<p>A novel strategy for synthesising segmented poly(urethane urea) (PUU) without using a chain extender but nevertheless with the opportunity to vary the hard segment content has been developed. The strategy is based on amine formation from isocyanate upon reaction with water. By adding a dissolved soft segment to an excess of diisocyanate followed by the addition of water in the gas phase, amines are formed <i>in situ</i>. Urea linkages are then formed when these amines react with the excess of isocyanate groups. The gas phase addition facilitates addition in a slow and continuous manner. The hard segment content can easily altered by varying the diisocyanate/soft segment ratio. Even though the strategy is shown to be applicable to different diisocyanates, the focus has been on the potentially biodegradable methyl-2,6-diisocyanatehexanoate (LDI) and 1.4-butanediisocyanate (BDI) and various well known biodegradable polyesters and polycarbonates. </p><p>All the synthesised materials exhibited pronounced phase separation and hydrogen bonding within the hard domains. However, a major increase in hydrogen bonding strength was seen when a symmetric diisocyanate was used instead of an asymmetric. Based on FTIR measurements, PUUs with BDI and a polydisperse hard segment can exhibit the same degree of phase separation and hydrogen bonding as the monodisperse product.</p><p>The elastic properties of this new group of PUUs were exceptional with an elongation at break from 1600% to almost 5000% and the elastic modulus could be varied from a few MPa up to a couple of hundreds. </p><p>Hydrolytic degradation was greater in the polyester-based than in the polycarbonate-based PUUs due to the more reactive ester bonds. Low mass loss but a considerable loss in molecular weight was seen in the polyester PUUs. The tensile strength decreased dramatically due to the loss of strain hardening.</p><p>An MTT seeding assay using human fibroblasts and an in vivo biocompatibility study were performed and no signs of cytotoxicity were seen and the inflammatory response was comparable to other inert polymers.</p><p>A biodegradable PUU with properties that can be tailored through an easy synthesis is here presented. </p>

Nowadays, polymer chemists undertake considerable efforts to achieve the preparation of new macromolecules and a perfect control over the macromolecular engineering, i.e. the mass parameters but also over the chain and end-group compositions, topology, etc… is definitively expected. In addition, more complex architectures, such as brush (co)polymers, jellyfish-like topologies…, are required to improve or drastically modify the physicochemical properties of the materials. As a direct consequence of the development of such complex molecular objects, sophisticated techniques are required for the in-depth characterization of the macromolecules, since the exact compositions and structures should be fully and unambiguously identified. Given the fact that the usual characterization tools such as Nuclear Magnetic Resonance (NMR) and Gel Permeation Chromatography (GPC) are extensively used, their abilities have been intensively developed to account for the increasing complexity and diversity of the targeted molecules. Nevertheless, all the usual techniques are averaging methodologies since they only provide pieces of information about the polymer mixture instead of affording data on the individual macromolecules. Since few decades, mass spectrometry (MS) has become as used as NMR and GPC for polymer characterization. In the context of large molecules analysis, MS undoubtedly underwent an impressive craze with the development of two modern ionization procedures, namely Electrospray Ionization (ESI) and Matrix-assisted Laser Desorption/Ionization (MALDI). Those ionization procedures permit the vaporization of macromolecules allowing the intact polymers to be analyzed without a too extensive level of degradation. ESI and MALDI are often considered as soft ionization methods since they offer the possibility to observe ions corresponding to the intact molecules. After their production in the ion source, ions corresponding to the polymer molecules can be mass analyzed by the mass spectrometer and important parameters such as the molecular weight distribution (Mn and Mw), polydispersity index (PDI), the nature of the monomer units and the end-groups can be derived from the measure of the mass-to-charge ratios of the produced ions. In the first part of the present thesis, we studied the MS behavior of different classes of polymers when submitted to ESI and MALDI ionizations. The investigations were devoted to the validation of MS as a truly reliable methodology for fragile polymers such as aliphatic polyesters for instance. In this context, a preliminary MS investigation on semi-telechelic polyethers revealed the importance of the source parameters for the characterization of polymers presenting fragile moieties. We also demonstrated the huge importance of the matrix molecule selection for the MALDI analyses of polymers. In particular, we introduced a new matrix for the MALDI measurements of electroconjugated polymers such as polythiophenes. After the study of the influence of the source parameters on the MS data, a complete study by single stage MS and double stage MS (MS/MS) on newly synthesized polylactides (PLA) was performed. The PLA samples were prepared following original procedures using carbene as catalyst. Finally, to achieve the MS study of PLA ions, we used ion mobility-mass spectrometry (IM-MS) experiments to obtained information on the tridimensional structure of the gas phase PLA ions. In particular, we put a special emphasis on the influence of the charge and size of the polymer chains on their gas-phase conformations. The conclusions derived from the MS/MS and IM-MS results were fully supported by theoretical calculations. In the second part of the thesis, the acquired MS experience was applied to the fine characterization of macromolecules presenting complex architectures obtained by two different polymerization procedures: (i) cobalt-mediated radical polymerization of inter alia acrylonitrile and vinyl acetate and (ii) ring-opening polymerization (ROP) of lactones using non-organometallic catalysts. In particular, mass spectrometry was used to tune the experimental conditions for the ROP of â-lactones using different phosphazenes as catalysts. As an ultimate conclusion, this work points to the very efficient synergy between polymer synthesis, mass spectrometry and theoretical calculations. We believe that this thesis paves the way for innumerable possibilities in the future.

