Despite the degradability and biocompatibility of poly(α-hydroxy acids), their utility remains limited because their thermal and mechanical properties are inferior to those of commodity polyolefins, which can be attributed to the lack of side-chain functionality on the polyester backbone. Attempts to synthesize high-molecular-weight functionalized poly(α-hydroxy acids) from O-carboxyanhydrides have been hampered by scalability problems arising from the need for an external energy source such as light or electricity. Herein, an operationally simple, scalable method for synthesizing stereoregular, high-molecular-weight (>200 kDa) functionalized polyesters have been developed by means of controlled ring-opening polymerization of O-carboxyanhydrides mediated by a highly redox reactive manganese complex and a zinc-alkoxide. Mechanistic studies indicated that the ring-opening process proceeded via the Mn-mediated decarboxylation with alkoxy radical formation (Chapter 2). In addition to the polymerization, a two-step facile chemical recycling strategy for poly(α-hydroxy acids) was developed to achieve closed-loop life cycles (Chapter 3). Moreover, this synthetic strategy is not limited to preparing homopolymers and block copolymers but also to producing stereoblock and gradient copolymers (Chapter 4). In particular, the gradient copolymers exhibited better ductility and toughness than their corresponding homopolymers and block copolymers, highlighting the potential feasibility of functionalized polyesters as strong and resilient polymeric materials (Chapter 5). Next, an atom-economical, scalable method for block copolymerization of O-carboxyanhydrides and epoxides to prepare functionalized poly(ester-b-carbonates) with high molecular weights (>200 kDa) was identified, that uses a single Lewis acidic zinc complex at room temperature in the absence of pressurized CO2 (Chapter 6). Kinetic studies showed that the first stage of the process, ring-opening polymerization of the O-carboxyanhydrides, exhibited zero-order kinetics, suggesting that the polymerization rate was independent of monomer concentration, thus allowing for a sharp switch in mechanism without a tapering effect (Chapter 7). The obtained poly(ester-b-carbonates) showed better toughness than their corresponding homopolymers and outperformed some commodity polyolefins (Chapter 8). Exploring this new chemical space of poly(ester-b-carbonates) via stereosequence-controlled synthetic methods would be a critical step toward improving this promising class of functionalized sustainable polymers (Chapter 9). / Doctor of Philosophy / Poly(α-hydroxy acids) is an environmentally friendly alternative to petrochemical polyolefins due to their excellent degradability and biocompatibility. However, it is difficult to synthesize high-molecular-weight functionalized polyesters on a large scale due to the inefficient catalysts and the need for external energy, such as light and electricity. Herein, a highly reactive Mn/Zn catalytic system for controllable O-carboxyanhydrides (OCAs) polymerization has been designed. Compared with the previously reported catalytic system, this method can be used to produce low-cost, large-scale preparation of high molecular weight (>200 kDa) polyesters without the need for external energy sources (Chapter 2). In addition, our synthesized polyesters can be completely degraded under mild conditions, thereby achieving a circular economy in the polyester industry (Chapter 3). More importantly, our operationally simple synthetic method could afford polyesters with different compositions, such as homopolymers, block copolymers, stereoblock copolymers, and gradient copolymers (Chapter 4). In particular, the obtained gradient copolymer is tough and ductile that could compete with commercial polyolefins in terms of mechanical and thermal properties, such as low-density polyethylene (LDPE) (Chapter 5). Next, we developed a single Lewis acidic zinc complex to achieve the copolymerization of OCA and epoxide to synthesize poly(ester-b-carbonates), which enriches the class of degradable polymers (Chapter 6). Moreover, this copolymerization showed unique reaction kinetics that enabled the perfectly clean switching of the polymerization mechanism during chain propagation (Chapter 7). The obtained poly(ester-b-carbonates) showed better toughness than their corresponding homopolymers and outperformed some non-degradable plastics (Chapter 8). The exploration of novel degradable polymers by sequence-controlled polymerization to replace non-degradable polyolefin on the market will continue in the near future (Chapter 9).

No description available.

<p>This thesis describes syntheses and characterization of star-like amphiphilic block copolymers consisting of poly(ethylene glycol) (PEG) as the hydrophilic block,polycarbonate as the hydrophobic block and an amine-containing dendrimer as the core molecule. The macromolecules were synthesized by either a convergent or adivergent approach that includes tandem click reactions and ring opening polymerizations (ROP) of methyl trimethyl carbonates (MTC) with differentfunctionalities. The ROP of MTC monomers was performed using organocatalysts that allow mild reaction condition and reasonable molecular weight distribution(PDI~1.3). These synthetic approaches provide the resultant polymers with three different conformations, which are; mikto-arm type, comb-block with short PEGbrushes, and linear block with long PEG chain. The star-like polymers that were synthesized were all water soluble and most of them formed nano aggregates inwater. Different morphologies were observed in AFM study depending on the polymer conformation. Interestingly, some of them had indications pointing towards alower critical solution temperature.</p>

Summary of the thesis This works aims at reporting a novel strategy that combines controlled ring-opening polymerization of lactones initiated by a cyclic tin(IV) dialkoxide and intramolecular cyclization by photo-cross-linking of pendant unsaturations next to the propagating sites. No linear species is ever involved in the polymerization, which allows higher molecular weight macrocycles to be prepared with high efficiency. Moreover, the synthetic route is very flexible to the point where macrocyclic polyesters with more complex although well-defined architectures, such as tadpole-shaped and sun-shaped copolyesters, can be tailored. Synthesis of well-defined star- and eight-shaped polyesters and twin tadpole-shaped amphiphilic copolymers has also been explored by using a spirocyclic tin(IV) alkoxide as initiator.

Telechelic polyesters have successfully been synthesized with lipase-catalyzed polymerization. The produced telechelics had a high degree of di­functionalization, high purity (requiring little or no workup) and controlled degree of polymerization. The syntheses were performed in one-pot one-step reaction systems. The use of protection/deprotection chemistry was not necessary, since the lipase selectivity was utilized in the syntheses. Two different types of lipase-catalyzed polymerizations were applied – ring-opening polymerization and polycondensation. In ring-opening polymerization telechelics were produced by a combination of initiation, α-functionalization, and linking through termination, w-func­tionalization. In polycondensation different types of end-cappers were used to synthesize telechelics. Several exampels of functional groups were used for end-functionalization - epoxide, methacrylate and tetraallyls. Enzyme kinetic schemes describing the different functionalization met­hods of polyesters are presented and discussed. Stoichiometry and different reaction conditions have been studied to understand the effects these functions have on the final structure of the synthesized telechelics. Polyesters are classified as biodegradable, and can also be synthesized from materials that can be extracted or fermented from renewable sources like plants. Lipase-catalysts have several beneficial attributes, like high selectivity, they are renewable and biodegradable, are non-toxic and metal-free and can operate under mild reaction conditions. The focus of this thesis has been on lipase-catalyzed syntheses and characterization of the produced telechelics, in addition some materials have been produced. Some uses of telechelics are surface modification, materials for block co-polymers, functional films and biomedical applications. / QC20100726

This thesis describes syntheses and characterization of star-like amphiphilic block copolymers consisting of poly(ethylene glycol) (PEG) as the hydrophilic block,polycarbonate as the hydrophobic block and an amine-containing dendrimer as the core molecule. The macromolecules were synthesized by either a convergent or adivergent approach that includes tandem click reactions and ring opening polymerizations (ROP) of methyl trimethyl carbonates (MTC) with differentfunctionalities. The ROP of MTC monomers was performed using organocatalysts that allow mild reaction condition and reasonable molecular weight distribution(PDI~1.3). These synthetic approaches provide the resultant polymers with three different conformations, which are; mikto-arm type, comb-block with short PEGbrushes, and linear block with long PEG chain. The star-like polymers that were synthesized were all water soluble and most of them formed nano aggregates inwater. Different morphologies were observed in AFM study depending on the polymer conformation. Interestingly, some of them had indications pointing towards alower critical solution temperature.

The novel chelating ligand, Me[NOON]H2 (N,N'-((ethane-1,2-diylbis(oxy))-bis(ethane-2,1-diyl))- bis(2,6-dimethylaniline)), have been synthesized successfully and characterized by NMR. The lithium complexes of the aryl diamide ligand have also been synthesized by n-BuLi react with neutral ligand, Me[NOON]H2. And the lithium complexes is a ether adduct according to the 1H NMR. The lithium complex, Me[NOON]Li2(OEt2) react with Ti(OiPr)4 and TiCl4(THF)2 to form the NOON titanium alkoxide and dichloride complexes respectively, and they have been characterized by 1H NMR and X-ray diffraction. These NOON titanium complexes are expected to be a catalyst for the ring opening polymerization of lactide or caprolactone in the future. The tantalum complexes of diphenolate phosphine ligands have been synthesized and characterized successfully by NMR, X-ray diffraction, and elemental analysis. The tantalum complexes, [tBuOPO]2TaX (X=Me, Et, H) is produced by the reaction of [tBuOPO]2TaCl with Grignard reagent (MeMgBr and EtMgCl) and superhydride(LiHBEt3). These tantalum complexes will be applied in dinitrogen activation in the future work.

