@article{sen_losey_gordon_argyropoulos_martin_2016, title={Ionic Liquid Character of Zinc Chloride Hydrates Define Solvent Characteristics that Afford the Solubility of Cellulose}, volume={120}, ISSN={1520-6106 1520-5207}, url={http://dx.doi.org/10.1021/acs.jpcb.5b11400}, DOI={10.1021/acs.jpcb.5b11400}, abstractNote={The recently described ionic liquid structure of the three equivalent hydrate of zinc chloride (ZnCl2·R H2O, R = 3, existing as [Zn(OH2)6][ZnCl4]) explains the solubility of cellulose in this medium. Only hydrate compositions in the narrow range of 3 - x < R < 3 + x with x ≈ 1 dissolve cellulose. Once dissolved, the cellulose remains in solution up to the R = 9 hydrate. Neutron diffraction and differential pair distribution function analysis of cellulose and model compound solutions (1 wt % cellulose in the R = 3 hydrate and 1 wt % ethanol in the R = 3 hydrate and the ZnCl2·3 ethanol liquid) coupled with detailed solubility measurements suggest that cellulose solubility occurs via coordination of the primary OH to the hydrated zinc cation with ring hydroxyls forming part of a second coordination shell around the cation of the ionic liquid.}, number={6}, journal={The Journal of Physical Chemistry B}, publisher={American Chemical Society (ACS)}, author={Sen, Sanghamitra and Losey, Bradley P. and Gordon, Elijah E. and Argyropoulos, Dimitris S. and Martin, James D.}, year={2016}, month={Feb}, pages={1134–1141} }
 @article{sadeghifar_sen_patil_argyropoulos_2016, title={Toward Carbon Fibers from Single Component Kraft Lignin Systems: Optimization of Chain Extension Chemistry}, volume={4}, ISSN={["2168-0485"]}, DOI={10.1021/acssuschemeng.6b00848}, abstractNote={Single component softwood kraft lignins have been sought after as precursors to carbon fibers. This noble goal can be achieved by adding carbon onto lignin via propargylation. The reactivity of propargylated lignins may then be modulated via methylation, thus eliminating the onset of gelation via phenoxyl radical initiated random polymerization. This article demonstrates that properly installed propargyl groups of an acetone soluble kraft lignin (ASKL) fraction can be thermally polymerized to high molecular weights in a controlled manner. In order to create single component chain extended softwood kraft lignin systems for carbon fiber applications, one needs to regulate the amount and the positioning of the propargyl groups on the lignin. This became possible, and it is now demonstrated that the propargylation of lignin needs to occur first, followed by methylation and not the other way around. Such a sequence offers substantial benefits for the onset of a Claisen rearrangement to occur between the propar...}, number={10}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Sadeghifar, Hasan and Sen, Sanghamitra and Patil, Shradha V. and Argyropoulos, Dimitris S.}, year={2016}, month={Oct}, pages={5230–5237} }
 @article{sen_patil_argyropoulos_2015, title={Methylation of softwood kraft lignin with dimethyl carbonate}, volume={17}, ISSN={["1463-9270"]}, DOI={10.1039/c4gc01759e}, abstractNote={Methylation of lignin is essential for inducing thermal stability when a multitude of thermoplastic applications are envisaged.}, number={2}, journal={GREEN CHEMISTRY}, author={Sen, Sanghamitra and Patil, Shradha and Argyropoulos, Dimitris S.}, year={2015}, pages={1077–1087} }
 @misc{sen_patil_argyropoulos_2015, title={Thermal properties of lignin in copolymers, blends, and composites: a review}, volume={17}, ISSN={["1463-9270"]}, DOI={10.1039/c5gc01066g}, abstractNote={Modulating thermal propertiesvialignin copolymers, blends, and composites.}, number={11}, journal={GREEN CHEMISTRY}, author={Sen, Sanghamitra and Patil, Shradha and Argyropoulos, Dimitris S.}, year={2015}, pages={4862–4887} }