A novel strategy for synthesising segmented poly(urethane urea) (PUU) without using a chain extender but nevertheless with the opportunity to vary the hard segment content has been developed. The strategy is based on amine formation from isocyanate upon reaction with water. By adding a dissolved soft segment to an excess of diisocyanate followed by the addition of water in the gas phase, amines are formed in situ. Urea linkages are then formed when these amines react with the excess of isocyanate groups. The gas phase addition facilitates addition in a slow and continuous manner. The hard segment content can easily altered by varying the diisocyanate/soft segment ratio. Even though the strategy is shown to be applicable to different diisocyanates, the focus has been on the potentially biodegradable methyl-2,6-diisocyanatehexanoate (LDI) and 1.4-butanediisocyanate (BDI) and various well known biodegradable polyesters and polycarbonates. All the synthesised materials exhibited pronounced phase separation and hydrogen bonding within the hard domains. However, a major increase in hydrogen bonding strength was seen when a symmetric diisocyanate was used instead of an asymmetric. Based on FTIR measurements, PUUs with BDI and a polydisperse hard segment can exhibit the same degree of phase separation and hydrogen bonding as the monodisperse product. The elastic properties of this new group of PUUs were exceptional with an elongation at break from 1600% to almost 5000% and the elastic modulus could be varied from a few MPa up to a couple of hundreds. Hydrolytic degradation was greater in the polyester-based than in the polycarbonate-based PUUs due to the more reactive ester bonds. Low mass loss but a considerable loss in molecular weight was seen in the polyester PUUs. The tensile strength decreased dramatically due to the loss of strain hardening. An MTT seeding assay using human fibroblasts and an in vivo biocompatibility study were performed and no signs of cytotoxicity were seen and the inflammatory response was comparable to other inert polymers. A biodegradable PUU with properties that can be tailored through an easy synthesis is here presented.

