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1	Synthesis and characterization of aliphatic hyperbranched polyesters Vuković, Jasna 22 November 2006 (has links) Two series of aliphatic hyperbranched (HB) polyesters have been synthesized from 2,2-bis(hydroxymethyl)propionic acid and di-trimethylolpropane using pseudo-one-step or one-step procedure. The structure and properties of these HB polyesters, investigated with different characterization techniques in solution, melt and solid state, were compared between each other, with commercial Boltorn HB polyesters and samples obtained by modification of the end -OH groups with ß-alanine or stearic acid. Seven HB polyesters were fractionated in order to obtain three fractions of each sample. The experimental results obtained from NMR spectroscopy, acid and hydroxyl number titration, GPC, vapour pressure osmometry, MALDI TOF and ESI mass spectrometry indicate that during the synthesis reactivity of terminal and linear -OH groups was not the same and that side reactions occurred in significant amount, which led to the lowering of the number average molar mass and broadening of the molar mass distribution. According to the results obtained from viscosimetry of diluted solutions and dynamic light scattering the best solvents for these HB polyesters are 0.7 mass % solution of LiCl in N,N-dimethylacetamide and N-methyl-2-pyrrolidinon (NMP). The limiting viscosity number and the hydrodynamic radius of the samples increase up to the sixth pseudo generation in these two solvents. Investigated HB polyesters behave as Newtonian liquids in concentrated solutions (c < 50 mass % in NMP) at T < 55 °C. The same was observed for the samples from fourth till sixth pseudo generation in melt at T > 70 °C. At all other experimental conditions used in this work these polymers show shear-thinning behaviour due to the high ability for the aggregation. Thermal stability of investigated HB polyesters increases with increasing number of the pseudo generation. The influence of the procedure for the synthesis and type of end groups on the properties of these polymers is discussed. Hyperbranched polyesters molar mass determination hydrodynamic radius diluted solution properties rheology thermal stability synthesis 30 - Chemie ddc:660
2	Advances in chain-growth control and analysis of polymer: boosting iodine-mediated polymerizations and mastering band-broadening effects in size-exclusion chromatography Wolpers, Arne 10 November 2014 (has links) No description available. 540 iodine-transfer polymerization (ITP) photopolymerization UV light size-exclusion chromatography band broadening skewing simulations chain-length dependence molar-mass determination correction Chemie (PPN62138352X)
3	Size Separation Techniques for the Characterisation of Cross-Linked Casein: A Review of Methods and Their Applications Raak, Norbert, Abbate, Raffaele Andrea, Lederer, Albena, Rohm, Harald, Jaros, Doris 11 June 2018 (has links) (PDF) Casein is the major protein fraction in milk, and its cross-linking has been a topic of scientific interest for many years. Enzymatic cross-linking has huge potential to modify relevant techno-functional properties of casein, whereas non-enzymatic cross-linking occurs naturally during the storage and processing of milk and dairy products. Two size separation techniques were applied for characterisation of these reactions: gel electrophoresis and size exclusion chromatography. This review summarises their separation principles and discusses the outcome of studies on cross-linked casein from the last ~20 years. Both methods, however, show limitations concerning separation range and are applied mainly under denaturing and reducing conditions. In contrast, field flow fractionation has a broad separation range and can be easily applied under native conditions. Although this method has become a powerful tool in polymer and nanoparticle analysis and was used in few studies on casein micelles, it has not yet been applied to investigate cross-linked casein. Finally, the principles and requirements for absolute molar mass determination are reviewed, which will be of increased interest in the future since suitable calibration substances for casein polymers are scarce. Casein Milchprotein Vernetzung Enzym Transglutaminase Glykation Gelelektrophorese Größenausschlusschromatographie Feldflussfraktionierung Molmassenbestimmung TU Dresden Publikationsfond casein milk protein cross-linking enzyme transglutaminase glycation gel electrophoresis size exclusion chromatography field flow fractionation molar mass determination TU Dresden Publishing Fund ddc:540 rvk:VA 1120
4	Size Separation Techniques for the Characterisation of Cross-Linked Casein: A Review of Methods and Their Applications Raak, Norbert, Abbate, Raffaele Andrea, Lederer, Albena, Rohm, Harald, Jaros, Doris 11 June 2018 (has links) Casein is the major protein fraction in milk, and its cross-linking has been a topic of scientific interest for many years. Enzymatic cross-linking has huge potential to modify relevant techno-functional properties of casein, whereas non-enzymatic cross-linking occurs naturally during the storage and processing of milk and dairy products. Two size separation techniques were applied for characterisation of these reactions: gel electrophoresis and size exclusion chromatography. This review summarises their separation principles and discusses the outcome of studies on cross-linked casein from the last ~20 years. Both methods, however, show limitations concerning separation range and are applied mainly under denaturing and reducing conditions. In contrast, field flow fractionation has a broad separation range and can be easily applied under native conditions. Although this method has become a powerful tool in polymer and nanoparticle analysis and was used in few studies on casein micelles, it has not yet been applied to investigate cross-linked casein. Finally, the principles and requirements for absolute molar mass determination are reviewed, which will be of increased interest in the future since suitable calibration substances for casein polymers are scarce. info:eu-repo/classification/ddc/540 ddc:540

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