Topology characterization by MALDI-ToF-MS of enzymatically synthesized poly(lactide-co-glycolide)

Lipase catalyzed copolymerization of the monomers lactide and glycolide by Pseudomonas cepacia employing a molar ratio of 80L/20G has been studied. The copolymers were characterized by MALDI-ToF-MS, DSC, SEC and NMR. MALDI-ToF-MS has successfully been used not only to determine end groups and chemical composition but even the microstructure of the copolymers. We demonstrated that for this lipase catalyzed copolymerization, the main product of the reaction at 100 °C was linear homopolymer of lactide while at 130 °C the main product was cyclic random copolymer

Topology characterization by MALDI-ToF-MS of enzymatically synthesized poly(lactide-co-glycolide)

Lipase catalyzed copolymerization of the monomers lactide and glycolide by Pseudomonas cepacia employing a molar ratio of 80L/20G has been studied. The copolymers were characterized by MALDI-ToF-MS, DSC, SEC and NMR. MALDI-ToF-MS has successfully been used not only to determine end groups and chemical composition but even the microstructure of the copolymers. We demonstrated that for this lipase catalyzed copolymerization, the main product of the reaction at 100 degrees C was linear homopolymer of lactide while at 130 degrees C the main product was cyclic random copolymer

Reactivity Ratios of Comonomers from a Single MALDI-ToF-MS Measurement at One Feed Composition

The reactivity ratios in a copolymerization are needed to predict the microstructure (random, gradient, block or alternating) of the produced copolymer. This microstructure reflects on the physical properties of the polymeric material. Conventional ways to determine these reactivity ratios demand in most cases tedious laboratory work and several experiments at different monomer feed compositions. Here, a novel method is described to derive these ratios from a single MALDI-ToF-MS spectrum obtained at one feed composition by employing either a Monte Carlo approach to numerically simulate a first order Markov chain or the analytical form of the first order Markov chain. A single MALDI-ToF-MS spectrum proved to give very good estimates of the reactivity ratios of comonomers from copolymer's synthesized by free radical polymerization, ring-opening polymerization of lactones and lactides, or ring-opening copolymerization of anhydrides plus epoxides

Silica-grafted diethylzinc and a silsesquioxane-based zinc alkyl complex as catalysts for the alternating oxirane-carbon dioxide copolymerization

A novel zinc silsesquioxane complex ([(c-C5H9)(7)Si7O11(OSiMePh2)](2)Zn4Me4 (1)) has been used as a model compound for silica-grafted zinc catalysts in the copolymerization of cyclohexene oxide and CO2. Complex 1 exists as a dimer in the solid state and is moderately active in the copolymerization, and polycyclohexene carbonates have been obtained with a carbonate content of 79-98%. Polymerizations with ZnEt2-treated silica particles resulted in polymer particles with (M) over bar (n) and (M) over bar (w) values and carbonate contents comparable to those of the polymers obtained with 1. It was further demonstrated that CO2 consumption can be followed online by monitoring the decrease of system pressure during the reaction. CO2 consumption has been interpreted in relation to both polycarbonate and cyclic carbonate formation. These measurements represent the intrinsic kinetics of this reaction, which appear to be directly related to CO2 pressure

CCDC 670959: Experimental Crystal Structure Determination

Related Article: R.Duchateau, W.J.van Meerendonk, S.Huijser, B.B.P.Staal, M.A.van Schilt, G.Gerritsen, A.Meetsma, C.E.Koning, M.F.Kemmere, J.T.F.Keurentjes|2007|Organometallics|26|4204|doi:10.1021/om700367x,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Reactivity Ratios of Comonomers from a Single MALDI–ToF–MS Measurement at One Feed Composition

The reactivity ratios in a copolymerization are needed to predict the microstructure (random, gradient, block or alternating) of the produced copolymer. This microstructure reflects on the physical properties of the polymeric material. Conventional ways to determine these reactivity ratios demand in most cases tedious laboratory work and several experiments at different monomer feed compositions. Here, a novel method is described to derive these ratios from a single MALDI-ToF-MS spectrum obtained at one feed composition by employing either a Monte Carlo approach to numerically simulate a first order Markov chain or the analytical form of the first order Markov chain. A single MALDI-ToF-MS spectrum proved to give very good estimates of the reactivity ratios of comonomers from copolymer's synthesized by free radical polymerization, ring-opening polymerization of lactones and lactides, or ring-opening copolymerization of anhydrides plus epoxides