O desenvolvimento de materiais biodegradáveis, a partir de biopolímeros, para embalagens ou coberturas tem grande interesse para a indústria de alimentos. Na elaboração desses materiais, os amidos e as proteínas são muito usados por serem abundantes na natureza, de baixo custo e apresentam propriedades de formar filmes. A cañihua (Chenopodium pallidicaule), grão alto-andino pouco explorado industrialmente, tem altos conteúdos de carboidratos (~58 %) e proteínas (~18 %), e apresenta potencial para ser utilizado como matéria-prima na extração de amido comercial. Diante desse contexto, o objetivo desse trabalho foi extrair e caracterizar o amido de duas variedades de cañihua, Cupi (CC) e Illpa (CI), e selecionar uma dessas variedades para o desenvolvimento de filmes a base de amido ou de farinha. Além disso, a variedade selecionada foi usada para obter um material rico em amido e proteínas, denominado de farinha, que também foi usado para a produção de filmes biodegradáveis. Os grãos de cañihua das variedades Illpa e Cupi são muito similares na forma e tamanho dos grãos, porém os conteúdos de lipídios e cinzas são maiores para CC e o teor de fibras, para a CI. A extração do amido foi feita com solução de hidróxido de sódio (0,25 % m/v) e suas características estruturais, físico-químicas e funcionais foram determinadas. O rendimento desse processo foi de aproximadamente 33 %, e o amido da variedade CC apresentou maiores teores de lipídeos. Os amidos de ambas as variedades, observados em microscópio de varredura eletrônica, apresentaram superfícies granulares lisas e com formatos esféricos de pequeno tamanho (D[3,2] ~ 0,96 µm). A distribuição de tamanho de partícula, o índice de cristalinidade, os espectros de FTIR, poder de inchamento, propriedades óticas e térmicas foram semelhantes, porém o teor de amilose foi maior para a variedade CC. Maiores valores de solubilidade e viscosidade (propriedades de pasta) foram observados para o amido da variedade Cupi e pode estar associado ao maior conteúdo de amilose. O amido da cañihua Cupi foi selecionado para a produção de filmes, por apresentar maiores teores de amilose e de lipídeos. Na obtenção da farinha de CC, usando soluções de NaOH e HCl (0,2 N), o rendimento foi estimado em 56 % (g/100 g de grãos). O teor de proteínas na farinha foi de 79 % (g/100 g sólidos) em relação ao grão. O alto conteúdo de proteínas favoreceu a formação de aglomerados que foram observados nas micrografias da farinha de CC, que apresentou diferenças nas propriedades óticas, de pasta e de solubilidade em relação ao amido da mesma variedade. Os filmes de amido ou farinha foram obtidos pelo método casting com adição de glicerol como plastificante (15 g/100 g de macromoléculas). A caracterização da microestrutura permitiu observar as diferenças físicas entre os filmes de amido ou farinha de cañihua Cupi, assim como as características estruturais foram úteis para explicar o comportamento das outras propriedades. Em umidades relativas altas, os filmes de amido ou farinha CC apresentam o mesmo comportamento de sorção de umidade e permeabilidade ao vapor de água, no entanto, em contato direito com a água (solubilidade e ângulo de contato), esses materiais apresentaram comportamento diferentes, sendo que os filmes de amido são mais resistentes. As diferenças nas propriedades mecânicas dos filmes de amido e farinha foram significativas (p>0,05). O coeficiente de permeabilidade ao oxigênio foi menor para os filmes de amido do que para a farinha de CC. / The development of biodegradable materials based on biopolymers, films or coatings, have great interest for the food industry. For the production of these materials, starches and proteins are widely used because they are abundant in nature, have low cost and have films-forming property. Cañihua (Chenopodium pallidicaule), high Andean region grain underexplored industrially, has high carbohydrate content (~ 58 %) and proteins (~ 18 %) contents, and has the potential to be used as raw material in commercial starch extraction. In this context, the objectives of this study were to extract and characterize starch from two varieties cañihua, Cupi (CC) and Illpa (CI) and select a variety to develop starch films. Furthermore, the selected variety was used to obtain a rich starch and protein material, known as flour, which was also used to produce biodegradable films. Cañihua grains Illpa and Cupi varieties are very similar in shape and size, but the content of fat and ash are higher for CC and fiber content for the CI. The extraction of starch was performed with sodium hydroxide solution (0.25 % w/v) and their structural, physicochemical and functional characteristics were determined. The yield of this process was approximately 33 %, and CC variety starch showed higher levels of lipids. Starches from both varieties