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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.
    Roy, Debmalya
    et al.
    DMSRDE, GT Road, Kanpur 208013, India;INM − Leibniz-Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.
    B, Vaishnav
    UPES, Bidholi, Dehradun 248007, India.
    Vayalil, Sarathlal Koyiloth
    UPES, Bidholi, Dehradun 248007, India.
    Gupta, Ajay
    UPES, Bidholi, Dehradun 248007, India.
    Prasad, N. Eswara
    DMSRDE, GT Road, Kanpur 208013, India.
    Sochor, Benedikt
    Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
    Schwartzkopf, Matthias
    Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology. Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.
    Kraus, Tobias
    INM − Leibniz-Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany;Colloid and Interface Chemistry, Saarland University, 66123 Saarbrücken, Germany.
    In Situ Study of Structure Formation under Stress in Stretchable Conducting Nanocomposites2023In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 14, no 25, p. 5834-5840Article in journal (Refereed)
    Abstract [en]

    One of the major limitations of flexible sensors is the loss of conductivity upon multiple stretching and bending cycles. Conducting fillers with two different geometries, carbon black and carbon nanotubes, were introduced in polydimethylsiloxane (PDMS) for physical insights into the structure formation of nanofillers by the application of periodic tensile stress. The loading of the nanofillers was selected beyond the percolation threshold to determine the cyclic stability of the resulting network channels. The surface chemistry of carbon nanotubes has been varied to understand the interfacial interactions at the molecular length scale. The combination of in situ stretching, annealing, and vis-à-vis conductometry of nanocomposite films with synchrotron-based ultra-small angle X-ray scattering experiments enables us to highlight the importance of the fractal dimensions of nanofillers for the molecular level interactions. The irreversible formation of nanofiller network geometries under cyclic stress and annealing was found to be responsible for the electrical properties of a flexible conducting film.

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