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  • 1.
    Ribca, Iuliana
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Sochor, Benedikt
    Deutsches-Elektronen Synchrotron (DESY).
    Betker, Marie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fiberprocesser. Deutsches-Elektronen Synchrotron (DESY).
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology. Deutsches-Elektronen Synchrotron (DESY).
    Lawoko, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Sevastyanova, Olena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Meier, Michael A.R.
    Institute of Organic Chemistry (IOC), Materialwissenschaftliches Zentrum MZE, Karlsruhe Institute of Technology (KIT), Straße am Forum 7, 76131 Karlsruhe, Germany;Institute of Biological and Chemical Systems─Functional Molecular Systems (IBCS-FMS), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
    Johansson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Impact of lignin source on the performance of thermoset resins2023In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 194, p. 112141-112141, article id 112141Article in journal (Refereed)
    Abstract [en]

    A series of different technical hardwood lignin-based resins have been successfully synthesized, characterized, and utilised to produce thiol-ene thermoset polymers. Firstly, technical lignin was fractionated and allylated, whereafter it was crosslinked with a trifunctional thiol. Structural and morphological characteristics of the lignin fractions were studied by 1H NMR, 31P NMR, SEC, FTIR, DSC, TGA, and WAXS. The hardwood lignin fractions have a high content of C5-substituted OH groups. The WAXS studies on lignin fractions revealed the presence of two π-π stacking conformations, sandwiched (4.08–4.25 Å) and T-shaped (6.52–6.91 Å). The presence of lignin superstructures with distances/sizes between 10.5 and 12.8 Å was also identified. The curing reaction of the thermosets was investigated by RT-FTIR. Almost all thermosets (excepting one fraction) reached 95% of the thiol conversion in less than 17 h, revealing the enhanced reactivity of the allylated hardwood lignin samples.

    The mechanical properties of the thermosets were investigated by DMA. The curing performance, as well as the final thermoset properties, have been correlated to variations in chemical composition and morphological differences of lignin fractions. The described results clearly demonstrate that technical hardwood lignins can be utilized for these applications, but also that significant differences compared to softwood lignins have to be considered for material design.

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    Impact of lignin source on the performance of thermoset resins
  • 2.
    Ribca, Iuliana
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology.
    Sochor, Benedikt
    Deutsches-Elektronen Synchrotron (DESY),.
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology.
    Lawoko, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Meier, Michael A. R.
    Institute of Organic Chemistry (IOC), Materialwissenschaftliches Zentrum MZE, Karlsruhe Institute of Technology (KIT).
    Johansson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Effect of Molecular Organization on the Properties of Fractionated Lignin-Based Thiol-Ene Thermoset MaterialsManuscript (preprint) (Other academic)
    Abstract [en]

    In this study, the combination of sequential solvent fractionation of technical Kraft lignin were followed by allylation of most OH functionalities to give highly functional thermoset resins. All lignin fractions were highly functionalized on the phenolic (≥95%) and carboxylic acid OH (≥85%), and to a significant extent on the aliphatic OH moieties (between 43 and 75%). The resins were subsequently cross-linked using thiol-ene chemistry. The high amount of allyl functionalities resulted in a high cross-link density. DMA measurements showed that thioether content dominates the performance of these thermosets with a glass transition temperature (Tg) between 73 and 99 °C and with a storage modulus between 1.9 and 3.8 GPa for all thermosets. The lignin fractions and lignin-based thermosets morphology, at nanoscale, was studied by wide angle X-ray scattering measurements (WAXS). Two π-π stacking interactions were observed: sandwich (≈4.1–4.7 Å) and T-shaped (≈5.5–7.2 Å). The introduction of allyl functionalities weakens the T-shaped π-π stacking interactions. A new signal corresponding to a distance of ≈3.5 Å was observed in lignin-based thermosets, which was attributed to a thioether organized structure. At the same time, a lignin superstructure, was observed with a distance/size corresponding to 7.9-17.5 Å in all samples.

  • 3.
    Wolfs, Jonas
    et al.
    Institute of Organic Chemistry (IOC), Materialwissenschaftliches Zentrum MZE, Karlsruhe Institute of Technology (KIT), Straße am Forum 7, 76131 Karlsruhe, Germany, Straße am Forum 7.
    Ribca, Iuliana
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Meier, Michael A.R.
    Institute of Organic Chemistry (IOC), Materialwissenschaftliches Zentrum MZE, Karlsruhe Institute of Technology (KIT), Straße am Forum 7, 76131 Karlsruhe, Germany, Straße am Forum 7; Institute of Biological and Chemical Systems − Functional Molecular Systems (IBCS-FMS), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany, Hermann-von-Helmholtz-Platz 1.
    Johansson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Polythionourethane Thermoset Synthesis via Activation of Elemental Sulfur in an Efficient Multicomponent Reaction Approach2023In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 11, no 9, p. 3952-3962Article in journal (Refereed)
    Abstract [en]

    For the transition toward a safer and more sustainable production of polymeric materials, new synthetic concepts need to be developed. Herein, we describe a catalytic, solvent-free synthesis approach for novel thionourethane thermoset materials, in which the diisothiocyanate reactant is generated in situ via a sulfurization of isocyanides with elemental sulfur, preventing the exposure and handling of the diisothiocyanate. In this one-pot procedure, castor oil fulfills a dual role: (i) acting as the solvent for the in situ diisothiocyanate synthesis in the first step and (ii) reacting as the polyol component in the subsequent thionourethane thermoset formation. The kinetics of the consecutive two steps were studied in detail via real-time IR measurements, and the thermoset crosslinking step was found to be thermally triggerable after the diisothiocyanate reactant is quantitatively formed, enabling high control over the curing process of the system. Differential scanning calorimetry, thermogravimetric analysis, and rheological measurements were performed to investigate the thermal and mechanical properties of the novel thionourethane thermosets and then compared to analogous polyurethane materials. Our results demonstrate an unprecedented approach for thermoset synthesis via an in situ reagent synthesis, i.e., the generation of isothiocyanates from isocyanides by catalytic activation of elemental sulfur, and subsequent thermally triggerable thermosetting with a polyol, resulting in materials with appealing properties.

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