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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The metabolism of itaconic acid by animal tissues

Adler, Julius, January 1957 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1957. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 80-84).
2

A process for melt grafting itaconic anhydride onto polyethylene

Hanipah, Suhaiza Hanim January 2008 (has links)
Currently, extensive research in using bio‐derived polymers is being done, highlighting the importance of sustainable, green polymeric materials. Some sustainable alternatives to synthetic polymers include lignin, starch, cellulose or blends of these with petroleum‐based polymers. In New Zealand, large quantities of animal derived proteins are available at very low cost, making it ideal as a sustainable alternative to petroleum‐derived polymers. However, the processability of most proteins is very difficult, but can be improved by blending with synthetic polymers, such as polyolefins. To improve, the compatibility between these substances, a functional monomer could be grafted onto the polyolefin chain. Using an appropriate functional group, the polyolefin could then react with certain amino acids residues in the protein. Lysine and cystein are the two most appropriate amino acid residues because of their reactivity and stability at a wide pH range. In this study, free radical grafting of itaconic anhydride (IA) onto polyethylene was investigated. IA was selected because it is capable of reacting with polyethylene and amino acid residues, such as lysine. The objective of the research was to identify and investigate the effect of reaction parameters on grafting. These were: residence time, temperature, initial monomer concentration as well as peroxide concentration and type. Grafting was characterized in terms of the degree of grafting (DOG), percentage reacted and the extent of side reactions. The reaction temperature was taken above the melting point of the polyethylene, monomer and decomposition temperature of the initiator. It was found that above 160 C polymer degradation occurred, evident from sample discolouration. A higher degree of grafting can be achieved by increasing the initial monomer concentration up to a limiting concentration. The highest DOG achieved was about 1.2 mol IA per mol PE, using 2 wt% DCP. When using 2 wt % peroxide, the limiting concentration was found to be 6 wt% IA, above which no improvement in DOG was achieved. It was found that DCP is much more effective at grafting, compared to DTBP because DTBP is more prone to lead to side reactions than DCP. iv It was found that a residence time of 168 seconds resulted in the highest DOG, corresponding to 4 extrusions in series. However, it was also found that an increase in residence time resulted in an increase in polymer degradation. The tensile strength of PE decreased after two extrusions when using DTBP, and three extrusions, when using DCP. Young's modulus decreased only slightly, while all samples showed a dramatic decrease in ductility, even after one extrusion. It was concluded that degradation had a more pronounced effect on mechanical properties than cross‐linking, and residence time should therefore not exceed three extrusions in series, which corresponded to about 126 seconds. It can be concluded that a high reaction temperature and high initiator concentration lead to a low degree of grafting, accompanied by high cross‐linking and increased degradation. On the other hand, high monomer concentration and high residence time lead to a high degree of grafting. Optimising grafting is therefore a trade off between maximal DOG and minimising side reactions such as cross‐linking and degradation and optimal conditions do not necessarily correspond to a maximum DOG. Other factors, such as the use of additives to prevent degradation should also be investigated and may lead to different optimum conditions.
3

