Abstract
Here, we report a new two-step enzymatic polymerization strategy for the synthesis of poly(octamethylene suberate) (POS) using an immobilized Pseudozyma antarctica lipase B (IMM-PBLI). The strategy overcomes the lack of enzymatic POS synthesis in solvent-free systems and increases the final polymer molecular weight. In the first step, the direct polycondensation of suberic acid and 1,8-octanediol was catalyzed by IMM-PBLI at 45 °C, leading to the production of prepolymers with molecular weights (MWs) of 2800, 3400, and 4900 g mol−1 after 8 h in miniemulsion, water, and an organic solvent (cyclohexane: tetrahydrofuran 5:1 v/v), respectively. In the second polymerization step, wet prepolymers were incubated at 60 or 80 °C, at atmospheric pressure, in the presence of IMM-PBLI, and without stirring. The final POS polymers showed a significant increase in MW to 5000, 5800, and 19,800 g mol−1 (previously synthesized in miniemulsion, water, or organic solvent, respectively). FTIR analysis of the final polymers confirmed the successful POS synthesis and a high degree of monomer conversion. This innovative two-step polymerization strategy opens up a new opportunity for implementing greener and more environmentally friendly processes for synthesizing biodegradable polyesters.
Highlights
The characterization of the different polyesters synthesized in this work showed that high yields of between 60 and 98% were obtained with molecular weights (MWs) of between 3500 and 7600 g mol−1, depending on the biocatalysts used
The polyester synthesis performed with the immobilized enzyme preparations, Novozym 435, CALB-Sigma, IMML51-T2150, and IMM-PBLI, were more efficient than those performed with the free enzyme preparation (PBL)
The use of the organic solvent in the first polymerization step resulted in poly(octamethylene suberate) (POS) of MW (16,200 and 19,800 g mol−1 ) at the end of the second polymerization step compared higher MW (16,200 and 19,800 g mol−1) at the end of the second polymerization step comto those returned when miniemulsion or water were used in the first step (Figure 5)
Summary
Associate Laboratory, i4HB—Institute for Health and Bioeconomy at Instituto Superior Técnico, University of Lisbon, 1049-001 Lisbon, Portugal
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