Flax fibers are often used as reinforcement for thermoset and thermoplastic to produce biocomposite products. These products exhibit numerous advantages such as good mechanical properties, low density, and biodegradability. Thermoplastics are usually reinforced with flax fiber using injection molding technology and limited research has been done on compression molded thermoplastic biocomposite. Therefore, commercial thermoplastic high density polyethylene (HDPE) and polypropylene (PP) were selected for developing compression molded flax reinforced biocomposites in this research project. The main goal of this research was to develop compression molded biocomposite board using Saskatchewan flax fiber and investigate the effect of flax fiber and processing parameters (molding temperature and molding pressure) on the properties of biocomposite. <p>The fiber was cleaned and chemically treated with alkaline and silane solution that modified the fiber surface. Chemical treatments significantly increased the mechanical properties due to better fiber-polymer interfacial adhesion and also reduced the water absorption characteristics. The silane treatment showed better results than alkaline treatment. Differential scanning calorimetry (DSC) test and scanning electron microscopy (SEM) test were performed to study the thermal and morphological properties of the untreated and chemically treated flax fiber. Flax fiber and thermoplastic resin was mixed using a single-screw extruder to ensure homogenous mixing. HDPE- and PP-based biocomposites were developed through compression molding with three different pretreated flax fiber (untreated, alkaline, silane treated fiber), three levels of fiber content, two levels of molding temperature and two levels of molding pressure. <p>Increase in fiber content increased composite color index, density, water absorption, tensile strength, Youngs modulus, bending strength, and flexural modulus. However for the HDPE composites, tensile and bending strength decreased after 20% flax fiber loading. For the PP composites the, tensile and bending strength decreased after 10% flax fiber loading. Analysis of variance (ANOVA) was performed to quantitatively show the significant effects of the process variables (molding temperature, pressure, and fiber content) and their interactions on the response variables (physical and mechanical properties of biocomposites). The duncan multiple range test (DMRT) was also performed to compare the treatment means. Superposition surface methodology was adapted for both HDPE and PP composites to determine the optimum values of process variables.

Flax fibers are often used as reinforcement for thermoset and thermoplastic to produce biocomposite products. These products exhibit numerous advantages such as good mechanical properties, low density, and biodegradability. Thermoplastics are usually reinforced with flax fiber using injection molding technology and limited research has been done on compression molded thermoplastic biocomposite. Therefore, commercial thermoplastic high density polyethylene (HDPE) and polypropylene (PP) were selected for developing compression molded flax reinforced biocomposites in this research project. The main goal of this research was to develop compression molded biocomposite board using Saskatchewan flax fiber and investigate the effect of flax fiber and processing parameters (molding temperature and molding pressure) on the properties of biocomposite. <p>The fiber was cleaned and chemically treated with alkaline and silane solution that modified the fiber surface. Chemical treatments significantly increased the mechanical properties due to better fiber-polymer interfacial adhesion and also reduced the water absorption characteristics. The silane treatment showed better results than alkaline treatment. Differential scanning calorimetry (DSC) test and scanning electron microscopy (SEM) test were performed to study the thermal and morphological properties of the untreated and chemically treated flax fiber. Flax fiber and thermoplastic resin was mixed using a single-screw extruder to ensure homogenous mixing. HDPE- and PP-based biocomposites were developed through compression molding with three different pretreated flax fiber (untreated, alkaline, silane treated fiber), three levels of fiber content, two levels of molding temperature and two levels of molding pressure. <p>Increase in fiber content increased composite color index, density, water absorption, tensile strength, Youngs modulus, bending strength, and flexural modulus. However for the HDPE composites, tensile and bending strength decreased after 20% flax fiber loading. For the PP composites the, tensile and bending strength decreased after 10% flax fiber loading. Analysis of variance (ANOVA) was performed to quantitatively show the significant effects of the process variables (molding temperature, pressure, and fiber content) and their interactions on the response variables (physical and mechanical properties of biocomposites). The duncan multiple range test (DMRT) was also performed to compare the treatment means. Superposition surface methodology was adapted for both HDPE and PP composites to determine the optimum values of process variables.

