Dimer Fatty Acid Research Articles

Distinguishing Artifactual Fatty Acid Dimers from Fatty Acid Esters of Hydroxy Fatty Acids in Untargeted LC-MS Pipelines.

Untargeted metabolomics is a powerful profiling tool for the discovery of possible biomarkers of disease onset and progression. Analytical pipelines applying liquid chromatography (LC) and mass spectrometry (MS)-based methods are widely used to survey a broad range of metabolites within various metabolic pathways, including organic acids, amino acids, nucleosides, and lipids. Accurate and complete identification of putative metabolites is an ongoing challenge in untargeted metabolomics studies. Highly sensitive instrumentation can result in the detection of adduct and fragment ions that form reproducibly and contain identifiable ions that are difficult to distinguish from metabolic pathway intermediates, which may result in false-positive identification. At concentrations as low as 10μM, free fatty acids have been found to form homo- and heterodimers in untargeted metabolomics pipelines that resemble the lipid class fatty acid esters of hydroxy fatty acids (FAHFAs), resulting in misidentification. This chapter details a protocol for LC-MS-based untargeted metabolomics using hydrophilic interaction chromatography (HILIC) that specifically aids in distinguishing artifactual fatty acid dimers from endogenous FAHFAs.

Injectable and photocurable precursors with their improved adhesive elastomeric films by nature-inspired marine mussels chemistry

Photocurable materials, capable of being delivered as liquids and rapidly cured in situ within seconds using UV light, are garnering increased interest in advanced minimally invasive procedures. Examining living organisms to extract novel principles and technologies, and subsequently applying them into synthetic materials to enhance their performances holds a central position in biomimetics (bioinspiration). In this exploration, we delve into the multifaceted world of marine mussel adhesion, emphasizing the pivotal role of 3,4-dihydroxy-L-phenylalanine (L-DOPA) in adhesive proteins. Simultaneously, we navigated the promising realm of elastomers derived from fatty acid dimers. 90° peeling test and fluorescence microscope indicate that the adhesiveness of the catechol-containing samples (5 % and 10 %) to the hydrophilic surface versus control samples were ∼ 4 and 8 times higher, respectively, as compared to within the tested group. Overall, our results suggest that the incorporation of methacrylated L-DOPA in the synthesis of photocured elastomeric networks leads to lower water contact angle and improved adhesiveness, creating new avenues for potential biomedical applications.

Toughening poly(lactic acid) by CaCO3 treated with waste lower purity dimer fatty acid

With the growing emphasis on environmental conservation, the utilization of biomass resources has garnered increasing attention. Dimer acid, derived from vegetable oils, serves as a high-quality chemical raw material while the waste lower purity dimer acid (WLPDA) will result in environmental pollution and resource wastage. In this work, WLPDA was employed as a surface modifier for calcium carbonate (CaCO3) particles with the aim of toughening of poly(lactic acid) (PLA). The addition of WLPDA demonstrates excellent modifying effects on CaCO3, achieving an activation index of 100% and an increased contact angle from 14° to around 120°. Furthermore, the PLA/WLPDA modified CaCO3 (D-CaCO3) composites exhibit noticeably toughening effects, with a maximum increase of 87% in impact strength. The improvement can be attributed to the favorable plastic deformation of interparticle ligaments following particle-matrix debonding and the long aliphatic chains of WLPDA. This research highlights the viability of replacing stearic acid with WLPDA as the surface modifier for inorganic fillers, providing a promising alternative for the toughening modification of polymers. Additionally, it presents a novel approach for the comprehensive utilization of dimer acid biomass resources.

