Block copolymers of poly(L-lactide) and poly(ε-caprolactone) or poly(ethylene glycol) prepared by reactive extrusion

✍ Scribed by W. M. Stevels; A. Bernard; P. Van De Witte; P. J. Dijkstra; J. Feijen

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 499 KB
• Volume: 62
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19961121)62:8<1295::aid-app20>3.0.co;2-5

✦ Synopsis

SYNOPSIS

Blends of poly(L-lactide) (PLLA) and poly(e-caprolactone) (PCL) were prepared in a corotating twin screw miniextruder (40 rpm, 200"). It was attempted to prepare multiblock copolymers by allowing a controlled number of transesterification reactions. Various catalysts (n-Bu,SnOMe, Sn(Oct)*, Ti(OBu)4, Y(Oct),, para-toluene sulphonic acid) were introduced to promote these transesterification reactions. However, PLLA degradation by ring-closing depolymerization was the dominant reaction in every case. Alternatively, after showing that L-lactide can be conveniently polymerized in the extruder, L-lactide and hydroxyl functionalized prepolymers of PCL or poly(ethy1ene glycol) (PEG) were fed to the extruder in the presence of stannous octoate. Monomer conversions of over 90% and effective transformation of all hydroxyl end groups present were generally reached. Di-and triblock copolymers could be prepared in this way with characteristics very similar to polymers prepared in a batch-type process, but with considerably reduced reaction times in a fashion, which is, in principle, scaleable to a continuous process for the production of such block copolymers.