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Polysaccharides and polypeptides are two types of biopolymers that are used in biomedical, industrial, and commercial applications. Both families of biopolymers are generally biodegradable, sustainable, and often exhibit low toxicity. Polysaccharides and polypeptides are polymers derived from natural resources and can be modified or synthesized through polymerization of various monomers. Polypeptides, specifically, are typically synthesized by polymerizing monomers such as N-carboxyanhydrides (NCAs) or N-thiocarboxyanhydrides (NTAs) to form homopolymers or random copolymers when using two different NCA/NTA monomers simultaneously. Chapter 1 begins with a background on polysaccharide and polypeptide-based materials with a focus on polysaccharide-block-polypeptide block copolymers. Previous work includes combining these two biopolymers through methods requiring post-polymerization purification. Chapter 1 introduces the field, challenges it faces, and how this work can help pose some solutions to these challenges. In this thesis, we utilized NTAs to synthesize polypeptides (Chapters 2 and 3) and as an H2S donor (Chapter 4). Combining polysaccharides and polypeptides into a block copolymer is useful for drug delivery and blend compatibilization applications. In Chapter 2, we synthesized a dextran-block-poly(benzyl glutamate) block copolymer that is amphiphilic; the differences in hydrophilicity among the two blocks allowed for nanostructures to form in situ in water, which we envision can be used for applications in drug delivery. Because nanostructures are formed in situ, this method negates the need for post-polymerization modification or purification, a requirement of many other nanostructure formation procedures. Coarse-grained molecular dynamics simulations were employed to shed light on interactions found on the molecular level. The interactions studied were then used to explain the nanostructures observed experimentally. In Chapter 3, we similarly formed another polysaccharide-block-polypeptide with the same poly(benzyl glutamate) polypeptide used in Chapter 2 but using ethyl cellulose for the polysaccharide. Poly(benzyl glutamate) is similar in structure to the commercial plastic polyethylene terephthalate (PET), a petroleum-based polymer that is not biodegradable. Therefore, this ethyl cellulose-block-poly(benzyl glutamate) BCP was used as compatibilizer to improve mixing in immiscible ethyl cellulose/PET blends. These blends afforded a more bio-derived alternative to PET/petroleum-based plastics. This chapter focuses on the synthetic efforts, a common challenge with polysaccharides, to produce this block copolymer as well as blend preparation and characterization. Chapter 4 utilizes an NTA as an H2S donor rather than a monomer for polymerization. H2S is an endogenous signaling gas that plays an important role in many organs and systems. In humans, H2S deficiency leads to a range of medical issues including hypertension, preeclampsia, liver diseases, and Alzheimer's disease. NTAs are advantageous for H2S delivery in the biomedical field due to their amino-acid origin and innocuous byproducts. The NTA donor in this work was attached to amylopectin via thiol-ene "click" photochemistry with the amino acid cysteine providing the thiol source on amylopectin. H2S release half-lives were in the range of several hours and depended on polymer molecular weight. Lastly, Chapter 5 summarizes the conclusions formed from these projects as well as potential future extensions from this work. / Doctor of Philosophy / Polysaccharides, long-chain sugars, and polypeptides, long-chain amino acid sequences, are two types of biopolymers that are used in biomedical, industrial, and other commercial applications. Both families of biopolymers are generally biodegradable, sustainable, and often exhibit low toxicity. Chapter 1 begins with a background on polysaccharide and polypeptide-based materials with a focus on polysaccharide-block-polypeptide block copolymers. Chapter 1 introduces the field, challenges it faces, and how this work can help pose some solutions to these challenges. In this thesis, we utilized N-thiocarboxyanhydrides (NTAs) to synthesize polypeptides (Chapters 2 and 3) and as an H2S donor (Chapter 4). In Chapter 2, we synthesized dextran-block-poly(benzyl glutamate), a polysaccharide-block-polypeptide block copolymer, that is both hydrophilic and hydrophobic. The differences in hydrophilicity among the two blocks allowed for nanostructures to form in situ in water, which we envision can be used for applications in drug delivery. Computational modeling was then employed to help explain the nanostructures observed experimentally. In Chapter 3, we similarly formed another type of polysaccharide-block-polypeptide. The polypeptide used is similar in structure to the commercial plastic polyethylene terephthalate (PET), a petroleum-based polyester that is not biodegradable. This block copolymer was then employed to improve mixing between blends of immiscible ethyl cellulose (polysaccharide) and PET. These blends afford a more bio-derived alternative to PET/petroleum-based plastics. This chapter focuses on the synthetic efforts, a common challenge with polysaccharides, to produce this block copolymer as well as blend preparation and characterization. Chapter 4 utilizes an NTA as an H2S donor rather than a monomer for polymerization. H2S is an endogenous signaling gas that plays an important signaling role in many organs and systems. In humans, H2S deficiency leads to a range of medical issues including hypertension, preeclampsia, liver diseases, and Alzheimer's disease. In this work, we synthesized a polymeric polysaccharide H2S donor with tunable release rates, which is beneficial for longer therapeutic time and increased patient compliance. Lastly, Chapter 5 summarizes the conclusions formed from these projects as well as potential future extensions from this work.

