Synthesis and Structure-Photophysical Property Relationships of T8, T10, T12 and Oligomeric Organic Functionalized Silsesquioxanes.

Silsesquioxanes with conjugated organic tethers (chromophores) offer high orders of functionality (> 8 tethers), unusual enhanced absorption, emission and charge separation over free chromophores, excited state electron delocalization, and high thermal stability. This dissertation presents the synthesis and characterization of organic functionalized T10 and T12 [RSiO1.5]10,12 molecules, with emphasis on their synthesis by fluoride catalyzed rearrangement from [RSiO1.5]n and an understanding of their unique photophysical properties targeting components in optoelectronic devices. Initial discussion focuses on the synthesis of silsesquioxanes from silica via conversion of rice hull ash (RHA) silica to spirosiloxanes [i.e. Si(2-methyl-2,4-pentane-diolato)2] by reaction with 2-Me-2,4-pentanediol and catalytic NaOH. The resulting spirosiloxane reacts with selected arylLi reagents to form mono-aryl-spirosiloxane, suggesting a pentacoordinate silicon based mechanism. These aryl-spirosiloxanes are then converted through fluoride catalysis to novel aryl-silsesquioxanes [RSiO1.5]8,10,12. Thereafter we detail the development of [RSiO1.5]10,12 materials by fluoride catalyzed rearrangement and its mechanisms. F--catalyzed rearrangement of polymeric and octameric SQs is indispensable to the synthesis of [RSiO1.5]10/12, and mixed [R1R2SiO1.5]10,12 molecules in up to 95% yield. [PhSiO1.5]10 is synthesized in the highest reported yield to date (~50%), and is used as a model system for mechanism studies. The likely mechanistic paths taken to form T10 and T12 SQs are analyzed by experiment with MALDI/NMR to identify intermediates and computational modeling for the most likely pathways. The most favorable pathway to T10 from T8 involves coincidental participation of fluoride and water with a net enthalpy of ~-24 kcal/mol. We also explore in detail the photophysical properties of [StilbenevinylSiO1.5]8,10,12, which show similar absorption and emission in solution, but decreasing fluorescence quantum efficiencies with increasing cage size, suggesting more chromophore interactions and non-radiative decay. [StilbenevinylSiO1.5]10 shows the highest two-photon absorption cross-section of this series (5.7 GM/chromophore), offering the best polarization and charge transfer character. Fluorescence upconversion fluorescence lifetime studies on [StilbenevinylSiO1.5]8,10,12 find ultrafast charge transfer dynamics (<1 ps) indicative of chromophore-chromophore interactions in the excited state, unobserved for stilbenvinylSi(OEt)3, suggesting excited state charge delocalization.PHDChemistryUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111393/1/furgaljc_1.pd

R-Silsesquioxane-Based Network Polymers by Fluoride Catalyzed Synthesis: An Investigation of Cross-Linker Structure and Its Influence on Porosity

Silsesquioxane-based networks are an important class of materials that have many applications where high thermal/oxidative stability and porosity are needed simultaneously. However, there is a great desire to be able to design these materials for specialized applications in environmental remediation and medicine. To do so requires a simple synthesis method to make materials with expanded functionalities. In this article, we explore the synthesis of R-silsesquioxane-based porous networks by fluoride catalysis containing methyl, phenyl and vinyl corners (R-Si(OEt)) combined with four different bis-triethoxysilyl cross-linkers (ethyl, ethylene, acetylene and hexyl). Synthesized materials were then analyzed for their porosity, surface area, thermal stability and general structure. We found that when a specified cage corner (i.e., methyl) is compared across all cross-linkers in two different solvent systems (dichloromethane and acetonitrile), pore size distributions are consistent with cross-linker length, pore sizes tended to be larger and π-bond-containing cross-linkers reduced overall microporosity. Changing to larger cage corners for each of the cross-linkers tended to show decreases in overall surface area, except when both corners and cross-linkers contained π-bonds. These studies will enable further understanding of post-synthesis modifiable silsesquioxane networks

Thermally Stable Fluorogenic Zn(II) Sensor Based on a Bis(benzimidazole)pyridine-Linked Phenyl-Silsesquioxane Polymer

