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Green reinforcement in polymer systems have shown great promise in reducing cost, negative environmental effects, and dependency on nonrenewable resources. Both natural fillers and composite regrind can increase mechanical performance, while reducing new resin inputs for polymer based components. PVC and Polyurethane foam are widely used in North America in high volumes. Ground corn cob greatly increased the modulus of a flexible PVC system while minimally reducing maximum strength. The corn cob also showed signs of being a suitable filler in a polyurethane foam composite panel at low concentrations with minimal changes in mechanical performance. Polyurethane composite regrind illustrated great potential being used in new polyurethane composite panels with acceptable material properties. Replacing just a few percent of polyurethane and PVC with green reinforcement could reduce new production of these polymers by millions of pounds per year in North America alone.

As new family of composite materials, polyrotaxanes, polymers containing rotaxane units, have interested scientists world wide in last few decades because of their new properties. Crown ethers have been widely used as the cyclic component in various polyrotaxanes. However, due to significant loss of threaded cyclic during polymerization, the driving force for threading remains unidentified. To prevent threaded cyclics from slipping off the backbone during polycondensation, a diol blocking group (BG) and a diacid chloride BG were prepared and incorporated into polyesters as monomers or comonomers. Using these BG's effectively reduced or prevented dethreading and thus indeed increased threading efficiency (m/n, average number of cyclics per repeat unit). The study also brought about new evidences for the formation of the polyrotaxanes, i.e., the hydrolytic recovery of threaded crown ether, different chemical shift of the threaded cyclic from the free species and nuclear Overhauser effect spectroscopy (NOESY) correlation. The threading efficiencies increased with lower polymerization temperature and increasing feed ratio of the cyclic vs. diol monomer. H-bonding between the crown ether and the OH groups of the diol monomers was identified as the driving force for threading and detailed threading and dethreading mechanisms were revealed. Co-polyurethane rotaxanes were also prepared by polymerization of diol BG, tetra(ethylene glycol) and 4,4'-methylenebis(p-phenyl isocyanate) (MDI) using 30C10 as solvent. Compared to that with the polyester backbone, dethreading was slower with the polyurethane because of H-bonding of the threaded cyclics with the in-chain NH groups. Interestingly, as proved by proton NMR spectra, the cyclics were locked at the NH sites in chloroform but pushed away from the site in DMSO. Thus these polyurethane rotaxanes were solvent switchable molecular shuttles with controlled microstructures. Based on H-bonding theory, a new method for the preparation of polyrotaxanes, a melt threading process, was demonstrated by threading "42C14" onto a preformed polyurethanes. The properties of the resulting polyurethane rotaxanes depended on threading efficiency (m/n): the higher m/n was, the lower the Tg was but the higher the intrinsic viscosity was. Novel topological polymers, mechanically-linked branched and crosslinked poly(methyl methacrylate)s were synthesized by pendant group modification of a preformed poly(methacryloyl chloride) with 5-hydroxymethyl-1,3-phenylene-1,3-phenylene-32-crown-10 (hydroxymethyl BMP32C10). The rotaxane structure was directly proved by NOESY. The polycondensation of di(hydroxymethyl)-BMP32C10, tetra(ethylene glycol) and MDI afforded similar mechanically-linked polyurethanes. The branching points were manifested by the complexation of the polyurethane with paraquat. The polydispersities (PDI) and topologies (linear, branched and crosslinked) of these polymers were simply controlled by the polymerization conditions; this will ultimately afford polymers with different processibility (melt viscosity) and mechanical properties, e.g., the slippage of the cyclics along the backbone ensures a higher elongation. The complexation between a preformed polymeric crown ether and paraquat afforded a novel class of main chain polyrotaxanes. The continuous titration method afforded accurate estimates of the equilibrium constant, enthalpy and entropy changes and thus polyrotaxanes with certain m/n can be simply designed. Compared to the starting polymers, polyrotaxanes had higher viscosity, higher glass transition temperature and different solubilities. A concept for the preparation of reversible branched and/or crosslinked homo- or co-polymers was invented, which was demonstrated by preparation of a reversibly branched polymer by self-assembly of a preformed polymeric crown ether and a polyurethane bearing paraquat moieties. This concept can be applied to increase the compatibility and the interfacial interaction for polymer blends and construct reversible networks. The present work is supported by the Division of Materials Research, National Science Foundation, through individual investigator grant DMR-93-20196. / Ph. D.

