Module 6: Polymerization The polymerization reaction is the final the conversion step in of used office paper to PLA (step ii, scheme 2). New catalysts for the ring-opening polymerization of lactide are currently an active area 2012 Therefore, phasize the of research. to em research aspect of the project, we decided to carry out the polymerization of lactide using an iron catalyst that was recently reported by one of us.13 The polymerization reaction also allowed for the demonstration of many common and useful techniques in polymer and organometallic chemistry (Figure 2). The catalyst precursor is air and moisture sensitive, so the students were able to learn how to handle air sensitive reagents using equipment such as inert atmosphere glove boxes, solvent purification systems, and high vacuum lines. Formation of poly(lactic acid) was monitored by H NMR spectroscopy S6 in the supporting Information) Additionaly, Figure analysis of the reaction was camed out using gel permeation chromatography (GPC) to monitor polymer molecular weights and molecular weight distnbutions. For laboratories that are not equipped with such spedalized equipment, there are that have been numerous other air and moisture stable cat developed for the polymerization of lactide. 420 Many of these catalysts, such as tin(i) 2-ethylhexanoate or 1,8 diazabicyclo [s.40]undec-7-ene (DBU), are inexpensive and are commercially available. In the absence of gel permeation chromatography or other types of size exclusion chromatog. raphy, the progress of the polymeraation reaction can easily be monitored by measuring the viscosity of the reaction mixture. Precipitation of the polymer in methanol solution also allows the students to analyze the macroscopic physical properties of the new material (eg, Ty T,, etc), which is very similar to plastics that they are more familiar with the industrial