Harnessing the Chemical Diversity of the Natural Product Magnolol for the Synthesis of Renewable, Degradable Neolignan Thermosets with Tunable Thermomechanical Characteristics and Antioxidant Activity

Abstract

Magnolol, a neolignan natural product with antioxidant properties, contains inherent, orthogonal, phenolic, and alkenyl reactive groups that were used in both direct thermoset synthesis, as well as the stepwise synthesis of a small library of monomers, followed by transformation into thermoset materials. Each monomer from the small library was prepared via a single step functionalization reaction of the phenolic groups of magnolol. Thermoset materials were realized through solvent-free, thiol-ene reactions, and the resulting cross-linked materials were each comprised of thioether and ester linkages, with one retaining the hydrophilic phenols from magnolol, another having the phenols protected as an acetonide, and two others incorporating the phenols into additional cross-linking sites via hydrolytically labile carbonates or stable ether linkages. With this diversity of chemical compositions and structures, the thermosets displayed a range of thermomechanical properties including glass transition temperatures, T, 29-52 °C, onset of thermal degradation, T, from about 290-360 °C, and ultimate strength up to 50 MPa. These tunable materials were studied in their degradation and biological properties with the aim of exploiting the antioxidant properties of the natural product. Hydrolytic degradation occurred under basic conditions (pH = 11) in all thermosets, but with kinetics that were dependent upon their chemical structures and mechanical properties: 20% mass loss was observed at 5, 7, 27, and 40 weeks for the thermosets produced from magnolol directly, acetonide-protected magnolol, bis(allyl carbonate)-functionalized magnolol, and bis(allyl ether)-functionalized magnolol, respectively. Isolated degradation products and model compounds displayed antioxidant properties similar to magnolol, as determined by both UV-vis and in vitro reactive oxygen species (ROS) assays. As these magnolol-based thermosets were found to also allow for extended cell culture, these materials may serve as promising degradable biomaterials.

Terpene- and terpenoid-based polymeric resins for stereolithography 3D printing

“…Solid polymers were cured for 12 h at 30°C, 80°C or 120°C prior to testing. 34 Samples were photocured for 30 min under ambient conditions and then placed in an isothermal oven at standard atmospheric pressure and moisture. After the cure cycle, samples were removed and allowed to cool to room temperature over 12 h prior to additional testing.…”

“…The displayed strains at break are relatively large for highly crosslinked thermosetting materials, particularly for the limonene system after post-curing at high temperatures. 34,36,37 Strain at break was found to correlate with the post-polymerisation post-cure temperature (ESI Fig. S17 †), with limonene displaying approximately 180% strain before break after post-curing at 120°C (after irradiation), but after a 30°C post-curing step of the same duration, fracture strain was only 77.3% (55.9% strain for the prepolymer) ( Fig.…”

Making Benzoxazine Greener and Stronger: Renewable Resource, Microwave Irradiation, Green Solvent, and Excellent Thermal Properties

“…As a bioactive compound, magnolol has been used as neurologically active agent in traditional Chinese and Japanese medicine for centuries. , Besides that, magnolol is a highly functional compound containing both phenolic and allyl groups, which allows for high-performance polymer synthesis. However, it was seldom used for polymer synthesis and never taken as the phenolic resource to prepare benzoxazine. Furfurylamine is one of the few readily available bio-based amines that can be obtained from agriculture byproducts.…”

4D Aliphatic photopolymer polycarbonates as direct ink writing of biodegradable, conductive graphite‐composite materials

“…[1,4,[8][9][10][11][12][13][14][15] Recently, degradable resins have begun gathering interest, with one important class of biodegradable polymers being polycarbonates, where aliphatic systems have been proposed for better tolerated, more biocompatible biomaterials relative to more traditional homopolyesters or acrylates, which may have health risks despite their widespread usage. [16][17][18][19][20][21][22] A variety of polycarbonates with tunable compositions, physical properties, and processing methods have been explored for pacemaker wire coatings and orthopedic joint replacements, among a host of other applications. [23][24][25][26][27] In aliphatic systems, poly(trimethyl carbonate) (PolyTMC) has been popular and many of its derivatives are being explored in attempts to broaden material functionality.…”