Novel Small Molecules and Tumor Cells

Strelko, Cheryl January 2012 (has links)
Thesis advisor: Mary F. Roberts / Thesis advisor: Eranthie Weerapana / Small molecules are of interest both as metabolites in tumor cell biology and as potential therapeutics in the fight against cancer. In this work, small molecules in both roles have been examined. Modulation of tumor cell metabolism holds promise as a strategy to combat cancer, and both glucose and glutamine have been identified as critical fuels for tumor cell growth and proliferation. However, the reason for glutamine addiction is poorly understood. The differential metabolism of glutamine and glucose was therefore examined using ¹³C labeling and NMR-based metabolomics in the VM-M3 tumor cell line, which requires both glucose and glutamine for survival and proliferation. In the course of this study, a novel mammalian metabolite itaconic acid was identified. Itaconic acid was detected in extracts and tissue culture media from the murine macrophage-derived tumor cell lines VM-M3 and RAW 264.7 as well as in primary macrophages. Production and secretion of itaconic acid was increased upon stimulation. LC-MS and NMR based metabolomics studies show that this metabolite is synthesized by the decarboxylation of cis-aconitate from the TCA cycle, and provided evidence for a novel mammalian homologue of the enzyme cis-aconitic decarboxylase. D-3-deoxy diC₈PI is a small molecule of interest as a potential cancer therapeutic. This compound was designed to induce apoptosis in tumor cells by competitively binding to the Akt PH domain and preventing Akt translocation. However, high resolution ³¹P field-cycling studies show that both D-3-deoxy diC₈PI and an inactive analogue L-3,5-dideoxy diC₈PI bind to the same site on the PH domain, which is distinct from the binding site of the ligand diC₈PI(3,4,5)P₃. This makes the aforementioned mechanism of cytotoxicity unlikely. Aggregation of the PH domain in the presence of soluble headgroup IP₆ was also observed, which may be related to a physiological function of this protein and invalidates at least one other binding assay. Investigation into alterations in signaling pathways in the MCF-7 breast cancer cell line showed that D-3-deoxy diC₈PI activates the p38MAPK pathway which results in CREB hyperphosphorylation. However, activation of this pathway appears to be compensatory and unrelated to the mechanism of action. D-3-deoxy diC₈PI also decreases levels of cyclin D1 and cyclin D3, which regulate the progression of the cell cycle. These decreases appear to be occurring at the transcriptional level rather than due to increased proteasomal degradation. The loss of these two proteins does not cause apoptosis in MCF-7 cells, but siRNA knockdown of specifically cyclin D1 inhibits proliferation. This is consistent with the cell cycle arrest observed upon D-3-deoxy diC₈PI treatment in these cells. These findings do not conclusively elucidate the mechanism of cytotoxicity of D-3-deoxy diC₈PI, but provide a characterization of some of its effects in the MCF-7 cell line which may be useful for further studies. / Thesis (PhD) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
4

I. Understanding Membrane Interactions of Bacterial Exoproteins; II. Identification and Characterization of a Novel Mammalian cis-Aconitate Decarboxylase

Cheng, Jiongjia January 2013 (has links)
