Title: Effects of CELF Pretreatment Severity on Lignin Structure and the Lignin-Based Polyurethane Properties

Abstract

Conversion of technical lignin into performance biopolymers such as polyurethane offers environmental and economic advantages when combined with production of biofuels from biomass sugars, presenting significant interest toward studying the role of pretreatment on lignin structure and functionality. Co-solvent enhanced lignocellulosic fractionation (CELF) pretreatment, employing acidic aqueous tetrahydrofuran (THF) mixtures, was developed to effectively break down the lignin-carbohydrate matrix and promote extraction of lignin from lignocellulosic biomass with desirable purity and yield. In this study, we report the effects of CELF pretreatment reaction severity on the molecular structure of CELF-extracted lignin and its impact toward the mechanical properties of the resulting lignin-based polyurethanes. Reaction temperature was found to play the most significant role, compared to reaction time and acidity, in manipulating structural features such as molecular weight, functionality and intra-polymer structure. At the severe reaction conditions at 180°C, the order of reactivity for primary lignin interlinkages characterized by semiquantitative HSQC NMR analysis were found to be β-ether > phenylcoumaran (β−5′) > resinol (β−β′) facilitating a high degree of depolymerization and yielding a high frequency of free phenolics and reduced aliphatic hydroxyl groups. All side-chain interlinkages were depleted converting guaiacyl subunits into condensed forms, while still retaining uncondensed syringyl subunits. Undermore » the mild 150°C temperature reaction, CELF lignin had higher molecular weight and retained more β-ether interlinkages. The results from CELF lignin-based polyurethane synthesis indicated that the tensile properties depended on the miscibility of CELF lignin with other components and low molecular weight cuts improved the dispersion of lignin in the polyurethane network. Pre-mixing of CELF with poly(ethylene glycol) (PEG) reduced the brittleness and improved the ductility of the CELF lignin-PEG polyurethanes.« less

Authors:

Wang, Yunyan ^[1]; Sengupta, Priya ^[2]; Scheidemantle, Brent ^[2]; Pu, Yunqiao Joseph  ^[3];

• Search DOE PAGES for author "Pu, Yunqiao Joseph"
• Search DOE PAGES for ORCID "0000-0003-2554-1447"

Wyman, Charles E. ^[4]; Cai, Charles M. ^[5]; Ragauskas, Arthur J.  ^[6]

• Search DOE PAGES for author "Ragauskas, Arthur J."
• Search DOE PAGES for ORCID "0000-0002-3536-554X"

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+ Show Author Affiliations

1. Univ. of Tennessee, Knoxville, TN (United States)
2. Univ. of California, Riverside, CA (United States)
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
4. Univ. of California, Riverside, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of California, Riverside, CA (United States)
6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)

Publication Date:

Wed Jul 08 00:00:00 EDT 2020

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1649027

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Frontiers in Energy Research

Additional Journal Information:

Journal Volume: 8; Journal Issue: 1; Journal ID: ISSN 2296-598X

Publisher:

Frontiers Research Foundation

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES