Rac lactide

All manipulations were performed in an MBRAUN stainless steel glovebox equipped with a gas purification system under a nitrogen atmosphere. All chemicals were purchased from Fisher Scientific and used as received unless stated otherwise. Dichloromethane, toluene and THF (HPLC grade) were dried on an Innovative Technology solvent purification system with activated alumina columns. Thiourea catalysts were prepared as previously described.^{7 ,15} L-lactide and RAC-lactide from Acros Organics were recrystallized from dry toluene prior to use. Benzyl alcohol was distilled from CaH₂ under high vacuum. Dialysis bags (MWCO = 3,000) were purchased from SpectraPor and stored in aqueous NaN₃ solution. NMR experiments were performed on a Bruker Avance 300 MHz spectrometer except decoupled experiments which were performed on a Varian 500 MHz NMR spectrometer. Size exclusion chromatography (SEC) was performed at 30 °C in dichloromethane (DCM) at 1.0 mL/min using a Agilent Infinity GPC system equipped with three Agilent PLGel columns 7.5 mm ×300 mm (5 μm; pore sizes = 10³, 10⁴, and 10⁵ Å) and multiwavelength detector (set to 254 nm) and refractive index detector connected in series. Molecular weight and M_w/M_n were determined versus PS standards (500 g/mol to 3150 kg/mol; Polymer Laboratories). MALDI–TOF data was acquired at the University of Akron Mass Spectrometry Center.