Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

With the emergence of novel and more effective drug therapies, increased importance is being placed upon the methods by which these drugs are being delivered to the body. In conventional drug delivery systems, there is very little control over the release of drug. The effective concentration at the target site can be achieved by intermittent administration of grossly excessive doses, which, often results in constantly, unpredictable variations in plasma concentrations, with the risk of reaching levels below or above the therapeutic range leading to marked side effects. A plethora of formulation strategies mainly based on polymeric/lipid nanoparticles, are described in literature. Even though these systems are therapeutically advantageous in comparison to conventional systems, they remain insensitive to the changing metabolic states of the body although the symptoms of most metabolic diseases follow a rhythmic pattern.A more appropriate and effective approach of managing some of these conditions lies in the chronotherapy. This approach allows for pulsed or self-regulated drug delivery which is adjusted to the staging of biological rhythms, since the onset of certain diseases exhibits strong circadian temporal dependence. In order to reach the objective of mimicking the biophysical and biochemical processes of pathological states, many innovations in material design for drug delivery systems (DDS) that are able to release the therapeutic payload-on-demand were done to release the therapeutic agent only when it is required, according to the physiological need. The development of multidisciplinary research teams has brought huge advantages in the design, fabrication and utilization of such smart systems, especially in the pharmaceutical field. Interestingly, numerous smart polymeric materials exhibit a response to a specific stimulus. A step further, the elaboration of purpose-built monomers can give rise to compounds with tunable sensitivities or multi-stimuli responsiveness. These smart polymers demonstrate an active responsiveness to environmental (or external) signals and change their physicochemical properties as designed (e.g. conformation, solubility, shape, charge or size). As far as the stimuli are concerned, they consist of physical (e.g. temperature, ultrasound, light, electricity, magnetic or mechanical stress), chemical (e.g. pH, ionic strength) and biological signals (e.g. enzymes, biomolecules). Due to the intrapersonal variabilities which may make internal stimuli hazardous, externally controlled systems rely on externally applied stimuli that are produced by stimuli-generating devices, which results in pulsed drug delivery. This type of delivery may be rapid and allows a transient release of a determined amount of drug within a short period of time immediately after a pre-determined off-release period. A novel strategy for the formation of multi-stimuli responsive materials endowed with pH, magnetic and light sensitivity was achieved. The approach relied on the incorporation of magnetic tetrahalogenoferrate(III) anions along a polymeric backbone based on poly(2-(N,N-dimethylamino) ethyl meth-acrylate) (PDMAEMA). Starting from the same PDMAEMA, quaternized pending amine groups with various halide derivatives gave rise to magnetic materials after anion metathesis. Measuring the magnetic susceptibility of these materials exhibited that the magnetic susceptibility increased as the substituted group size decreased (become smaller) which was apparently related to the steric hindrance around the ionic pendants. Additionally, a good correlation between the magnetic susceptibility and ferric content was found. Additional experimental and theoretical Raman analyses allowed the determination of the nature of the magnetic species constituting the materials. This strategy further offers the opportunity to tailor the magnetic response through partial ammonium salt formation. In order to merge the magnetic properties of ferric-based materials with another stimuli-responsive functionality, random copolymers containing DMAEMA (D) with diazobenzene (A) unit were prepared. So, three copolymers PDA were synthesized (with targeted D/A ratios 4/6 (PDA4), 6/4 (PDA6) and 8/2 (PDA8)). Meanwhile, different degrees of amine quaternization (10, 50 and 100 %) were applied, which led to the following polymeric salts PDAX/Y where X = 4, 6, 8 (referring to the percentage of the DMAEMA unit) and Y = 10, 50 and 100 (referring to the percentage of quaternized amine groups). Finally, the aforementioned materials were converted into magnetic polymers by anion exchange. As a result, magnetic responses correlated well with amount of iron oxide in these compounds and the amount of ionic pending groups along the backbone. Moreover, the remaining tertiary amines conferred pH sensitivity to the polymers whereas the diazobenzene units ensured light responsiveness through the well-established trans-to-cis isomerization.In order to functionalize these materials in the pharmaceutical field, an intelligent delivery system was prepared. Firstly, an attempt to formulate riboflavin-5’-phosphate sodium (RPS) loaded on PDA8 microspheres