The effect of structure on the dilute solution properties of branched polysaccharides studied with SEC and AsFlFFF

Cereal arabinoxylans, guar galactomannans, and dextrans produced by lactic acid bacteria(LAB) are a structurally diverse group of branched polysaccharides with nutritional and industrial functions. In this thesis, the effect of the chemical structure on the dilute solution properties of these polysaccharides was investigated using size-exclusion chromatography(SEC) and asymmetric flow field-flow fractionation (AsFlFFF) with multiple-detection. The chemical structures of arabinoxylans were determined, whereas galactomannan and dextran structures were studied in previous investigations. Characterization of arabinoxylans revealed differences in the chemical structures of cereal arabinoxylans. Although arabinoxylans from wheat, rye, and barley fiber contained similar amounts of arabinose side units, the substitution pattern of arabinoxylans from different cereals varied. Arabinoxylans from barley husks and commercial low-viscosity wheat arabinoxylan contained a lower number of arabinose side units. Structurally different dextrans were obtained from different LAB. The structural effects on the solution properties could be studied in detail by modifying pure wheat and rye arabinoxylans and guar galactomannan with specific enzymes. The solution characterization of arabinoxylans, enzymatically modified galactomannans, and dextrans revealed the presence of aggregates in aqueous polysaccharide solutions. In the case of arabinoxylans and dextrans, the comparison of molar mass data from aqueous and organic SEC analyses was essential in confirming aggregation, which could not be observed only from the peak or molar mass distribution shapes obtained with aqueous SEC. The AsFlFFF analyses gave further evidence of aggregation. Comparison of molar mass and intrinsic viscosity data of unmodified and partially debranched guar galactomannan, on the other hand, revealed the aggregation of native galactomannan. The arabinoxylan and galactomannan samples with low or enzymatically extensively decreased side unit content behaved similarly in aqueous solution: lower molar mass samples stayed in solution but formed large aggregates, whereas the water solubility of the higher-molar-mass samples decreased significantly. Due to the restricted solubility of galactomannans in organic solvents, only aqueous galactomannan solutions were studied. The SEC and AsFlFFF results differed for the wheat arabinoxylan and dextran samples. Column matrix effects and possible differences in the separation parameters are discussed, and a problem related to the non-established relationship between the separation parameters of the two separation techniques is highlighted. This thesis shows that complementary approaches in the solution characterization of chemically heterogeneous polysaccharides are needed to comprehensively investigate macromolecular behavior in solution. These results may also be valuable when characterizing other branched polysaccharides.Erilaisia analyysimenetelmiä hyödyntämällä luotettavaa tietoa haaroittuneiden polysakkaridien liuosominaisuuksista Arabinoksylaanit, galaktomannaanit ja dekstraanit ovat joko kasvi- tai mikrobiperäisiä polysakkarideja. Viljoissa esiintyvät arabinoksylaanit muodostavat yhdessä beetaglukaanin kanssa pääasiallisen ravintokuidun lähteen ravinnossa. Galaktomannaania saadaan guar-kasvin paloista ja sitä käytetään yleisesti elintarviketeollisuudessa sakeutusaineena (guarkumi E 412). Dekstraanit ovat puolestaan maitohappobakteerien tuottamia eksopolysakkarideja, joilla on paljon sovelluksia. Dekstraaneja käytetään esimerkiksi lisäaineina kosmetiikassa, kliinisissä sovelluksissa plasman laajentajina ja standardiaineina kromatografiassa. Lisäksi dekstraaneja käytetään elintarviketeollisuudessa emulgaattoreina, sakeuttajina ja stabilaattoreina. Näiden jo mainittujen sovellusten lisäksi näitä kaikkia uusiutuvia biopolymeerejä voitaisiin hyödyntää vieläkin tehokkaammin mm. selluloosan ja tärkkelyksen rinnalla, joilla on selkeästi enemmän käyttösovelluksia. Polysakkaridien kemiallinen rakenne ja sekä fysikaaliset ominaisuudet tulee kuitenkin tuntea tarkasti, jotta uusia sovelluksia voidaan kehittää. Tässä työssä tutkittiin polysakkaridien rakenteen vaikutusta niiden liuosominaisuuksiin laimeissa liuoksissa, jolloin voidaan saada tietoa yksittäisten molekyylien ominaisuuksista. Eri viljoista peräisin olevien arabinoksylaanien rakenteet olivat luontaisesti erilaiset. Lisäksi polysakkaridien rakenteita muokattiin spesifisillä entsyymeillä. Haaroittuneiden polysakkaridien liuosominaisuuksien tutkiminen on haastavaa, sillä kemiallisen rakenteen vaihtelu on suurta näytemolekyylien välillä. Lisäksi, suurin osa haaroittuneiden polysakkaridien tutkimuksesta on toistaiseksi keskittynyt amylopektiiniin, joka on tärkkelyksen rakennekomponentti, sekä glykogeeniin. Polymeerien karakterisointi on kehittynyt paljon viime vuosikymmeninä, mutta sovellukset on kehitetty lähinnä synteettisille polymeereille. Tässä tutkimuksessa hyödynnettiin kokoekskluusiokromatografiaa (SEC) ja asymmetristä poikittaisvirtauskenttävirtausfraktiointia (AsFlFFF). Molemmissa erotusmenetelmissä käytettiin useita detektoreita moolimassan, molekyylikoon, konformaation ja rajaviskositeetin määrittämiseksi kunkin näytteen kokojakaumalle. Kemiallinen rakenne vaikutti tutkittujen polysakkaridien liuosominaisuuksiin. Vaikka arabinoksylaanien ja galaktomannaanien rakenne on samankaltainen, niiden liuoskäyttäytymisessä havaittiin eroja. Dekstraaneissa on myös pidempiä haaroja, toisin kuin arabinoksylaaneissa ja galaktomannaaneissa, jotka hallitsevat molekyylien käyttäytymistä liuoksessa. Tämän tutkimuksen tulokset osoittavat, että rakenteellisesti heterogeenisten biopolymeerien liuosominaisuuksista voidaan saada luotettavaa tietoa kahta erotusmenetelmää vertaamalla, eri liuottimia hyödyntämällä, sekä eri detektiomenetelmiä yhdistämällä

Towards a Benign and Viable Rhodium Catalyzed Hydroformylation of Higher Olefins: Economic and Environmental Impact Analyses, Solvent Effects and Membrane-based Catalyst Separation

Researchers at the Center for Environmentally Beneficial Catalysis (CEBC) had previously reported a novel rhodium-based hydroformylation process concept based on the use of CO2-expanded liquids (CXLs) to intensify rates and obtain higher linear/branched aldehydes selectivity at relatively mild temperatures (30-60 °C) and pressures (~4 MPa). This dissertation continues investigations aimed at addressing the fundamental and practical issues associated with this concept. ReactIR studies of Rh/triphenylphosphine-catalyzed 1-octene hydroformylation, complemented by microkinetic and reactor modeling investigations revealed that the intrinsic kinetic rate constants are of similar magnitude with or without CO2 addition to the reaction mixture. This implies that the enhanced reaction rate observed in CXL is due to the increased hydrogen solubility in that medium. Environmental impact analysis revealed that the overall toxicity index for the CEBC process is approximately 40 times less than the Exxon process against which the CEBC process was benchmarked. Economic analysis of the CXL concept revealed that at an aldehyde production rate of 19,900 kg / (kg Rh h), 99.8% rhodium has to be recovered per pass for the CEBC process to be competitive with the Exxon process. Assuming a similar hydroformylation turnover frequency, rhodium recovery levels that exceed this criterion for economic viability were successfully demonstrated in a membrane-based nano/ultra-filtration reactor system using polymer supported phosphorus ligands, synthesized and provided by researchers from the Department of Chemistry. During continuous filtration of a toluene-based solution containing polymer-supported Rh complexes, the Rh and P concentrations in the permeate, quantified using ICP analysis, were on the order of a few tens of ppb. During continuous 1-octene hydroformylation studies in the membrane reactor at a syngas pressure of 0.6 MPa and 60 °C, the 1-octene conversion and product (mostly aldehydes) concentrations reached a steady state with the Rh concentrations in the permeate stream being lower than 120 ppb. However, the conversions and product concentrations during the continuous run are lower than those obtained in a batch ReactIR under identical operating conditions. This is attributed to syngas starvation in the membrane reactor that might be caused by inadequate mixing. In complementary investigations, it was found that the dissolution of CO2 in the organic phase (to create CO2-expanded liquids) decreases the viscosities of the mixtures with increasing CO2 pressure. This offers an opportunity to enhance mixing and also tune the membrane flux so as to increase the throughput of the membrane filter. The demonstrated technology concept, when fully optimized, should find applications in a variety of other applications in homogeneous catalysis, including hydrogenation and carbonylation of conventional and biomass-based substrates

Advanced High Resolution Electrospray Ionization Mass Spectrometric Protocols for Imaging Complex Polymer Chain Structures