From Oxidized Fatty Acids to Dimeric Species: In Vivo Relevance, Generation and Methods of Analysis

The occurrence of free fatty acids (FFAs) and the generation of reactive oxygen species (ROS) such as hydroxyl radicals (HO●) or hypochlorous acid (HOCl) is characteristic of inflammatory diseases, for instance, rheumatoid arthritis. Unsaturated fatty acids react with ROS yielding a variety of important products such as peroxides and chlorohydrins as primary and chain-shortened compounds (e.g., aldehydes and carboxylic acids) as secondary products. These modified fatty acids are either released from phospholipids by phospholipases or oxidatively modified subsequent to their release. There is increasing evidence that oligomeric products are also generated upon these processes. Fatty acid esters of hydroxy fatty acids (FAHFAs) are considered as very important products, but chlorinated compounds may be converted into dimeric and (with smaller yields) oligomeric products, as well. Our review is structured as follows: first, the different types of FFA oligomers known so far and the mechanisms of their putative generation are explained. Industrially relevant products as well as compounds generated from the frying of vegetable oils are also discussed. Second, the different opinions on whether dimeric fatty acids are considered as “friends” or “foes” are discussed.

Kinetics of reaction between hydrogenated dimer fatty acid C36 and 4,4′-methylene bis(cyclohexylamine): determination of thermodynamic constants

Kinetics of reaction between hydrogenated dimer fatty acid C36 and 4,4′-methylene bis(cyclohexylamine): determination of thermodynamic constants

The utilization of glycerol and xylitol in bio-based vitrimer-like elastomer: Toward more environmentally friendly recyclable and thermally healable crosslinked rubber

Eco-friendly rubbers developed from renewable materials and using covalent adaptive networks (CANs) are a family of sustainable materials that has recently attracted enormous interest from both industry and academia. In this study, vitrimer-like elastomers based on epoxidized natural rubber (ENR) were synthesized by cross-linking with dimer fatty acid (DFA). The addition of a small amount of bio-based polyol, namely the sugar alcohol glycerol (GLY) or xylitol (XYL), into the elastomeric vitrimer significantly enhanced its physical and viscoelastic properties. The glycerol-containing vitrimer tended to have reduced maximum torque, modulus, and crosslink density, while the opposite trend was found when xylitol was loaded in ENR50 vitrimer. Therefore, the mechanical and thermal properties of ENR50 vitrimer, as well as H-bond formation, can be manipulated by incorporating different types and concentrations of bio-based polyols. Importantly, a β-hydroxy ester formed in ENR50 can undergo an exchange reaction between the ester and hydroxyl group, a so-called dynamic exchange transesterification reaction, enabling thermo-healing and recycling. The formation of a denser network in polyol-treated ENR50 vitrimer may suppress the mobility of chain segments, affecting speeds of exchange reaction and stress relaxation. The ENR50 vitrimer with sugar alcohols shows several remarkable features in its mechanical performance and dynamic properties and points to an alternative for achieving green production, circular economy, and environmentally friendly processes.

Structural Studies of Monounsaturated and ω-3 Polyunsaturated Free Fatty Acids in Solution with the Combined Use οf NMR and DFT Calculations-Comparison with the Liquid State.

Molecular structures, in chloroform and DMSO solution, of the free fatty acids (FFAs) caproleic acid, oleic acid, α-linolenic acid, eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA) are reported with the combined use of NMR and DFT calculations. Variable temperature and concentration chemical shifts of the COOH protons, transient 1D NOE experiments and DFT calculations demonstrate the major contribution of low molecular weight aggregates of dimerized fatty acids through intermolecular hydrogen bond interactions of the carboxylic groups, with parallel and antiparallel interdigitated structures even at the low concentration of 20 mM in CDCl3. For the dimeric DHA, a structural model of an intermolecular hydrogen bond through carboxylic groups and an intermolecular hydrogen bond between the carboxylic group of one molecule and the ω-3 double bond of a second molecule is shown to play a role. In DMSO-d6 solution, NMR and DFT studies show that the carboxylic groups form strong intermolecular hydrogen bond interactions with a single discrete solvation molecule of DMSO. These solvation species form parallel and antiparallel interdigitated structures of low molecular weight, as in chloroform solution. This structural motif, therefore, is an intrinsic property of the FFAs, which is not strongly affected by the length and degree of unsaturation of the chain and the hydrogen bond ability of the solvent.