observed in scanning electron microscope, showed smooth granular surfaces and spherical shapes of small size (D3,2 ~ 0.96 µM). The particle size distribution, crystallinity index, FTIR spectra, swelling power, thermal and optical properties were similar, but the amylose content was higher for CC variety. Higher values of solubility and viscosity of pasting properties were observed for CC variety starch and may be associated with higher amylose contents. Cañihua Cupi starch was selected to produce films, due to the higher amylose and lipid content. CC flour was also extracted with NaOH solution and adjusting the pH to 5.0 with HCl (0.2 N) in the protein precipitation step, the yield of this extraction process was estimated at 56 %. The protein content of the flour was 79 % compared to this fraction in the grain. The high protein content favors the agglomerates formation which was observed in the CC flour micrographs that showed differences in solubility, optical and pasting properties. The starch or flour films were obtained by casting method with addition of glycerol (15 g/100 g of macromolecules), as plasticizer. The characterization of the microstructure allowed observation of physical differences between starch or flour films of cañihua Cupi, and also structural characteristics were useful to explain the behavior of the other properties. When submitted to high relative humidity, films exhibited the same moisture sorption capacity behavior and water vapor permeability, however in films were in direct contact to water (solubility analysis and contact angle), the behavior of starch and flour films were different, being the structures of the starch films most resistant. Differences in mechanical properties of starch and flour films were significant (p>0.05). The oxygen permeability coefficient was lower for cañihua Cupi starch films than cañihua Cupi flour films.

O amido é um ingrediente com grande versatilidade de aplicação, e as sementes de jaca, fruto bem difundido, porém pouco aproveitado no Brasil, contêm uma quantidade considerável de amido, sendo ainda fonte de ferro e proteínas. Dessa maneira, os objetivos desse projeto foram a obtenção da farinha de sementes de jaca das variedades mole e dura, a extração do amido utilizando diferentes solventes, e a caracterização de suas propriedades físico-químicas, estruturais e funcionais, bem como a caracterização reológica de dispersões/géis de amido em cisalhamento estacionário e oscilatório. A extração alcalina do amido, além de reduzir significativamente o conteúdo de lipídeos e proteínas, deixando o amido mais puro, promoveu um aumento no teor de amilose e influenciou diretamente as características de inchamento e solubilidade, que apresentaram aumento significativo a partir da temperatura de 70 °C. O aumento da temperatura ocasionou aumento no poder de inchamento e solubilidade, que foi mais pronunciado para a variedade dura, porém esses valores ainda foram considerados baixos (< 17%). Os amidos de sementes de jaca apresentaram grânulos lisos, arredondados e em forma de sino, com formato mais truncado para o amido extraído com hidróxido de sódio. O diâmetro médio dos grânulos de amido foi menor para a extração alcalina, mas sempre com comportamento monomodal. Foi observado um padrão de difração de Raios-X do tipo A para todas as amostras estudadas, e o índice de cristalinidade foi maior para os amidos de sementes de jaca dura, com uma redução estimada em 70% para os amidos obtidos por extração alcalina. A temperatura de gelatinização dos amidos de semente de jaca foi considerada alta (70-100 °C). Os amidos de sementes de jaca dura obtidos na extração com água apresentaram maiores valores de viscosidade de pico e de Breakdown, que representa menor resistência mecânica. A extração com solução de NaOH 0,1 M aumentou a tendência a retrogradação de ~36% (extração aquosa) para 64% e 45% dos amidos de sementes de jaca das variedades mole e dura, respectivamente. Todas as amostras apresentaram comportamento pseudoplástico (n < 1) nas concentrações e temperaturas estudadas, e as dispersões e/ou géis de amido obtidos pela extração alcalina com NaOH apresentaram menor tixotropia e maiores valores de viscosidade. Os modelos Lei da Potência e Herschel Bulkley apresentaram ótimos ajustes aos pontos experimentais (R² ~0,998) para as amostras com 2 e 6 % de amido, respectivamente, porém para a concentração de 5%, o melhor modelo foi função da variedade do fruto usado na obtenção do amido. A dependência das propriedades reológicas com a temperatura foi analisada pela equação de Arrhenius e a energia de ativação foi baixa (15-25 kJ/mol). Quanto ao comportamento viscoelástico, as amostras com 5 e 6% de amido apresentaram comportamento de gel fraco e o aumento da concentração desse polissacarídeo produziu um aumento na