was made using double emulsion evaporation method. Meanwhile, prednisolone (PRD) microspheres were prepared using s/o/w emulsion technique. Subsequently, coating systems of cochineal red tablets were developed. These tablets were coated with polymer solution (using each of three types of copolymers: PDA8, PDA6, and PDA4) until the desired percentage of the coating was achieved (10, 15, and 20 % w/w). The cumulative release profiles of cochineal red tablets coated with PDA8, PDA6, and PDA4 showed a pH-sensitive release behavior. The release in the neutral media (pH ≈ 7.0) was very slow (less than 3 % after one hour). Then, after changing the pH to 1.2, an increase in the release of cochineal was observed. Furthermore, the cumulative release of cochineal red was at the highest value for the PDA8 and the lowest for PDA4 depending on the percentage of PDMAEMA moieties. Moreover, by increasing the percentage of the coating from (10, 15 to 20 % w/w), the cumulative release of cochineal decreased. Therefore, the copolymer PDAX can be used for controlling the release of drug by changing the pH value.Finally, the cochineal tablets coated with PDA6 (10 %) showed features of light sensitivity. The release of cochineal red from coated tablets was only due to the switching in the conformational trans/cis isomerization of azobenzene moieties upon irradiation, which was confirmed by comparing the release of coated tablets with uncoated tablets upon irradiation. / Doctorat en Sciences biomédicales et pharmaceutiques (Pharmacie) / info:eu-repo/semantics/nonPublished

Ce travail concerne la modification de surface de nanoparticules magnétiques (MNP) par des copolymères réactifs renfermant des cycles azlactone, aux fins de l’élaboration de nano-supports destinés à l’immobilisation de biomolécules. Trois stratégies basées sur des techniques de polymérisation radicalaire contrôlée ont été mises en œuvre.Dans la première, un copolymère poly(méthacrylate de poly(éthylène glycol)-stat-2-vinyl-4,4-diméthylazlactone) (poly(PEGMA-stat-VDM)) a été préparé par polymérisation radicalaire par transfert d’atome (ATRP) selon la technique « grafting from » à partir des MNP et utilisé pour la bioconjugaison de thymine peptide nucleic acid (PNA). La présence de l’écorce polymère et l’immobilisation du PNA ont été confirmées par différentes techniques complémentaires (FTIR, VSM).La deuxième stratégie est basée sur l’élaboration de MNP greffées pour la bioconjugaison de l’acide folique, via l’ARTP du PEGMA et de la VDM. L’analyse par microscopie électronique à transmission (TEM) a montré qu’après bioconjugaison les MNP possèdent une très bonne aptitude à la dispersion en milieu aqueux.La troisième stratégie met en œuvre la technique «grafting onto » de copolymères poly(oxyde d’éthylène)-bloc-poly(2-vinyl-4,4-dimethylazlactone) (PEO-b-PVDM) pour la préparation de nanosupports magnétiques recyclables. Des copolymères à blocs PEO-b-PVDM ont été préparés par la technique de polymérisation RAFT puis greffés sur des MNP fonctionnalisées amino-silane. Les analyses en TEM et par spectroscopie de corrélation de photons ont révélé l’aptitude à la dispersion aqueuse et à la formation de nanoclusters. Les clusters ainsi obtenus ont été utilisés en tant que nanosupports magnétiques recyclables pour l’adsorption d’anticorps. / We herein report the surface modification of magnetite nanoparticle (MNP) with copolymers containing active azlactone rings via a grafting ‘from’ and grafting ‘onto’ controlled radical polymerization (CRP) for use as a nano-solid support for immobilization with biomolecules. Three different approaches were presented as following. First, synthesis of poly(poly(ethylene glycol) methyl ether methacrylate-stat-2-vinyl-4,4-dimethylazlactone) (PEGMA-stat-VDM)-grafted MNP via a grafting ‘from’ atom transfer radical polymerization (ATRP) and its application as a platform for conjugating thymine peptide nucleic acid (PNA) monomer were presented. The presence of polymeric shell and the immobilization of thymine PNA on MNP core were confirmed by fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometry (VSM) techniques. The second strategy is based on the synthesis of MNP grafted with PEGMA and VDM via ATRP for conjugation with folic acid (FA). The existence of PEGMA and VDM in the structure was characterized by FTIR, TGA and VSM. After the FA conjugation, Transmission Electron Microscopy (TEM) results indicated that the FA-conjugated MNP having high VDM content exhibited good dispersibility in water.Third, the synthesis of MNP grafted with poly(ethylene oxide)-block-poly(2-vinyl-4,4-dimethylazlactone) (PEO-b-PVDM) block copolymer via a grafting ‘onto’ strategy and its application as recyclable magnetic nano-support for adsorption with antibody were studied. PEO-b-PVDM diblock copolymers were first synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization and then grafted onto amino-functionalized MNP. TEM images and photo correlation spectroscopy (PCS) indicated an improvement in the particle dispersibility in water after coating with the copolymers. The nanoclusters with PEO-b-PVDM copolymer coating were used as recyclable magnetic nano-supports for adsorption with antibody.