Chemistry of Dimer Acid Production from Fatty Acids and the Structure-Property Relationships of Polyamides Made from These Dimer Acids.

While there is abundant literature on using a wide range of biomaterials to make polymers for various adhesive applications, most researchers have generally overlooked developing new adhesives from commercially available bio-based dimerized fatty acids. Some of the literature on the chemistry taking place during the clay-catalyzed dimerization of unsaturated fatty acids is generally misleading in that the mechanisms are not consistent with the structures of these dimers and a by-product isostearic acid. A selective acid-catalyzed interlayer model is much more logical than the widely accepted model of clay-catalyzed Diels-Alder reactions. The resulting dimers have a variety of linkages limiting large crystal formation either as oligomeric amides or polyamides. These highly aliphatic fatty acid dimers are used to make a wide range of hot melt polyamide adhesives. The specific structures and amounts of the diacids and diamines and their relative ratios have a big effect on the bio-based polyamide mechanical properties, but analysis of the structure-property relationships has seldom been attempted, since the data are mainly in the patent literature. The diacids derived from plant oils are valuable for making polyamides because of their very high bio-based content and highly tunable properties.

Effects of fatty acid modified epoxy resin on long‐chain epoxy and its physical properties

AbstractThe tendency of epoxy resins to form three‐dimensional structures can make them brittle, which restricts their use in various applications even if they have great mechanical properties. Due to the expansion of epoxy resin application to electric automotives and aerospace as carbon fiber resistance plastics (CRFPs), it is desirable to synthesize epoxy resins that is more impact resistant. Herein, the synthesis of flexible epoxy resin FMER‐F and FMER‐J is reported. These epoxy resins were based on bisphenol F and J diglycidy ether. The dimeric fatty acid modified epoxy resins (FMERs) were synthesized by reacting acid anhydride modified epoxy resins (AMERs) with dimeric fatty acids. To obtain thermosetting epoxy polymers, the epoxy resin was mixed with a curing agent and an accelerator and, subsequently, it was cured at a high temperature. The mechanical properties of various epoxy polymers were analyzed to evaluate the change in the performance of the materials. The flexural strength of the composition with 10 parts per hundred resin (phr) of FMER‐F increased by 21%. The impact strength of the composition with 30 phr of FMER‐J increased by 27%. FMERs were found to be used as toughening agents in epoxy resins and composites because of their ability to enhance mechanical properties.

Topological network design toward high‐performance vegetable oil–based elastomers

AbstractAs a kind of bio‐derived feedstock, vegetable oil (VO) shows great potential to replace petroleum‐based monomers to develop sustainable polymer materials because of its easy availability, low cost, bio‐renewable, and environmentally friendly nature. However, due to the high cross‐linking density and amorphous nature, directly cured VOs generally tend to be brittle and weak. To date, it is still difficult to adopt VOs and their derivatives as structural materials to prepare high‐performance elastomers. To address this important issue, a multi‐scale topology design strategy was proposed in this work. First, topology regulation and functionalization of VO‐based networks were realized by managing functional groups proportion during the bulk polymerization of epoxidized soybean oil with dimer fatty acids. Furthermore, a second polymer (SN) network was introduced into the VO‐based network as a protective layer via interfacial cross‐links. The generated VO‐based elastomers (VOEs) exhibit unprecedented comprehensive properties (VO content ≥70 wt.%, Tg as low as −24.4°C, toughness up to 6.8 MJ/m3). Besides, the VOEs also exhibit excellent reprocessability and self‐healing capability. Overall, this work developed a novel kind of VOEs with significant comprehensive advantages and provided important inspiration for the preparation of high‐performance elastomers through multi‐scale topology regulation.

