Digital Light Processing (DLP) is a 3D printing technology that enables the fabrication of complex, high-resolution structures; however, the mechanical properties of DLP-printed objects are often limited by the resins used. This study focuses on developing and characterizing bio-based polyester UV-curable resins with tunable mechanical properties optimized for DLP 3D printing. Bio-based polyester resins were synthesized by direct esterification polycondensation reaction of itaconic and/or succinic acids with 1,2-propane-, 1,4-butane-, and/or 1,8-octanediols followed by blending with triethylene glycol dimethacrylate. The bio-renewable nature of the resin components provides several advantages over traditional petroleum-derived resins. The diacid and diol monomers come from renewable feedstocks such as corn, soybean, and vegetable oils rather than finite fossil fuel reserves. Furthermore, bio-renewable materials lower dependence on petrochemicals and increase the sustainability of 3D printing. The effects of diacid structure and diol chain length on resin properties were systematically investigated. Chemical characteristics were investigated by NMR and FTIR and suggested successful synthesis of the desired bio-based polyesters. By varying the molecular design, diacid, and diol building blocks, the molecular weight, crosslink density, and mechanical performance were tailored. The liquid resins were characterized by gel permeation chromatography and rheological measurements, and solid UV-cured objects were characterized by static and dynamic tensile testing. Rheological studies confirmed all resin formulations displayed shear-thinning behavior ideal for DLP printing. Mechanical testing revealed that varying diacid and diol components could modulate tensile elastic modulus and elongation at break from 0.1-1.0 GPa and 3.5-8.5%, respectively. Printability was assessed by printing a resolution test structure on a DLP 3D printer equipped with a 405 nm LED source. This ability to tailor the properties of bio-based polyester resins by molecular design provides an avenue for fabricating high-performance DLP-printed objects targeted for specific applications ranging from prototypes to end-use products.

Pretreatment and fractionation technologies have been used to separate and isolate biomass polymers for conversion into fuels, chemicals, and other products. A great deal of work has focused on dialing in reaction conditions (e.g., time, temperature, acid concentration, etc.) that are amenable to isolating an uncondensed lignin product that could be converted into high value aromatic platform molecules. Pretreatment severity emerged as a term that combines time, temperature, and acid concentration into a single value that can be used to compare various pretreatment technologies. However, combining the effects of these conditions into a single term, while convenient, confounds the effects that these conditions have on lignin quality, both individually and when combined with each other. Moreover, pretreatment and fractionation reactors do not have a severity “knob,” and several different sets of conditions could mathematically achieve the same severity but have different effects on the resulting lignin product slate. In this study, we set out to model the effects of time (10-30 min), temperature (140-180 °C), and acid concentration (0.025-0.1 M H2SO4) on lignin yield (up to quantitative), molecular weight (Mw = 700-2000 g/mol), and hydroxyl group content (3.55-6.06 mmol OH/g) using the co-solvent enhanced lignocellulosic fractionation (CELF) process on switchgrass. Our results show that lignin yield is most sensitive to acid concentration, with an additional 4.96% yield per 10 mM of acid. In addition, molecular weight is sensitive to acid concentration and temperature, with a decrease of 77.9 g/mol per 10 mM of acid and a decrease of 19.3 g/mol per °C. Moreover, total hydroxyl group content decreases at a rate of 89 μmol total OH per g lignin per min at short time (t = 12 min, T = 160 °C) and is increases at a rate of 125 μmol total OH per g lignin per min at long time (t = 28 min, T = 160 °C). Finally, our results demonstrate that residence time does not have a statistically significant effect on yield or molecular weight within the studied ranges, which could have implications for continuous and flow-through processes, where short residence times could lead to substantial cost savings. Overall, these results demonstrate that practitioners can design a process that maximizes one or more of industrially relevant lignin properties by exerting careful control of fractionation conditions, which could ultimately lead to greater utilization of lignin for fuels, chemicals, and other products.