A 2,6-bis(2-benzimidazolyl) pyridine-linked silsesquioxane-based semi-branched polymer was synthesized, and its photophysical and metal-sensing properties have been investigated. The polymer is thermally stable up to 285 °C and emits blue in both solid and solution state. The emission of the polymer is sensitive to pH and is gradually decreased and quenched upon protonation of the linkers. The initial emission color is recoverable upon deprotonation with triethylamine. The polymer also shows unique spectroscopic properties in both absorption and emission upon long-term UV irradiation, with red-shifted absorption and emission not present in a simple blended system of phenylsilsesquioxane and linker, suggesting that a long-lived energy transfer or charge separated state is present. In addition, the polymer acts as a fluorescence shift sensor for Zn(II) ions, with red shifts observed from 464 to 528 nm, and reversible binding by the introduction of a competitive ligand such as tetrahydrofuran. The ion sensing mechanism can differentiate Zn(II) from Cd(II) by fluorescence color shifts, which is unique because they are in the same group of the periodic table and possess similar chemical properties. Finally, the polymer system embedded in a paper strip acts as a fluorescent chemosensor for Zn(II) ions in solution, showing its potential as a solid phase ion extractor

Avoiding Carbothermal Reduction: Distillation of Alkoxysilanes from Biogenic, Green, and Sustainable Sources

The direct depolymerization of SiO2 to distillable alkoxysilanes has been explored repeatedly without success for 85 years as an alternative to carbothermal reduction (1900 °C) to Simet, followed by treatment with ROH. We report herein the base‐catalyzed depolymerization of SiO2 with diols to form distillable spirocyclic alkoxysilanes and Si(OEt)4. Thus, 2‐methyl‐2,4‐pentanediol, 2,2,4‐trimethyl‐1,3‐pentanediol, or ethylene glycol (EGH2) react with silica sources, such as rice hull ash, in the presence of NaOH (10 %) to form H2O and distillable spirocyclic alkoxysilanes [bis(2‐methyl‐2,4‐pentanediolato) silicate, bis(2,2,4‐trimethyl‐1,3‐pentanediolato) silicate or Si(eg)2 polymer with 5–98 % conversion, as governed by surface area/crystallinity. Si(eg)2 or bis(2‐methyl‐2,4‐pentanediolato) silicate reacted with EtOH and catalytic acid to give Si(OEt)4 in 60 % yield, thus providing inexpensive routes to high‐purity precipitated or fumed silica and compounds with single Si−C bonds.No detours: The base‐catalyzed depolymerization of SiO2 from different sources with diols led directly to distillable alkoxysilanes, including spirocyclic compounds, thus providing inexpensive routes to high‐purity silica and compounds with single Si−C bonds (see scheme): The alkoxysilanes could be converted either into Si(OEt)4 by treatment with EtOH and a catalytic amount of acid or into high‐purity precipitated (ppt) or fumed silica.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137495/1/anie201506838-sup-0001-misc_information.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137495/2/anie201506838.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137495/3/anie201506838_am.pd

High Surface Area, Thermally Stable, Hydrophobic, Microporous, Rigid Gels Generated at Ambient from MeSi(OEt)3/(EtO)3SiCH2CH2Si(OEt)3 Mixtures by F−‐Catalyzed Hydrolysis

High surface area materials are of considerable interest for gas storage/capture, molecular sieving, catalyst supports, as well as for slow‐release drug‐delivery systems. We report here a very simple and fast route to very high surface area, mechanically robust, hydrophobic polymer gels prepared by fluoride‐catalyzed hydrolysis of mixtures of MeSi(OEt)3 and bis‐triethoxysilylethane (BTSE) at room temperature. These materials offer specific surface areas up to 1300 m2 g−1, peak pore sizes of 0.8 nm and thermal stabilities above 200 °C. The gelation times and surface areas can be controlled by adjusting the solvent volume (dichloromethane), percent fluoride (as nBu4NF or TBAF) and the BTSE contents. Polymers with other corners and linkers were also explored. These materials will further expand the materials databank for use in vacuum insulation panels and as thermally stable release and capture media.Simple fluoride‐catalyzed polymerization of methyltriethoxysilane and bistriethyoxysilylethane leads to the formation of amorphous materials with little post‐synthesis processing. These materials have surface areas up to 1300 m2 g−1, densities as low as 0.06 g mL−1 and non‐polar solvent uptake of about 500 % by mass.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141416/1/chem201704941.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141416/2/chem201704941_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141416/3/chem201704941-sup-0001-misc_information.pd

