<p>The use of degradable biomedical materials has during the past decades indeed modernized medical science, finding applications in e.g. tissue engineering and drug delivery. The key question is to adapt the material with respect to mechanical properties, surface characteristics and degradation profile to suit the specific application. Degradation products are generally considered non-toxic and they are excreted from the human body. However, large amounts of hydroxy acids may induce a pH decrease and a subsequent inflammatory response at the implantation site.</p><p>In this study, macromolecular design and a combination of cross-linking and adjusted hydrophilicity are utilized as tools to control and tailor degradation rate and subsequent release of degradation products from biomedical polyester-ethers. A series of different homo- and copolymers of -caprolactone (CL) and 1,5-dioxepan-2-one (DXO) were synthesized and their hydrolytic degradation was monitored in phosphate buffer solution at pH 7.4 and 37 °C for up to 546 days. The various materials comprised linear DXO/CL triblock and multiblock copolymers, PCL linear homopolymer and porous structure, and random cross-linked homo- and copolymers of CL/DXO using 2,2’-bis-(ε-caprolactone-4-yl) propane (BCP) as a cross-linking agent.</p><p>The results showed that macromolecular engineering and controlled hydrophilicity of cross-linked networks were useful implements for customizing the release rate of acidic degradation products in order to prevent the formation of local acidic environments and thereby reduce the risk of inflammatory responses in the body.</p>

Significant progress has been made in the field of living/controlled polymerizations over the past decades. The advance in living/controlled polymerizations has enabled the design and tailoring of structurally well-defined macromolecules with complex architectures. Polymers with complex molecular architectures often exhibit properties that are distinct from their linear counterparts. This dissertation aims to exploit the unique properties of rationally designed complex polymer structures to address the challenges related to the preparation of polymeric and hybrid nanostructures, as well as to explore and fundamentally understand the morphology or properties of new macromolecular architecture. The studies presented in this dissertation addressed the challenges (e.g., poor size uniformity, limited accessible compositions) in the formation of polymeric or hybrid nanostructured materials based on the self-assembled polymer micelle approach via rational design of complex spherical star polymer architectures with tailor-made compositions and functionalities through living/controlled polymerizations, as well as investigated the morphology and self-assembly behavior of a newly designed cyclic brush copolymer grafted with P3HT as the side chains. The novel and robust star macromolecular templating strategy developed in this study will open the access to a wide range of structurally and functionally well-defined polymeric and hybrid nanostructured materials with tailor-made compositions and shapes. The findings presented in the work will provide fundamental insights or practical strategies for rational design of polymers with complex macromolecular architectures via living/controlled polymerizations.

There has been considerable interest over the past decade in the preparation and applications of copolymers of ethylene with functionalized polar olefins. Such copolymers are expected to exhibit a variety of potentially very useful properties such as paintability, adhesion to polar surfaces, and miscibility with polar polymers such as polyesters and polyamides, but there are limitations associated with producing copolymers of ethylene with polar monomers via Ziegler-Natta processes. Many classes of Ziegler-Natta catalysts, especially those of the early transition metals (Ti and Zr), are highly oxophilic and hence are poisoned by functionalities such as -OH groups. This problem can in principle be alleviated by implementing the use of protecting groups such as –OSiMe3, which has previously been shown to be an effective masking agent both for steric reasons and because O-Si π bonding decreases the Lewis basicity of the ether oxygen atom. One can also utilize late transition metal catalyst systems, which are generally less Lewis acidic and therefore less susceptible to poisoning by functional groups. In this thesis the results of an investigation of the copolymerization of ethylene with CH2=CH(CH2)nOSiMe3 (n = 1, 2, 8) will be presented. We have been using MAO activated dibromo[1,4-bis(2,6-diisopropylphenyl)acenaphthenediimine]nickel(II) (D) as catalyst, as this system is known to produce reasonably linear polyethylene and hence may be expected to produce essentially LLDPE containing –(CH2)nOSiMe3 branches. The latter can be hydrolyzed to give polar –(CH2)nOH branches. / Thesis (Master, Chemistry) -- Queen's University, 2009-01-31 14:43:09.93

No description available.