Chemical reductions of lignin are useful to remove oxygen and create product slates that can function as renewable platform molecules for new fuels and chemicals. Catalytic transfer hydrogenolysis (CTH) is an underexplored method to conduct reductions of lignin that obviates the use of dangerous and non-renewable hydrogen gas. While noble metals are used extensively as catalysts for transfer hydrogenation, one major challenge for their deployment is related to their sustainability. In this work, we synthesized mixed-metal oxides of earth-abundant Co and Ni. We characterized these catalysts using powder x-ray diffraction (XRD) and tested their reactivity for CTH of acetophenone. Among the catalysts we tested, we noted that the spinel NiCo2O4 demonstrated the highest conversion of acetophenone (75%) and highest selectivity for ethylbenzene (90%), so we applied it to valorization of switchgrass lignin extracted under mild operating conditions by cosolvent enhanced lignocellulosic fractionation (CELF). The catalytically depolymerized lignin showed an increase in selectively deoxygenated monomeric compounds. Using 2D-NMR spectroscopy, we demonstrated the lignin displayed highly reduced aliphatic carbons resulting from the reduction reaction at the Cα sites mediated by our catalyst material. These results are critical to the further development of the lignin-first biorefinery as they demonstrate the use of sustainable catalyst materials and mild transformation conditions to generate and refine a suite of new bioproducts.

Finding an alternative to fossil-based resins which is renewable, sustainable, and affordable is an important step to enable large-scale industrial manufacturing using stereolithography. Lignin has shown some potential to fulfil these requirements. However, examples that contain Kraft lignin, which is produced industrially at a rate of 70 million tons per year, are relatively scarce compared to examples using organosolv lignin or lignin model compounds. In this work, we fractionated and modified Kraft lignin and blended it with a commercially available stereolithography resin produce 3D printed objects. We thoroughly characterized the lignin, the resins, and the 3D printed objects, and conclude that while our modification scheme allows for smooth incorporation of large amounts Kraft lignin into resins (up to 10% (w/w), or 10 times the amount previously demonstrated as possible), and the lignin itself aids in the photopolymerization process (Ec = 662(2) mJ·cm-2 for the base case, Ec = 0.763(1) mJ·cm-2 for resins containing 10% (w/w) lignin), the printed objects are weaker (σ = 20(1) MPa) and more brittle (ε = 1.12(5)%) than the control that contains no Kraft lignin (σ = 46.3(5) MPa, ε = 3.95(9)%). Together, these results demonstrate the importance of lignin modifications to create miscible blends for stereolithography resins but highlight the need for further understanding how these modifications can simultaneously enhance photo- and mechanical properties of printed objects. These are an important first step towards creating 3D printable objects that contain industrially relevant lignin.

This study examined the REACH program, a Research and Extension Experiences for Undergraduates (REEU) program, aimed at improving agricultural literacy and career development among community college students. This study employed a one-group pretest-posttest design using the Perceptions of Agriculture and Agricultural Careers questionnaire (quantitative) and participants’ written responses to an open-ended question about agricultural career and academic plans (qualitative). Data were collected on the first and last day of the program to compare benchmarks to student achievement. The scaled responses were analyzed using the Wilcoxon signed-rank test, a nonparametric test. The open-ended responses were analyzed using content analysis. REACH Scholars developed more specific career plans and more favorable perceptions of personal job opportunities and their own capabilities in agriculture during the program. Regarding occupational requirements, the scholars’ perception that many agricultural leaders had a college education significantly improved over the course of the REACH program. Despite these improvements, their views about agricultural occupations in general, including food processing, food inspection, forestry, and natural resources management, were not significantly different from pretest to posttest. This study demonstrated an effective evaluation strategy for evaluating undergraduate research programs in agriculture and the allied sciences. Recommendations include strategies for greater outcome evaluation of REEU programs.

Cellulose nanofibrils (CNFs) exhibit characteristics that make them a desirable addition to new composite materials. CNFs are usable in a wide variety of applications such as coatings, personal and healthcare products, packaging, and advanced structural materials. They can also help overcome some performance issues with objects 3D printed by stereolithography (SLA) including dimensional instability and poor mechanical properties. However, CNFs are hydrophilic, making their dispersion in hydrophobic resins common to SLA difficult. Therefore, improvement of performance properties will not be fully realized. In this work, we treated TEMPO-oxidized CNFs (TOCNFs) with the hydrochloride salt of lauroyl arginate ethyl ester (LAE⋅HCl), a cationic surfactant, to investigate how this coating would affect the performance properties of multicomponent uncured SLA resins and subsequently printed objects. We hypothesized this coating would enhance the dispersion of the cellulose nanomaterials when compared to their uncoated counterparts, which would lead to quantifiable differences among the sample groups. We found that the viscosity of a commercial 3D printing resin (0.34 Pa·s at 30 Hz) increased by nearly an order of magnitude upon addition of even 1 wt.%. uncoated TOCNFs (2.96 Pa·s at 30 Hz). Moreover, the tensile strength (19.9(5) MPa) and modulus (0.65(5) GPa) of objects printed from the commercial resin decreased when adding 4 wt.% uncoated TOCNF (12.5(2) MPa and 0.58(8) GPa, respectively). In contrast, resins having 4 wt.% TOCNFs coated with LAE were less viscous (1.25 Pa·s at 30 Hz), and objects printed from them had enhanced tensile strength (24.7(7) MPa) and modulus (0.78(8) GPa) when compared to both the unadulterated resin and that having uncoated TOCNFs. Our findings show the general utility of using a surfactant with cellulose nanomaterials to homogenize multicomponent resins for 3D printing composite materials with enhanced performance properties.

