Further characterization of the purified PLA obtained by PD 4-tBu Zn2I3 (1) provided evidence for both transesterification and initiation by an iodide-opened epoxide. Thus matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) analysis resulted in peaks of near equal intensity separated by 72, half the mass of lactide (Section S8.2). The major peaks observed by MALDI-TOF correspond to PLA chains end-functionalized with an iodo-isopropoxy (ICH2CH(CH3)O-) ester and a hydroxyl (17, Table ). Both of these end groups are also visible by 1 H NMR analysis (Figure .3). This end-group functionalization corresponds to a mechanism of coordination-insertion polymerization by a dizinc alkoxide, initiated by iodide-opening of propylene oxide. NMR also shows no evidence for epimerization. ------Conditions: [l-lactide]0 = 1.0 M in propylene oxide at room temperature, 100 equiv. with respect to zinc. a Conversions obtained by 1 H NMR assay. b Theoretical molecular weight (theo. Mn) was calculated as (% conversion of lactide)*100*144. c Number-average molecular weight (Mn) and dispersity (Ð) determined by gel permeation chromatography with polystyrene standards using the correction factor of 0.58.