Effect of pressure and monomer concentration on ring-opening enzymatic polymerization of globalide in pressurized propane

Propane is considered an alternative in enzymatic polyester synthesis due to its favorable enzymatic interactions and mild operating pressures. In this study, enzymatic polymerizations were carried out by ring-opening polymerization of the monomer globalide at 65 °C, using pressurized propane as solvent. Mass ratios of propane:globalide of 1:2, 1:1, and 2:1 were evaluated, as well as pressure conditions of 30, 70, 110, and 150 bar. The enzyme concentration was kept at 5 % relative to globalide mass, with a fixed reaction time of two hours. Results showed monomer conversions up to 93 % and molecular weights ranging from 17.5 kDa to 125.9 kDa, surpassing those with pressurized CO₂. Working pressure had an effect in monomer conversion, suggesting that both the increase in propane viscosity as well as the confinement of the system (compressibility) play important roles in the reaction, but depending on the working pressure, one of the effects will be dominant.