elasticidade do material. Os módulos de armazenamento (G\') associados à elasticidade do gel de amido aumentaram durante o seu resfriamento nos ensaios de varredura de temperatura, o que pode ser relacionado à recristalização da amilose durante esse processo e mantiveram-se praticamente constantes no aquecimento isotérmico a 80 °C, sugerindo boa estabilidade térmica do gel. A farinha isolada da semente de jaca pode ser considerada fonte de fibras e apresentou elevados teores de proteínas (~14-16%) e ferro (~85-150 mg/kg). A distribuição do tamanho de partículas da farinha apresentou comportamento bimodal, com grânulos arredondados, presença de fibras e uma matriz proteica envolvendo os grânulos de amido. As propriedades de pasta revelaram maior pico de viscosidade para a farinha de semente de jaca mole. As características encontradas sugerem que os amidos de semente de jaca poderiam ser aplicados na produção de filmes biodegradáveis, e a farinha da semente de jaca poderia ser utilizada em substituição parcial à farinha convencional na fabricação de bolos e biscoitos. / Starch is an ingredient with great versatility of application, and the seeds of jackfruit, a well spread fruit but little exploited in Brazil, contain a considerable amount of starch, being a source of iron and proteins. Thus, the aimes of this project were to obtain the jackfruit seed flour of hard and soft varieties, extraction of starch using different solvents and characterization of its physicochemical, structural and functional properties, as the rheological characterization of dispersion/gels starch under steady and oscillatory shear. Alkaline extraction of starch significantly reduced the content of lipids and proteins, leaving to a purest starch, and promoted an increase in amylose content, besides, directly influenced the swelling and solubility characteristics, which showed a significant increase from the temperature of 70 ° C. The increase in temperature caused an increase in the power of swelling and solubility, which was more pronounced for the hard variety, but these values are still considered low (<17%). Jackfruit seeds starch granules showed smooth, rounded, bell-shaped, and they had more truncated form when starch was extracted with sodium hydroxide. The average diameter of the starch granules was lower for alkaline extraction, but always with monomodal behavior. It was observed diffraction pattern of X-rays of type A for all samples, and the crystallinity index was higher for the starches of hard jackfruit seeds with an estimated reduction of 70% to starches obtained by alkaline extraction. The gelatinization temperature of starches jackfruit seed was considered high (70-100 °C). The hard jackfruit seed starches obtained in the aqueous extraction had higher peak viscosities and Breakdown, what means lower mechanical strength. Extraction with 0.1 M NaOH solution increased the retrogradation of ~ 36% (aqueous extraction) to 64% and 45% of jackfruit seed starch varieties of soft and hard, respectively. All samples exhibited pseudoplastic behavior (n <1) at the concentrations and temperatures studied, and starch dispersions and /or gels obtained by alkaline extraction with NaOH showed lower thixotropy and higher viscosities. Power Law and Herschel Bulkley models showed great adjustments to the experimental points (R² ~ 0.998) for samples with 2 and 6% starch, respectively, but for the concentration of 5%, the best model was a function of the fruit variety used on starch extraction. The dependence of the rheological properties with temperature was examined by the Arrhenius equation and activation energy was low (15-25 kJ / mol). In concern to the viscoelastic behavior, samples of 5 and 6% of starch showed a behavior of weak gel and the increase in concentration of this polysaccharide produced an increase in the elasticity of the material. The storage modulus (G \') associated with the elasticity of the starch gel increased during its cooling in the temperature sweep tests, which may be related to the recrystallization of amylose during this process and remained practically constant in the isothermal heating at 80 °C, suggesting good thermal stability of the gel. The isolated jackfruit seed flour may be considered source of fiber and showed high levels of proteins (~ 14-16%) and iron (~ 85-150 mg / kg). Particle size distribution of the flour showed bimodal behavior with rounded beads, fibers and the presence of a protein matrix surrounding the starch granules. Pasting properties revealed higher peak viscosity for the soft jackfruit seeds flour. The characteristics found suggest that jackfruit seed starch could be applied in the production of biodegradable films, and jackfruit seed flour could be used in partial replacement of conventional flour in the manufacture of cakes and cookies.