Synthesis of a polymer with benzoxazine units in the main chain backbone by a trifunctional phenol, a difunctional amine, and paraformaldehyde was achieved. Thermal, mechanical and spectroscopic characterization and the viscosity properties of the synthesized polymer were studied. In the first step of this study, a fast and feasible method for the synthesis of the benzoxazine precursors was developed since some methods mentioned in the literature about the synthesis of the benzoxazine derivatives last long time. The second step was to polymerize the benzoxazine precursors thermally. The curing of benzoxazine precursors was done via ring opening polymerization at 150 oC and a final polymerization was observed at about 250 oC. 1H NMR, 13C NMR and FT-IR spectroscopies revealed the characteristic peaks for the formation of benzoxazine ring. Among them, 13C NMR gave important clue on the formation of the benzoxazine. The thermal characterization of the benzoxazine precursors and the polymers indicated that the ring opening polymerization of these precursors started at around 110 oC and a final polymerization was about at 230 oC. Differential Scanning Calorimetry thermograms of the polybenzoxazine indicated a secondary transition at around 270 oC. An onset decomposition of the benzoxazine oligomers started around 100 oC in Thermal Gravimetric Analysis thermograms performed under N2 atmosphere and two major maximum weight losses were observed at 273 oC and 439 oC. However, polybenzoxazine showed a starting degradation at about 260 oC and the maximum weight loss temperatures were seen at 296 oC and 465 oC. Viscosity variation of the reaction mixture was studied by Ubbelohde Viscometer at 30 oC. Viscosity results indicated that the increase in the intrinsic viscosity of the reaction mixture till 50th minute and followed by a decrease due to possible branching and the intra-crosslinking of the benzoxazine oligomers. Mechanical properties of the polymer films, prepared by compression molding at 180 0C, were investigated. Test results showed that low tensile strength whereas comparatively high elongation.

The use of novel hyperbranched aminosilica (HAS) materials created through the ring-opening polymerization of aziridine from mesoporous silica supports was proposed for the adsorption of CO2 from dilute sources. The limits of the adsorptive performance of these adsorbents were investigated via the preparation of sets of materials with a range of aminopolymer loadings on several different silica supports with different pore space characteristics. Relationships were determined between the materials' amine loadings and the CO2 adsorption performance. Adsorbents with substantial remaining pore volume displayed universal adsorption kinetics when normalized by amine loading. However, materials with blocked pores displayed substantially slower adsorption kinetics due to hindered mass transfer. In both humid and dry conditions, the HAS adsorbent was found to have a surprisingly large CO2 capacity in light of the 250-fold reduction in CO2 partial pressure from 10% CO2 (flue gas application) to 400 ppm CO2 (air capture application). Finally, a new series of linear aminosilicas was created through the reaction of existing aminosilicas with N-protected-aziridines. Specifically, reaction of aminosilane-functionalized silicas with N-methylaziridine resulted in the linear growth of methylaminoethyl groups, effectively increasing the amine loading of the adsorbent by a stoichiometric amount of an additional amine per attached silane.