A series of segmented polyurethanes (SPU's) potentially suitable for blood contacting applications were synthesized. Various soft segment monomers (polypropylene glycol, PPG, MW 1000; PPG 2000; polyethylene glycol, PEG, MW 1500) and chain extenders (ethylene diamine; 1,3 diamino hydroxy propane; and 4,5 dihydroxy-m-benzene disulphonic acid disodium salt, Tiron®) were used to prepare polymers with a range of chemical and physical characteristics. Several of these polymers were novel with respect to the presence of functional groups in the hard segment. The principal objective was to assess the effect of these groups on the physical properties, and to some extent on the blood compatibility of SPU's. Initially the SPU's were characterized to determine the course of the novel polymerizations. Nuclear magnetic resonance (NMR) was used to determine if the hydroxyl group of the chain extender 1,3 diamino hydroxy propane remained unreacted. Although the lack of model compound studies made the results inconclusive, it was estimated, using ¹H NMR, that about 87% of the hydroxyl groups remained unreacted. Sulphur analysis of sulphonate-containing SPU's, formed using Tiron®, showed very low sulphur contents compared to the expected values, suggesting that the repeat units of the SPU's were different from those based on simple stoichiometry. Low angle laser light scattering (LALLS) was used to determine M̅w but did not always produce interpretable results. Electron spectroscopy for chemical analysis (ESCA) was performed on cast films of the polymers to determine chemical composition at the surface. The ESCA data obtained at varying take-off angles showed that the soft segment domains were enriched at the surface. The nitrogen content expected of several of the SPU's was twice that found by ESCA. Again this suggests that the repeat unit of these SPU's is different from the ideal repeat unit based on the stoichiometry used. Mechanically the polymers behaved as expected in terms of stress-strain data. PPG 2000-based SPU's had greater extensibility but lower tensile strength compared to the corresponding PPG 1000-based SPU's. PEG-based polymers had very low mechanical strength and this was attributed to the absorption of water from the environment by these hydrophilic materials. PPG 1000-based polymers showed the best overall mechanical performance from a biomaterial perspective. As a means of assessing the response of blood to these materials, the adsorption of fibrinogen on film coated tubes was studied, both from single protein solutions and from plasma. Fibrinogen "capacity" of the polymer surfaces obtained from the single protein data was strongly dependent on soft segment type and was in the order PPG 1000>PPG 2000> PEG 1500. As with most other materials previously studied, adsorption of fibrinogen from plasma was transient (Vroman effect). This effect was evident as peaks in curves of adsorption versus plasma concentration. The peak heights were found also to be in the order PPG 1000>PPG 2000> PEG 1500. These peak heights are in general also lower than for other, more thrombogenic materials, and may indicate the affinity of the surface for fibrinogen relative to other proteins in plasma. From these observations it is tempting to associate thromboresistance with minimal fibrinogen adsorption. / Thesis / Master of Science (MS)

The synthesis of novel polyurethanes for use in blood contacting applications was investigated. A series of polyurethanes containing biologically active groups in the hard segment was synthesized. Sulphonate-containing polyurethanes were produced using a sulphonated chain extender (biphenyl diamino disulphonic acid) and these polymers were subsequently reacted to incorporate arginine methyl ester groups via sulphonamide bonds. The novel polyurethanes were initially evaluated using elemental sulphur analysis and nitrogen analysis, gel permeation chromatography and Fourier transform infrared spectroscopy to verify reaction of the sulphonated chain extender and addition of arginine methyl ester. Three sulphonated polyurethanes covering a range of sulphonate content were produced by varying the prepolymer and hard segment lengths. These three polymers and the three corresponding arginine methyl ester containing polymers were characterized to relate both bulk and surface structure to physical and biological properties. Elemental analysis, gel permeation chromatography and Fourier transform infrared spectroscopy were used to characterize the molecular structure. These techniques provided results consistent with the expected reaction mechanisms. Electron spectroscopy for chemical analysis and contact angle measurements were used to analyse the surface structure. Preliminary contact angle data indicate that the sulphonated polyurethane surfaces are hydrophilic, but further investigation is required before a firm conclusion can be reached. ESCA results indicate that while soft segment surface enrichment is taking place there are significant numbers of sulphonate groups present at the polyurethane surface. Mechanically these polymers have similar ultimate tensile strength but lower elongation than polyurethanes produced using aliphatic diamines, like ethylene diamine. This is probably due to increased microphase segregation arising partly from incompatibility of the aromatic chain extender with the aliphatic soft segment and possibly partly to ion cluster formation. The incorporation of arginine methyl ester groups increases both the elongation and the tensile strength, probably due to reduced phase segregation. Fibrinogen adsorption experiments in plasma were conducted to evaluate the blood response of these polymers. The plasma adsorption "isotherms" for the novel polyurethanes do not show transient fibrinogen adsorption (Vroman effect) which has been observed on a number of other surfaces including a wide range of polyurethanes. Instead, the initially adsorbed fibrinogen remains adsorbed. Also the levels of fibrinogen adsorption from plasma are three to four times greater than observed on previously studied surfaces. Conversion of some of the sulphonate groups to sulphonamide-bonded arginine methyl ester restores the Vroman effect and results in lower levels of retained fibrinogen. These data suggest the possibility of a specific interaction between sulphonate groups and fibrinogen. / Thesis / Master of Engineering (ME)

