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Rapid Synthesis and MALDI-ToF Characterization of Poly(ethylene oxide) Multiarm Star Polymers
2009
Multiarm PEO star polymers with a purely aliphatic polyether structure have been synthesized using hyperbranched polyglycerol (PG) with different molecular weights as a multifunctional initiator. Different degrees of deprotonation of the initiator were studied with respect to molecular weight control. The results show that the degree of deprotonation is a crucial parameter for the synthesis of well-defined polymers with controlled molecular weights. Partial deprotonation of the PG hydroxyl groups (5-8%) was proven to represent an optimum for the synthesis of star polymers with molecular masses close to the theoretical values. Molecular weights of the stars ranged between 9 000 and 30000g · …
Hyperbranched Polyglycerols with Elevated Molecular Weights: A Facile Two-Step Synthesis Protocol Based on Polyglycerol Macroinitiators
2009
Hyperbranched polyglycerol (PG) is established as one of the few hyperbranched polymers that offer the possibility to control molecular weight up to Mn = 6000 g/mol. This work introduces a facile 2-step strategy that relies on the use of a low molecular weight PG (Mn = 500 and 1000 g/mol) as a macroinitiator for the slow addition of glycidol, permitting to overcome previous limitations concerning molecular weights and molecular weight control. A systematic investigation of the effect of the degree of deprotonation on the control of the polymerization reaction has been carried out. A series of hyperbranched PGs with molecular weights up to Mn = 24000 g/mol has been obtained under fully contr…
Evaluating chemical ligation techniques for the synthesis of block copolypeptides, polypeptoids and block copolypept(o)ides: a comparative study
2015
In this work, we describe the synthesis of block copolypeptides, polypeptoids and block copolypept(o)ides by chemical ligation techniques. Polysarcosine (PSar), poly(N-e-trifluoroacetyl-L-lysine) (PLys(TFA)) and poly(γ-benzyl-L-glutamate) (PGlu(OBzl)) homopolymers of different polarities and end group functionalities but with similar average degrees of polymerization (Xn = 50 and 100) could be obtained by ring opening polymerization (ROP) of α-amino acid N-carboxyanhydrides (NCA) and postpolymerization modification reactions. In the next step, these polymers were applied to copper(I)-catalyzed azide–alkyne coupling (CuAAC), strain-promoted azide–alkyne coupling (SPAAC) and native chemical l…
Polymerization of long chain alkyl glycidyl ethers: a platform for micellar gels with tailor-made melting points
2018
Controlled polymerization of long-chain alkyl glycidyl ethers (AlkGE) under anionic ring opening polymerization conditions is enabled by the addition of a crown ether (18-crown-6, K+). Homopolymers with molecular weights in the range of 4000 to 9000 g mol−1 and side chain melting temperatures of 14 °C (C12-AlkGE) and 43 °C (C16-AlkGE), respectively were synthesized. Furthermore, a series of amphiphilic ABA polyether triblock copolymers with polyethylene glycol (PEG) as the hydrophilic central block (Mn = 6k, 10k, and 20k g mol−1) with total molecular weights in the range of 7000 to 28 000 g mol−1 and narrow dispersity (1.12 to 1.34) were prepared. Separate melting endotherms of the triblock…
Synthesis and polymerization of active ester monomers based on 4-vinylbenzoic acid
2007
Abstract Nine active ester monomers based on 4-vinylbenzoic acid have been synthesized. Under free radical polymerization conditions these monomers could successfully be polymerized yielding reactive polymers with molecular weights of around M n = 20.000–50.000 g/mol and molecular weight distributions M w / M n of around or below 2 in good yields. Polymer analogous reactions with amines have been investigated by time-resolved FT-IR spectroscopy and it was found that especially poly(pentafluorophenyl 4-vinylbenzoate) featured a significant reactivity, such that polymer analogous reactions proceeded quantitatively with amines within less than 5 min at 0 °C.