Well-defined central functionalized asymmetric tri-block copolymers (CFABC) were designed as a new type of polymer brush surface modifier, with a short central functionalized block that can form chemical bonds with a suitable substrate surface. A combination of sequential living anionic polymerization and polymer modification reactions were used for the synthesis of two CFABCs: PS-b-poly(4-hydroxystyrene)-b-PMMA and PS-b-poly(4-urethanopropyl triethoxysilylstyrene)-b-PMMA. GPC and NMR characterization indicated that the block copolymers possessed controlled molecular weights and narrow molecular weight distributions. CFABC polymer brushes were successfully prepared by chemically grafting PS-b-poly(4-urethanopropyl triethoxysilylstyrene)-b-PMMA onto silicon wafer surfaces. AFM, XPS and ellipsometry were used to confirm the CFABC polymer brush structures and thickness. The surface properties of CFABC polymer brush modified silicon wafer substrates subjected to different environmental parameters were studied. Reversibly switchable surface energies were observed when the polymer brush modified surfaces were exposed to solvents with different polarities. The phenomenon was attributed to the chain configuration auto-adjustment in the polymer brush systems. The same mechanism was also used to explain the enhanced adhesion capability between the modified surfaces and different polymer materials (PS and PMMA). Phase behaviors of polymer thin films on unmodified and CFABC polymer brush modified silicon wafer surfaces were also studied. For thin films of polymer blends, PS blend PS-co-PMMA, the effects of film thickness, chemical composition and temperature on the phase separation mechanism were investigated. The phase behavior in thin films of triblock copolymers with or without central functionalities were compared to reveal the role of the central functionalized groups in controlling film structures. Finally, the presence of CFABC polymer brush at the interface between PS-b-PMMA diblock copolymer thin film and silicon wafer substrate was found to decrease the characteristic lamellar thickness in the thin film. A mechanism of tilted chain configurations in the thin film due to the interactions with the CFABC polymer brushes was proposed. / Ph. D.

The major challenge of the research was to characterize and develop concepts for establishing structure/property relationships between the functionality of the polymer backbone, the states of water and the membrane transport properties. Most of the hydrocarbon based random copolymers reported in the literature show reduced proton conductivity at low water content. This was attributed to the formation of an isolated morphology. Over the last few years our group has synthesized thermally stable multiblock copolymers with varying chemical structures and compositions. Block copolymers consist of two or more incompatible polymers (i.e. blocks) that are chemically conjoined in the same chain. The transport properties of the multiblock copolymers showed a strong dependence on the morphology in contrast to the random copolymers. Irrespective of the nature of the backbone, the transport properties scaled with the block lengths of the copolymers. An increase in block length for a given series of block copolymer was associated with improved proton conduction, particularly under partially hydrated conditions compared to the random copolymers. The structure-property relationship of the proton conductivity and self-diffusion coefficient of water was obtained as a function of the volume fraction of water for all the random and block copolymers. At a given volume fraction, the block copolymers displayed both higher self-diffusion coefficients of water and proton conductivities relative to the random copolymers. This improvement in transport properties indicates the presence of desired and favorable morphology for the blocks. For DMFC applications, the block copolymers also showed low methanol permeability and high selectivity. The states of water in the copolymers were characterized using DSC and NMR relaxation techniques. At similar ionic contents, the free water concentration increased with increasing block lengths. The distribution of the states of water in the copolymers correlates to transport properties. This knowledge, coupled with the state of water experiments, transport measurements, and chemical structure of the copolymers provided a fundamental picture of how the chemical nature of a phase separated copolymer influences its transport properties. The experimental procedure involved impedance spectroscopy, DSC, TGA, FTIR, DMA, pulse gradient stimulated echo (PGSE) NMR, NMR relaxation experiments and various electrochemical fuel cell performance experiments. / Ph. D.

