Filtern
Erscheinungsjahr
- 2019 (13) (entfernen)
Dokumenttyp
- Zeitschriftenartikel (12)
- Vortrag (1)
Schlagworte
- Cyclization (5)
- MALDI-TOF MS (5)
- Polylactide (5)
- Catalyst (3)
- Catechol (2)
- Crosslinking (2)
- Polyurethane (2)
- 2-oxazoline (1)
- AET (1)
- Artificial weathering (1)
- Asymmetrical flow field flow fractionation (AF4) (1)
- Capillary electrophoresis (CE) (1)
- Cationic ring opening polymerization (1)
- Cyclic (1)
- Degradation (1)
- Fundamentals (1)
- Inlet ionization (1)
- Ion mobility (1)
- Klassifizierung (1)
- Lactide (1)
- MALDI Imaging (1)
- MALDI TOF MS (1)
- MALDI-TOF Massenspektrometrie (1)
- MOF (1)
- Matrices (1)
- Microwave (1)
- Moisture (1)
- Molecular masses (1)
- Multivariate Analyse (1)
- Nanoparticles with same nominal diameter (1)
- Phenolic acid (1)
- Pollenkörner (1)
- Polymer (1)
- ROPPOC (1)
- Ring-expansion polymerization (1)
- Ring-opening polymerization (1)
- Salicylate (1)
- Stereocomplex (1)
- Surface coating (1)
- Thermal degradation (1)
- Tin(II)octanoate (1)
- Toxicity (1)
- Two-dimensional off-line coupling (1)
- UV degradation (1)
- Vacuum ionization (1)
Organisationseinheit der BAM
- 6 Materialchemie (13)
- 6.3 Strukturanalytik (13)
- 1 Analytische Chemie; Referenzmaterialien (1)
- 1.2 Biophotonik (1)
- 1.7 Organische Spuren- und Lebensmittelanalytik (1)
- 5 Werkstofftechnik (1)
- 5.6 Glas (1)
- 6.6 Physik und chemische Analytik der Polymere (1)
- 7 Bauwerkssicherheit (1)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (1)
Eingeladener Vortrag
- nein (1)
A comparison of tributyltin chloride, dibutyltin dichloride,and butyltin trichloride as catalysts of ring-opening polymerizations(ROPs) of l-lactides at 160°C in bulk reveals increasing reactivity in the above order, but only the least reactive catalysts, Bu3SnCl, yield a uniform reaction product, namely cyclic poly(L-lactide)s with weight average molecular weights (Mw ́s) in the range of 40,000–80,000. A comparison of dimethyltin , dibutyltin , and diphenyltin dichlorides resulted in the following order of reactivity: Me2SnCl2<Bu2SnCl2<<Ph2SnCl2. In this series also, the most reactive catalyst yields cyclic polylactides, but the extent of cyclization varies with the molecular weight. The formation of cyclic polylactides is explained by ROP combined with simultaneous polycondensation involving end-to-end cyclization (ROPPOC method). ROP of meso-lactide at 80 or 60°C yields even-numbered linear chains as main products, a result supporting the ROPPOC mechanism.
Five new cyclic catalysts were prepared by a new synthetic method from tin(II)-2-ethyhexanoate and silylated catechols, silylated 2,2´dihydroxybiphenyl or silylated 1,1´-bisnaphthol. These catalysts were compared with regard to their usefulness as catalysts for the ring expansion polymerization (REP) of L-lactide in bulk at 160 °C, and with two different tin(IV) derivatives of 1,1´binaphthol. Best results were obtained using seven-membered cyclic tin(II)bisphenoxides, which yielded colorless cyclic poly(l-lactide)s free of racemization with weight average molecular weights (Mw) up to 305 000 g mol-1. Furthermore, these catalysts were active even at a lactide/catalyst ratio of 20 000/1. Our new results were superior to those obtained from all other previously published catalysts yielding cyclic poly(L-lactide). The seven-membered cycles also proved to be more active than tin(II) 2-ethylhexanoate with and without the addition of alcohol.