Thesis advisor: Mary F. Roberts / Secreted phosphatidylinositol-specific phospholipase Cs (PI-PLCs) are often virulence factors in pathogenic bacteria. Understanding how these enzymes interact with target membranes may provide novel methods to control bacterial infections. In this work, two typical PI-PLC enzymes, from Bacillus thuringiensis (Bt) and Staphylococcus aureus (Sa), were studied and their membrane binding properties were examined and correlated with enzymatic activity. BtPI-PLC is kinetically activated by allosteric binding of a phosphatidylcholine (PC) molecule. MD simulations of the protein in solution suggested correlated loop and helix motions around the active site could regulate BtPI-PLC activity. Vesicle binding and enzymatic studies of variants of two proline residues, Pro245 and Pro254, that were associated with these motions showed that loss of the correlated motions between the two halves of PI-PLC were more critical for enzymatic activity than for vesicle binding. Furthermore, loss of enzyme activity could be rescued to a large extent with PC present in a vesicle. This suggests that binding to PC changes the enzyme conformation to keep the active site accessible. SaPI-PLC shows 41.3% sequence similarity with BtPI-PLC but has very different ways its activity is regulated. While it is kinetically activated by PC it does not in fact bind to that phospholipid. Enzymatic and membrane interaction assays showed that SaPI-PLC has evolved a complex, apparently unique way to control its access to PI or GPI-anchored substrate. (i) An intramolecular cation-pi latch facilitates soluble product release under acidic conditions without dissociation from the membrane. (ii) There is a cationic pocket on the surface of enzyme that likely modulates the location of the protein. (iii) Dimerization of protein is enhanced in membranes containing phosphatidylcholine (PC), which acts not by specifically binding to the protein, but by reducing anionic lipid interactions with the cationic pocket that stabilizes monomeric protein. SaPI-PLC activity is modulated by competition between binding of soluble anions or anionic lipids to the cationic sensor and transient dimerization on the membrane depleted in anionic phospholipids. This protein also served as a way to test the hypothesis that a cation-pi box provides for PC recognition site. This structural motif was engineered into SaPI-PLC by forming N254Y/H258Y. This variant selectively binds PC-enriched vesicles and the enzyme binding behavior mimics that of BtPI-PLC. Itaconic acid (ITA) is a metabolite synthesized in macrophages and related cell lines by a cis-aconitate decarboxylase (cADC). cADC activity is dramatically increased upon macrophage stimulation. In this work, the cell line RAW264.7 was used to show that cADC activity upon stimulation requires de novo protein synthesis. MS analyses of partially purified RAW264.7 protein extracts from stimulated cells show a large increase for immunoresponsive gene 1 protein (IRG1) and siRNA knockdown of the IRG1 reduces cADC activity upon stimulation. Suspected active site residues of IRG1 were identified by mutagenesis studies of the recombinant protein based on a homology structure model of fungal cADC. The cloning and overexpression of this enzyme should help clarify the cofactor-independent decarboxylation mechanism of this mammalian enzyme as well as open up future studies into the specific role of ITA in the mammalian immune system and cancers. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
5