An examination of the ordering process of block copolymer microstructure with respect to concentration was performed. Specifically, the process of solution casting block copolymer films was studied using small-angle X-ray scattering (SAXS). A method for determining the volume fraction of ordered phase in solution as the system dried was developed and used to analyze the solution casting process in several different block copolymer films in the neutral solvent toluene; these polymers include poly(styrene-b-butadiene), poly(styrene-b-isoprene-b-styrene), poly(styrene-b-butadiene-b-styrene), and several poly(methyl methacrylate-b-butyl acrylate-b-methyl methacrylate) polymers with different block fractions. A method was also developed for studying different drying rates of these films at a constant temperature. Temperature quenches of poly(styrene-b-isoprene-b-styrene) were performed to evaluate the effect of concentration on ordering rate. In all cases studied, an ordering layer was observed where self-assembly was thermodynamically favorable. This layer steadily grew until it reached the bottom substrate, resulting in a two-step ordering process. In the case of the styrene/diene copolymers, a constant polymer concentration was observed in the ordering layer as it grew to encompass the entire film. Kinetic entrapment was observed in the case of the diblock copolymer, as the system with a medium drying rate with respect to the other two experienced faster kinetics than the other two systems. For the two triblock copolymers, it was found that similar kinetics were observed with respect to the ordering layer concentration, largely due to skinning on the surface allowing time for lower sections of the film to order more completely. In the acrylate copolymers studied, the kinetics were not able to be evaluated with respect to drying rate. This was due to domain compression that cause a disordering of ordered microstructure as solvent was removed. This disordering was attributed to interfacial disruption caused by the compression in the film. In addition, a significant decrease in domain spacing was observed to occur in the vertical direction as a result of compression in that direction and pinning of the film to the substrate in the horizontal direction. Finally, the Avrami kinetic model was fit to several concentration of styrene/isoprene triblock copolymers as they ordered after a temperature quench. A U-shaped curve was observed in the system, as a result of competition between chain mobility effects and thermodynamic effects that occur as polymer concentration increases away from the CODT. It was found that the Avrami exponent remained constant over all concentrations, and an empirical model was fit to find the various rate constants at each polymer concentration. / Ph. D. / Block copolymers are polymers consisting of two or more separate regions made up of different types of polymer chains. Under favorable conditions, these chains will phase separate into ordered structures, with different components being made up of each block. Because they are attached to each other, these structures are in the size range of 10-100nm. For example, a phase separated styrene/butadiene block copolymer of a particular composition can form cylindrical structures where the cylinders are made up of polystyrene, and the surrounding matrix is made up of polybutadiene. These structures can greatly influence the properties of block copolymers, allowing them to be used for everything from lithography to fuel cell membranes. A common method for the production of block copolymer films for applications such as fuel cell membranes is solution casting, where a polymer in a solvent is spread on a surface and the solvent is allowed to dry. The rate of this drying is a parameter that is not often taken into account when designing a process, despite the fact that it can have an effect on the resulting structure. Thus, insight into how the ordering of structures in a film during film drying can be used to improve processing of these materials. Using a computer model to determine the concentration profile of solvent throughout the film, and combining this with x-ray scattering data taken during drying at different rates, it was determined that there was a layer in which ordering could proceed, or ordering layer, that steadily grew as the film dried. This ordering layer continued to grow until it encompassed the entire film. In the diblock (styrene/butadiene) copolymer that was studied, it was found that a medium drying rate produced the fastest ordering. This drying condition balanced the driving force for ordering created by the increased drying rate and the ability of the chains to arrange, which would have been reduced upon faster drying. This effect was not seen in the two triblock copolymers (styrene/butadiene/styrene and styrene/isoprene/styrene). In the triblock copolymers, the ordering rate only depended on bulk ordering layer concentration. This was attributed to the presence of a skin on the surface, which slowed ordering throughout the films. In the case of the acrylate triblocks that were studied, the ordering rate trend could not be determined, as compression in the film due to the removal of solvent caused ordered structures to disorder after they formed. Finally, a model was fit to the styrene/isoprene/styrene at different solvent concentrations. The different concentrations produced a U-shaped curve with respect to ordering time, resulting again from competition between driving force and the ability of the chains to rearrange.

