Synthesis of Novel Biomass-derived Diol and Epoxide Monomers for Coatings Applications
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Abstract
There are few monomers or precursors in the polymer industry that are more ubiquitous than bisphenol A (BPA). According to the CDC, about 5-6 billion pounds of BPA are produced worldwide annually. For the synthesis of coatings and polymeric materials, BPA is polymerized directly as a diol into polycarbonates or, to a lesser extent, glycidated into an epoxy monomer or resin. For coatings applications, BPA epoxy resins are utilized in protecting metal cans from acidic foods and beverages to heavy machinery like farm equipment from weather-related corrosion. In part, this popularity has led to scrutiny of the popular monomer from a few different perspectives. Since BPA is petroleum-derived, there is an effort to find a renewably sourced alternative from a sustainability perspective. Additionally, the structural similarity of BPA and the hormone estradiol make BPA an endocrine disruptor. This combined with its widespread applications, means BPA could be a larger issue than previously understood.
To meet that challenge, many researchers, Sibi group included, have turned to biomass-derived “building-block” chemicals. Biomass feedstocks contain unique structures not easily obtained from petroleum sources. While avoiding detrimental structure-activity relationships associated with BPA, the newly synthesized compound would need to retain or mimic the structure-property relationships of BPA-containing polymers for coatings applications.
The cellulosic monomer, 2,5-furandicarboxylic acid (FDCA), with exciting similarities to and some improvements upon petroleum-derived terephthalic acid was known, and its oxidative family of furans was being explored at the start of this project. A collection of furan diols was synthesized from 5-hydroxymethylfurfural (HMF), 2, 5-diformylfuran (DFF) and FDCA were synthesized by alkylation with various alkyl groups resulting in mono-, di-, and tetraalkylated diols, respectively. Depending on the alkyl group, certain materials properties were anticipated from these furanic diols.
The diols were screened for estrogenic, androgenic, anti-thyroid activity via CALUX assays. The cytotoxicity of the diols were also determined via cell death studies. From those results, few low molecular weight furan diols do not exhibit any observable activity as endocrine disruptors or an observable cytotoxicity. Subsequently, a selection of furanic diols were glycidated for use in epoxy coating synthesis.