Preparação e avaliações comparativas das propriedades físico-químicas entre os hidrogéis de poliacrilato de sódio e de ácido itacônico para potencial aplicação como biomaterial / Comparative evaluations and preparation of physical-chemical properties between sodium polyacrylate and itaconic acid hydrogels for potential application as biomaterial.

Raquel Takaya 15 December 2014 (has links)
Introdução: Produtos confeccionados a partir de materiais não biodegradáveis têm trazido um grande problema para a sociedade nos dias de hoje. A facilidade de utilização e manipulação dos produtos descartáveis leva a um aumento do consumo, podendo gerar danos para o meio ambiente, quando não há forma eficiente para o tratamento do mesmo. Materiais como fraldas, absorventes e curativos são exemplos de bens de consumo que apresentam Poliacrilato de Sódio, o qual é um polímero superabsorvente não biodegradável, como o principal constituinte destes produtos. O Poliacrilato de Sódio tornou-se muito conhecido a partir da década de 80 quando as fraldas descartáveis começaram a ser comercializadas. Atualmente, são consumidas aproximadamente 18 bilhões de fraldas todos os anos, apenas nos Estados Unidos. Devido aos impactos ambientais que este composto tem gerado, a ciência tem buscado polímeros que possam substituir o Poliacrilato de Sódio nas suas principais características, como superabsorção e alta cinética de intumescimento. Objetivo: No âmbito de desenvolver materiais que possam substituí-lo, buscou-se, neste trabalho, um monômero que apresentasse, em sua molécula, a presença de cadeia carboxílica a qual é a parte altamente hidrofílica. Metodologia: Neste trabalho, foi explorado o monômero de ácido Itacônico como possível substituinte do Poliacrilato de Sódio. Esta substância, além de ser caracterizada pela presença de estruturas hidrofílicas, também é biodegradável. Foram feitas análises de grau de intumescimento do material tanto na forma de gel quanto na forma microgel. A morfologia e a biodegradabilidade do material também foram estudadas. Concomitantemente, foi realizada a padronização do Poliacrilato de sódio para que este fosse utilizado como instrumento comparativo para a avaliação do grau de intumescimento, morfologia e degradabilidade. Hidrogéis de ácido itacônico foram assim analisados e avaliados com o hidrogel de poliacrilato de sódio e os resultados comparados. Resultados: Embora o grau de intumescimento do gel de ácido itacônico não tenha alcançado o mesmo grau de intumescimento do gel de poliacrilato de sódio, os resultados foram bons, uma vez que houve grande absorção de solução pelo gel de ácido itacônico. Além disso, sua biodegradabilidade mostrou resultados fascinantes pela rapidez de degradação e formação de fungos nas amostras. Contudo, são necessários mais estudos, uma vez que a reprodutibilidade do grau de intumescimento do gel 12,5% não foi satisfatória em outros experimentos. Outro obstáculo encontrado no estudo foi a necessidade de se obter uma técnica melhor para a análise da cinética de intumescimento dos géis dos polímeros usados no estudo. A seleção de um polímero ou monômero ideal deve ser caracterizada pela superabsorção, alta cinética de intumescimento, baixo custo, curto tempo de manipulação, baixa toxicidade e biodegradabilidade. Embora as pesquisas sobre o ácido itacônico ainda se encontram em andamento, ele é considerado uma substância promissora para o futuro dos materiais biodegradáveis. / Introduction:Products made from non-biodegradable materials have brought a major problem for society. The easiness of the utilization and manipulation of disposable products leads to an increased consumption, and, consequently, damages to the environment. Besides, most of the discharged of these materials have no efficient treatment affecting the modern society. Materials such as diapers, sanitary napkins and dressings are examples of consumer goods which contain in their main structure sodium polyacrylate, a non-biodegradable superabsorbent polymer. Since 1980, sodium polyacrylate has become well known when disposable diapers began to be marketed. Nowadays, superabsorbent components mainly diapers are consumed in large scale reaching about 18 billion diapers consumed every year only in the U.S. Due to the environmental impacts that sodium polyacrylate has generated, science has sought polymers that can replace sodium polyacrylate in its main features such as high swelling degree and swelling kinetics. Goal: In the ambit to develop materials that can replace sodium polyacrylate, this work focuses on a monomer that has in its molecule, the presence of carboxylic chain which is a highly hydrophilic part. Methodology: In this work it was searched the monomer of itaconic acid as a possible material to replace sodium polyacrylate. This monomer not only has hydrophilic structure in its molecule, but also is biodegradable. During the program, it was made analyses of swelling degree both in gel and in microgel forms. The morphology of its structure and the biodegradability were also studied. Concomitantly, it was made the standardization of sodium polyacrylate to be utilized as a comparative instrument assessing the high swelling degree, morphology and degradability. Itaconic acid hydrogels were analyzed and assessed and the outcomes compared with sodium polyacrylate. Results: Although the swelling degree of itaconic acid has not reached similar results to sodium polyacrylate, the results can still be considered good since the swelling degree of itaconic acid was high. Furthermore, its biodegradability showed excellent results due to the short time of degradation and fungus formation in all samples. However, more studies are necessary, inasmuch as the reproducibility of swelling degree of the itaconic acid 12.5% gel was not satisfactory enough in other experiments. Another obstacle encountered in the study has been the need for a more precise technique for the analysis of the swelling kinetics of the polymers used. The selection of an ideal polymer must present high swelling degree, high kinetics of swelling, low cost, short handling time, low toxicity and high biodegradability. Although the researches about the Itaconic acid have still been undertaken, it is considered a promising substance for the future of biodegradable material.
6