Isolation and Characterization of Precise Dye/Dendrimer Ratios

Fluorescent dyes are commonly conjugated to nanomaterials for imaging applications using stochastic synthesis conditions that result in a Poisson distribution of dye/particle ratios and therefore a broad range of photophysical and biodistribution properties. We report the isolation and characterization of generation 5 poly(amidoamine) (G5 PAMAM) dendrimer samples containing 1, 2, 3, and 4 fluorescein (FC) or 6‐carboxytetramethylrhodamine succinimidyl ester (TAMRA) dyes per polymer particle. For the fluorescein case, this was achieved by stochastically functionalizing dendrimer with a cyclooctyne “click” ligand, separation into sample containing precisely defined “click” ligand/particle ratios using reverse‐phase high performance liquid chromatography (RP‐HPLC), followed by reaction with excess azide‐functionalized fluorescein dye. For the TAMRA samples, stochastically functionalized dendrimer was directly separated into precise dye/particle ratios using RP‐HPLC. These materials were characterized using 1 H and 19 F NMR spectroscopy, RP‐HPLC, UV/Vis and fluorescence spectroscopy, lifetime measurements, and MALDI. High definition : Two approaches for the formation of generation 5 PAMAM samples containing precise dye/dendrimer ratios are presented. The first approach, using direct separation based on dye hydrophobicity, generated a set of TAMRA‐containing dendrimers, and the second, using click chemistry, generated a set of fluorescein‐containing dendrimer (see figure).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106970/1/chem_201304854_sm_miscellaneous_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106970/2/4638_ftp.pd

Towards a better understanding of the benefits and risks of country food consumption using the case of walruses in Nunavik (Northern Quebec, Canada)

Food insecurity affects Inuit communities. One solution is to consume locally harvested foods, named country foods. However, some country foods are not eaten as often as before, and pressures including contaminants and environmental changes threaten the health of Arctic fauna, thus its suitability for local consumption. By combining Inuit Knowledge with laboratory data, our study assessed the benefits and risks of walrus consumption by Inuit in Nunavik, Québec, Canada. It aimed to increase understanding of: 1) the hunt of healthy Atlantic walruses (Odobenus rosmarus rosmarus); 2) the safe preparation of walruses; 3) the nutritional benefits and risks of consuming walruses. To do so, we interviewed 34 hunters and Elders from Nunavik. Levels of mercury, omega-3 polyunsaturated fatty acids and selenium were evaluated from locally harvested walruses. Through the Nunavik Trichinellosis Prevention Program, a total of 755 Atlantic walrus samples, collected between 1994 and 2013, were tested for Trichinella nativa. Information on botulism was reviewed. While interviews informed on how to select healthy walruses and prepare them for consumption, laboratory analyses revealed that walruses had elevated levels of omega-3 fatty acids and selenium but low levels of mercury compared to some other wildlife. Only 3% of the 755 walruses were infected with T. nativa. Most walruses' infections were found within individuals from the South East Hudson Bay stock, where Inuit have thus decided to stop hunting since mid-2000s. Finally, although the number of outbreaks of trichinellosis related to the consumption of walruses has significantly reduced in Nunavik, botulism could continue to be an issue when igunaq (i.e. aged walrus) is not properly prepared. With the support of the Nunavik Trichinellosis Prevention Program and transmission of Inuit knowledge on igunaq preparation, the consumption of Atlantic walruses has the potential to help address issues related to food insecurity in Nunavik in the future

“Just because you have a land claim, that doesn’t mean everything’s going to fall in place”: An Inuit social struggle for fishery access and well-being