The synthesis of dipyridyl functionalized polysulfones with improved hydrophilicity, enhanced membrane morphology and excellent ATRP polymeric ligand properties was conducted by the following method: (a) the formation of lithiated polysulfone from unmodified polysulfone and the subsequent reaction with 2,2'-vinylidenedipyridine in tetrahydrofuran at -78 oC under argon atmosphere to afford the corresponding dipyridyl functionalized polysulfone. The stoichiometry of the reaction affects the degree of functionalization of the product. When equimolar amounts of 2,2'-vinylidenedipyridine are added to the lithiated polysulfone, the degree of functionalization obtained was 45%. However, the addition of 10% and 20% molar excess of 2,2'-vinylidenedipyridine to the corresponding lithiated polysulfone produced dipyridyl functionalized polysulfones with degrees of functionalization of 80% and 95%, respectively; and (b) the membranes obtained from unmodified polysulfone as well as dipyridyl functionalized polysulfones were characterized by atomic force microscopy, scanning electron microscopy, pure water permeation measurements and contact angle measurements. Amine chain end functionalized polystyrene and poly(methyl methacrylate) were prepared by Atom Transfer Radical Polymerization (ATRP) methods as follows: (a) •-Aminophenyl functionalized polystyrene was prepared in quantitative yields by ATRP methods using a new primary amine functionalized initiator adduct, formed in situ by the reaction of 1-(4-aminophenyl)-1-phenylethylene and (1-bromoethyl)benzene in the presence of copper (I) bromide/2,2'-bipyridyl as catalyst in diethyl ether at 110 oC, for the polymerization of styrene.(b) New •-bis(aminophenyl) and •,ω-tetrakis(aminophenyl) functionalized polymers were prepared in quantitative yields by the ATRP method using the following synthetic strategy: (i) the initiation of styrene polymerization with a new primary diamine functionalized initiator adduct, generated in situ by the reaction of stoichiometric amounts of 1,1-bis(4-aminophenyl)ethylene with (1-bromoethyl)benzene in the presence of copper (I) bromide/2,2'-bipyridyl as catalyst, afforded •-bis(aminophenyl) functionalized polystyrene; and (ii) •-bis(aminophenyl) functionalized poly(methyl methacrylate) was prepared by the ATRP method using the primary diamine functionalized initiator adduct as initiator for methyl methacrylate polymerization; and (iii) well defined •,ω-tetrakis(aminophenyl) functionalized polystyrene was prepared by the post ATRP chain end modification reaction of •-bis(aminophenyl) functionalized polystyrene with 1,1-bis(4-aminophenyl)-ethylene at the completion of the polymerization reaction. (c) Similarly, •-bis(4-dimethylaminophenyl) functionalized polystyrene was prepared by using a new tertiary diamine functionalized initiator adduct, formed in situ by treatment of equimolar amounts of 1,1-bis[(4-dimethylamino)phenyl]-ethylene with (1-bromoethyl)benzene in the presence of copper (I) bromide/2,2'-bipyridyl as the catalyst in diphenyl ether at 110 oC for the initiation of styrene polymerization by the ATRP method. Furthermore, the ATRP of methyl methacrylate, initiated by the new tertiary diamine functionalized initiator adduct, produced •-bis(4-dimethylaminophenyl) functionalized poly(methyl methacrylate). In addition, •,ω-tetrakis(4-dimethylaminophenyl) functionalized polystyrene was synthesized via a post ATRP chain end modification reaction of •-bis(4-dimethylaminophenyl) functionalized polystyrene with equimolar amounts of 1,1-bis[(4-dimethylamino)phenyl]ethylene at the completion of the polymerization process. vi Quantitative yields of the different amine functionalized polymers with predictable number average molecular weights (Mn = 1.3 x 103 – 16.4 x103 g/mol), narrow molecular weight distributions (Mw/Mn = 1.03 – 1.29) and controlled chain end functionality were obtained. Polymerization kinetics data was employed to determine the controlled/living character of each ATRP reaction leading to the formation of the different amine chain end functionalized polymers. The polymerization processes were monitored by gas chromatographic analyses. Polymerization kinetics measurements for all reactions show that the polymerizations follow first order rate kinetics with respect to monomer consumption. The number average molecular weight of the amine functionalized polymers increases linearly with percentage monomer conversion and polymers with narrow molecular weight distribution were obtained. The ATRP of