Gold, as a chemically inert metal, does not form a stable oxide, but has strong specific interactions with sulfur functions. It has been found that thiols or disulfides can chemisorb to gold under mild conditions (room temperature), and form densely packed monolayers on the gold surface due to the high density of binding sites (gold atoms). Thus, it is possible to form closely packed and stable monolayers of thiolates containing desirable bioactive moieties. Thiol-gold chemistry may therefore be considered as a potentially important tool in the surface modification of materials for biomedical applications. In order to develop surfaces with antithrombogenic properties, a number of thrombin inhibitors (heparin, hirudin and PPACK) have been bonded or immobilized to the material surfaces. In the present study, a series of short peptides, cys-pro-arg (CPR), cys-phe-pro-arg (CFPR) and cys-(D)-phe-pro-arg (C[D]FPR), analogues of PR and FPR respectively, were chosen as potential thrombin inhibitors to attach to gold-coated polyurethane surfaces via the cysteine residue. Their inhibitory activity against thrombin was verified by a chromogenic substrate assay. C(D)FPR, showed a relatively high level of inhibition activity. The surfaces were characterized by water contact angle, XPS, AFM, SEM, ellipsometry, and infrared reflection-absorption spectroscopy, and the adsorption of thrombin from buffer and modified plasma was investigated. It was found that the peptide modified gold surfaces adsorbed significantly more thrombin than the unmodified control surfaces. The C(D)FPR-modified gold surface showed the highest thrombin adsorption both from buffer and plasma. This results is in accord with previous studies showing that the D form of phenylalananine in the FPR peptide creates a favourable site geometry for binding to thrombin. The activity of thrombin adsorbed on these peptide modified gold surfaces was also investigated using a chromogenic substrate assay. Inhibition of adsorbed thrombin was demonstrated, and the C(D)FPR surface showed the strongest inhibitory activity. The presence of thrombin on the peptide surfaces following exposure to modified plasma was verified by elution of proteins and identification of thrombin in the eluate. Probing of the eluates with antibodies to 25 plasma proteins showed that the peptide surfaces are relatively non-adsorptive, suggesting they have some degree of selectivity for thrombin binding. / Thesis / Master of Engineering (ME)

From the 1960s to the 1980s, many schools throughout the country installed synthetic flooring in indoor gymnasiums that contained mercury which was used as a catalyst in the polyurethane formulation. Many of these floors now have been found to be releasing mercury vapors into the school gymnasiums, leading to a concern that these mercury concentrations might be elevated enough to cause harmful effects. This paper examines data that have been collected from 57 different school gymnasiums using portable devices, such as the Lumex RA-915+ Portable Mercury Vapor Analyzer, and aggregated for analyses, then compares this data to that obtained in chamber tests performed on samples obtained directly from a gymnasium with mercury-containing floors. The overall objective of this paper is to determine if the chamber tests can adequately emulate mercury emissions in school gymnasiums, and using the results of the laboratory experiments, successfully analyze the emissions curve to determine what factors drive the profile. The laboratory testing was successful in emulating the condition of a school gymnasium, as data collected from the laboratory setting was comparable to the measured field data. The average mercury concentration in the gymnasium yielded an emission rate 3.1E-05 ug/m2s, while the calculated laboratory emission rate was 3.2E-05 ug/m2s, a negligible difference. The overall objective was met, as it was determined that floor samples taken from a gymnasium could be measured in the laboratory with similar results to those screened in the actual gym with handheld devices. Additionally, using the data collected in the chamber experiments, the emissions profile was characterized. / Master of Science