Nos últimos anos, pesquisas sobre a produção de nanocristais de amido (NCA) receberam interesse crescente devido a suas diversas aplicações, principalmente como material de reforço de matrizes poliméricas. Nesse contexto, o amido de quinoa (AQ) apresenta características desejáveis na produção de NCA tais como tamanho de grânulo pequeno e conteúdo de amilose relativamente baixo. Assim, o objetivo desta pesquisa foi produzir NCA de quinoa (NCAQ) por hidrólise ácida em diferentes temperaturas (30, 35 e 40) °C. Além disso, foi estudado o efeito da adição dos NCAQ nas propriedades estruturais e físicas de filmes de amido de mandioca. O AQ apresentou diferentes percentagens de hidrólise, no quinto dia, 63%, 73% e 91% para (30, 35 e 40) °C, respectivamente. O AQ (k = 0,59 dias-1) foi hidrolisado mais rápido que o amido de milho ceroso (k = 0,39 dias-1) a 40 °C. O rendimento dos NCAQ diminuiu com o incremento da temperatura de 30 a 40 °C; enquanto que a cristalinidade relativa dos NCAQ não foi alterada (~35%). A morfologia dos NCAQ produzidos a 30 °C foi irregular com tamanho micrométrico, enquanto que os produzidos a 35 e 40 °C apresentaram forma de paralelepípedo com tamanhos entre (50 e 100) nm e (400 e 900) nm (agregados). O diâmetro hidrodinâmico e as propriedades térmicas dos NCAQ diminuíram com o aumento da temperatura da hidrólise; enquanto que a intensidade das bandas FTIR e o potencial zeta aumentaram. As propriedades indicaram que NCAQ foram produzidos somente a (35 e 40) °C com rendimentos de 22,7% e 6,8%, respectivamente. Dessa forma, considerando o rendimento e a temperatura de transição, os NCAQ produzidos a 35 °C foram selecionados para aplicação em filmes de amido de mandioca. Os filmes foram preparados pela técnica do casting, com 4 g de amido de mandioca/100 g de dispersão filmogênica; 25 g glicerol/ 100 g de amido; e 0; 2,5; 5,0 e 7,5 g de NCAQ/ 100 g de amido. Os difratogramas de raios X confirmaram a presença dos NCAQ nos filmes. A adição de NCAQ nos filmes aumentou a rugosidade e o ângulo de contato em concentrações de 5% e 7,5%, a resistência à tração e o módulo elástico, os parâmetros de cor L* e a* em concentrações 7,5%, e a opacidade; enquanto que diminuiu a deformação na ruptura, a permeabilidade ao vapor de água na concentração de 5%, e o brilho. Outras propriedades dos filmes como espessura, umidade, solubilidade, propriedades térmicas não foram alteradas pela adição de NCAQ. Os resultados indicaram que os NCAQ produzidos a 35 °C podem ser usados como reforço em filmes nanocompósitos para melhorar suas propriedades mecânicas. / Recently researches on starch nanocrystals (SNC) production have become of interest due to their many applications, especially as reinforcement in polymeric matrices. Quinoa starch (QS) has desirable characteristics for SNC production such as small granule size and relatively low amylose content. Thus, the objective of this research was to produce quinoa SNC (QSNC) by acid hydrolysis at different temperatures (30, 35 and 40) °C. Furthermore, the effect of QSNC addition on the structural and physical properties of cassava starch films was studied. QS presented different percentages of hydrolysis on the fifth day, 63%, 73% and 91% for (30, 35 and 40) °C, respectively. QS (0.59 days-1) was hydrolyzed more rapidly than waxy maize starch (0.39 days-1) at 40 °C. QSNC yields decreased with temperature increase from (30 to 40) °C, while the relative crystallinity