Carbon composites are attractive to a variety of high-impact applications, such as carbon fibers, batteries, and vehicle parts, due to their multifunctional properties. The properties of carbon are highly dependent on the allotrope the carbon takes and the functionality, impurities, and defects contained within the structure. The increase in demand for sustainable carbon sources in energy storage devices motivates interest in understanding synthesis parameters of lignin value-added products. Also, as the dependence on oil for fuel decreases, alternative sources for carbon in many applications will be needed. In this work, the thermochemical conversion of lignin powders from different feedstocks was evaluated via small and wide-angle X-ray scattering techniques to resolve the amorphous, disordered, and crystalline domains present in the lignin carbons. Scattering analyses indicated an evolution of hierarchical structures along with an increase in ordered domains as a function of carbonization temperature. Qualitative and quantitative methods were used to describe isotropic scattering intensity profiles at multiple length scales. The use of power law models in the mesoscopic region served as the basis to describe morphological changes related to structural features, for example, graphene stacking, degree of roughness, and surface fractals. Kraft softwood and switchgrass produced carbon powder with the most crystalline domains and the least surface roughness. Softwoods reached the highest degree of crystallinity followed by switchgrass samples and had less variability in particle sizes. These results suggest lignin carbons extracted from softwoods and switchgrass are viable substitutes for graphite. Interpretation of X-ray scattering data from lignin carbon powders elucidates feedstock- and processing-dependent morphological features across multiple length scales providing a straightforward framework to evaluate the feasibility of leveraging lignin carbons for producing tunable application-specific materials.

As the second most abundant biopolymer on earth, and as a resource recently becoming more available in separated and purified form on an industrial scale due to the development of new isolation technologies, lignin has a key role to play in transitioning our material industry towards sustainability. Additive manufacturing (AM), the most efficient-material processing technology to date, has likewise made great strides to promote sustainable industrial solutions to our needs in engineered products. Bringing lignin research to AM has prompted the emergence of the nascent "lignin 3D printing" field. This review presents the recent state of art of this promising field and highlights its challenges and opportunities. Following a review of the industrial availability, molecular attributes, and associated properties of technical lignins, we review R&D efforts at implementing lignin systems in extrusion-based and stereolithography (SLA) printing technologies. Doing so underlines the adage of lignin research that "all lignins are not created equal," and stresses the opportunity nested in this chemical diversity created mostly by differences in isolation conditions to molecularly select and tune the attributes of technical lignin systems towards desirable properties, be it by modification or polymer blending. Considering the AM design process in its entirety, we finally propose onward routes to bring the full potential to this emerging field. We hope that this review can help promote the unique value and overdue industrial role of lignin in sustainable engineered materials and products.

Despite recent successes in incorporating lignin into photoactive resins, lignin photo-properties can be detrimental to its application in UV-curable photopolymers, especially in specialized engineered resins for use in stereolithography printing. We report on chemical modification techniques employed to reduce UV absorption by lignin and the resulting mechanical, thermal, and cure properties of these modified lignin materials. Lignin was modified using reduction and acylation reactions and incorporated into a 3D printable resin formulation. UV–Vis absorption at the 3D printing range of 405 nm was reduced in all modified lignins compared to the unmodified sample by 25% to ≥ 60%. Resins made with the modified lignins showed an increase in stiffness and strength with lower thermal stability. Studying these techniques is an important step in developing lignin for use in UV-curing applications and further the effort to valorize lignin towards commercial use.

