Replacing Tin in Lactide Polymerization: Design of Highly Active Germanium‐Based Catalysts

Abstract

Most germane: Hexacoordinate germanium(IV) species exhibit unprecedented activities, yet controlled behavior, as initiators for the ring-opening polymerization of rac-lactide to form polylactide polymers.

End‐functionalized polylactides using a calcium‐based precatalyst: Synthesis and insights by mass spectrometry

“…For these reasons PLA has found extensive applications in numerous fields particularly in biomedical and pharmaceutical areas, such as the production of resorbable sutures, bioabsorbable implants for bone fixation, scaffolds for tissue engineering and carriers for controlled drug release systems . Ring opening polymerization (ROP) of lactide initiated by stannous octoate (tin(II)−2‐ethylhexanoate) is the most common strategy to produce PLA, since stannous octoate is highly active towards the ROP of lactide and able to produce high molar mass PLA in bulk or in solution. Due to increasing concerns associated with the toxicity of tin compounds, its low control over the polymerization process with respect to tacticity and targeted molar masses, different catalyst/initiator systems for ROP of lactide have been investigated during the last decades .…”

“…Ring opening polymerization (ROP) of lactide initiated by stannous octoate (tin(II)−2‐ethylhexanoate) is the most common strategy to produce PLA, since stannous octoate is highly active towards the ROP of lactide and able to produce high molar mass PLA in bulk or in solution. Due to increasing concerns associated with the toxicity of tin compounds, its low control over the polymerization process with respect to tacticity and targeted molar masses, different catalyst/initiator systems for ROP of lactide have been investigated during the last decades . Organocatalyzed ROP of lactide has been studied extensively by Waymouth and Hedrick resulting in metal–free polymers with predictable molar masses and narrow polydispersities .…”

Versatile cobalt complexes for initiating immortal ring‐opening polymerization (ROP) of lactide (LA), mediating living radical polymerization of t‐butyl acrylate (tBA) and catalyzing copolymerization of LA and tBA by combination of ROP and organometallic‐mediated radical polymerization

“…Polylactide (PLA) and polyacrylate are well‐known biocompatible and degradable polymers as replacements for synthetic (petroleum‐based) materials . For the synthesis of PLA, industrially, ring‐opening polymerization (ROP) of lactide (LA) is the commonest method in the melt using tin carboxylate initiators, but the toxicity associated with most tin compounds is a considerable drawback in the case of biomedical applications . In this field, there are still demands for highly active, nontoxic and stable complexes that can be easily handled.…”

“…In this field, there are still demands for highly active, nontoxic and stable complexes that can be easily handled. Nowadays, complexes of germanium, aluminium, zinc, magnesium, copper, and so on, show promise for ROP of LAs. However, cobalt has been recognized to be biocompatible for a long period of time, and some cobalt complexes that not only meet all the demands mentioned above but also are cheaper than other complexes have been successfully used as efficient catalysts in the synthesis of biodegradable polyesters .…”

Controlled ring‐opening polymerization of l‐lactide and ε‐caprolactone catalyzed by aluminum‐based Lewis pairs or Lewis acid alone

“…Thus, development of new catalysts or initiators for the ROP of cyclic esters has been required. Many other catalysts and/or initiators, including catalysts based on other metals and organocatalysts such as dimethylaminopyridine, 1,8‐diazabicycloundec‐7‐ene and N ‐heterocyclic carbenes, have extensively been studied for this process . However, some articles reported lower toxicity of Al 3+ compounds than that of Sn 2+ compounds …”