An AB2 monomer, dimethyl 5-(2-hydroxyethoxy)isophthalate was prepared on a scale of 3kg. It was successfully polymerised in the melt and the influence of reaction conditions and catalysts was studied. Structural and physical characterisation of these materials was performed using variety of analytical techniques, including SEC and MALDI-TOF MS. The polymerisations yielded high molecular weight materials with a broad polydispersity. All polymers were cyclised, the proportion of cyclised species increased with time, generally until complete cyclisation was achieved. The polymerisation process conditions were varied and a reaction protocol establishing a degree of reproducibility was achieved. Catalysts were found to promote polycondensation, cyclisation and transesterification reactions. The trends of increase in molecular weights were similar to those observed in uncatalysed reactions. Catalysts based on divalent metals showed a higher activity compared to those based on tri- and tetravalent metals. Qualitatively alcoholysis and cyclisation occurred at about the same rate whether catalysed or uncatalysed and ester-ester interchange was significantly slower under all circumstances. There were only relatively small differences between the effects of the catalysts investigated, apart from Vertec 400AC, which caused very fast reaction and yielded an insoluble product of unidentified structure. A new route to the synthesis of an A(_2)B monomer, methyl 3,5-bis(2-hydroxyethoxy)benzoate, was also reported. The monomer was synthesised on a 10g scale and successfully polymerised. The polymer samples were functionalised with acetoxy groups and characterised by SEC and MALDI-TOF MS. Evidences for the presence of polycondensation, cyclisation and ester-ester interchange reactions were observed. Growth in molecular weights and in cyclisation for poly(methyl 3,5-bis(2-hydroxyethoxy)benzoate)s was faster than that for poly(dimethyl 5-(2-hydroxyethoxy)isophthalate)s prepared under same conditions.

Lignosulphonates are by‐products from the sulphite pulping process for the manufacture ofspecialty dissolving pulps and paper. During the liberation of the cellulose, the lignin isfractionated and solubilised through covalent addition of sulphonic acid groups at variouspositions in the structure. The formed sulphonated lignin, lignosulphonate is then furtherisolated and refined. The amphiphilic nature of lignosulphonates has enabled them to be used as additives to varioussuspensions to improve their dispersion and stability. The by far largest utilisation oflignosulphonates is as dispersants in concrete. Here, lignosulphonates act by dispersing cementparticles to prevent flocculation, un‐even particle distribution and reduced strengthdevelopment. The dispersion is achieved through steric and electrostatic repulsion of the cementparticles by the lignosulphonate polymer. This behaviour is intimately linked with the overallsize and amount of charged groups in the dispersing polymer. Traditional modifications oflignosulphonates have been limited to removal of sugars, filtration and fractionation. Thesemodifications are not sufficient for utilisation of lignosulphonates in high‐strength concrete. Heresynthetic dispersants and superplasticisers are used which are considerably more efficient evenat low dosages. To compete with these, additional modifications of lignosulphonates are likely tobe necessary. The molecular weight and functional group composition have been identified anddescribed as the most interesting parameters that can be modified. Currently, no suitable method exists to increase the molecular weight of lignosulphonates.Oxidation by the natural radical initiating enzyme laccase is an interesting tool to achieve suchmodifications. In this thesis several aspects of the mechanism through which this enzyme reactswith lignin and lignosulphonate structures have been elucidated through model compoundstudies. Further studies showed that laccase alone was a highly efficient tool for increasing themolecular weight of commercial lignosulphonates at low dosages and in short incubation times.Immobilisation of the laccase to a solid support to enable re‐utilisation was also investigated. Modification of functional group composition of lignosulphonates was achieved throughozonolysis and the Fenton’s reagent, a mixture of hydrogen peroxide and iron(II)acetate.Introduction of charged carboxylic groups was achieved through opening of the benzyl rings oflignosulphonates. It was found that a two‐stage process consisting of laccase oxidation followedby ozonolysis was an efficient technique to create a polymer enriched with carboxylic acidgroups with a sufficient molecular size. Oxidation by the Fenton’s reagent was shown to yield similar modifications as the combinedlaccase/ozonolysis treatment albeit with less pronounced results but with a large level of controlthrough variation of a number of reaction parameters. The Fenton’s reagent can therefore be aninteresting alternative to the aforementioned two‐stage treatment. These modifications are interesting for large‐scale applications not only because of theirsimplicity in terms of reaction parameters but also because of the ubiquity of the used enzymeand the chemicals in the pulp and paper industry. / QC 20110427

