Effect of reaction temperature on the physicochemical properties of poly(pentadecanolide) obtained by enzyme-catalyzed ring-opening polymerization

Differences on physicochemical properties of poly(pentadecanolide) (PPDL) synthesized by enzymatic ring-opening polymerization at two different temperatures, 70 and 90 °C, using Novozyme 435 were assessed. PPDL synthesized at 90 °C presents lower molecular weight and crystallinity than the one prepared at 70 °C. It was detected by FTIR that PPDL synthesized at 90 °C presents a large amorphous phase with more terminal OH groups. A difference in the melting and crystallization behavior was detected by differential scanning calorimetry, where the melting of the PPDL synthesized at 90 °C presents multiple melting and crystallization events at lower temperature than those exhibit by PPDL synthesized at 70 °C which presents a well-defined single melting and crystallization event. The differences in melting and crystallization behavior are attributed to the presence of a larger amorphous phase in PPDL synthesized at 90 °C due to increased number of terminal OH groups that disrupt the crystalline structure. Thermal stability is also higher in PPDL synthesized at 70 °C since the onset of decomposition starts 50 °C above that observed in PPDL obtained at 70 °C.