was not altered (~35%). The morphology of QSNC produced at 30 °C was irregular with micrometric size while those produced at 35 °C and 40 °C presented parallelepiped shapes with sizes between 50 nm and 100 nm and 400 nm to 900 nm (aggregates). The hydrodynamic diameter and the thermal properties of QSNC decreased with temperature increase, while the FTIR band intensities and the zeta potential increased. The properties indicated that quinoa QSNC were only obtained at (35 and 40) °C with yields of 22.8% and 6.8%, respectively. QSNC produced at 40 °C presented lower yield and crystallinity than waxy maize SNC, but a lower hydrodynamic diameter. Thus, based on the yield and transition temperature, QSNC produced at 35 °C was selected for application in cassava starch films. The films were prepared by casting technique, with 4 g of cassava starch / 100 g of film forming dispersion; 25 g glycerol / 100 g starch; and 0; 2.5; 5.0 and 7.5 g of QSNC / 100 g of starch. X-ray diffractograms confirmed the presence of QSNC in the films. Addition of QSNC to films increased the roughness and the contact angle at 5.0% and 7.5% concentrations, the tensile strength and elastic modulus, the color parameters L* and a* at 7.5% concentration, and the opacity; while decreasing deformation at break, water vapor permeability at 5.0% concentration, and gloss. Other film properties such as thickness, moisture content, solubility, thermal properties were not affected by QSNC addition. The results indicated that the QSNC produced at 35 ° C can be used as reinforcement in nanocomposite films to improve their mechanical properties.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23223号 / 工博第4867号 / 新制||工||1760(附属図書館) / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 大北 英生, 教授 辻井 敬亘, 教授 田中 一生 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

No description available.

Crystallisation of epoxy resins based on bisphenol A and bisphenol F is the natural property of these oligomers. However, manufacturers of paints and other systems based on these epoxy resins, strive to slow down the crystallisation process as much as possible, thereby prolonging the shelf life and improving the competitiveness of their products. The main aim of the thesis is generalisation of the factors influencing the crystallisation process of epoxy resins based on bisphenol A and bisphenol F, verifying new approaches to the possibility of influencing the crystallisation process and determining the possibility of using a certain degree of epoxy resins crystallinity based on bisphenol A and bisphenol F in the preparation and production of epoxy resinbased coating systems.

The thesis deals with HDPE modification by crosslinking. In the theoretical part, data available in the literature were reviewed. Modifications of the selected HDPE copolymer grade were carried out in a kneading device Brabender using 25 ml chamber size. After having optimized process conditions, there were performed a series of experiments in dependence on concentration of the initiator. Reological properties of polymer samples were investigated by melt flow indexes measured under different conditions. Changes in crystallinity and melting temperatures were evaluated from DSC heat flow measurements. The samples meeting characteristics supposed were selected for measuring complex viscosity on the Rheometer AR-G2 TA and for testing some mechanical properties on the device Zwick.

