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No description available.

The work described in this thesis was concerned with the synthesis and attempted Ring Opening Metathesis Polymerisations (ROMP) of a series of monocyclic phospholenes and organophosphorus derivatives of bicyclo[2.2.1]heptene using a variety of catalysts and conditions. This thesis comprises five chapters. The first chapter deals with the background of fire retardancy, industrial water treatment and ROMP. Chapter two describes the synthesis and characterisation of some potential organophosphorus monomers. Chapter three gives details of the attempted ROMP of the potential monomers prepared in chapter two. Investigations into the possible preparation of oligomers using a variety of chain transfer agents are described in chapter four. The conclusions and proposals for future work are outlined in the final chapter.

The objective of the project was to develop halogen and phosphorous free flame retardant polyamide 66 composites using magnesium hydroxide, either alone or in admixtures. In common with alumina trihydrate (ATH), magnesium hydroxide has attracted considerable attention over the last twenty years, as a halogen and phosphorous free alternative for both thermoplastics and elastomers. However, owing to its greater thermal stability magnesium hydroxide can be added to thermoplastics (such as polyamide 66) which are melt processed at temperatures where alumina trihydrate is impractical due to premature degradation. There are problems however, using such a flame retardant system, due to the high filler loadings (~60 wt%) required to achieve adequate flame retardancy, which leads to detrimental effects on both processing and mechanical properties.

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The major objectives of this research were to examine the bioaccumulation parameters [depuration rates (kd), half life (t1/2) and biomagnification factor (BMF)] of individual isomers of hexabromocyclododecane (HBCD, C12H18Br6) in fish and to test the hypothesis of in vivo bioisomerization. This was done by exposing three groups of juvenile rainbow trout (Oncorhynchus Mykiss) to food fortified with known concentrations of an individual diastereoisomer (α, β, γ) for 56 days (uptake phase) followed by 112 days (depuration phase) of unfortified food. A fourth group of fish were exposed to unfortified food for the duration of the experiment. Fish (n=4) from all four aquaria were sacrificed on days 0, 7, 14, 56, 63, 70, 112 and 168 and muscle tissue was extracted and analyzed for diastereoisomer concentrations by high performance liquid chromatography tandem mass spectrometry (LC/MS/MS). Bioaccumulation of the γ diastereoisomer was linear during the uptake phase while the α and β diastereoisomers were found to increase exponentially with respective doubling times of 14.1 and 20.5 days. Both the β and γ diastereoisomers followed first order depuration kinetics with calculated t1/2’s of 94 ± 25 and 84 ± 51 (± 1 × standard error) days, respectively. The BMF for the α diastereoisomer (BMF = 4.1) was one and a half times greater than the β-diastereoisomer (BMF = 2.6) and about one fifth larger than the γ-diastereoisomer (BMF = 3.6). The large BMF for the α diastereoisomer is consistent with this diastereoisomer dominating higher trophic level organisms in wildlife. Although the BMF of the β diastereoisomer suggests that it will biomagnify, because it is present in small quantities in commercial mixtures it is rarely detected in environmental samples. Results from these studies also provide evidence of bioisomerization of the β and γ diastereoisomers. Most importantly, the α diastereoisomer which was recalcitrant to bioisomerization by juvenile rainbow trout in this study and known to be the dominant diastereosiomer in fish, was bioformed from both the β and γ diastereoisomers. To our knowledge, this is the first report of bioisomerization of a halogenated organic pollutant in biota. / May 2006