Tailor-Made Bio-Based Non-Isocyanate Polyurethanes (NIPUs)

Non-isocyanate polyurethanes (NIPUs) based on biobased polyamines and polycarbonates are a sustainable alternative to conventional polyurethanes (PU). This article discloses a novel method to control the crosslinking density of fully biobased isocyanate-free polyurethanes, synthesized from triglycerides carbonated previously in scCO2 and different diamines, such as ethylenediamine (EDA), hexamethylenediamine (HMDA) and PriamineTM-1075 (derived from a dimerized fatty acid). As capping substances, water or bioalcohols are used in such a way that the crosslinking density can be adjusted to suit the requirements of the intended application. An optimization of the NIPU synthesis procedure is firstly carried out, establishing the polymerization kinetics and proposing optimal conditions set for the synthesis of the NIPUs. Then, the influence of the partial blocking of the active polymerization sites of the carbonated soybean oil (CSBO), using monofunctional amines, on the physical properties of the NIPUS is explored. Finally, the synthesis of fully biobased NIPUs with a targeted crosslinking density is achieved using hybrid NIPUs, employing partially carbonated oil and H2O or ethanol as blockers to achieve the desired physical properties in a very precise manner.

NMR and DFT studies of monounsaturated and ω-3 polyunsaturated free fatty acids in the liquid state reveal a novel atomistic structural model of DHA

Structures of low-energy conformers of caproleic acid (CA; 10:1 cis-9), oleic acid (OA; 18:1 cis-9), α-linolenic acid (ALA; 18:3 cis-9,12,15 ω-3), eicosapentaenoic acid (EPA; 20:5 cis-5,8,11,14,17 ω-3), and docosahexaenoic acid (DHA; 22:6 cis-4,7,10,13,16,19 ω-3) in the liquid state, based on detailed 1D NOE and density functional theory calculations of 1H NMR chemical shifts are presented. Transient 1D NOE experiments with variable mixing time showed significant through-space proximity of the CH2–COOH protons and the terminal CH3– groups. Variable temperature 1H NMR experiments revealed strong intermolecular centro-symmetric cyclic hydrogen bond interactions of the carboxylic groups of the monounsaturated oleic and caproleic acids (δ(COOH) ∼ 12.0–12.4 ppm), ALA and EPA (δ(COOH) ∼ 11.0 ppm). On the contrary, the carboxylic proton of DHA is strongly shielded with δ(COOH) ∼ 8.5 ppm. DFT calculations were interpreted in terms of aggregates of dimerized fatty acids with parallel and antiparallel interdigitated structures. The antiparallel arrangement was found to be in excellent agreement with experimental 1D NOE NMR data. For the dimeric DHA, a flip-flop process between a classical intermolecular centro-symmetric hydrogen bond through carboxylic groups and a novel intramolecular hydrogen bond between the carboxylic group and the terminal ω-3 double bond is demonstrated.

Preparation and Properties of Vegetable-Oil-Based Thioether Polyol and Ethyl Cellulose Supramolecular Composite Films

Ethyl cellulose (EC), an important biomass-based material, has excellent film-forming properties. Nevertheless, the high interchain hydrogen bond interaction leads to a high glass transition temperature of EC, which makes it too brittle to be used widely. The hydroxyl group on EC can form a supramolecular system in the form of a non-covalent bond with an effective plasticizer. In this study, an important vegetable-oil-based derivative named dimer fatty acid was used to prepare a novel special plasticizer for EC. Dimer-fatty-acid-based thioether polyol (DATP) was synthesized and used to modify ethyl cellulose films. The supramolecular composite films of DATP and ethyl cellulose were designed using the newly-formed van der Waals force. The thermal stability, morphology, hydrophilicity, and mechanical properties of the composite films were all tested. Pure EC is fragile, and the addition of DATP makes the ethyl cellulose films more flexible. The elongation at the break of EC supramolecular films increased and the tensile strength decreased with the increasing DATP content. The elongation at the break of EC/DATP (60/40) and EC/DATP (50/50) was up to 40.3% and 43.4%, respectively. Noticeably, the thermal initial degradation temperature of the film with 10% DATP is higher than that of pure EC, which may be attributed to the formation of a better supramolecular system in this composite film. The application of bio-based material (EC) is environmentally friendly, and the novel DATP can be used as a special and effective plasticizer to prepare flexible EC films, making it more widely used in energy, chemical industry, materials, agriculture, medicine, and other fields.

