Telechelic and star-shaped poly(L-lactide)s by means of bismuth(III) acetate as initiator.
L-lactide was polymerized as concentrated solution in chlorobenzene with Bi(OAc)3 as initiator. When tetra(ethylene glycol) was added as co-initiator (CoI), telechelic polylactides having two CH-OH end groups were obtained. With 1,1,1-tri(hydroxy methyl)propane (THMP) as co-initiator, three-armed stars having three CH-OH end groups were formed. Analogously, tetrafunctional star-shaped poly(L-lactide)s were obtained with pentaerythritol as co-initiator. The chain lengths were varied via the monomer/CoI ratio. Time-conversion curves proved that Bi(OAc)3 is slightly less reactive as initiator than tin(II) 2-ethylhexanoate. However, bismuth acetate (or other carboxylates) have a particularly low toxicity as documented in the literature and by numerous Bi3+-containing pharmaceutical products.
Institut für Technische und Makromolekulare Chemie, Bundesstrasse 45, D-20146 Hamburg, Germany. kricheld@chemie.uni-hamburg.de
Hans R
HR
Kricheldorf
Heiko
H
Hachmann-Thiessen
Gert
G
Schwarz
D000085:Acetates / Q000032:analysis / Q000737:chemistry*; D001729:Bismuth / Q000032:analysis / Q000737:chemistry*; D002240:Carbohydrate Sequence; D008969:Molecular Sequence Data; D011091:Polyesters / Q000032:analysis / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014783:Viscosity
D000085:Acetates; D011091:Polyesters; C033616:poly(lactide); D001729:Bismuth