The polycondensation of long-chain α,ω-diesters with long-chain α,ω-diols, prepared by means of catalytic conversion of plant oils, affords linear aliphatic polyesters. They contain both long crystallizable polyethylene-like hydrocarbon segments and ester moieties in the backbone. In a convenient catalytic onestep process a high-purity polycondensation grade dimethyl-1,19-nonadecanedioate monomer is obtained directly from the technical grade methyl ester of high oleic sunflower oil. Likewise, dimethyl-1,23-tricosanedioate is derived from methyl erucate. The successful scale-up renders both intermediates available on a 100 g scale. Injection molded parts of polyester-19.19 and-23.23 with a number average molecular mass of M n = 3 × 10 4 g mol −1 possess an elongation at break of >600% and a Young's modulus of 400 MPa. Electrospinning produces non-woven meshes. The polyesters prepared even enable film extrusion and represent new blend components for a variety of thermoplastics including polyethylene. Scheme 1 Main products of the isomerizing carbonylation and selfmetathesis, respectively, of unsaturated fatty acid esters. † Electronic supplementary information (ESI) available: Stress-strain curves, DMA traces, and rheology master curve of polyester-23.23, image of test bar for tensile testing before and after strain experiment, additional rheological data.
The highly reactive [4,4′-bi(1,3-dioxolane)]-2,2′-dione (BDC), also being referred to as erythritol dicarbonate and butadiene dicarbonate, enables the facile isocyanate-free tailoring and melt-processing of bio-based polyhydroxyurethane (PHU) materials. Both the direct carbonation of erythritol and the chemical fixation of CO2 with 2,2′-bioxirane, obtained by epoxidation of bioethanol-derived butadiene, afford high purity BDC in high yields. According to the FTIR spectroscopic model study BDC reacts with primary alkylamines at room temperature even in the absence of catalysts. High BDC reactivity is essential for producing high molar mass linear PHU thermoplastics via melt-phase polyaddtition with aliphatic diamines. Opposite to conventional isoycanate-mediated polyurethane syntheses erythritol units are incorporated into the polyurethane backbone without requiring the use of protective groups. As a function of the diamine structures and copolymer compositions the PHU properties vary from hard to soft and elastomeric. Typically isophorone diamine (IPDA) and trimethylhexamethylenediamine (TMHMDA) serve as building blocks for hard segments whereas highly flexible diamines such dimer fatty acid-derived diamidoamines render PHU soft and elastomeric. This study elucidates how copolymer composition and reaction parameters such as temperature, catalyst, and stabilizer addition influences PHU molar masses as well as mechanical and thermal properties. For the first time, owing to extraodinary BDC reactivity, melt-phase BDC polyaddition with diamines is competitive with conventional reactive processing of polyurethane thermoplastics using isocyanates. Moreover this versatile isocyanate-free synthetic route offers a great variety of options for fabricating unconventional bio-based PHUs and carbohydrate urethanes unparalleled by conventional polyurethanes.
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.
Glycerol serves as the exclusive bio feedstock for the preparation of high purity sorbitol tricarbonate (STC) as new intermediate for poly(carbohydrate−urethane) thermosets and 100% bio-based non-isocyanate polyhydroxyurethane (NIPU) coatings. In this process, glycerol-based acrolein is dimerized, carbonated, and oxidized, thus producing the highly reactive diepoxy functional ethylene carbonate (DOC), which by facile chemical CO 2 fixation yields high purity STC. Opposite to most state-of-the-art multifunctional five-membered cyclic carbonates and regardless of the feedstock used for its manufacture, STC enables amine curing at ambient temperature even in the absence of catalysts. According to FT-IR and NMR spectroscopic analyses of the amine/carbonate reaction kinetics, the internal cyclic carbonate group is 3 times more reactive with respect to the two terminal carbonate groups. This is attributed to the electronwithdrawing effect of terminal cyclic carbonates. Curing STC with a blend of bio-based flexible and rigid diamines such as dimer fatty acid-based diamine (Priamine 1074) and isophorone diamine affords poly(carbohydrate−urethane) thermosets and NIPU coatings exhibiting substantially improved thermal and mechanical properties.
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