Resumen de Synthesis and Characterization of a Hyperbranched Copolymer
This experiment involves the cationic ring-opening copolymerization of glycidol (2,3-epoxy-1-propanol) with propylene oxide and is suitable for undergraduate polymer chemistry or advanced organic synthesis laboratory courses. Students are introduced to hyperbranched polymers and learn how to use a combination of analytical techniques in constructing a coherent picture of polymer structure. The reaction mechanism involves active participation by the hydroxyl functional group (of glycidol) in a cationic polymerization, from which protic species are usually, but not always, excluded. This critical feature, which is responsible for the extensive branching in the polymer, helps students learn the difference between the so-called "active chain end" and "activated monomer" propagation mechanisms. The short, straightforward synthesis, which uses commonly available laboratory equipment and commercially available chemicals, is carried out at room temperature and proceeds in high yield. GC monitoring of the reaction and NMR and FTIR analysis yield information about polymer structure and confirm chain branching. The stable polymer product is checked for solubility and further examined by gel permeation chromatography and differential scanning calorimetry, yielding results consonant with the structural information gained by spectroscopic means.