A variety of materials were used to fabricate nanocoatings using layer-by-layer (LbL) assembly to reduce the flammability of cotton fabric. The most effective brominated flame retardants have raised concerns related to their toxicity and environmental impact, which has created a need for alternative flame retardant chemistries and approaches. Polymer nanocomposites typically exhibit reduced mass loss and heat release rates, along with anti-dripping behavior, all of which are believed to be due to the formation of a barrier surface layer. Despite these benefits, the viscosity and modulus of the final polymeric material is often altered, making industrial processing difficult. These challenges inspired the use of LbL assembly to create densely layered nanocomposites in an effort to produce more flame-retardant coatings. Laponite and montmorillonite (MMT) clay were paired with branched poly(ethylenimine) to create thin film assemblies that can be tailored by changing pH and concentration of aqueous deposition mixtures. Both films can be grown linearly as a function of layers deposited, and they contained at least 70 wt percent of clay. When applying these films to cotton fabric, the individual fibers are uniformly coated and the fabric has significant char left after burning. MMT-coated fabric exhibits reduced total heat release, suggesting a protective ceramic surface layer is created. Small molecule, POSS-based LbL thin films were also successfully deposited on cotton fabric. With less than 8 wt percent added to the total fabric weight, more than 12 wt percent char remained after microscale combustion calorimetry. Furthermore, afterglow time was reduced and the fabric weave structure and shape of the individual fibers were highly preserved following vertical flame testing. A silica-like sheath was formed after burning that protected the fibers. Finally, the first intumescent LbL assembly was deposited on cotton fabric. SEM images show significant bubble formation on fibers, coated with a 0.5 wt percent PAAm/1 wt percent PSP coating after burning. In several instances, a direct flame on the fabric was extinguished. The peak HRR and THR of coated fabric has 30 percent and 65 percent reduction, respectively, compared to the uncoated control fabric. These anti-flammable nanocoatings provide a relatively environmentally-friendly alternative for protecting fabrics, such as cotton, and lay the groundwork for rendering many other complex substrates (e.g., foam) flame-retardant without altering their processing and desirable mechanical behavior.

The major objectives of this research were to examine the bioaccumulation parameters [depuration rates (kd), half life (t1/2) and biomagnification factor (BMF)] of individual isomers of hexabromocyclododecane (HBCD, C12H18Br6) in fish and to test the hypothesis of in vivo bioisomerization. This was done by exposing three groups of juvenile rainbow trout (Oncorhynchus Mykiss) to food fortified with known concentrations of an individual diastereoisomer (α, β, γ) for 56 days (uptake phase) followed by 112 days (depuration phase) of unfortified food. A fourth group of fish were exposed to unfortified food for the duration of the experiment. Fish (n=4) from all four aquaria were sacrificed on days 0, 7, 14, 56, 63, 70, 112 and 168 and muscle tissue was extracted and analyzed for diastereoisomer concentrations by high performance liquid chromatography tandem mass spectrometry (LC/MS/MS). Bioaccumulation of the γ diastereoisomer was linear during the uptake phase while the α and β diastereoisomers were found to increase exponentially with respective doubling times of 14.1 and 20.5 days. Both the β and γ diastereoisomers followed first order depuration kinetics with calculated t1/2’s of 94 ± 25 and 84 ± 51 (± 1 × standard error) days, respectively. The BMF for the α diastereoisomer (BMF = 4.1) was one and a half times greater than the β-diastereoisomer (BMF = 2.6) and about one fifth larger than the γ-diastereoisomer (BMF = 3.6). The large BMF for the α diastereoisomer is consistent with this diastereoisomer dominating higher trophic level organisms in wildlife. Although the BMF of the β diastereoisomer suggests that it will biomagnify, because it is present in small quantities in commercial mixtures it is rarely detected in environmental samples. Results from these studies also provide evidence of bioisomerization of the β and γ diastereoisomers. Most importantly, the α diastereoisomer which was recalcitrant to bioisomerization by juvenile rainbow trout in this study and known to be the dominant diastereosiomer in fish, was bioformed from both the β and γ diastereoisomers. To our knowledge, this is the first report of bioisomerization of a halogenated organic pollutant in biota.

