comparison; the study shows that the molecular weight depends on time and conversion, and that the conversion is sensitive to the content of linear impurities and the average ring size of cyclic mixtures. Part II: Polyrotaxanes are novel polymeric materials comprised of linear polymer molecules and threaded macrocycles with no covalent bond between the two components. With potential movements of the cyclic component and judicious combinations of the two components of different properties, these materials have brought interesting changes of physical properties, such as morphology, crystallinity, solubility, viscosity, etc. In this part of the dissertation, a new family of polyrotaxanes with poly(arylene ether)s as backbones and crown ethers as cyclic components are described. These include linear poly(arylene ether) based polyrotaxanes and hyperbranched poly(ether ether ketone) based polyrotaxanes; both are synthesized via aromatic nucleophilic substitution reactions. Preliminary studies show that these polymers exhibit great enhancement of solubility. The polymers form emulsions in water and methanol which are normally non-solvents for the poly(arylene ether) backbones. In some cases, they are even soluble in water to form a clear solution. The attempted syntheses of polyrotaxanes using aromatic macrocycles described in Part I was not successful, with no indication of threading. / Ph. D.

Les membranes nanofibreuses obtenues par électro-filage sont couramment utilisées pour diverses applications biomédicales telles que les pansements ou la régénération tissulaire, en raison de leur grande porosité et de leur morphologie mimant la structure des tissus humains. Au cours de cette thèse, nous avons étudié deux stratégies différentes, toutes deux basées sur l'utilisation de la cyclodextrine, pour fonctionnaliser ces membranes avec des molécules d'intérêt biologique. Dans un premier temps, des membranes nanofibreuses à base de complexe de polyélectrolyte ont été élaborées à partir de carboxyméthylcellulose et de chitosane pour des applications de type pansements. Du bleu de méthylène, connu pour son activité antibactérienne, a été incorporé dans les fibres, seul ou en tant que complexe d'inclusion avec la cyclodextrine. Les tests préliminaires sont très prometteurs quant à l’efficacité bactéricide de ces matériaux. Une seconde approche visant à élaborer des nanofibres fonctionnelles à base de poly(ε-caprolactone) (PCL) a également été étudiée. Le PCL étant très peu fonctionnalisable, des complexes d’inclusion entre ce polyester et les cyclodextrines, appelés pseudo-polyrotaxanes (pPR), ont été préparés. Des fibres cœur:peau ont ensuite été produites en ajoutant les pPR en surface des fibres. Afin de vérifier la réactivité et l’accessibilité des fonctions hydroxyles des cyclodextrines, un fluorophore a été greffé sur les fibres. Ce type de réaction ouvre de nouvelles voies de fonctionnalisation des fibres de PCL jusqu’alors inexplorées. / Electrospun nanofibrous membranes have proven to be ideal scaffolds for biomedical applications such as wound dressing and tissue engineering, mostly due to their high porosity and their morphology that mimics the structure of human tissues. In this work, we investigated two different strategies based on the use of cyclodextrins to functionalize these scaffolds with molecules of interest. Scaffolds made of polyelectrolyte complexes of carboxymethylcellulose and chitosan were first prepared by blend or coaxial electrospinning for wound dressing applications. Methylene blue, a molecule known to present antibiotic activity, was added, alone or as an inclusion complex with cyclodextrin, in the polymer solution before electrospinning. The preliminary biological assessment suggested that the fibrous membranes exhibited good antibacterial activity. In a second part, electrospun poly(ε-caprolactone) (PCL) scaffolds were prepared for tissue engineering applications. As this polyester can not easily be functionalized, PCL and cyclodextrins were combined to form pseudo-polyrotaxanes (pPRs) with various architectures. Core:shell PCL:pPR fibres were prepared by coaxial electrospinning. Fluorescein isothiocyanate was then grafted onto the fibre surface to prove the presence of available and reactive cyclodextrin hydoxyl groups at the surface of the PCL fibres. This reaction opens the way for innovative and versatile biofunctionalization of PCL.