Commonly used thermoplastic biodegradable polymers are generally brittle and lack appreciable elasticity at physiological temperature and thereby fail to mimic the elastic nature of many human soft tissues such as blood vessels. Thus, there is a need for biomaterials which exhibit elasticity. Biodegradable elastomers are promising candidates whose elasticity more closely parallels that of soft tissues. In this research, we developed hybrid biodegradable elastomers comprised of organic and inorganic polymer components in a block copolymer system: poly(e-caprolactone) (PCL) and poly(dimethylsiloxane) (PDMS), respectively. A block structure maintains the distinct properties of the PCL and PDMS components. These elastomers may be useful for the tissue engineering of soft tissues as well as for shape memory polymer (SMP) devices. Tri-block macromers of the form PCLn-block-PDMSm-block-PCLn were developed to permit systematic variations to key features including: PDMS block length, PCL block length, PDMS:PCL ratio, and crosslink density. The macromer was capped with acrylating groups (AcO) to permit their photochemical cure to form elastomers. Thus, a series of biodegradable elastomers were prepared by photocrosslinking a series of macromers in which the PCL blocks varied (n = 5, 10, 20, 30, and 40) and the PDMS block was maintained (m = 37). All elastomers displayed hydrophobic surface properties and high thermal stability. These elastomers demonstrated systematic tuning of mechanical properties as a function of PCL block length or crosslink density. Notable was strains at break as high as 814% making them suitable for elastomeric bioapplications. Elastomers with a critical PCL block length (n = 30 or 40) exhibited shape memory properties. Shape memory polymers based on an organic-inorganic, photocurable silicon-containing polymer system is a first of its kind. This SMP demonstrated strain fixity of 100% and strain recovery near 100% after the third thermomechanical cycle. Transition from temporary to permanent shape was quite rapid (2 sec) and at temperatures near body temperature (60 degrees C). Lastly, porous analogues of the biodegradable elastomers were created using a novel porogen - salt leaching technique. Resulting porous elastomers were designed for tissue engineering scaffolds or shape memory foams.

In this study a microbial polyester, poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV), and its blends were wet or electrospun into fibrous scaffolds for tissue engineering. Wet spun fiber diameters were in the low micrometer range (10-50 &amp / #956 / m). The polymer concentration and the stirring rate affected the properties the most. The optimum concentration was determined as 15% (w/v). Electrospun fiber diameters, however, were thinner. Solution viscosity, potential, distance between the syringe tip and the collector, and polymer type affected the morphology and the thickness of beads formed on the fibers. Concentration was highly influential / as it increased from 5% to 15% (w/v) fiber diameter increased from 284 &plusmn / 133 nm to 2200 &plusmn / 716 nm. Increase in potential (from 20 to 50 kV) did not lead to the expected decrease in fiber diameter. The blends of PHBV8 with lactide-based v polymers (PLLA, P(L,DL-LA) and PLGA (50:50)) led to fibers with less beads and more uniform thickness. In vitro studies using human osteosarcoma cells (SaOs-2) revealed that wet spun fibers were unsuitable because the cells did not spread on them while all the electrospun scaffolds promoted cell growth and penetration. The surface porosities for PHBV10, PHBV15, PHBV-PLLA, PHBV-PLGA (50:50) and PHBV-P(L,DL)LA were 38.0&plusmn / 3.8, 40.1&plusmn / 8.5, 53.8&plusmn / 4.2, 50.0&plusmn / 4.2 and 30.8&plusmn / 2.7%, respectively. Surface modification with oxygen plasma treatment slightly improved the cell proliferation rates. Consequently, all scaffolds prepared by electrospinning revealed a significant potential for use in bone tissue engineering applications / PHBV-PLLA blend appeared to yield the best results.

