Joshua M. Sadler

Lignin Model Compounds as Bio-Based Reactive Diluents for Liquid Molding Resins

Lignin is a copious paper and pulping waste product that has the potential to yield valuable, low molecular weight, single aromatic chemicals when strategically depolymerized. The single aromatic lignin model compounds, vanillin, guaiacol, and eugenol, were methacrylated by esterification with methacrylic anhydride and a catalytic amount of 4-dimethylaminopyridine. Methacrylated guaiacol (MG) and methacrylated eugenol (ME) exhibited low viscosities at room temperature (MG: 17 cP and ME: 28 cP). When used as reactive diluents in vinyl ester resins, they produced resin viscosities higher than that of vinyl ester-styrene blends. The relative volatilities of MG (1.05 wt% loss in 18 h) and ME (0.96 wt% loss in 18 h) measured by means of thermogravimetric analysis (TGA) were considerably lower than that of styrene (93.7 wt% loss in 3 h) indicating the potential of these chemicals to be environmentally friendly reactive diluents. Bulk polymerization of MG and ME generated homopolymers with glass transition temperatures (T(g)s) of 92 and 103 °C, respectively. Blends of a standard vinyl ester resin with MG and ME (50 wt % reactive diluent) produced thermosets with T(g)s of 127 and 153 °C, respectively, which are comparable to vinyl ester-styrene resins, thus demonstrating the ability of MG and ME to completely replace styrene as reactive diluents in liquid molding resins without sacrificing cured-resin thermal performance.

Vanillin-based resin for use in composite applications

Lignin is an abundant, renewable material that has the potential to yield valuable, low molecular weight, single aromatic chemicals when strategically depolymerized. In order to generate a highly bio-based thermoset for use in polymer composites, a lignin-derived chemical, vanillin, was methacrylated in a two-step, one-pot synthesis to produce a vinyl ester resin (87 cP at 25 °C) with a 1 : 1 mole ratio of a mono-functional monomer, methacrylated vanillin, to cross-linking agent, glycerol dimethacrylate. The synthetic scheme was solventless, required little catalyst and moderate reaction temperatures while generating no by-products. Upon resin curing, a hard, transparent thermoset with a broad glass transition, Tg = 155 °C (based on the tan δ maximum), and a temperature of maximum decomposition rate, Tmax, of 426 °C was produced. Overall, a potentially 100% bio-based thermoset was synthesized possessing comparable thermo-gravimetric and thermo-mechanical properties to commercial vinyl ester-based thermosets.

Isosorbide as the structural component of bio-based unsaturated polyesters for use as thermosetting resins.

In recent years, the development of renewable bio-based resins has gained interest as potential replacements for petroleum based resins. Modified carbohydrate-based derivatives have favorable structural features such as fused bicyclic rings that offer promising candidates for the development of novel renewable polymers with improved thermomechanical properties when compared to early bio-based resins. Isosorbide is one such compound and has been utilized as the stiffness component for the synthesis of novel unsaturated polyesters (UPE) resins. Resin blends of BioUPE systems with styrene were shown to possess viscosities (120-2200 cP) amenable to a variety of liquid molding techniques, and after cure had Tgs (53-107 °C) and storage moduli (430-1650 MPa) that are in the desired range for composite materials. These investigations show that BioUPEs containing isosorbide can be tailored during synthesis of the prepolymer to meet the needs of different property profiles.

Isosorbide-methacrylate as a bio-based low viscosity resin for high performance thermosetting applications

In recent years, the bio-refining industry has developed a number of cyclic molecules with unique attributes derived from renewable carbohydrate feedstocks. Isosorbide is one such compound that has a distinctive fused bicyclic ring system that provides a scaffold for the development of novel bio-based resin systems. We synthesized isosorbide-methacrylate (IM) by the direct esterification of isosorbide using highly reactive species such as methacryloyl chloride or methacrylic anhydride and a base catalyst. IM is a low viscosity (157 cP) cross-linking resin that free radically reacts to form a thermoset polymer with extent of cure at 85%. The resulting polymer has a Tg greater than 240 °C and main degradation temperature of ∼400 °C. Mechanical test results showed that IM had a modulus of ∼4 GPa and strength of 85 MPa. These thermal and mechanical properties show that IM has a significantly higher temperature operating window than any known vinyl ester resin and has similar performance to expensive high temperature epoxy resins. As such, this material has good potential for use in composite applications where a moderate to high temperature free radical cured polymer matrix is needed.

Experimental Data Extraction and in Silico Prediction of the Estrogenic Activity of Renewable Replacements for Bisphenol A.

Bisphenol A (BPA) is a ubiquitous compound used in polymer manufacturing for a wide array of applications; however, increasing evidence has shown that BPA causes significant endocrine disruption and this has raised public concerns over safety and exposure limits. The use of renewable materials as polymer feedstocks provides an opportunity to develop replacement compounds for BPA that are sustainable and exhibit unique properties due to their diverse structures. As new bio-based materials are developed and tested, it is important to consider the impacts of both monomers and polymers on human health. Molecular docking simulations using the Estrogenic Activity Database in conjunction with the decision forest were performed as part of a two-tier in silico model to predict the activity of 29 bio-based platform chemicals in the estrogen receptor-α (ERα). Fifteen of the candidates were predicted as ER binders and fifteen as non-binders. Gaining insight into the estrogenic activity of the bio-based BPA replacements aids in the sustainable development of new polymeric materials.