 @article{argyropoulos_sadeghifar_cui_sen_2014, title={Synthesis and Characterization of Poly(arylene ether sulfone) Kraft Lignin Heat Stable Copolymers}, volume={2}, ISSN={["2168-0485"]}, DOI={10.1021/sc4002998}, abstractNote={In this effort we aim at documenting our understanding of using the phenolic hydroxyl groups of technical softwood kraft lignin in replacing the multifunctional phenolic component required for the synthesis of poly(arylene ether) sulfones. To do this we use a two-pronged approach that uses fractionated softwood kraft lignin whose phenolic hydroxyl groups have been systematically protected in order to avoid gelation when copolymerized with 4, 4′-diflourodiphenyl sulfone (DFDPS). This has been done by careful 31P NMR profiling of the various hydroxyl groups present in the lignin as a function of the degree of phenolic hydroxyl group protection. For all copolymers, weight average molecular weights (Mw), polydispersity indices (PDI), glass transition temperatures (Tg), and thermal stability profiles (TGA) were obtained, providing an integrated picture of the scientific and technological ramifications of this work. Overall, this effort provides the foundations for creating lignin copolymers of controlled and m...}, number={2}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Argyropoulos, Dimitris S. and Sadeghifar, Hasan and Cui, Chengzhong and Sen, Sanghamitra}, year={2014}, month={Feb}, pages={264–271} }
 @article{sen_sadeghifar_argyropoulost_2013, title={Kraft Lignin Chain Extension Chemistry via Propargylation, Oxidative Coupling, and Claisen Rearrangement}, volume={14}, ISSN={["1526-4602"]}, DOI={10.1021/bm4010172}, abstractNote={Despite its aromatic and polymeric nature, the heterogeneous, stochastic, and reactive characteristics of softwood kraft lignin seriously limit its potential for thermoplastic applications. Our continuing efforts toward creating thermoplastic lignin polymers are now focused at exploring propargylation derivatization chemistry and its potential as a versatile novel route for the eventual utilization of technical lignins with a significant amount of molecular control. To do this, we initially report the systematic propargylation of softwood kraft lignin. The synthesized derivatives were extensively characterized with thermal methods (DSC, TGA), (1)H, (13)C, and quantitative (31)P NMR and IR spectroscopies. Further on, we explore the versatile nature of the lignin pendant propargyl groups by demonstrating two distinct chain extension chemistries; the solution-based, copper-mediated, oxidative coupling and the thermally induced, solid-state, Claissen rearrangement polymerization chemistries. Overall, we show that it is possible to modulate the reactivity of softwood kraft lignin via a combination of methylation and chain extension providing a rational means for the creation of higher molecular weight polymers with the potential for thermoplastic materials and carbon fibers with the desired control of structure-property relations.}, number={10}, journal={BIOMACROMOLECULES}, author={Sen, Sanghamitra and Sadeghifar, Hasan and Argyropoulost, Dimitris S.}, year={2013}, month={Oct}, pages={3399–3408} }
 @article{sen_martin_argyropoulos_2013, title={Review of Cellulose Non-Derivatizing Solvent Interactions with Emphasis on Activity in Inorganic Molten Salt Hydrates}, volume={1}, ISSN={2168-0485 2168-0485}, url={http://dx.doi.org/10.1021/SC400085A}, DOI={10.1021/sc400085a}, abstractNote={During cellulose dissolution in non-derivatizing solvents, the inter- and intramolecular hydrogen bonds of the polymer are deconstructed. This occurs either by hydrogen bond formation between one or more components of the solvent systems and the hydroxyl groups of the cellulose or by coordination bond formation between the metal ion present in the medium and the hydroxyl group of cellulose molecules. None of the polymer molecules are actually chemically modified during dissolution. In the first part of this review, we examine the literature pertaining to the different interaction mechanisms between cellulose and non-derivatizing solvent systems with emphasis on the inorganic molten salt hydrates. In the second part of this effort, we further review inorganic molten salt hydrates from the point of view of the changes they impart to the physical properties of the cellulose and the various chemical reactions that can be performed in it.}, number={8}, journal={ACS Sustainable Chemistry & Engineering}, publisher={American Chemical Society (ACS)}, author={Sen, Sanghamitra and Martin, James D. and Argyropoulos, Dimitris S.}, year={2013}, month={Jun}, pages={858–870} }