styrene, catalyzed by a novel dipyridyl functionalized polysulfone/CuBr supported catalyst system, afforded well defined polystyrene with predictable number average molecular weight and narrow molecular weight distribution in a controlled/living free radical polymerization process. The substituted 1,1-diphenylethylene initiator precursor derivatives and the functionalized polymers were characterized by nuclear magnetic resonance spectrometry, fourier transform infrared spectroscopy, thin layer chromatography, column chromatography, size exclusion chromatography, non-aqueous titrations, differential scanning calorimetry and thermogravimetrical analysis. / Chemistry / M. Sc. (Chemistry)

L'objectif de ce travail fut d'intensifier des procédés de polymérisation radicalaire par transfert d'atomes (ATRP) du méthacrylate de 2-(dimétylamino)éthyle (DMAEAMA) au moyen de technologies de microréaction (microréacteurs, micromélangeurs) et de paramètres de procédé (géométrie du réacteur, température, pression ... ).L'impact du prémélange sur les caractéristiques d'un copolymère statistique du DMAEMA et du méthacrylate de benzyle synthétisé dans des microréacteurs hélicoïdaux (CT) fut étudié en utilisant des principes différents de micromélange: bilamination, multilamination interdigitale (!MM) et jet d'impact. Des caractéristiques bien mieux contrôlées ont été obtenues avec !'IMM et l'intensification du procédé (Pl) a été clairement démontrée encomparaison d'un réacteur fermé ; en effet des masses molaires et conversions plus élevées ainsi que de plus faibles indices de polymolécularité (PDI) ont été obtenus pour des temps de passage inférieurs. Pour la production de PMADAME linéaire, le PI a également été réalisé par augmentation de la température et de la pression (jusqu'à 1 OO bars). Toutefois de trop hautes températures se sont avérées préjudiciables notamment pour de longs temps de passage. L'effet de l'augmentation du taux de cisaillement (via la longueur du réacteur) ne fut bénéfique qu'en régime dilué à un stade précoce de la réaction lorsque les masses molaires sont encore faibles. Comparés aux CT, un mélange interne favorisé par une technique d'inversion de flux s'est révélé être une stratégie très efficace pour réduire davantage le PDI et obtenir des masses molaires et conversions plus élevées. Des polymères branchés synthétisés en microréacteurs à inversion de flux (CFI) par ATRP en présence d'inimère présentèrent une structure plus ramifiée soulignant ainsi la supériorité des CFI sur les CT et réacteurs fermés en termes de PDI et d'efficacité de branchement. Considérant les caractéristiques des CFI, l'augmentation d'échelle des microréacteurs fut considérée par accroissement de leur diamètre. La productivité du procédé a été augmentée d'un facteur 4 tout en gardant un bon contrôle sur les caractéristiques macromoléculaires. Ainsi fut-il démontré que l'inversion de flux est un moyen très efficace pour contrebalancer l'effet négatif d'une augmentation du diamètre du microréacteur. / The aim of this work was to intensify Atom Transfer Radical polymerization (ATRP) processes for the production of DMAEMA-based (co)polymers by relying on microreaction technology tools (microreactor, micromixers) and process parameters (reactor geometry, temperature, pressure ... ). Impact of premixing on macromolecular characteristics of P(DMAEMA-co-BzMA) synthesized in coiled tube (CT) microreactors was studied using different micromixing principles: bilamination, interdigital multilamination (IMM) and impact jet.Better controlled characteristics were obtained with !MM and process intensification (PI) was clearly demonstrated in comparison with batch mode as higher molecular weights, increased monomer conversions and lower polydispersity indices (PDI) were obtained for lower residence times. For the production of linear PDAEMA, PI was also achieved by application of elevated temperature and pressure (up to 100 bars). However, high temperature was found to be detrimental for long residence times. Effect of increased shear rate (i.e. reactor length) was found only beneficial in dilute regime at the early stage of the polymerization reaction when molecular weights are low. ln comparison with CT reactors, internal mixing promoted by flow inversion technique was found to be quite an effective strategy to reduce further PDI and obtain higher molecular weights and monomer conversions. Branched polymers synthesized by self condensing vinyl copolymerization (SCVCP) adapted to ATRP in tubular coil flow inverter (CFI) microreactors exhibited higher branched structure highlighting the superiority of CFI microreactor over CT and batch reactors in terms of PD! and branching efficiency. Finally, considering such features of CFI, attempt was made to scale-up microreactors by increasing their diameter. lt was found that process throughput can be increased by more than a factor of 4 while keeping a good control over macromolecular characteristics. Thus itwas demonstrated that flow inversion is quite effective to counter balance the detrimental effect of an increase in microreactor diameter.

