Abstract
Modification of lignin with poly(ε-caprolactone) is a promising approach to valorize industrial low-value lignins and to advance the bioeconomy. We have synthesized lignin grafted poly(ε-caprolactone) (lignin-g-PCL) copolymers via ring-opening polymerization of ε-caprolactone with different types of lignins of varying botanical sources (G-type pine lignin, S/G-type poplar lignin, and C-type Vanilla seeds lignin) and lignin extraction methods (Kraft and ethanol organosolv pulping). The lignin-g-PCL copolymer showed remarkably improved compatibility and dispersion in acetone, chloroform, and toluene in comparison to non-modified lignins. The structure and thermal properties of the lignin-g-PCL were investigated using Fourier-transform infrared spectroscopy (FTIR), 31P nuclear magnetic resonance (NMR), 2D heteronuclear single quantum correlation (HSQC) NMR, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). We have found that all the technical lignins were reactive to the copolymerization reaction regardless of their plant source and isolation methods. The molecular weights of the synthesized lignin-g-PCL copolymers were positively correlated with the content of aliphatic lignin hydroxyls, suggesting that the copolymerization reaction tends to occur preferentially at the aliphatic hydroxyls rather than the phenolic hydroxyls of lignin. Thermal analyses of the lignin-g-PCL copolymers were studied, and in general, a reduction of melting temperature and crystallinity percentage in comparison to the neat PCL was observed. However, the thermal behavior of lignin-g-PCL copolymers varied depending on the lignin feedstocks employed in the copolymerization reaction.
Original language | English |
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Pages (from-to) | 189-199 |
Number of pages | 11 |
Journal | New Biotechnology |
Volume | 60 |
DOIs | |
State | Published - Jan 25 2021 |
Funding
ML acknowledges the Center for Renewable Carbon, University of Tennessee Institute of Agriculture, and the University of Tennessee Agricultural Experiment Station and AgResearch for financial support. AJR acknowledges the financial support from the University of Tennessee for his Tennessee Governor's Chair's funding. This work was partially supported by the Center for Bioenergy Innovation (CBI), a U.S DOE Bioenergy Research Center supported by the Office of Biological and Environmental Research in the DOE Office of Science. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The U.S. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). ML acknowledges the Center for Renewable Carbon, University of Tennessee Institute of Agriculture, and the University of Tennessee Agricultural Experiment Station and AgResearch for financial support. AJR acknowledges the financial support from the University of Tennessee for his Tennessee Governor’s Chair’s funding . This work was partially supported by the Center for Bioenergy Innovation (CBI) , a U.S DOE Bioenergy Research Center supported by the Office of Biological and Environmental Research in the DOE Office of Science . The views and opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights.
Keywords
- Lignin
- lignin copolymer
- polycaprolactone
- ring-opening polymerization