Tissue engineering is an interdisciplinary field that seeks to address the needs by applying the principles of chemistry, biology and engineering for the development of viable substitutes that restore and maintain the function of human bone and cartilage tissues. In tissue engineering, scaffolds play an important role as temporary supports for the transplantation of specific cells and tissues. In this study, poly(ester-urethane)urea (PEUU) and poly(caprolactone) (PCL) scaffolds were fabricated. Scaffolds were characterized by SEM. Porosities of scaffolds vary from 67 % to 80 %. Controlled drug delivery systems release drugs at predetermined rates for extended periods. In this study / firstly poly(lactic-co-glycolicolide/tricalcium phosphate) (PLGA/TCP) and poly(L-lactide)/tricalcium phosphate (PLLA/TCP) composites loaded with Gentamicin or Vancomycin were prepared as controlled drug delivery systems for the local treatment of osteomyelitis. The release behavior of drugs were monitored by UV-VIS spectrometer. It was shown that, Vancomycin loaded samples released higher amounts of drug than the samples loaded with Gentamicin. Secondly, porous ceramic samples were coated with PLGA and PLLA and they were loaded with dexamethasone. The release behavior of samples were monitored by UV-VIS spectrometer.The cubic ceramics released higher amounts of dexamethasone than cylindrical ceramics. When the mechanical properties of porous ceramic samples were concerned, PLLA coated samples had better mechanical properties.

In the first part of the study, birchwood xylan-lignin film formation was studied. After film forming effect of lignin on pure birchwood xylan was demonstrated, the minimum lignin concentration necessary to form films was determined as 1.1% (lignin/xylan). So, it was determined that keeping about one percent lignin in xylan (w/w) was sufficient for film formation. Biodegradability of the lignin-birchwood xylan composite films was investigated enzymatically using 0.21 U / ml xylanase in an accelerated test. All the films containing lignin were hydrolyzed by xylanase showing biodegradability of the films. Colors of the birchwood xylan-lignin composite films containing different lignin concentrations were compared. Deviations of the color from the reference color were similar between the films. In the second part of the study, photocatalytic antimicrobial film production was investigated on wheat gluten-based films. In order to produce antimicrobial films, wheat gluten films were coated with a semiconductor, titanium dioxide (TiO2), applying different procedures. Coated films were illuminated and photocatalytical inactivation of Escherichia coli on films were determined by antimicrobial tests. The coating procedure in which titanium dioxide (TiO2) was produced from titanium tetraisopropoxide (TTIP) in aqueous-nitric acid and aqueous-hydrochloric acid solutions gave the best antimicrobial result but the films turned out to be deformed and brittle. Spreading TiO2 sol-gel on semi-dried wheat gluten films resulted in flexible and undeformed films having about 40% antimicrobial activity.

Mainly used food packaging materials are petro-chemical based polymers which present environmental problems since they are not biodegradable and ecologically sustainable. In this study, biodegradable biofilms are produced from xylan, extracted from cotton stalk which is an agricultural biowaste without nutritional value. Antimicrobial property was given to the biofilms with either titanium dioxide sol-gel coatings or titanium dioxide powder addition into the biofilm forming solutions. The antimicrobial activities of biofilms were tested against Escherichia coli. Among two different sol-gels coated and at different temperatures dried biofilms, BWX and CSX-50 biofilms treated at 120&deg / C and coated with SiO2/TiO2 showed 88&plusmn / 1% and 75&plusmn / 2% antimicrobial activities, respectively. Same samples treated at the same conditions but coated with non-SiO2 added TiO2 sol-gel yielded 63&plusmn / 3% and 63&plusmn / 2% antimicrobial activities, respectively after 2 h black light illumination. So, it was determined that the highest photocatalytic antimicrobial property was achieved with SiO2/TiO2 coated biofilms. Moreover different concentrations of TiO2 powder were integrated into xylan based biofilms and 100% photocatalytic inactivation was gathered at 5% (w/w) TiO2 addition achieved at both biofilms at the end of 90 min black light illumination. Biodegradability properties of the biofilms were investigated in soil burial test during 180 days and 10% (w/w) TiO2 powder added CSX-50 biofilms were recorded to be 91% biodegradable where non-powder added blank biofilms was found to be 95% biodegradable.