Die systematische Strukturaufklärung von Makromolekülen ist ein wesentlicher Bestandteil zum tiefgehenden Verständnis von makromolekularen Prozessen. Der Zugang zur exakten Strukturaufklärung ist durch die Verwendung von hoch-auflösender Elektrospray-Ionisation (ESI MS) gewährleistet. Die milden Ionisierungsbedingungen sind unentbehrlich um intakte kovalente Bindungen in der Polymerkette sicherzustellen. Die vorliegende Doktorarbeit behandelt die Strukturaufklärung verschiedener komplexer makromolekularer Systeme mittels ESI-Orbitrap MS. Für die exakte Massenbestimmung ist die Hochauflösung entscheidend, die durch das Design der Orbitrap und die Datenverarbeitung bereitgestellt wird. Hierdurch ermöglicht sich die präzise Untersuchung einzelner Spezies und deren Isotopen-muster. Diese bildet die Grundlage nachfolgender Strukturaufklärungen, da das experimentelle mit dem simulierten (aus der zuvor bestimmten chemischen Strukturformel) Isotopenmuster verglichen wird. Zuvor ist die zuverlässige Ionisierung unpolarer Polykohlenwasserstoffe (z.B. Polystyrol und Polybutadien) unerlässlich, die durch die Anlagerung von Chlorid-Ionen gewährleistet wird. Hierfür wird das Massenspektrometer in einer für negative Ionen sensitive Betriebsweise gesetzt. Die Anlagerung von Halogeniden an aromatische oder olefinische Strukturelemente ist bemerkenswert stark, sodass eine Mehrfachionisierung hervorgerufen wird. Darüber hinaus kann die Verteilung des Ladungszustands der Polykohlenwasser-stoffe durch einfache Zugabe von sog. ‘Supercharging’ Agenzien (z.B. Sulfolan oder Propylencarbonat) beeinflusst werden. Die hier neuentwickelte Methode zur Anlage-rung von Chlorid-Ionen bildet die Grundlage zur Aufklärung verschiedenster funk-tionaler Makromoleküle, unter anderem von polyionischen Flüssigkeiten und Poly-meren mit Nitroxid-Sturkturelementen. Des Weiteren können degradierbare Stu-fenwachstumspolymere effizient in die Gasphase versetzt und somit vermessen werden. ESI MS profitiert auch durch eine vorangeschaltete Größenausschlusschromatographie (SEC-ESI MS). Hierdurch können intramolekular vernetzte Polymere – sogenannte Einzelkettennanopartikel – charakterisiert werden, wodurch ein direkter Einblick in die Chemie des Faltungsprozesses ermöglicht wird. Mittels der entwickelten Methode können sogar komplexe Ter- oder Quaterpolymere strukturell aufklären werden

Ionomeric blends of pyridine containing polymers with sulfonated PET/

An investigation of acid-base interactions and zinc transition-metal complexations in ionomeric blends of sulfonated poly(ethylene terephthalate) (PET) with pyridine containing polymers will be discussed in relation to the level of specific intermolecular interactions, as measured with FTIR, and the degree of compatibilization, as observed from DSC and DMTA. Two pyridine containing polymer systems were evaluated: (1) a novel main-chain thermotropic liquid crystalline polyester containing pyridine dicarboxylate units, and (2) poly(ethyl acrylate-co-4-vinyl pyridine). Model thermotropic liquid crystalline polyester systems were developed and screened based on a set of macromolecular structure requirements directed toward future blends studies with PET and PBT. The first investigation discussed the preparation and characterization of TLCPs based on the biphenyl mesogen, 4,4\sp\prime-bis(6-hydroxyhexoxy)- biphenyl, BHHBP. Two series of TLCPs were prepared and characterized by CPOM, DSC, and WAXD. Both series of polymers exhibited smetic A phase types. The second investigation discussed the preparation and characterization of thermotropic liquid crystalline polyester based on the triad mesogen monomer, 4,4\sp\prime- (terephthaloyldioxy)dibenzoyl dichloride, (ClHTHCl). Various dihydroxy flexible spacers having chemical substituents similar in structure to the repeat units of PET and/or PBT were copolymerized with ClHTHCl and evaluated by CPOM, DSC, and WAXD. From this investigation, a series of polymers were characterized as an enantiotropic nematics. From this series, a candidate was selected as a model system, where the composition of flexible spacers was: 75% bis(4-hydroxybutyl) terephthalate and 25% 1,6-hexanediol. The flexible spacers of the model system was then modified to contain pyridine dicarboxylate units. This modified model system (TLCP\sb{\rm N}) was characterized as having a similar phase and phase-temperature relationship when compared to the model system. Upon development and characterization of TLCP\sb{\rm N}, ion exchange procedures were developed to exchange the sodium ions of PET-SO\sb3Na for hydrogen and subsequently hydrogen ions for zinc. Stoichiometric blends of both the free acid and zinc neutralized form of sulfonated PET were prepared and characterized by FTIR, DSC, and DMTA. For both these blends there was no evidence for specific intermolecular interactions or compatibilization. In the final investigation, both the free acid and zinc neutralized forms of sulfonated PET were blended with poly(ethyl acrylate-co-4-vinyl pyridine). The stoichiometric blends were prepared and characterized similar to the previous study. A zinc blend containing 77% sulfonated PET (7% SO\sb3Zn) and 23% poly(ethyl acrylate-co-4-vinyl pyridine) (10.6% VP) appeared to be predominately single phase by DSC and partially phase separated by DMTA. Where similar blends containing 58% poly(ethyl acrylate-co-4-vinyl pyridine) (5.2% VP) appear partially phase separated by both DSC and DMTA