The present work represents a systematical study of the growth of columnar, metallic thin films deposited under highly oblique vapor incidence on planar substrates. Oblique angle deposition is a physical vapor deposition technique that is based on the self-shadowing effect. This enables the fabrication of highly porous thin films that are composed of three-dimensionally separated, micro-, and nano-sized columns. For this study, metals that cover a wide range of melting points and crystal structures have been chosen, and the observed growth characteristics are compared with each other to gain information about the growth of obliquely deposited metallic thin films in general. Among the various parameters that have an influence on the growth of columnar thin films, in the focus of this work are the angle of the incoming particle flux, substrate rotation frequency, and substrate temperature as well as the influence of the residual gas atmosphere. The first part deals with a morphological analysis of the columnar, metallic thin films by scanning electron microscopy (SEM). The columnar shape, the columnar tilt angle, and the thin film porosity are investigated depending on the incidence flux direction as well as substrate temperature and rotation. It is examined how a reduction of the substrate temperature down to 77 K - realized by a liquid nitrogen cooled sample holder - influences the growth of the columnar thin films. Further, it is analyzed how substrate rotation influences the local deposition geometry and accordingly the growth behavior of tilted columns, spirals, screws, and upright columns. Based on geometrical considerations, a theoretical model is proposed and compared with the made observations. The second part focusses on the high-resolution local structure analysis of individual columns via (scanning) transmission electron microscopy (TEM). On the one hand, the columnar structure is analyzed depending on the substrate temperature and substrate rotation via high resolution TEM. On the other hand, the crystallinity of individual columns is studied along the entire column by nanobeam electron diffraction. This technique is also applied to gain information about the orientation of the crystallites at the substrates surface and to investigate the selection processes of crystalline orientations during the growth. Moreover, the presented studies reveal under which conditions single crystalline columns are forming. In the final part, the texture of the columnar, metallic thin films is analyzed depending on the film thickness, the angle of the incoming particle flux as well as on the substrate temperature. X-ray diffraction (XRD) measurements, such as pole figures, are applied to determine the orientation of the lattice planes in the columns depending on the incident flux direction and on the substrate temperature. The observations are backed by reflection high-energy electron diffraction (RHEED) investigations. A model is developed that enables to explain why the tilt of the lattice directions in the columns is not equal to the tilt angle of the columns. A further theoretical model is introduced that enables to roughly estimate the tilt angle of the lattice direction that ensures the fastest vertical columnar growth.:1 MOTIVATION 7 2 BASICS OF OBLIQUE ANGLE DEPOSITION 9 2.1 Thin film growth by oblique deposition 9 2.1.1 Physical vapor deposition 9 2.1.2 Nucleation 10 2.1.3 Shadowing 11 2.1.4 Structure of individual columns 12 2.2 Sculpturing thin films on the nanometer scale 13 2.2.1 Angle of the incoming particle flux 13 2.2.2 Substrate rotation 16 2.2.3 Substrate temperature 17 2.3 Application areas for metallic nanostructured thin films 20 3 EXPERIMENTAL DETAILS 23 3.1 Sample fabrication 23 3.1.1 General deposition system setup and evaporation process 23 3.1.2 Crucibles, substrates, and sample holders 25 3.1.3 Controlling substrate movement and temperature 26 3.1.4 Controlling film thickness and deposition rate 29 3.2 Sample characterization 30 3.2.1 Scanning electron microscope (SEM) 30 3.2.2 Transmission electron microscopy (TEM) 31 3.2.3 X-Ray Diffraction (XRD) and In-Plane Pole Figure measurements (IPPF) 33 3.2.4 Reflection high-energy electron diffraction (RHEED) 36 3.2.5 Raman scattering spectroscopy 36 4 MORPHOLOGICAL ANALYSIS OF COLUMNAR THIN FILMS 39 4.1 Oblique angle deposition 40 4.1.1 Deposition at room temperature 40 4.1.2 Deposition at different temperatures 43 4.2 Glancing angle deposition 61 4.2.1 Continuous substrate rotation 61 4.2.2 Discrete substrate rotation 66 4.3 Summary of results 69 5 STRUCTURAL ANALYSIS OF INDIVIDUAL COLUMNS 71 5.1 Oblique angle deposition 71 5.1.1 Tilted columns grown at room temperature 71 5.1.2 Tilted columns grown at different substrate temperatures 78 5.2 Glancing angle deposition 82 5.2.1 Vertical columns grown by continuous substrate rotation 82 5.2.2 Zigzag columns grown by discrete substrate rotation 85 5.3 Discussion 87 5.4 Summary of results 89 6 TEXTURE ANALYSIS OF COLUMNAR THIN FILMS 91 6.1 Influence of the film thickness 91 6.2 Influence of the incoming flux direction 99 6.3 Influence of the substrate temperature 110 6.4 Summary of results 116 7 SUMMARY AND CONCLUSIONS 119 8 LIST OF LITERATURE 123 9 LIST OF ABBREVIATIONS 134 10 LIST OF VARIABLES AND CONSTANTS 136 11 ACKNOWLEDGEMENTS 139 PUBLICATION LIST 140 SELBSTSTÄNDIGKEITSERKLÄRUNG 143

