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

Ring-Opening Co- and Terpolymerization of an Alicyclic Oxirane with Carboxylic Acid Anhydrides and CO2 in the Presence of Chromium Porphyrinato and Salen Catalysts

Copolymerization of cyclohexene oxide (CHO) with alicyclic anhydrides applying chromium tetraphenylprophyrinato (TPPCrCl, 1) and salophen (SalophenCrCl, 2) catalysts resulted in polyesters or poly(ester-co-ether)s, depending on the nature of the catalyst, presence of a cocatalyst, solvent and type of anhydride. The combination of 1 as catalyst and 4-N,N-dimethylamino-pyridine (DMAP) as cocatalyst in the copolymerization of CHO with succinic anhydride (SA), cyclopropane-1,2-dicarboxylic acid anhydride (CPrA), cyclopentane-1,2-dicarboxylic acid anhydride (CPA) or phthalic anhydride (PA) invariably resulted in a completely alternating topology and therefore a pure polyester. Contrarily, 2 in combination with DMAP did not afford pure polyesters for the copolymerization of CHO with SA or CPrA but did render the alternating topology when CPA or PA was used as anhydride comonomer. Water proved to be an efficient bifunctional CTA affording a,¿-hydroxyl-terminated polyesters without loss of catalytic activity. When CO2 was introduced as additional monomer to CHO and the anhydrides, both 1 and 2 in combination with DMAP as cocatalyst afforded perfect poly(ester-co-carbonate)s. The presence of CO2 effectively prevents the undesirable side reaction of oxirane homopolymerization

Zwitterionic bis(phenolate)amine lanthanide complexes for the ring-opening polymerisation of cyclic esters

The reaction of Sm{N(SiMe3)2}3 with the bis(phenol)amines H2O2NR (H2O 2NR = RCH2CH2N(2-HO-3,5-C 6H2tBu2)2; R = OMe, NMe2 or Me) gave exclusively zwitterions Sm(O2N R)(HO2NR). For R = OMe or NMe2 these were efficient catalysts for the ring-opening polymerisation of e-caprolactone and d,l-lactide with a tendency to form cyclic esters; in contrast, no polymerisation was observed for R = Me. © The Royal Society of Chemistry

Catalytic Ring-Opening Polymerization of Renewable Macrolactones to High Molecular Weight Polyethylene-like Polymers

The catalytic ring-opening polymerization of macrolactones to polyethylene-like polyesters was investigated using aluminum??salen complexes as the initiators. Contrary to the common understanding that high molecular weights in these reactions can only be achieved by enzymatic ring-opening polymerization due to the absence of ring tension in macrolactones, the aluminum??salen complexes produces poly-(pentadecalactone)s with number-average molecular weights (Mn) of over 150 000 g/mol. Moreover, the same catalyst is also active in catalyzing the ROP of small and medium size lactones, which makes these aluminum??salen complexes highly potential catalysts for the cROP of lactones irrespective of ring size. These results show that it is possible to polymerize macrolactones to high molecular weight polyethylene-like polymers using cheap and robust metal-based catalysts. Even the so-called medium-sized lactones (ring size: 9??12) can be polymerized with a reasonably good activity to high molecular weight products, which is truly exceptional. These results complement the common theory of ring-tension-driven cROP

Catalytic Ring-Opening Polymerization of Renewable Macrolactones to High Molecular Weight Polyethylene-like Polymers

The catalytic ring-opening polymerization of macrolactones to polyethylene-like polyesters was investigated using aluminum-salen complexes as the initiators. Contrary to the common understanding that high molecular weights in these reactions can only be achieved by enzymatic ring-opening polymerization due to the absence of ring tension in macrolactones, the aluminum-salen complexes produces poly(pentadecalactone)s with number-average molecular weights (M-n) of over 150 000 g/mol. Moreover, the same catalyst is also active in catalyzing the ROP of small and medium size lactones, which makes these aluminum-salen complexes highly potential catalysts for the cROP of lactones irrespective of ring size. These results show that it is possible to polymerize macrolactones to high molecular weight polyethylene-like polymers using cheap and robust metal-based catalysts. Even the so-called medium-sized lactones (ring size: 9-12) can be polymerized with a reasonably good activity to high molecular weight products, which is truly exceptional. These results complement the common theory of ring-tension-driven cROP

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