Preparação e avaliações comparativas das propriedades físico-químicas entre os hidrogéis de poliacrilato de sódio e de ácido itacônico para potencial aplicação como biomaterial / Comparative evaluations and preparation of physical-chemical properties between sodium polyacrylate and itaconic acid hydrogels for potential application as biomaterial.

Takaya, Raquel 15 December 2014 (has links)
Introdução: Produtos confeccionados a partir de materiais não biodegradáveis têm trazido um grande problema para a sociedade nos dias de hoje. A facilidade de utilização e manipulação dos produtos descartáveis leva a um aumento do consumo, podendo gerar danos para o meio ambiente, quando não há forma eficiente para o tratamento do mesmo. Materiais como fraldas, absorventes e curativos são exemplos de bens de consumo que apresentam Poliacrilato de Sódio, o qual é um polímero superabsorvente não biodegradável, como o principal constituinte destes produtos. O Poliacrilato de Sódio tornou-se muito conhecido a partir da década de 80 quando as fraldas descartáveis começaram a ser comercializadas. Atualmente, são consumidas aproximadamente 18 bilhões de fraldas todos os anos, apenas nos Estados Unidos. Devido aos impactos ambientais que este composto tem gerado, a ciência tem buscado polímeros que possam substituir o Poliacrilato de Sódio nas suas principais características, como superabsorção e alta cinética de intumescimento. Objetivo: No âmbito de desenvolver materiais que possam substituí-lo, buscou-se, neste trabalho, um monômero que apresentasse, em sua molécula, a presença de cadeia carboxílica a qual é a parte altamente hidrofílica. Metodologia: Neste trabalho, foi explorado o monômero de ácido Itacônico como possível substituinte do Poliacrilato de Sódio. Esta substância, além de ser caracterizada pela presença de estruturas hidrofílicas, também é biodegradável. Foram feitas análises de grau de intumescimento do material tanto na forma de gel quanto na forma microgel. A morfologia e a biodegradabilidade do material também foram estudadas. Concomitantemente, foi realizada a padronização do Poliacrilato de sódio para que este fosse utilizado como instrumento comparativo para a avaliação do grau de intumescimento, morfologia e degradabilidade. Hidrogéis de ácido itacônico foram assim analisados e avaliados com o hidrogel de poliacrilato de sódio e os resultados comparados. Resultados: Embora o grau de intumescimento do gel de ácido itacônico não tenha alcançado o mesmo grau de intumescimento do gel de poliacrilato de sódio, os resultados foram bons, uma vez que houve grande absorção de solução pelo gel de ácido itacônico. Além disso, sua biodegradabilidade mostrou resultados fascinantes pela rapidez de degradação e formação de fungos nas amostras. Contudo, são necessários mais estudos, uma vez que a reprodutibilidade do grau de intumescimento do gel 12,5% não foi satisfatória em outros experimentos. Outro obstáculo encontrado no estudo foi a necessidade de se obter uma técnica melhor para a análise da cinética de intumescimento dos géis dos polímeros usados no estudo. A seleção de um polímero ou monômero ideal deve ser caracterizada pela superabsorção, alta cinética de intumescimento, baixo custo, curto tempo de manipulação, baixa toxicidade e biodegradabilidade. Embora as pesquisas sobre o ácido itacônico ainda se encontram em andamento, ele é considerado uma substância promissora para o futuro dos materiais biodegradáveis. / Introduction:Products made from non-biodegradable materials have brought a major problem for society. The easiness of the utilization and manipulation of disposable products leads to an increased consumption, and, consequently, damages to the environment. Besides, most of the discharged of these materials have no efficient treatment affecting the modern society. Materials such as diapers, sanitary napkins and dressings are examples of consumer goods which contain in their main structure sodium polyacrylate, a non-biodegradable superabsorbent polymer. Since 1980, sodium polyacrylate has become well known when disposable diapers began to be marketed. Nowadays, superabsorbent components mainly diapers are consumed in large scale reaching about 18 billion diapers consumed every year only in the U.S. Due to the environmental impacts that sodium polyacrylate has generated, science has sought polymers that can replace sodium polyacrylate in its main features such as high swelling degree and swelling kinetics. Goal: In the ambit to develop materials that can replace sodium polyacrylate, this work focuses on a monomer that has in its molecule, the presence of carboxylic chain which is a highly hydrophilic part. Methodology: In this work it was searched the monomer of itaconic acid as a possible material to replace sodium polyacrylate. This monomer not only has hydrophilic structure in its molecule, but also is biodegradable. During the program, it was made analyses of swelling degree both in gel and in microgel forms. The morphology of its structure and the biodegradability were also studied. Concomitantly, it was made the standardization of sodium polyacrylate to be utilized as a comparative instrument assessing the high swelling degree, morphology and degradability. Itaconic acid hydrogels were analyzed and assessed and the outcomes compared with sodium polyacrylate. Results: Although the swelling degree of itaconic acid has not reached similar results to sodium polyacrylate, the results can still be considered good since the swelling degree of itaconic acid was high. Furthermore, its biodegradability showed excellent results due to the short time of degradation and fungus formation in all samples. However, more studies are necessary, inasmuch as the reproducibility of swelling degree of the itaconic acid 12.5% gel was not satisfactory enough in other experiments. Another obstacle encountered in the study has been the need for a more precise technique for the analysis of the swelling kinetics of the polymers used. The selection of an ideal polymer must present high swelling degree, high kinetics of swelling, low cost, short handling time, low toxicity and high biodegradability. Although the researches about the Itaconic acid have still been undertaken, it is considered a promising substance for the future of biodegradable material.
7

Co-production Of Xylanase And Itaconic Acid By Aspergillus Terreus Nrrl 1960 On Agricultural Biomass And Biochemical Characterization Of Xylanase