Microgravity Science and Applications: Program Tasks and Bibliography for Fiscal Year 1996

NASA's Microgravity Science and Applications Division (MSAD) sponsors a program that expands the use of space as a laboratory for the study of important physical, chemical, and biochemical processes. The primary objective of the program is to broaden the value and capabilities of human presence in space by exploiting the unique characteristics of the space environment for research. However, since flight opportunities are rare and flight research development is expensive, a vigorous ground-based research program, from which only the best experiments evolve, is critical to the continuing strength of the program. The microgravity environment affords unique characteristics that allow the investigation of phenomena and processes that are difficult or impossible to study an Earth. The ability to control gravitational effects such as buoyancy driven convection, sedimentation, and hydrostatic pressures make it possible to isolate phenomena and make measurements that have significantly greater accuracy than can be achieved in normal gravity. Space flight gives scientists the opportunity to study the fundamental states of physical matter-solids, liquids and gasses-and the forces that affect those states. Because the orbital environment allows the treatment of gravity as a variable, research in microgravity leads to a greater fundamental understanding of the influence of gravity on the world around us. With appropriate emphasis, the results of space experiments lead to both knowledge and technological advances that have direct applications on Earth. Microgravity research also provides the practical knowledge essential to the development of future space systems. The Office of Life and Microgravity Sciences and Applications (OLMSA) is responsible for planning and executing research stimulated by the Agency's broad scientific goals. OLMSA's Microgravity Science and Applications Division (MSAD) is responsible for guiding and focusing a comprehensive program, and currently manages its research and development tasks through five major scientific areas: biotechnology, combustion science, fluid physics, fundamental physics, and materials science. FY 1996 was an important year for MSAD. NASA continued to build a solid research community for the coming space station era. During FY 1996, the NASA Microgravity Research Program continued investigations selected from the 1994 combustion science, fluid physics, and materials science NRAS. MSAD also released a NASA Research Announcement in microgravity biotechnology, with more than 130 proposals received in response. Selection of research for funding is expected in early 1997. The principal investigators chosen from these NRAs will form the core of the MSAD research program at the beginning of the space station era. The third United States Microgravity Payload (USMP-3) and the Life and Microgravity Spacelab (LMS) missions yielded a wealth of microgravity data in FY 1996. The USMP-3 mission included a fluids facility and three solidification furnaces, each designed to examine a different type of crystal growth

The interaction of cellulose with xyloglucan and other glucan-binding polymers

This thesis examines the interaction of xyloglucan, the major hemicellulosic component of type I primary plant cell walls, with cellulose. Initial attempts to form xyloglucan-cellulose complexes by in vitro association methods are described, which gave low levels of interaction, with features not similar to those found in primary wall networks. The majority of the work focusses on the use of the bacterium Acetobacter aceti ssp. xylinum (ATCC 53524), which synthesise highly pure, crystalline cellulose as an extracellular polysaccharide. Addition of xyloglucan to a cellulose-synthesising bacterial culture results in the formation of cellulose-xyloglucan networks with ultrastructural and molecular features similar to those of the networks of higher plants. Applicatioon of the bacterial fermentation system is extended to incorporate the polysaccharides glucomannan, galactomannan, xylan, mixed-linkage glucan, pectin and carboxymethylcellulose, all of which impart unique architectural and molecular effects on the composistes formed. Preliminary data on the mechanical properties of composite structures under large and small deformation conditions are also described