In the frame of this thesis different calix[4]resorcin- and calix[4]pyrogallolarene derivatives were used as platform for the synthesis of novel star polymers and dendritic structures. The objectives of this work can be portrayed under the following points: First: Synthesis and modification of calix[4]resorcin- and calix[4]pyrogallolarenes with a varying number and varying type of functional sites and their precise characterization by modern NMR techniques and single crystal X-ray diffraction. Second: Synthesis of well-defined star polymers and dendrimers with different number of arms and accordingly dendrons, based on calix[4]resorcin- and calix[4]pyrogallolarenes, via convenient polymerization and generation growth reactions and analysis of the obtained products by different methods (MALDI-TOF-MS, SEC-RI and SEC-MALLS, NMR).

Controlled radical polymerization (CRP) can be viewed as the middle ground between living anionic polymerization (LAP) and conventional free radical polymerization (FRP). It combines the precise control over polymer structure offered by LAP, under a tolerant reaction condition similar to FRP. One of the most studied CRP is atom transfer radical polymerization (ATRP), with over 10,000 papers published since its introduction in 1995. Despite the numerous studies, knowledge on its fundamental mechanism is still lacking, as evident from the lack of expression for full MWD and polydispersity that account for termination reaction. Since termination is unavoidable in ATRP, the existing expressions give inaccurate predictions as dead chains accumulate. In this study, we derived expressions for full MWD at low conversion and for polydispersity. These expressions allow us to quantify and gain better understanding on the contribution of termination. In addition, the resulting polydispersity expression shows better agreement than the existing equation when correlated with experiment data. In addition to the aforementioned questions, there are also controversies regarding the kinetics of surface-initiated ATRP, with researchers divided into two schools of theories. We evaluated the validity of these theories by comparing their predictions to experimental trends. Both theories were found to be inadequate in explaining all the experimental observations, thus triggering an investigation of the graft density. Graft density is an important determining property for polymer brushes, yet little is known about what affects its final value. Through simulations, we investigated the effect of experiment factors on the grafting density. A decrease in the amount of deactivator is found to decrease the grafting density, which could be explained by an increase in the number of monomers added per activation cycle. This knowledge allows us to explain the conflicting experiment observations regarding the growth trends of polymer layers reported in the literatures. / Thesis / Doctor of Philosophy (PhD) / Polymer materials are used almost everywhere in our daily life from clothing to water bottle. This wide range of applications owes to the nearly infinite possible properties that polymer can possess. Different polymerization processes to synthesize polymers have their own weaknesses and strengths. Herein we investigated the fundamental mechanism of one of the currently most attractive polymerization systems, atom transfer radical polymerization (ATRP). This process allows the synthesis of polymers with precisely tailored chain microstructures, making it possible to create polymer with sophisticated properties. Using modeling approaches, we derived explicit expressions for determining chain properties, allowing detailed investigation of how various factors affect these properties. Through these investigations, we obtained better understanding on the mechanism of ATRP in solution and on surface. This knowledge is crucial in providing insight and guiding experimental designs for better control over the material properties.