Αντικείμενο της παρούσας εργασίας ήταν η σύνθεση μιας σειράς τριπολυμερών και ενός πεντασυσταδικού συμπολυμερούς, καθώς και η μελέτη του τρόπου αυτό-οργάνωσής τους σε αραιά υδατικά διαλύματα στα οποία μεταβάλλεται το pH. Τα συμπολυμερή που συντέθηκαν είχαν δομικές μονάδες πολυ(βίνυλο-2-πυριδίνη) P2VP, πολυ(αιθυλενοξείδιο) PEO και πολύ(ε-καπρολακτόνη) PCL. Για την σύνθεση αυτών χρησιμοποιήθηκαν πρόδρομα συμπολυμερή δυο και τριών συστάδων, τα οποία είχαν συντεθεί μέσω ζωντανού ανιονικού πολυμερισμού, και στην συνέχεια με την μέθοδο του πολυμερισμού διάνοιξης δακτυλίου {Ring Opening Polymerization(ROP)} πραγματοποιήθηκε η προσθήκη της ε-CL. Η προσθήκη αυτή πραγματοποιήθηκε με αντίδραση του [Sn(Oct)2] με το ελεύθερο υδροξύλιο του αιθυλενοξειδίου δημιουργώντας έτσι ένα σύμπλοκο που αποτελεί τον εκκινητή, σύμφωνα με τον μηχανισμό εισαγωγής-σύμπλεξης. Ο χαρακτηρισμός των πολυμερών που συντέθηκαν πραγματοποιήθηκε μέσω της Χρωματογραφίας Αποκλεισμού Μεγεθών (SEC) και της Φασματοσκοπίας Πυρηνικού Μαγνητικού Συντονισμού (NMR). Στην συνέχεια προβήκαμε στη μελέτη αραιών υδατικών διαλυμάτων συναρτήσει του pH δυο πολυμερών από αυτά που συνθέσαμε, του πεντασυσταδικού PCL-PEO-P2VP-PEO-PCL και του τριπολυμερούς P2VP-PEO-PCL. Η μελέτη αυτή έγινε μέσω πειραμάτων σκέδασης του φωτός (στατική σκέδαση στις 900 και δυναμική σκέδαση) και μέσω της Ηλεκτρονικής Μικροσκοπίας Σάρωσης (SEM). Τα πολυμερή αυτά αποτελούνται από P2VP της οποίας η συμπεριφορά διαφοροποιείται με τις αλλαγές του pH μετατρέποντάς την σε έναν κατιονικό υδρόφιλο πολυηλεκτρολύτη σε χαμηλές τιμές αυτού, ενώ καθίσταται ηλεκτρικά ουδέτερη καθώς το pH αυξάνει, με αποτέλεσμα να γίνεται υδρόφοβη λόγω της αποπρωτονίωσής της. Η συμπεριφορά αυτή της P2VP σε συνδυασμό με τον υδρόφιλο χαρακτήρα του PEO και τον υδρόφοβο χαρακτήρα της PCL σε όλες τις τιμές του pH, οδήγησε στην δημιουργία πολυμοριακών συσσωματωμάτων σε ορισμένη περιοχή του pH. Μάλιστα το πεντασυσταδικό πολυμερές σχηματίζει σφαιρικά μικκύλια στην συγκεκριμένη περιοχή. Τέλος πρέπει να αναφερθεί ότι η πρωτοτυπία της παρούσας εργασίας εστιάζεται στο γεγονός ότι δεν έχουν μελετηθεί στο παρελθόν συμπολυμερή PCL με PEO και P2VP. Η ιδιότητα των συμπολυμερών που συνθέσαμε να σχηματίζουν πολυμοριακά συσσωματώματα και μικκύλια, ίσως αποβεί πολύ χρήσιμη σε πολλούς τομείς της βιομηχανίας και της βιοϊατρικής. / This project deals with the synthesis of triblock and pentablock copolymers, which were studied in aqueous solutions as a function of pH. The copolymers, which we synthesized, were Poly(2-vinil pyride)-Poly(ethylene oxide)-Poly(ε-caprolactone) (P2VP-PEO-PCL) and Poly(ε-caprolactone)-Poly(ethylene oxide)-Poly(2-vinil pyride)- Poly(ethylene oxide)-Poly(ε-caprolactone) (PCL-PEO-P2VP-PEO-PCL). The triblock and pentablock copolymers were synthesized via the method of Ring Opening Polymerization (ROP), using as initiator the stannous octoate [Sn(Oct)2]. For the triblock copolymers’ synthesis we used the diblock P2VP-PEO, which was synthesized via the method of living anionic polymerization, and for the pentablock copolymer’s synthesis we used the triblock PEO-P2VP-PEO, which was synthesized via the same method. The molecular weights and polydispersities were determined by Size Exclusion Chromatography and their compositions by 1H NMR. The properties of these copolymers were studied in aqueous solutions as a function of pH, by several experimental techniques such as static and dynamic light scattering and Scanning Electron Microscopy (SEM). The copolymers self organized in different nano structured self-assemblies which depend on the solution pH exhibiting therefore a stimuli responsive behavior.