Kocabas, Aytac 01 June 2010 (has links) (PDF)
Production of xylanase and itaconic acid (IA) from Aspergillus terreus NRRL 1960 from agricultural residues was investigated in this study. Two different media were tested and the medium having itaconic acid inducing capacity was chosen for further studies due to its high xylanase and IA production capacity. The best xylan concentration was found as 2% (w/v). Addition of commercial xylanase to production culture resulted in higher initial simple sugar concentration which increased IA production slightly but decreased xylanase production. Among tested agricultural residues / corn cob, cotton stalk and sunflower stalk, the highest xylanase production was obtained on corn cob. Increasing the corn cob concentration and applying wet heat pretreatment increased the xylanase production level. In a two-step fermentation process, 70000 IU/L xylanase production was achieved in a medium containing 7% wet heat treated corn cob followed by 17 g/L IA production in a medium containing 10% glucose. Molecular weight and isoelectric point of xylanase were found as 19 kDa and pH 9.0, respectively. The enzyme was optimally active at 50&deg / C and pH 6.5-7.0. Kinetic experiments at 50&deg / C and pH 7.0 resulted in apparent Km and Vmax values of 2.5&plusmn / 0.05 mg xylan/mL and 50.2&plusmn / 0.4 IU/&micro / g protein, respectively. The major products of birchwood xylan hydrolysis were determined by thin layer chromatography as xylobiose and xylotriose. These findings indicate that the enzyme could be advantageous for use in different industrial applications due to its low molecular weight and its potential use for xylooligosaccharide production.
8

Funkcionalizace biodegradabilních polymerů anhydridem kyseliny itakonové / Functionalization of biodegradable polymers by itaconic anhydride

Michlovská, Lenka January 2009 (has links)
Předložená diplomová práce se zabývá přípravou biodegradabilního termosenzitivního triblokového kopolymeru na bázi polyethylenglykolu, kyseliny polymléčné a polyglykolové (PLGA-PEG-PLGA) a dále pak především jeho modifikací anhydridem kyseliny itakonové (ITA), který dodá kopolymeru jak reaktivní dvojné vazby tak i funkční karboxylové skupiny důležité pro reakci s biologicky aktivními látkami. Hlavním cílem bylo optimalizovat reakční podmínky pro dosažení nejvyššího stupně navázání ITA na polymer za vzniku ITA/PLGA-PEG-PLGA/ITA. Uvedený kopolymer je po vytvoření heterogenního kompozitu např. s hydroxyapatitem vhodný pro biomedicíncké aplikace především v oblasti tkáňového inženýrství jako dočasná náhrada či fixace tvrdých tkání (kostí). V teoretické části uvedené práce jsou na základě literární rešerše obecně popsány hydrogely, jejich rozdělení, síťování a degradace. Stručně jsou rozepsány fyzikální a chemické vlastnosti a syntéza jednotlivých biomateriálů použitých při syntéze, anhydridu kyseliny itakonové a jejich kopolymerů. Experimentální část popisuje detailně syntézu PLGA-PEG-PLGA kopolymeru polymerací za otevření kruhu pomocí vakuové linky a Schlenkových technik. Byla sledována i kinetika polymerace s navržením nejvhodnějších podmínek syntézy. Uvedený kopolymer byl následně modifikován anhydridem kyseliny itakonové opět katalytickou reakcí za otevření kruhu. V důsledku optimalizace reakčních podmínek byl sledován vliv teploty, rozpouštědla, času a čistoty vstupních látek. Výsledný ITA/PLGA-PEG-PLGA/ITA kopolymer byl charakterizován pomocí 1H NMR, FT-IR a GPC metody. Byly sledovány kinetiky polymerace PLGA-PEG-PLGA kopolymeru a to z přesublimované a nepřesublimované kyseliny polymléčné a polyglykolové. V obou případech probíhala kinetika reakcí bez přítomnosti rozpouštědla při 130 °C po dobu 3 hodin s konverzí asi 90 %. Delší čas neměl vliv na růst konverze. U kinetiky z nepřesublimovaných monomerů byl sledován během několika prvních minut prudký nárůst konverze a pak již byl průběh konstantní, na čase nezávislý. Výsledná polydisperzita kopolymeru byla 1,26 a molekulová hmotnost 7155 g/mol. Optimálních podmínek bylo dosaženo u polymerace z přesublimovaných monomerů, kdy byl nárůst konverze do hodnoty 88 % získané během 2,5 hodin téměř lineární (polymerace byla živá) a poté byl progres konstantní. Byl získán přesně definovaný PLGA-PEG-PLGA kopolymer o molekulové hmotnosti 7198 g/mol a polydisperzitě 1,20. Nejlepších podmínek při syntéze ITA/PLGA-PEG-PLGA/ITA kopolymeru bylo dosaženo reakcí bez přítomnosti rozpouštědla při 110 °C po dobu 1,5 hodiny s přesublimovaným anhydridem kyseliny itakonové, kdy bylo na původní kopolymer navázáno 76.6 mol. %. Výsledná molekulová hmotnost kopolymeru (5881 g/mol) s polydisperzitou 1,37 stanovená pomocí GPC se shodovala s vypočítanou molekulovou hmotností z 1H NMR i s teoretickou molární hmotností (Mn(teor)/Mn(GPC)/Mn(NMR) = 1/0,89/0,96).
9