L'adsorption de protéine sur une surface artificielle solide est un phénomène fondamental qui détermine la réponse biologique d'un organisme vivant entrant dans n'importe quel matériel d'implant. Donc, l'adaptation de surfaces pour l'adsorption de protéine contrôlée est au coeur de beaucoup de champs de recherche d'aujourd'hui incluant la science de matériels et la biotechnologie. Dans ce contexte, les matériels sensibles de stimulus qui peuvent changer leurs propriétés comme une réponse à une petite monnaie dans leur environnement physicochimique attirent un grand intérêt comme ils permettent la création de surfaces avec des propriétés commutables pour le contrôle d'adsorption de protéine. Dans cette thèse, nous faisons un rapport sur la conception et l'élaboration de films minces sensibles de stimulus multi et de nanotubes. À cette fin, nous avons employé la couche-par-couche robuste et polyvalente… / Protein adsorption on a solid artificial surface is a fundamental phenomenon that determines the biological response of a living organism entering any implant material. Therefore, tailoring surfaces for controlled protein adsorption is at the heart of many of today's research fields including biotechnology and materials science. In this context, stimuli-responsive materials that are able to change their properties as a response to a small change in their physico-chemical environment are attracting a great interest as they allow the creation of surfaces with switchable properties for the control of protein adsorption. In this thesis, we report on the design and elaboration of multi stimuli-responsive thin films and nanotubes. For this purpose, we employed the robust and versatile layer-by-layer (LbL) assembly technique to incorporate block copolymers made of poly(acrylic acid) PAA and poly(N-isopropylacrylamide) PNIPAM with tunable and well-controlled block lengths. The combination of ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and infrared data reveal the possibility to build up (PAH/PAA-b-PNIPAM)n multilayers. The stimuli-responsive properties of these LbL films were examined by monitoring the adsorption of proteins by means of QCM-D and fluorescence measurements, while varying (i) temperature, (ii) pH, (iii) ionic strength, or (iv) a combination of the above parameters. It appears that all these stimuli strongly influence the amount of adsorbed proteins. In short, these new PNIPAM block copolymer-based LbL coatings are easy to build on substrates of various nature and geometry (including nanoporous membranes).

Stimuli responsive polymers (SRP) have attracted a lot of attention, due to their potential and promising applications in many fields, as protein-ligand recognition, on-off switches for modulated drug delivery or artificial organs. Poly(N-isopropylacrylamide) (PNIPAM) is one of the most widely studied polymers due to its lower critical solution temperature (LCST) at ~ 32° C in aqueous solution. Additionally, glycopolymers, where free sugar units are present, have potentially interesting applications especially in bio-recognition where sugars play an important role. In this work, our interest was focused on the synthesis of glycomonomers and its block- and random- copolymers with NIPAM. NIPAM homopolymers with an active chain transfer unit at the chain end could be prepared by RAFT. They were used as macro-chain transfer agents to prepare a variety of sugar containing responsive block copolymers from new glycomonomers by the monomer addition concept. The LCSTs of the aqueous solutions of the copolymers are affected strongly by the comonomer content, spacer chain length of the glycomonomer and the chain architecture of the copolymers. These polymers were coated on a solid substrate by spin coating and crosslinked by plasma immobilization. Characterization of the polymers was performed by nuclear magnetic resonance spectroscopy (NMR), ultraviolet (UV), dynamic light scattering (DLS, detection of aggregation behaviour) and gel permeation chromatography (GPC). Polymer films were investigated by ellipsometry, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) regarding their surface properties. Afterwards sulfation of sugar – OH groups was performed in order to obtain heparin like structure, as heparin exhibits numerous important biological activities, like good interaction with diverse proteins. Finally, affinity of the polymers (sulfated and non sulfated form) on a solid support to the endothelial cells was investigated.