In this study, we propose a complete biomass fractionation strategy where all three major biopolymers, namely, cellulose, hemicellulose, and lignin, are separated with higher efficiency and purity. Sequential treatment of hybrid poplar wood using autohydrolysis (160 degrees C,60 min) and 1-ethyl-3-methylimidazolium acetate activation (60 degrees C,3 h) resulted in significantly improved enzymatic saccharification and fractionated 85% cellulose and 67% hemicellulose. The resulting solid fraction contained 90% (w/w) lignin, which was equal to 71% yield based on the original biomass composition. The proposed two-step pretreatment process improved lignin yield by 77% and 23% compared to the single-stage ionic liquid activation or autohydrolysis, respectively. Structural characterization by 2D nuclear magnetic resonance spectroscopy and small-angle neutron scattering revealed that the isolated lignin sustained minimal modifications to interunit linkages and exhibited high thermotolerance as well as unique functionality, thereby highlighting the benefits of this process for lignin fractionation.

Fluorescent carbon dots (CDs) with amplified photoluminescence (PL) intensity were synthesized using recycled hot-water extraction wastes of lignocellulosic biomass according to a bio-refinery concept without carbonization of the entire biomass. The recycled waste liquid was obtained by pre-extracting biomass with pressurized hot-water under 120-180 degrees C for 30 and 60 min. CDs with controlled N-doping were obtained by a hydrothermal carbonization strategy of the pre-extraction liquid at 220 degrees C for 5 h. The main chemical component of preextraction hydrolysates was analyzed by high-performance liquid chromatography (HPLC). The effects of hydrolyzed sugars and other heteroatom-containing extracts on fluorescence of CDs were investigated by measuring the PL performance. The superior biomass-based CDs exhibited tunable quantum yields (QYs) of 6.2 %-11.8 % with hot-water extractions as precursor without carbonization destruction of the entire biomass. CDs with higher QYs could serve as an effective luminescent sensing platform for probes, temperature sensing, and anti-counterfeit applications.

Ball milling CaI2 and [KN(SiMe3)(2)] in a 1:1 ratio without solvent, and then extracting the ground material with toluene, yields the synthetically valuable neutral amide [Ca(N(SiMe3)(2))(2)] in good yield, without the contamination by calciate species that complicates solution metathesis routes. The effects on yield of grinding time, milling frequency, and calcium halide identity are also examined.

Mixed-metal oxides possess a wide range of tunability and show promise for catalytic stabilization of biomass pyrolysis products. For materials derived from layered double hydroxides, understanding the effect of divalent cation species and divalent/trivalent cation stoichiometric ratio on catalytic behavior is critical to their successful implementation. In this study, four mixed-metal oxide catalysts consisting of Al, Zn, and Mg in different stoichiometric ratios were synthesized and tested for ex-situ catalytic fast pyrolysis (CFP) using pine wood as feedstock. The catalytic activity and deactivation behavior of these catalysts were monitored in real-time using a lab-scale pyrolysis reactor and fixed catalyst bed coupled with a molecular beam mass spectrometer (MBMS), and data were analyzed by multivariate statistical approaches. In comparing Mg- and Zn-Al catalyst materials, we demonstrate that the Mg-Al materials possessed greater quantities of basic sites, which we attribute to their higher surface areas, and they produced upgraded pyrolysis vapors which contained less acids and more deoxygenated aromatic hydrocarbons such as toluene and xylene. However, detrimental impacts on carbon yields were realized via decarbonylation and decarboxylation reactions and coke formation. Given that the primary goals of catalytic upgrading of bio-oil are deoxygenation, reduction of acidity, and high carbon yield, these results highlight both promising catalytic effects of mixed-metal oxide materials and opportunities for improvement.

Despite recent successes incorporating lignin into photoactive resins, lignin photo-properties can be detrimental to its application in UV-curable photopolymers, especially to customized, engineered resins for use in stereolithography printing. We report on chemical modification techniques employed to reduce UV absorption in lignin and the resulting mechanical, thermal, and cure properties in these lignin-containing materials. Pine lignin was modified using acetylation and reduction reactions and incorporated into a printable resin formulation. Modified lignin displayed enhanced printing properties because UV absorption at the 3D printable range was reduced in all acylated lignin from 25% up to greater than 60%. Resins made with the modified lignin showed increased stiffness and strength with lower thermal stability. Investigating these techniques is an important step in developing lignin for use in UV-curing applications and furthers the effort to valorize lignin toward commercial use.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.