Aluminum ion pair complexes containing an octahedral bis-ligated aluminum cation and a tetrahedral tetraphenoxide aluminate anion have been shown to polymerize lactide into poly-lactic acid (PLA). The structure of the active catalyst was investigated through the synthesis of aluminum complexes in different coordination environments were distinguishable by 27Al NMR (octahedral δ 23 ppm and tetrahedral δ 42 ppm). The bis-ligated octahedral cation with tetrachloro aluminate (27Al NMR signals at δ 23 and 103 ppm) and lithium tetraphenoxide aluminate (27Al NMR signal at δ 46 ppm) were prepared, studied with 27Al NMR, and their lactide polymerization activity assessed. Since neither fragment exhibited polymerization characteristics similar to the original system, the ion pair complex was further studied with variable temperature 27Al NMR.

Polymerization of lactide by aluminum ion pairs studied with 27Al NMR

249th National Meeting (2015)

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