Polyethoxy-silanes are of considerable commercial interest in Brake Fluid formulations. The synthesis of a polymeric Brake Fluid base material, known industrially as Silane Racing Fluid (SRF) isreported, along with the preparation of a series of reference compounds. The fluid contained a mixture of polymeric glycol silanes with theformula andn = 0,1,2, etc. The molecular weights of these compounds weredistributed over a range from 164 to at least 1200. The referencecompounds synthesised were monomeric, with the structure MenSi(OR1 where n = 0,1 ,2 and -OR1 represents varying chain length glycol units, including. The compounds prepared were characterised using a variety of analytical techniques including Si NMR, Size Exclusion Chromatography (SEC) and Mass Spectrometry. The partial hydrolysis of SRF and several of the reference compounds, including is also described. Reactions were monitored qualitatively by Si NMR spectroscopy. Molar ratios of water to si lane were in the range of 2:1 to ~14:1. The technique allowed the identification 'in situ' of labile partial hydrolysis products, before they condensed to more stable siloxanes. In further studies the hydrolysis of several polyethoxy-silanes is reported, in dilute aqueous solution. The reactions were monitored quantitatively by two techniques, ultra-violet spectrophotometry and an extraction method. In the spectrophotometric experiment the hydrolysis of was studied. Pseudo first order kinetics was observed, which was found to be specific Acid/Base catalysed over the pH range studied (4-9). The extraction method relied upon n-hexane specifically extracting the starting material. An Infra-red spectrometer was used to determine the quantity of starting material present after extraction, by monitoring the Si-O-C stretching frequency ~1100 cm. Pseudo first order rate constants were obtained for the hydrolysis of and (0Me)3 . The results indicated specific Acid/Base catalysis over the pH range studied (5-9). The kinetic results described are in good agreement with recent studies reported using Trialkoxysilanes.

No description available.

Various technical lignins, e.g. industrial Softwood Kraft lignin (SKL), are now largely available while they are generally underutilized due to their heterogeneous and complicated structures and/or the poor properties. SKL has here been modified by physical, chemical and biochemical methods for preparation of lignin microspheres, phenol substitution in phenol-formaldehyde (PF) resin preparation and preparation of highly efficient fertilizers. Physically, a brand-new slow and exhaustive solution evaporation process was developed for the highly efficient and productive preparation of microsphere structures. Highly homogenous SKL hollow microspheres were obtained and for the first time, urea encapsulating SKL microspheres were similarly prepared which could be an excellent controlled release urea fertilizer. Chemically, Mannich reaction (one type of amination) was deeply investigated by including for the first time an LC-MS study of vanillin reaction, resulting in the establishment of a fast and reliable lignin reactivity (for phenol substation in PF resin) quantification method. In addition, SKL was functionalized using the Mannich reaction or esterification, leading to an improved hydrophobicity and compatibility for blending with polylactic acid (PLA). Using dip-coating technique for the first time, PLA-functionalised SKL-coated urea pellets were prepared, leading expectedly to a highly efficient urea fertilizer with simultaneous controlled- and slow- release and biological stabilization effects. Biochemically, SKL was demethylated via incubation with different laccase-mediator combinations, which in principle will increase its reactivity in PF resin preparation. However, polymerization occurred which would decrease the reactivity.  The overall effects need to be further investigated. Conclusively, broader or larger scale SKL applications can expectedly be realized after the development of SKL modifications tailored towards the optimum desired structures and properties. / <p>QC 170912</p>

Biotemplating is the art of using a biological structure as a scaffold which is decorated with a functional material. In this fashion the structures will gain new functionalities and biotemplating offers a simple route of mass-producing mesoscopic material with new interesting properties. Biological structures are abundant and come in a great variety of elaborate and due to their natural origin they could be more suitable for interaction with biological systems than wholly synthetic materials. Conducting polymers are a novel class of material which was developed just 40 years ago and are well suited for interaction with biological material due to their organic composition. Furthermore the electronic properties of the conducting polymers can be tuned giving rise to dynamic control of the behavior of the material. Self-assembly processes are interesting since they do not require complicated or energy demanding processing conditions. This is particularly important as most biological materials are unstable at elevated temperatures or harsh environments. The main aim of this thesis is to show the possibility of using self-assembly to decorate a conducting polymer onto various biotemplates. Due to the intrinsic variety in charge, size and structure between the available natural scaffolds it is difficult, if not impossible, to find a universal method. In this thesis we show how biotemplating can be used to create new hybrid materials by self-assembling a conducting polymer with biological structures based on DNA, protein, lipids and cellulose, and in this fashion create material with novel optical and electronic properties.