Modifikace PLA reaktivní extruzí / Modification of PLA using reactive extrusion

Matláková, Jana January 2012 (has links)
Diplomová práce se zabývá roubováním maleinanhydridu a anhydridu kyseliny itakonové na kyselinu poly(mléčnou) (PLA). U modifikované kyseliny poly(mléčné) byla sledována závislost konverze monomerů na různých molárních poměrech monomer/iniciátor při teplotách 180°C a 200°C. Množství naroubovaného monomeru bylo stanovováno acidobazickou titrací a pomocí FT-IR spektroskopií. Vliv stupně naroubování na krystalinitu modifikované PLA byl zjišťován pomocí diferenční kompenzační kalorimetrie, DSC. Degradace PLA byla orientačně pozorována pomocí indexu toku taveniny, MFI.
10

Reaktivní zpracování polypropylénu / Reactive Modification of Polypropylene

Matláková, Jana January 2017 (has links)
The theoretical part describes the principles of the free-radical induced grafting and the influence of various parameters on the reactions course. The literature research summarizes the latest knowledge in the field of the reactive modification of polypropylene (PP), it is mainly focused on the PP modification using an unsaturated acid anhydrides. Theoretical part describes the various procedures and modification of technology in order to increase the grafting yield of maleation. The experimental part is determined by the influence of the stabilizers concentration, the peroxide structure, and the binary mixture of monomers on the grafting yield and the reaction course. In the first part, the critical stabilizers concentration was determined based on the experimentally obtained relationship between the grafting yield and the stabilizers concentration. A kinetic schema of grafting of MAH onto PP in the presence of stabilizers has been proposed and compared with the experimental results. The effect of the stabilizers on the extent of the undesirable b-scission was evaluated based on the melt flow rate (MFR) and the rheological curves of PP-g-MAH. In the second part, the effect of the peroxide structure and the concentration of reactants on the grafting yield of PP modification with MAH and itaconic anhydride (IAH) was observed. The initial grafting yield Rg has been experimentally determined and compared with a defined area of theoretical values of Rg. The extent of b-scission was significantly influenced by the structure and the concentration of peroxide, as shown by the results of MFR and the rheological curves of PP-g-MAH. The last part of the doctoral thesis is focused on the assessment of the combination of MAH and IAH as comonomers on the grafting yield. At first, the reference polymers were prepared using the solution polymerization of MAH, and IAH, and copolymerization of MAH with IAH. The reference polymers were analyzed by FTIR, DSC, WAXS to confirm the probable copolymerization of MAH and IAH. The dependence of the reaction enthalpy on the reaction time was observed using simulations of bulk polymerization of MAH, IAH and mixtures MAH and IAH "in situ" in isothermal calorimeter. PP was subsequently modified with a combination of MAH and IAH as comonomers in order to assess its effect on the grafting yield

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