Oxidation and subsequent catalytic carbonation of limonene, gained from orange peels, afford high purity limonene dicarbonate (LC) as a versatile building block for tailoring linear and cross-linked non-isocyanate polyurethanes (NIPU) from renewable resources. Spectroscopic investigations reveal so far unknown highly colored carbonation byproducts which are successfully removed to yield crystalline LC. Melt-phase polyaddition of a dimer fatty acid based diamine and its diamine-terminated LC-prepolymers with carbonated 1,4-butanediol diglycidyl ether (BDGC) produces 100% bio-based linear NIPU thermoplastics. Side-reactions occurring during polymerization account for decreasing molar mass with increasing LC content. Curing carbonated pentaerythritol glycidyl ether (PGC)/LC blends with 1,5-diaminopentane, gained from lysine, enables tailoring of 100% bio-based NIPU thermosets exhibiting unconventional property profiles. The incorporation of small amounts high purity LC substantially improves NIPU glass temperature, stiffness, and strength without sacrificing elongation at break. High purity LC prevents color formation of LC-based NIPU coatings.

Chemical fixation of the greenhouse gas carbon dioxide with diepoxides followed by melt-phase polyaddition of the resulting difunctional cyclic carbonates with 1,12diaminododecane (DDA) yields semicrystalline polyhydroxurethane (PHU) thermoplastics. Also, 100% biobased semicrystalline PHU thermoplastics are feasible. Opposite to conventional polyurethane syntheses, neither isocyanates nor phosgene are required as intermediates. Preferably, melt-phase polyaddition is performed in a twin-screw compounder in the absence of catalysts, which also catalyze side-reactions. Calorimetric measurements and small-angle X-ray scattering reveal the fundamental structure−property relationships governing PHU crystallization. The PHU melting temperatures vary between 40 and 115 °C, and PHU Young's moduli range from 220 to 1430 MPa. Moreover, non-isocyanate PHU thermoplastic elastomers (TPHE) are readily tailored via melt-phase polyaddition of diamine-terminated flexible PHU prepolymers serving as soft segments combined with semicrystalline PHU as hard segments. As verified by means of thermal analysis (DSC), dynamic mechanical analysis (DMA), X-ray diffraction (SAXS), and microscopy (AFM), the careful balance between soft and semicrystalline hard-segment incorporation accounts for nanophaseseparation, which in the past has failed as a result of phase intermixing resulting from strong hydrogen bonding between soft and hard segments. For the first time, tailored PHU thermoplastics are employed in extrusion-based additive manufacturing by means of fused deposition modeling (FDM) or fused filament fabrication (FFF). Clearly, the presence of hydroxyl groups and their hydrogen bonding improves filament fusion and adhesion essential for achieving mechanical properties similar to PHU melt extrusion without encountering warpage.

Liquid acrylic oligourethanes are components of photocurable thermoset resins for applications ranging from coatings to 3D printing technologies like stereolithography. Traditionally they are derived from isocyanates which are highly moisture sensitive and do not tolerate hydroxy groups. Herein we report on a versatile non-isocyanate route toward tailoring hydroxyurethane methacrylates (HUMA) and their oligomers for photo cross-linking and 3D printing. The key intermediate is (2-oxo-1,3-dioxolan-4-yl)­methyl methacrylate, also referred to as methacrylated glycerol carbonate, obtained by the chemical fixation of carbon dioxide with glycidyl methacrylate. Upon aminolysis with di- and polyfunctional aliphatic amines, the ring-opening reaction of the cyclic carbonate group yields HUMA. No handling of isocyanates is required. The HUMA molecular architectures govern photo cure as well as thermal and mechanical properties. An alternative strategy toward molecular design of polyfunctional acrylics exploits chemical modification of the pendant hydroxy groups, e.g., by esterification with methacrylic acid anhydride. The resulting higher acrylate functionality accounts for improving Young’s modulus from 3160 to 4200 MPa and increasing the glass transition temperature from 86 to 173 °C with respect to HUMA-based formulations.

Crystallization of long n-alkyl side chains within the confined environment of nonisocyanate polyhydroxyurethane (PHU) networks renders PHUs thermoresponsive, enabling thermomechanical programming of temperature-induced shape changes. Key intermediates of shape memory PHUs are highly branched, semicrystalline polyamidoamine curing agents tailored by amidation of a polyamine-terminated hyperbranched polyethylenimine with semicrystalline long chain behenic acid. Both cure temperature and content of n-alkyl side chains, varied independently, govern crystallization behavior, phase separation and mechanical properties of semicrystalline PHU networks obtained by curing pentaerythritol-based polyfunctional cyclic carbonates with hyperbranched, semicrystalline polyamidoamines. As compared to conventional PHUs, the incorporation of hydrophobic, crystalline n-alkyl side chains significantly lowers hydrophilicity. Typically, the n-alkyl side chains of behenic amides in PHU networks melt at temperatures varying between 40 and 75 °C. According to analyses by means of atomic force microscopy (AFM) and differential scanning calorimetry (DSC) crystallization of the behenic amide side chains accounts for nanophase separation producing nanocrystalline PHUs with programmable shapes. Hence, controlled PHU crystallization and PHU nanostructure formation afford thermomechanical programming of PHU triple-shape memory materials memorizing two different shapes in addition to the original shape within a single shape memory cycle. Opposite to conventional polyurethanes, triple-shape memory PHUs require neither the use of isocyanates nor phosgene.

Bisphenol A glycidyl methacrylate (BisGMA) is well established as photocurable resin in dental restoratives and 3D printing. At present there are raising concerns regarding the estrogen‐mimicking bisphenol A (BPA) contamination of health care and consumer products. It is an important challenge to substitute BPA‐based resins for bio‐based cycloaliphatic monomers while lowering resin viscosity without sacrificing high stiffness and glass temperature. Particularly high viscosity is critical for 3D printing by photopolymerization. Unlike BPA the cyclic monoterpene limonene, extracted from citrus fruit peels, is safe in human uses. Herein it is reported on limonene‐based dimethacrylate (LDMA) tailored for 3D printing application and derived from limonene oxide (LO) and methacrylic acid (MA). Residual MA is converted into glycerol dimethacrylate (GDMA) serving as an in situ reactive diluent. The influences of temperature, catalysts, MA/LO stoichiometry, and the addition of glycidyl methacrylate (GMA) and magnesium oxide on the LDMA‐based resin performance are elucidated. As compared to BisGMA (560 Pa s) LDMA‐based resins exhibit significantly lower viscosity (5–117 Pa s) governed by the MA/LDMA molar ratio and the GMA addition. At 30 wt% LDMA content photocured resin yields thermosets having high Young’s Modulus (3.4–3.7 GPa), tensile strength (88–98 MPa), and glass transition temperature (119–135 °C), surpassing the performance of the corresponding BisGMA‐based resins.