Biomass upcycling of waste rPET to higher-value new-easy-recyclable microcellular thermoplastic (co)polyamide foams and hot-melt adhesives

Poly(ethylene terephthalate) (PET) is one of the extremely used fossil-based products in the chemical industry, accounting for about 13% of the world's production. Today, most PET waste accumulates in landscapes or the environment, causing severe pollution. From the perspective of sustainability, scientists have tried to recycle waste PET through chemical and mechanical methods. Mechanical recycling offers some limitations because of the properties of the final product decrease from the second cycle. Rather, chemical recycling has attracted much attention because it can selectively convert plastic waste into high-value-added products including fuel, monomer, and refinery feedstock. Therefore, in this study, the chemical depolymerization of PET was investigated experimentally. After successfully deconstructing waste PET into polymerizable N1, N4-bis(6-aminohexyl)terephthalamide (BAHT) monomer, the obtained BAHT was combined with a bioderived dimer fatty acid (DA; renewable content 100%) building block for the synthesis of bio-based thermoplastic (co)polyamides (TPCPAs) via solvent-free melt polycondensation. The obtained TPCPAs underwent a scCO2 foaming process to give the higher value-added microcellular foams. Interestingly, scCO2 foaming has zero formamides, which meets the safety requirements and is suited to commercial uses. Moreover, TPCPA foams showed an excellent shape recovery property and recyclability due to the entangled DA structure. Adhesive tests also show that TPCPAs exhibit a higher Tpeel strength (185.2 N/cm–420.5 N/cm) than commercial PA glues. This strategy to recycle PET into value-added biomass TPCPAs has a promising application prospect.

Dimer fatty acid and fatty amide effects on the properties of synthetic-based drilling fluids

This paper mainly deals with the analysis of chemical modification on a dimer of fat acid to evaluate the effect on synthetic drilling fluids. The performance of drilling fluids in the deepwater fields is negatively impacted by the elevation of rheological parameters. A required property of the drilling fluid is a minimal sensitivity of the rheological properties with respect to temperature, leading to a flat-rheology system. A proposed fatty amide was synthesized via condensation reaction between saturated dimer fatty acid and diethanolamine. In this reaction, it was used N,N′-dicyclohexylcarbodiimide as coupling agent and 4-dimethylaminopyridine as catalyst. The synthesized material was characterized by FTIR, 13C NMR, solubility tests and surface tension. Next, the precursor dimer fatty acid and the synthesized fatty amide were initially applied on a visual stability test in invert emulsion systems before application in synthetic drilling fluids. Spectroscopic analyses confirmed that fatty amide was successfully synthesized. Surface tension measurements showed that both dimer fatty acid and the fatty amide amide have not surfactant properties. However, when both products were applied in synthetic drilling fluids, electrical stability and HPHT filtration tests proved the ability to stabilize emulsion systems, probably, as network agents. In addition, the drilling fluids containing dimer fatty acid and fatty amide presented minimal viscosity sensitivity in the temperature range of 4–49 °C, at ambient pressure and 344 bar, leading to flat-rheology synthetic drilling fluids.

Preparation and thermal stability of bio-based Na/Zn composite liquid stabilizers for poly(vinyl chloride)

