Green Synthesis of Thermoplastic Composites from a Terpenoid-Cellulose Ester

Abstract

Herein we report a green route to thermoplastics from cellulose, the terpenoid geraniol, and fossil fuel byproduct sulfur with an overall atom economy of 90% over three steps. The only stoichiometric byproducts are NaCl and water. The process involves (1) oxidation of cellulose, (2) amino acid-catalyzed esterification, and (3) cross-linking of olefins with sulfur to give GCS x (x = wt % sulfur, varied from 80–90%). The thermoplastics exhibit flexural strengths and moduli competitive with some commercial materials and are recyclable without loss of strength. The method delineated herein should be applicable to many combinations of saccharide and terpenoid precursors to facilitate similarly green routes to a range of sustainably sourced materials.

Inverse vulcanization of octenyl succinate-modified corn starch as a route to biopolymer–sulfur composites

“…58 Sulfur ranks (R S , average number of sulfur atoms per crosslinking polysulfur chain) were calculated to be 170 and 69 for OSS 95 and OSS 90 , respectively (calculations and raw data provided in the ESI † and accompanying Table S2 and eqn (S2)). The R S in OSSx composites are towards the high end of the range reported for previously-reported biopolymer-sulfur composites prepared by inverse vulcanization of methylpropene-derivatized cellulose (PCS x , R S = 24-58), 58 geraniol-derivatized cellulose (GCS 90 , R S = 22), 59 allyl lignin (LS x , R S = 49-96), 46 or allylated lignocellulose biomass (APS x , R S = 20-21). 40,41 A comparison of several properties for OSSx and these related biopolymer-sulfur composites is provided in Table 2.…”

“…55 In our previous work, we have noted that retention of biopolymer crystallinity is a potential contributing factor in compatibilizing sulfur and biopolymer comonomers as well as for imbuing strength to the resultant cellulose-sulfur composites. 3,21 The incorporation of hydrophobic alkyl chains should also improve miscibility/ compatibilization with sulfur for more facile reaction than has been observed in some cellulose-sulfur systems. 56 Modification with OSA also provides another site for modification, a carboxylic acid side chain, which could be further functionalized to incorporate additional olefins to increase crosslink density, although this avenue is not described in the current work.…”

“…[27][28][29][30][31] Similar HSMs can be prepared from the reaction of aryl halides or anisole derivatives with sulfur as well, although polymerization of these monomers proceeds via different mechanisms than simple inverse vulcanization. [32][33][34][35] In addition to the aforementioned applications of HSMs, our group has recently reported numerous high-strength composite materials prepared by the reaction of sulfur with bio-derived monomers including fatty acids, [36][37][38][39] triglycerides, 42 terpenoids, 21,43 amino acid derivatives, 44 lignin derivatives, 22,35,45,46 cellulose derivatives, 3,21 and raw lignocellulosic biomass sources. 40,41 In terms of commercialization of biopolymer-derived materials, starch-derived films and composites have recently gained tremendous interest because starch is remarkably simple to solubilize, derivatize and process compared to cellulose.…”

Morphological and mechanical characterization of high-strength sulfur composites prepared with variably-sized lignocellulose particles

“…The longer heating times required for PS 90 (72 h versus 2 h for PSS-X) likely results in some destruction of the native peanut shell structure which we have previously shown to be disadvantageous in cellulose systems. 19 As previously noted, attempts to prepare composites analogous to PS 90 by heating sulfur with unfractionated peanut shells for shorter times led to visibly heterogeneous materials, so a direct comparison of PSS-X to that hypothetical direct control material is not possible. Fractionation thus proved to be successful in reducing reaction time, thereby preserving the native structure of the lignocellulosic components, and reducing energy requirements for composite preparation, but at the expense of material homogenization and reproducibility of material properties.…”

“…To meet this goal the organic component to be reacted with waste sulfur must be renewably-sourced and preferably carbon negative to minimize or eliminate contributions to CO 2 emission. Towards this end, researchers have demonstrated successful HSM production by reacting sulfur with fatty acids, 25,31,33 terpenoids, 19,21,57,[73][74][75] starch, 18,24 lignin, 12,17,28,29 cellulose, 13,19 and lignocellulosic biomass derivatives. 16,17 Some of those biologically-derived materials do not possess the olefin functionalities needed for inverse vulcanization and therefore require derivatization or use of alternative reaction strategies.…”