Bioinspired Enzymatic Synthesis of Terpenoid-Based (Meth)acrylic Monomers: A Solvent-, Metal-, Amino-, and Halogen-Free Approach

Abstract

In an attempt to pave the way toward the substitution of petroleum-based monomers for monomers from sustainable and renewable resources, this work investigates the synthesis of a portfolio of new (meth)­acrylic monomers using terpenoids as raw materials that can be conveniently extracted from wood waste and citrus fruits. The synthetic process is based on the enzymatic catalysis of the esterification of terpenoids and is solvent-, metal-, amino-, and halogen-free, overcoming the limitations of the common esterification techniques. The effect of employing microwaves in combination with the enzyme and the effect of the acyl donor choice [(meth)­acrylic acids vs (meth)­acrylic anhydrides] were studied. The process yielded complete conversion and then high-purity monomers with a variety of structures that would allow them to substitute many of the most commonly used petrochemical (meth)­acrylic monomers.

Microwave-Assisted Ultrafast RAFT Miniemulsion Polymerization of Biobased Terpenoid Acrylates

“…Long-term sustainability requires finding renewable alternatives to the currently used petrochemical-based polymers. − Terpenoids are abundant biobased materials that are obtained from byproducts of the paper industry . These compounds possess a hydroxyl group that can be esterified in a relatively easy way to obtain biobased (meth)­acrylic monomers. − In addition, the variety of chemical structures of the terpenoids allows polymers to be synthesized that cover the range of glass transition temperatures ( T g ) of the currently used petrochemical-based (meth)­acrylates. For example, the T g of poly­(tetrahydrogeraniol acrylate) is −46 °C and that of poly­(cyclademol methacrylate) is 96 °C .…”

“…Tetrahydrogeraniol acrylate (THGA), cyclademol acrylate (CycA), nopol acrylate (NopA), and citronellol acrylate (CitA) were synthesized by enzymatic esterification as detailed in a recent publication. 10 In summary, the terpenoid (20 mM) and acrylic anhydride at molar ratio (1:1) were introduced in a 10 mL tubular bottom flask. Novozym 435 (5% w/w) was then added to the reactants and stirred to start the reaction at 40 °C.…”

A self-crosslinking monomer, α-pinene methacrylate: understanding and exploiting hydrogen abstraction

“…[8][9][10][11] Recently, there has been a flurry of papers reporting other routes to polymerisation of terpenes. [12][13][14][15][16][17][18][19][20][21][22][23] We reported the development of new (meth)acrylate based monomers directly derived from terpenes 24 with these monomers readily polymerising via free radical polymerisation, in the presence of a thiol chain transfer agent (CTA), 25 to produce polymers with a wide range of physical properties. Most significantly poly(α-pinene methacrylate) (Pα-PMA) exhibited a T g of ∼180 °C, much higher than those observed in the well-known commodity petroleum based polymers such as PS (100 °C), 26 PMMA (105 °C) 26 and a value that even approaches that of poly(isobornyl methacrylate), IBMA, (199 °C).…”

Linalool Derivatives for Natural Product-Based 4D Printing Resins

“…Natural products are appealing alternatives to petrochemical sources for polymers, because of their potential to push society toward a more sustainable, circular economy, as well as inherent functionality in many cases. , A popular class of such natural materials is terpenes, of which terpenoids such as linalool are one example. Terpenes have found use in a variety of different polymeric applications, including the development of degradable polyesters and polycarbonates, high T g and performance polymers, and even as initiators or monomers in controlled polymerizations. − The successful utilization of terpenes has generally required modifications to terpenoids or terpenes, such as limonene oxide produced from d -limonene or with epoxidized soybean oils. − Often this yields polymers with degradable backbones, such as with polyesters and polycarbonates synthesized from limonene oxide; the common alternative is the formation of degradable side chains after functionalization with acrylates. ,− More recently, this second strategy has been exploited toward 3D printing of natural products, making use of the available functional groups for modification followed typically by free radical crosslinking to produce nondegradable backbones. − For example, retinol has been conjugated with poly­(vinyl alcohol) for drug delivery applications, cyclodextrane has been functionalized with acrylate groups for vat photopolymerization, linalool and citronellol were grafted to oligomeric chitosan, , and myrcenol has been projected toward producing functional copolymers and brushes . However, there are other strategies toward photopolymerization 3D printing, such as thiol-ene chemistry, which has been widely utilized for postfabrication functionalization but only sparingly used for additive manufacturing. ,− …”