In this work, the adduct of maleic anhydride and methyl eleostearate (MAME) and dimer fatty acid (DFA) were converted to the sodium and zinc salts (L-Zn-MAME, L-Na-MAME, L-Zn-DFA, and L-Na-DFA), respectively, which were subsequently turned into Na/Zn composite liquid stabilizers(LTS-Na/Zn-MAME and LTS-Na/Zn-DFA) by formula combination. Na salts, Zn salts and mixed Na/Zn salts from these fatty acid salts were used as thermal stabilizers for poly(vinyl chloride) (PVC). The chemical structures of MAME, DFA, and their liquid zinc and sodium salts were verified using Fourier transform infrared (FTIR) spectra. Thermal stability and mechanical properties of the sodium and zinc salts, and their Na/Zn composite liquid stabilizers derived from MAME and DFA for PVC were investigated using discoloration and dynamic mechanical analyses, TGA-FTIR-MS, thermal decomposition kinetics, and Congo red and tensile tests. Thermal stability of pure PVC is poor, but membrane thermal stability can be improved by integrating thermal stabilizers. Results show that L-Na-MAME has an outstanding synergistic effect with the commercial general calcium/zinc stearate composite heat stabilizer(CaSt2/ZnSt2). CaSt2/ZnSt2/LTS-Na-MAME, LTS-Na/Zn-MAME and CaSt2/LTS-Zn-DFA/LTS-Na-DFA also have a better heat-stabilizing impact on PVC than CaSt2/ZnSt2, especially LTS-Na/Zn-MAME can more effectively enhance the primary coloring of PVC. In comparison to blank PVC and PVC/CaSt2/ZnSt2, both PVC/LTS-Na/Zn-MAME and PVC/LTS-Na/Zn-DFA display a larger elongation at break and acceptable tensile strength. The new stabilizers can largely enhance the heat stability of PVC resins, endowing PVC products with good plasticization performance, and can fully or partially replace the general calcium zinc stearate composite heat stabilizer and other heat stabilization products.

A new type of unsaturated polyester resin with epoxy functionalized nano‐silica and dimer fatty acid: Preparation and property

AbstractThe surface of reactive nano‐silica coated with a silage coupling agent containing the epoxy group (denoted as E‐SiO2) and dimer fatty acids (DFA) were allowed to participate in the in‐situ polycondensation reaction of unsaturated polyester resin (UPR), thus obtaining E‐SiO2/DFA/UPR hybrid material. Fourier transform infrared spectrometer, scanning electron microscope, and X‐ray energy dispersive spectrometer were used to analyze the structure of the material, morphology of tensile section, and the element composition of the section. It was found that E‐SiO2 grafted onto the DFA/UPR backbone by chemical bonds, and the material exhibited ductile fracture with Si element on the fracture surface. Thermogravimetric analysis, differential scanning calorimetry, stress–strain test, tensile test, bending test, hardness test, and water resistance test, the influence of the content of E‐SiO2 on the thermal stability, mechanical properties, and water resistance of the materials was studied. The results show that E‐SiO2 has a good reinforcing and toughening effect for the in‐situ polymerized E‐SiO2/DFA/UPR composite due to the chemical reaction between the epoxy group of E‐SiO2 and the hydroxyl group (carboxyl group) of DFA/UPR. A heterogeneous network structure was formed in the cured E‐SiO2/DFA/UPR composites. The mechanical properties and thermal properties of E‐SiO2 nanocomposites were improved. When 0.8 wt% E‐SiO2 was added, the tensile strength, Young's modulus, flexural strength, flexural stress, elongation at break, and Shore A hardness increased by 37.03%, 69.18%, 86.81%, 86.80%, 14.0%, and 14.71%, respectively, compared to DFA/UPR. At the same time, the addition of E‐SiO2 also improved the water resistance of hybrid materials.

Influence of the chain extender of a segmented polyurethane on the properties of polyurethane-modified asphalt blends