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18297号 / 工博第3889号 / 新制||工||1597(附属図書館) / 31155 / 京都大学大学院工学研究科高分子化学専攻 / (主査)教授 赤木 和夫, 教授 山子 茂, 教授 秋吉 一成 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Natural nanominerals are abundant in Earth's critical zone and important in innumerable environmental processes that affect water quality. The chemical behavior of many natural nanominerals is related to their extreme small size (<10 nm) and high surface area. Atomic structural and chemical heterogeneity are also important factors affecting nanoparticle reactivity, and are a consequence of the mechanisms and complex (natural) conditions by which they form. The relationships between these factors remain poorly understood and limit our ability to predict the formation, transformation, and chemical behavior of natural nanominerals in the environment. We are using a poorly crystalline ferric hydroxysulfate nanomineral, schwertmannite, as a model system to understand the effect of formation conditions, specifically solution chemistry, on its physico-chemical characteristics. Previous studies indicate schwertmannite has highly variable bulk sulfate (Fe/S molar from 3-15) and water contents (Caraballo et al., 2013). In addition, both natural and synthetic schwertmannites have recently been described as "polyphasic" (i.e., consisting of sulfate-poor, goethite-like ordered domains embedded in a sulfate-rich, amorphous material) from observations using transmission electron microscopy (French et al., 2012). We hypothesize that solution chemistry at the time of schwertmannite formation directly affect its composition and structure. Using a factorial experiment design, we investigated the effects of increasing solution sulfate concentration ([SO4]/[Fe] at 1, 2, 3 and 5) and pH (2.4-5.6) on the crystallinity and composition of the products. Ferric hydroxide and hydroxysulfate solids were precipitated in batches by the rapid oxidation of Fe(II) by hydrogen peroxide, similar to what is seen in natural environmental systems. Sulfate and hydroxide concentrations were varied by addition of NaSO4 and NaOH, respectively. Solids were characterized using synchrotron X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), inductively coupled plasma-mass spectrometry (ICP-MS), scanning electron microscopy (SEM), and high resolution- transmission electron microscopy (HR-TEM). Our results show that schwertmannite is the only precipitate formed at low pH and that goethite rapidly becomes dominant at pH > 3.5. High-resolution TEM showed our synthetic schwertmannite samples consist of poorly crystalline goethite-like nanodomains within an amorphous solid, similarly seen in previous results. ICP-MS results reveal a narrow Fe/S molar ratio of 4.5 ±0.1 for our synthetic schwertmannite, which suggests that schwertmannite chemical composition does not depend strongly on pH or initial solution sulfate concentration. Increasing pH from 2.4 to 3.2 also has little effect on the crystallinity, bulk Fe/S ratio and water contents of schwertmannite. Increasing solution [SO4]/[Fe] also has little to no impact on crystallinity, water content or the amount of sulfate incorporated in schwertmannite. Thus, schwertmannite crystallinity and composition is not affected by initial solution sulfate and concentration under our experimental conditions. Thermal analysis allows us to independently measure OH and SO4 content in synthetic schwertmannite. In doing so, we propose a more accurate chemical formula (Fe8Oz(OH)24-2z-2x(SO4)x). The average stoichiometry based on thermal analysis of schwertmannite precipitated at [SO4]/[Fe] = 1 and pH ranging from ~2.4 2.9 is Fe8O6.51(OH)8.4(SO4)1.28. Interestingly, the calculated number of moles of oxygen is less than 8, which suggests that the standard formula Fe8O8(OH)8-2x(SO4)x is incorrect. These results for synthetic samples provide important constraints for future studies aimed at better understanding the formation, compositional variability and chemical behavior of natural schwertmannite. / Master of Science