No / Microcarrier cell culture systems provide an attractive alternative to the conventional monolayer cell culture for cell amplification, due to their high surface area-to-volume ratio. Unlike enzymatic methods for removing cells from microcarriers after cell culture, which can lead to irreversible damage of the cells, microcarriers which release cells by temperature adjustment have been developed. This was achieved by grafting a temperature-responsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), on the microcarrier surface. This review comprehensively presents various methods to prepare such thermo-responsive microcarriers based on PNIPAAm. These methods include the grafting-to technique, grafting-from technique, grafting-through technique, along with methods leading to PNIPAAm hydrogel beads, seeded polymerization, and non-covalent adsorption. The methods for controlling PNIPAAm grafting density, molecular weight and molecular architecture are also outlined. Further, the efficiency of cell attachment, proliferation and thermally-induced detachment of such thermo-responsive microcarriers is introduced and compared. (C) 2015 Elsevier Ltd. All rights reserved.

Η δυνατότητα να συνδυαστούν οι ιδιότητες οργανικών και ανόργανων συστατικών σε ένα μοναδικό νανοδομημένο υβριδικό υλικό αποτελεί μία σημαντική επιστημονική πρόκληση στο σχεδιασμό υλικών, τα οποία μπορούν να εμφανίζουν νέες βελτιωμένες ιδιότητες και να τύχουν προηγμένων εφαρμογών. Τα υβριδικά υλικά, γενικά, μπορούν να ταξινομηθούν σε δύο μεγάλες κατηγορίες: στην κατηγορία I (class I), όπου οι δύο φάσεις συνδυάζονται μέσω ασθενών αλληλεπιδράσεων, και στην κατηγορία II (class II), όπου οι δύο φάσεις είναι σταθερά συνδεδεμένες. Στην παρούσα εργασία διερευνήθηκε η δυνατότητα εφαρμογής νανοδομημένων υβριδικών υλικών ως ετερογενείς καταλύτες στη διεργασία παραγωγής βιοντίζελ από διαφόρων ειδών έλαια. Κατά τη διεργασία αυτή, η οποία καλείται μετεστεροποίηση ή μεθανόλυση, τριγλυκερίδια αντιδρούν με μια αλκοόλη παρουσία ισχυρού οξέος ή βάσης προς παραγωγή εστέρων και γλυκερίνης. Σε πρώτη φάση, εστιάσαμε στη σύνθεση και το χαρακτηρισμό class I και class II υβριδικών οργανικών/ανόργανων υλικών αποτελούμενων από έναν ανόργανο πυρήνα διοξειδίου του πυριτίου (silica), ο οποίος θα περιβάλλεται από πολυμερικές αλυσίδες. Έτσι, στην προσπάθεια σύνθεσης υβριδικών υλικών class I αξιοποιήθηκαν οι πιθανές αλληλεπιδράσεις καθαρών και αμινοτροποποιημένων νανοσωματιδίων διοξειδίου του πυριτίου με υδατοδιαλυτά συμπολυμερή P(SSΗ-co-MA) του στυρενοσουλφονικού οξέος (SSH), με το μηλεϊνικό οξύ (ΜΑ), τα οποία φέρουν τόσο καρβοξυλικές όσο και σουλφονικές ομάδες. Ως αποτέλεσμα του όξινου χαρακτήρα των πολυμερών, τα υβριδικά νανοσωματίδια θα μπορούσαν δυνητικά να χρησιμοποιηθούν ως όξινοι καταλύτες κατά την παραγωγή του βιοντίζελ. Στην προσπάθεια σύνθεσης class II υβριδικών υλικών αξιοποιήθηκε κυρίως ο πολυμερισμός ελευθέρων ριζών μέσω μεταφοράς ατόμου (ATRP), μονομερών όπως στυρενοσουλφονικό νάτριο (SSNa), Ν-ισοπροπυλακρυλαμίδιο (NIPAM) και 2-(διμεθυλαμινο)μεθακρυλικός αιθυλεστέρας (DMAEMA). Για την εκκίνηση του πολυμερισμού χρησιμοποιήθηκαν νανοσωματίδια silica χημικά τροποποιημένα με 3-αμινοπροπυλοτριαιθοξυσιλάνιο και ακολούθως με 2-χλωροπροπιονυλοχλωρίδιο. Εναλλακτικά, χρησιμοποιήθηκαν νανοσωματίδια silica χημικά τροποποιημένα με 3-χλωροπροπυλoτριαιθοξυσιλάνιο (ATRP πολυμερισμός), ή βινυλοτριμεθοξυσιλανιο (πολυμερισμός ελευθέρων ριζών, FRP). Ο χαρακτηρισμός των δειγμάτων