Polymeric fibres, films, coatings and moulded products are ubiquitous in modern society, and are used in applications as diverse as packaging materials, clothing, medical devices, etc. Mechanistic and kinetic considerations are useful in the development of efficient catalysts for controlled selective polymerisations, which is essential for the production of polymeric materials possessing properties tailored to suit their application. Mercury-based compounds are used as catalysts in many applications of the synthesis of polyurethanes such as the production of polyurethane elastomers. Due to the environmental impact of mercury, there is a need to replace such catalysts with complexes based on benign metals. Group 4 metals are an attractive option, both in terms of reactivity and their benign environmental nature. A series of novel complexes have been synthesised, fully characterised, and their activity and selectivity investigated in a model reaction. The molecular structures of a number of potential catalysts have been determined by single crystal X-ray diffraction experiments. These potential catalysts have been screened in the model reaction utilising in situ reaction monitoring in order to acquire kinetic data. A method to study catalyst selectivity has also been developed. The results of these kinetic and selectivity studies are presented in this thesis and compared to the industrial phenylmercury neodecanoate catalyst system. A selection of well-defined complexes which have been synthesised as part of this body of work have also been evaluated in the preparation of polyurethane elastomers. Physical characterisation techniques such as Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and Scanning Electron Microscopy (SEM) have been used for this purpose.

Polyurethane network binders were synthesized using polyethylene glycol (PEG) prepolymers, cellulose acetate butyrate (CAB), curative [Desmodur N100 (N100) or Desmodur N3200 (N3200)], and catalyst [dibutyltin dilaurate (DBTDL)]. Triacetin (TA) was added as plasticizer before the reaction. Polyurethanes were prepared by varying the molar ratio of ¡VNCO/-OH, weight ratio of TA/PEG, molecular weight of PEG, the amount of catalyst, the order of adding catalyst and curative, and the stirred time. Synthesized polyurethanes were characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), tensile tests, and swelling tests to study their reaction, degradation, thermal, and mechanical properties. When the ratio of ¡VNCO/-OH was between 1.2 and 1.4, polyurethane gave the best mechanical properties. Additionally, the quenched polyurethane had a lower degree of crystallinity When the weight ratio of TA and PEG was bigger than 2, crystallization of polyurethane could be minimized during the tensile testing or after quenching. In this study, it was found that PEG with molecular weight of 4000 yielded the best mechanical properties. These results indicate that better and uniform mechanical properties can be obtained by using enough stirring time via varying the amount of catalyst and adding catalyst before curing agent.

Polymer coated sheet metal components find diverse applications in many industries. The manufacturing of the components generally involves forming of sheet metal into the desired shape and coating of the formed part with organic coating. An alternative manufacturing route is to coat the sheet metal first before forming. The change in the manufacturing sequence can potentially improve cost and reduce environmental impact. This approach, however, requires the coating to survive the deformation process. Thus, the effect of plastic deformation on coating adhesion is of primary interest to many engineers and researchers. This research aims at developing a methodology to predict the adhesion of coating after metal forming processes. A pull-off apparatus that measures the coating pull-off stress was used to indicate the coating adhesion strength. Several types of specimen were designed to obtain uniaxial tension, biaxial tension, and tension-compression deformation modes on pre-coated sheet by using a uniaxial tensile tester. Experimental results from two selected polymer coated sheet metals show that coating adhesion was affected by plastic deformation. An analytical model based on a virtual interface crack concept was developed to indicate the adhesion potential of the coating-substrate interface. From interfacial fracture mechanics, the initial adhesion potential is defined as the energy release rate characterized by the virtual interface crack and the initial pull-off stress. The analytical model was used to predict coating adhesion loss after deformation in uniaxial tension mode. The analytical model predictions agreed well with experimental results. Finite element analysis tool was applied to simulate more complex deformation modes in stamping of coated sheet meals. The stress field near the interface crack tip was used to calculate the energy release rate and predict the adhesion loss under different deformation modes. The predictions obtained from numerical method are also in good agreements with the experimental results in biaxial tension and tension-compression modes. The research has led to a better understanding of the effects of plastic deformation on coating adhesion. The developed adhesion test methods can be used to generate useful information on coating durability for diverse practical use. It is also expected that the results of the research will facilitate the development of better polymer coated sheet metal to be used in sheet metal forming processes.