Thin membranes with dense periodic arrays of nanoscopic voids were fabricated using the principles of supramolecular assembly and self-organization in polymers. Such nanoporous membranes can be used as templates for synthesis and patterning of various organic and inorganic materials. In this thesis 4-vinylpyridine fragments of polystyrene-block-poly(4-vinylpyridine) (PS-PVP) were associated with the molecules of two different low molar mass additives, 2-(4'-hydroxybenzeneazo)benzoic acid (HABA) and 3-n-pentadecyl phenol (PDP), via hydrogen bonds. The choice of an additive and a solvent is a key factor which influences the morphologies of the PS-PVP+HABA associates (supramolecular assemblies) in thin films. The reversible association via hydrogen bonds allows the amphiphilic molecules of PDP to phase segregate on the free air interface. Unlike, the molecules of HABA remain associated within cylindrical and lamellar domains formed by the PVP block. A solvent used for film deposition influences the orientation of PVP+HABA domains with respect to the confining interfaces. The films deposited from 1,4-dioxane – a good solvent for PS and a bad one for PVP+HABA – demonstrated the perpendicular orientation of PVP+HABA domains. Meanwhile, the preparation of films from a chloroform solution – a good solvent for both PS and PVP+HABA – led to the parallel alignment. The orientation was independent on the film thickness (within the studied range of 20–100 nm) and insensitive to the chemical nature of a substrate. The orientation of the domains was shown to switch upon exposure to vapors of the above mentioned solvents from the parallel to perpendicular orientation and vice versa. Moreover, the swelling of the films in solvent vapors resulted in the significant improvement of the domain ordering. Extraction of HABA with selective solvent transformed of PVP+HABA domains into channels with reactive PVP chains on the walls. The resulted membranes with the perpendicular oriented channels (the diameter about 8 nm, the inter-channel distance 24 nm) were used as a template for the creation of ordered arrays of nanodots from nickel, chromium and gold.

In the project, our purpose is the synthesis of segmented block copolymers using novel selectively reacting bi-functional coupling agents which have recently been developed by Jakisch at al. Both couplers have one oxazoline group that reacts with carboxylic groups and one oxazinone group that reacts with hydroxyl or amino groups. It was intended to synthesize segmented block copolymers by combination of amino or hydroxyl terminated pre-polymers and carboxylic terminated chain extenders using the above mentioned coupling agents. Several prepolymers were selected such as hydroxyl terminated liquid polybutadiene (PBD-OH), hydroxyl terminated liquid natural rubber (LNR) and amino terminated liquid polybutadiene-b-acrylonitrile (PBAN) and poly(propylene glycol)-bis(2-aminopropylether) (PPO). They were selected as soft polymer segments in the segmented block copolymers aimed for. Additionally, various di-carboxylic acids were chosen as chain extenders. The resulting block copolymers are phase separated materials with a crystalline hard phase. This was demonstrated by two glass transition temperatures corresponding to the soft and hard segments and various melting regions of the hard chain extenders. For these new materials, the controlled phase separation morphology in nano-size was evidenced by TEM. A hard domain size of about 2-5 nm surrounded by a soft matrix was observed on the micro-photographs. This is consistent with the low hard segment content and the segment alternation (A-B)n in multi-block copolymers. With respect to the mechanical properties, a relationship between tensile strength and the average molar mass of the block copolymers was found out. The samples behave as rubber-like thermoplastic materials. The tensile properties depend on the degree of polymerization and the polymer distribution. The reinforcement ability of the hard domains in a physical network was achieved as expected. As a consequence, the obtained final products have mechanical properties like a typical elastomeric material.