Green manufacturing and reducing our cultural dependency on petrochemicals have been topics of growing interest in the past decade, particularly for three-dimensional (3D) printable photopolymers where often toxic solvents and reagents have been required. Here, a simple solvent-free, free-radical polymerization is utilized to homo- and copolymerize limonene and β-myrcene monomers to produce oligomeric photopolymers (M n < 11 kDa) displaying Newtonian, low viscosities (∼10 Pa × s) suitable for thiol–ene photo-cross-linking, yielding photoset materials in a digital light processing (DLP)-type 3D printer. The resulting photosets display tunable thermomechanical properties (poly­(limonene) displays elastic moduli exceeding 1 GPa) compared with previous works focusing on monomeric terpenes as well as four-dimensional (4D) shape memory behavior. The utility of such photopolymers for biomedical applications is briefly considered on the premise of the hydrophilic nature (measured by contact angle) as well as their cytocompatibility upon seeding films with macrophages. These terpene-derived, green 4D photopolymers are shown to have promising physical behaviors suitable for an array of manufacturing and 3D printing applications.

Ring-opening copolymerization (ROCOP) of polyesters may be used to achieve a wide variety of functional polymers using commercial monomer libraries, but primarily make use of metallic catalysts such as tin, magnesium, or cobalt complexes. However, the limitations of such catalysts include toxicity risks and environmental concerns for both the desired application, such as biomaterials, and the end-of-life consideration. There is a need for cleaner, friendlier, and less expensive routes to polymeric materials and devices. Therefore, organobasecatalyzed ROCOP is an intriguing opportunity to improve both the safety and the structural control of the resultant polyesters. Here, organobases with and without supramolecular thiourea co-catalysts are demonstrated for ROCOP of functional polyesters made of cis-4cyclohexene-1,2-dicarboxylic anhydride and allyl glycidol ether, with ROCOP performed in bulk, open-air conditions. The catalysts resulted in molecular weights of >25 kDa while maintaining controlled polymerization behaviors and a dispersity of <1.3. The role of the thiourea co-catalysts is further explored, with a proposed mechanism for initiation of the ROCOP system. The resultant polyesters are utilized in vat polymerization four-dimensional (4D) printing using thiol-ene cross-linking to manufacture complex prototypes that display shape memory. The role of molecular weight on physical properties, including mechanical and thermal behaviors, is explored along with hydrolytic degradation rates, shape memory responsiveness, and cytocompatibility. Ultimately, the use of organobase catalysis for ROCOP of polyester photopolymer is shown to be an efficient, tunable method of controlling resultant physical properties for improving the environmental friendliness, as well as biomaterial potential.

Stereoselective aliphatic polyesters were synthesized through the ring opening copolymerization of cyclic anhydrides and epoxides using a tin catalyst to yield Mn ~ 10-13 kDa macromolecules (Đ < 1.6). Isomerization...

Shape memory poly­(β-hydroxythioether) foams were produced using organobase catalyzed reactions between epoxide and thiol monomers, allowing for the rapid formation of porous media within approximately 5 min, confirmed using both rheology and physical foam blowing. The porous materials possess ultralow densities (0.022 g × cm–3) and gel fractions of approximately 93%. Thermomechanical characterizations of the materials revealed glass transition temperatures tunable from approximately 50 to 100 °C, elastic moduli of approximately 2 kPa, and complete strain recovery upon heating of the sample above its glass transition temperature. The foams were characterized for their ability to take up oil from an aqueous multilayered ideal environment, revealing more than 2000% mass of oil (relative to the foam mass) could be collected. Importantly, while post-fabrication functionalization was possible with isocyanate chemistry followed by addition of hexadecanethiol or 3,3-bis­(hexadecylthio)­propan-1-ol, the oil collection efficiency of the system was not significantly enhanced, indicating that these materials, as porous media, possess unique attributes that make them appealing for environmental remediation without the need for costly modifications or manipulations.

There is an ever-growing push toward sustainability and green manufacturing in a wide array of industries, especially 3D printing, which is now recognized as a viable manufacturing method. The number of studies focusing on leveraging additive manufacturing of natural products continues to grow, with key areas of interest including exciting chemistries or modifications of natural products toward 3D printable materials, advancements in prototypes or products by changing feedstocks to green or bioderived alternatives, and the introduction of added functionalities or properties. This includes concepts such as processing natural or bioderived polymers into filament for extrusion-based 3D printing, the design of photopolymer resins and inks for vat photopolymerizations, jet printing, or direct ink writing processes, and the use of powders for selective laser sintering. The strategies employed to achieve materials suitable for 3D printing, the physical properties of the materials, and the resultant applications including strengths and limitations, will be explored in this review. Overall, the advancements in the field are leading to future opportunities in biomaterials and medical devices, electronics and batteries, and environmental remediation and water purification.