κατά περίπτωση έγινε με φασματοσκοπία πυρηνικού μαγνητικού συντονισμού υδρογόνου (1H NMR), φασματοσκοπία υπερύθρου με μετασχηματισμό Fourier (FTIR), θερμοσταθμική ανάλυση (TGA) και τιτλοδότηση οξέος-βάσεως. Στο τελευταίο μέρος της εργασίας ελέγχθηκε η καταλυτική δράση κάποιων εκ των συντεθέντων υλικών στην αντίδραση μεθανόλυσης της τριοξικής γλυκερόλης, χρησιμοποιώντας την τεχνική 1H NMR. Διαπιστώθηκε πως τα αμινοτροποποιημένα νανοσωματιδία silica εμφανίζουν σημαντική καταλυτική δράση. Αντίθετα η ικανότητα των υβριδικών οργανικών/ανόργανων υλικών silica-NH2(B)/P(SSH50-co-MA50), silica-NH2(D)/P(SSH75-co-MA25), και silica-VTMS-PDMAEMA να δρουν ως όξινοι ή βασικοί καταλύτες της ίδιας αντίδρασης είναι πολύ περιορισμένη. / The possibility to combine the properties of organic and inorganic components in a unique nanostructured hybrid material is a major scientific challenge in designing novel materials exhibiting improved properties and finding advanced applications. Hybrid materials generally can be classified into two categories: class I, where the two phases are combined through weak interactions, and class II, where the two phases are covalently connected. The aim of the present study was to develop novel hybrid organic/inorganic nanomaterials, potentially applied as heterogeneous catalysts in the biodiesel production process. In this process, called transesterification or methanolysis, triglycerides from various oils react with an alcohol in the presence of a strong acid or base to produce the respective esters and glycerin. In the first part of this work, we focused on the synthesis and characterization of class I and class II hybrid organic/inorganic nanomaterials consisting of an inorganic silicon dioxide (silica) core and a polymer shell. Thus, for the class I hybrid materials we took advantage of the weak interactions between net or amino-functionalized silica nanoparticles and water-soluble P(SSH-co-MA) copolymers of styrene sulfonic acid (SSH), with maleic acid (MA), carrying both carboxyl and sulfonic groups. These hybrid nanoparticles could potentially be used as acidic catalysts in the production of biodiesel, as a consequence of the acidic nature of the polymer used. For the class II hybrid materials, we mostly applied atom transfer radical polymerization (ATRP) of monomers such as sodium styrene sulfonate (SSNa), N-isopropylacrylamide (NIPAM) and 2-(dimethylamino) ethyl methacrylate (DMAEMA). To initiate the polymerization, silica nanoparticles chemically modified with 3-aminopropyltriethoxysilane and subsequently with 2-chloropropionylchloride were used. Alternatively, we also used silica nanoparticles chemically modified with 3-chloropropyltriethoxysilane (ATRP polymerization), or vinyltrimethoxysilane (free radical polymerization, FRP). In all cases, the products were characterized through a combination of techniques, such as proton nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and acid-base titration. In the latter part of this work, the catalytic activity of some materials in the methanolysis process of glycerol triacetate was investigated, using the 1H NMR technique. It was found that the aminofunctionalized silica nanoparticles exhibit significant catalytic activity, whereas the ability of the hybrid materials silica-NH2(B)/P(SSH50-co-MA50), silica-NH2(D)/P(SSH75-co-MA25) and silica-VTMS-PDMAEMA to act as acidic or basic catalysts is very limited.

No description available.