Commercial fishing supports coastal communities around the world and fishing livelihoods are often interwoven into local societies, including culture, identity, knowledges, and economies, particularly for many Indigenous Peoples globally. Through a case study with co-management board members in Nunatsiavut, Labrador, Canada, we explore how access to commercial fisheries is a determinant of Inuit well-being. Interviews with fisheries co-managers were conducted and analysed deductively and inductively using a conceptual well-being framework to characterize the ways in which commercial fisheries intersect with Inuit well-being. Our results highlight how commercial fisheries in Nunatsiavut have been a longstanding way of life, with multiple familial connections, and are interwoven with the social, economic, and political components of Indigenous culture and identity. Participants described how the fishing livelihood in Nunatsiavut was put at risk due to overfishing by foreign fleets who exploited Inuit waters during the cod fishery’s formative years. Extensive narrative about fisher committees and community organizing highlighted how political participation and self-determination efforts in the 1970 s led to a measure of sustainability through new Northern Shrimp access. Despite periodic success stories, the Inuit commercial fishery remains in a social struggle. The results show how the fishery has continued with multiple injustices and forms of inequity. The combination of events over time, shared through stories, highlight that these small-scale Inuit fisheries were subject to ocean grabbing or ocean dispossession. Based on these results, future research that facilitates an Inuit vision of Nunatsiavut’s fishing sector is critical, and reclamation policies that facilitate new pathways forward for reconciliation to centre Inuit well-being are needed. Furthermore, these results illustrate how Inuit identified well-being indicators could be adopted for immediate baseline monitoring and to measure progress

Indicators of ocean health and human health: developing a research and monitoring framework

This is the final version of the article. Available from NIEHS via the DOI in this record.We need to critically assess the present quality of the marine ecosystem, especially the connection between ecosystem change and threats to human health. In this article we review the current state of indicators to link changes in marine organisms with eventual effects to human health, identify research opportunities in the use of indicators of ocean and human health, and discuss how to establish collaborations between national and international governmental and private sector groups. We present a synthesis of the present state of understanding of the connection between ocean health and human health, a discussion of areas where resources are required, and a discussion of critical research needs and a template for future work in this field. To understand fully the interactions between ocean health and human health, programs should be organized around a "models-based" approach focusing on critical themes and attributes of marine environmental and public health risks. Given the extent and complex nature of ocean and human health issues, a program networking across geographic and disciplinary boundaries is essential. The overall goal of this approach would be the early detection of potential marine-based contaminants, the protection of marine ecosystems, the prevention of associated human illness, and by implication, the development of products to enhance human well-being. The tight connection between research and monitoring is essential to develop such an indicator-based effort.This work was funded by the National Institute of Environmental Health Sciences, the Intergovernmental Oceanographic Commission (UNESCO), and the Bermuda Biological Station for Research, Inc. (contribution 1615)

“We’re Made Criminals Just to Eat off the Land”: Colonial Wildlife Management and Repercussions on Inuit Well-Being

Across Inuit Nunangat, Inuit rely on wildlife for food security, cultural continuity, intergenerational learning, and livelihoods. Caribou has been an essential species for Inuit for millennia, providing food, clothing, significant cultural practices, and knowledge-sharing. Current declines in many caribou populations—often coupled with hunting moratoriums—have significant impacts on Inuit food, culture, livelihoods, and well-being. Following an Inuit-led approach, this study characterized Inuit-caribou relationships; explored Inuit perspectives on how caribou have been managed; and identified opportunities for sustaining the Mealy Mountain Caribou. Qualitative data were collected in Rigolet, Nunatsiavut, Labrador, Canada through 21 in-depth interviews and two community open houses. Data were analyzed using constant comparative methods and thematic analysis. Rigolet Inuit described: how conservation management decisions had disrupted important connections among caribou and Inuit, particularly related to food, culture, and well-being; the socio-cultural and emotional impacts of the criminalization of an important cultural practice, as well as perceived inequities in wildlife conservation enforcement; and the frustration, anger, and hurt with not being heard or included in caribou management decisions. These results provide insights into experiences of historic and ongoing colonial wildlife management decisions, and highlight future directions for management initiatives for the health and well-being of Inuit and caribou