Systematic investigation of functional core variation within hyperbranched polyglycerols
2008
A novel series of hyperbranched polyether polyols with various n-alkyl amine cores (mono- and bifunctional) and photoactive cores (benzylamine and 1-naphthylmethylamine) have been prepared. Polymerization of glycidol was carried out in two ways, starting directly from primary amine initiators and from bisglycidolized amine initiators. NMR spectroscopy and size exclusion chromatography (SEC) showed good control over the molecular weights only, when bisglycidolized amines were used. Molecular weights and polydispersity of the hyperbranched polyglycerols prepared with these initiator-cores were in the range of 1600 to 8400 g/mol and of 1.5 to 2.5, respectively. MALDI-ToF mass spectrometry conf…
Polymerizations of Cyclic Esters Catalyzed by Titanium Complexes Having Chalcogen-Bridged Chelating Diaryloxo Ligands
2002
A series of titanium complexes having tellurium-bridged chelating bis(aryloxo) ligands, [TiX2{2,2‘-Te(4-Me-6-tBu-C6H2O)2}]2 (5: X = Cl; 6: X = OiPr), catalyzed the ring-opening polymerization of cyclic esters such as e-caprolactone, δ-valerolactone, and l-lactide. The strong dependence of polymerizations on the solvent was observed in this catalytic system. When the polymerizations of e-caprolactone and l-lactide were carried out in toluene at 100 °C, tellurium-bridged bis(aryloxo)titanium complex 5 was found to give polymers with rather broad molecular weight distribution due to back-biting. When the polymerizations of e-caprolactone and l-lactide was carried out in anisole or in dioxane…
SiO2-supported vanadium magnesium mixed oxides as selective catalysts for the oxydehydrogenation of short chain alkanes
2001
Abstract Unsupported and SiO 2 -supported VMgO mixed oxides catalysts have been prepared, characterized and tested in the oxidation of propane, n -butane and propylene. Mg-vanadates are observed by XRD, IR and Raman spectroscopy in both pure and supported VMgO catalysts, although the effective Mg/V ratio, in the VMgO phases formed, depends on the silica content. Since SiO 2 reacts partially with MgO during the calcination step, forming Mg 2 SiO 4 , the effective Mg/V ratio depends on the silica content. In this sense, pyro -Mg 2 V 2 O 7 is mainly formed on supported catalysts with Mg/V atomic ratios lower than 4, while ortho -Mg 3 V 2 O 8 is observed on supported catalysts with Mg/V atomic …
Polymerization of ε-caprolactone using heterobimetallic lanthanocene complexes
1997
The chiral heterobimetallic complexes Li[Ln(η 5 :η 1 -C 5 R 4 1 SiMe 2 NCH 2 CH 2 R 2 ) 2 ] (ln= Y, Lu; C 5 R 4 1 = C 5 Me 4 , C 5 H 4 , 3-C 5 H 3 tBu; R 2 = OMe, NMe 2 ) have been found to polymerize e-caprolactone to give a polymer of high molecular weight (M n > 20000) and moderate polydispersity (M w /M n < 2). Failure to observe a correlation between monomer/initiator ratio and molecular weight suggest a polymerization mechanism different from a pseudo-anionic mechanism
Magnesium, Oxidative Stress, and Aging Muscle
2014
Abstract Magnesium (Mg) deficiency, aside from having a negative impact on the energy production pathways required by the mitochondria to generate ATP, also reduces the threshold antioxidant capacity of the aging organism and its resistance to free-radical damage. Mg acts as an antioxidant against free radical damage of the mitochondria. Chronic Mg deficiency results in excessive production of oxygen-derived free radicals and low-grade inflammation. Chronic inflammation and oxidative stress have been identified as pathogenic factors in several age-related conditions. Aging is often associated with Mg inadequacy, muscle loss, and sarcopenia. Although the importance of magnesium as a determin…