The major objectives of this research were to examine the bioaccumulation parameters [depuration rates (kd), half life (t1/2) and biomagnification factor (BMF)] of individual isomers of hexabromocyclododecane (HBCD, C12H18Br6) in fish and to test the hypothesis of in vivo bioisomerization. This was done by exposing three groups of juvenile rainbow trout (Oncorhynchus Mykiss) to food fortified with known concentrations of an individual diastereoisomer (α, β, γ) for 56 days (uptake phase) followed by 112 days (depuration phase) of unfortified food. A fourth group of fish were exposed to unfortified food for the duration of the experiment. Fish (n=4) from all four aquaria were sacrificed on days 0, 7, 14, 56, 63, 70, 112 and 168 and muscle tissue was extracted and analyzed for diastereoisomer concentrations by high performance liquid chromatography tandem mass spectrometry (LC/MS/MS). Bioaccumulation of the γ diastereoisomer was linear during the uptake phase while the α and β diastereoisomers were found to increase exponentially with respective doubling times of 14.1 and 20.5 days. Both the β and γ diastereoisomers followed first order depuration kinetics with calculated t1/2’s of 94 ± 25 and 84 ± 51 (± 1 × standard error) days, respectively. The BMF for the α diastereoisomer (BMF = 4.1) was one and a half times greater than the β-diastereoisomer (BMF = 2.6) and about one fifth larger than the γ-diastereoisomer (BMF = 3.6). The large BMF for the α diastereoisomer is consistent with this diastereoisomer dominating higher trophic level organisms in wildlife. Although the BMF of the β diastereoisomer suggests that it will biomagnify, because it is present in small quantities in commercial mixtures it is rarely detected in environmental samples. Results from these studies also provide evidence of bioisomerization of the β and γ diastereoisomers. Most importantly, the α diastereoisomer which was recalcitrant to bioisomerization by juvenile rainbow trout in this study and known to be the dominant diastereosiomer in fish, was bioformed from both the β and γ diastereoisomers. To our knowledge, this is the first report of bioisomerization of a halogenated organic pollutant in biota.

To address my first objective, I opportunistically collected road-killed bobcats (n=44) throughout Illinois during 2013-2014, and analyzed their liver tissue for the presence of PCBs, PBDEs, and various other alternative halogenated flame retardants. Concentrations of ∑PCBs ranged from 76.4 ng/g lw to 3782 ng/g lw (median 562.97 ng/g lw). Male bobcats had significantly higher concentrations of PCBs than females (p = 0.04). Concentrations of ∑PBDEs (including all detectable PBDE congeners) ranged from 8.3 to 1920 ng/g lipid weight (median: 50.3 ng/g lw). Among the alternative flame retardants screened, Dechloranes (including anti- and syn-Dechlorane Plus and Dechlorane-602, 603, and 604), tetrabromo-o-chlorotoluene (TBCT), and hexabromocyclododecane (HBCD) were also detected frequently, with median concentrations of 28.7, 5.2, and 11.8 ng/g lw, respectively. Dechlorane analogue compositions in bobcats were different from that reported in other studies, suggesting species- or analogue-dependent bioaccumulation, biomagnification, or metabolism of Dechlorane chemicals in different food webs. My findings, along with previously reported food web models, suggest Dechloranes may possess substantial bioaccumulation and biomagnification potencies in terrestrial mammalian food webs. Thus, attention should be given to these highly bioavailable flame retardants in future environmental biomonitoring and risk assessments in a post-PBDE era. To address my second objective I collected raccoons (n=32) from various sites across Illinois and Missouri during 2013-2015. Liver tissues were analyzed for the presence of PBDEs and Dechloranes. ∑PBDE concentrations ranged from 19.1 ng/g lw to 2124 ng/g lw (median = 98.0 ng/g lw) and did not differ between gender or age of raccoon. Although nonsignificant (p=0.06), adult raccoons appeared to have greater PBDE concentration loads compared to juveniles. These nonsignificant differences are likely due to large variation in contaminant concentrations, possibly reflecting differences in individual raccoon diet and behavior. This is the first study reporting bioaccumulation of halogenated flame retardants in a wild felid in North America, and also the first report of PBDE accumulation in North American raccoons. The wide detection of Dechloranes, HBCD and TBCT in bobcats suggests a broad exposure of these alternative flame retardants in terrestrial apex predators in terrestrial ecosystems. The comparatively high levels of PBDEs in raccoons also suggest that biota in terrestrial habitats are still widely exposed to and susceptible to the bioaccumulation of these flame retardants.