This paper reviews the influence of the hard segment (HS) chemical structure on the properties of thermoplastic polyurethanes based on dimer fatty acid soft segments, and on their resulting blends with bitumen. Three types of hard segments were used which consist in 4,4′-methylene bis(phenyl isocyanate) (MDI) reacted either with 1,4-butanediol (BDO), 1,4:3,6-dianhydro D-sorbitol (isosorbide) or 2-ethyl-1,3-hexanediol (EHDO). The characterization of thermoplastic polyurethanes (TPUs) containing 13 wt% HS was conducted by differential scanning calorimetry, dynamic mechanical analysis, Hansen solubility parameters measurements and morphology analysis. The use of Hansen solubility parameters combined with thermal and swelling analyses provides information about the quality of phase separation occurring in the neat TPUs. Phase separation depends on the hard segments used and on their ability to self-organize within crystalline structures. Morphology analysis and swelling measurements of the TPU blended with bitumen by fluorescence microscopy show that the swelling of the polymer is highly dependent on the quality of phase separation between soft and hard segments in the pure polymer as well as on the compatibility of these segments with bitumen. Highly phase separated TPUs offer elasticity improvement to the bituminous blend.

In Vivo Biocompatibility of an Innovative Elastomer for Heart Assist Devices.

Cardiac surgical approaches require the development of new materials regardless of the polyurethanes used for pulsatile blood pumps; therefore, an innovative biomaterial, a copolymer of poly(ethylene terephthalate) and dimer fatty acid (dilinoleic acid) modified with D-glucitol, hereafter referred to as PET/DLA, has been developed, showing non-hemolytic and atrombogenic properties and resistance to biodegradation. The aim of this work was to evaluate in vivo inflammatory responses to intramuscular implantation of PET/DLA biomaterials of different compositions (hard to soft segments). Two copolymers containing 70 and 65 wt.% of hard segments, as in poly(ethylene terephthalate) and dilinoleic acid in soft segments modified with D-glucitol, were used for implantation tests to monitor tissue response. Medical grade polyurethanes Bionate II 90A and Bionate II 55 were used as reference materials. After euthanasia of animals (New Zealand White rabbits, n = 49), internal organs and tissues that contacted the material were collected for histopathological examination. The following parameters were determined: peripheral blood count, blood smear with May Grunwald–Giemsa staining, and serum C-reactive protein (CRPP). The healing process observed at the implantation site of the new materials after 12 weeks indicated normal progressive collagenization of the scar, with an indication of the inflammatory–resorptive process. The analysis of the chemical structure of explants 12 weeks after implantation showed good stability of the tested copolymers in contact with living tissues. Overall, the obtained results indicate great potential for PET/DLA in medical applications; however, final verification of its applicability as a structural material in prostheses is needed.

Biobased Linear and Crystallizable Polyhydroxy(amide-urethane)s from Diglycerol Bis(cyclic carbonate) and the Polyamides of Dimer Fatty Acids

Diglycerol and dimer acid (DA) are used as precursors for the solvent- and catalyst-free synthesis of fully biobased non-isocyanate polyurethanes to replace toxic isocyanates and petroleum-based reactants. Linear polyhydroxy(amide-urethane)s (L-NIPHAUs) were synthesized via the melt aminolysis copolymerization between diglycerol dicarbonate (DGDC) and diamino-telechelicoligoamides (DAPAhs) from DA and hexamethylenediamine (HDA). By changing the DA/HDA molar ratios, the structures of DAPAhs and L-NIPHAUs were regulated in a simple and straightforward manner. Atomic force microscopy (AFM) and dynamic mechanical analysis (DMA) of the L-NIPHAUs reveal that the huge polarity difference between the hard segments (HSs) and soft segments (SSs) leads to nanophase separation. The N-amidohexylene-diglycerolbis(hydroxyurethane)-N′-amidohexylene and N-amido-hexylene-N′-amido segments form double HSs, while the bulky nonpolar DA residues serve as SSs. L-NIPHAUs also exhibit semicrystalline structures with good thermal stability evidenced by wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA). They possess Tm ranging from 94 to 110 °C and tunable mechanical properties with a tensile strength of 7.3–12.1 MPa and strain at break of 311–858%. Introducing DA segments increases the hydrophobicity of L-NIPHAUs and the water contact angle and decreases the surface energy. L-NIPHAUs also show excellent solvent resistance in organic solvents, thanks to their intramolecular hydroxyurethane hydrogen bonding, three-dimensional inherent intermolecular hydrogen bonding networks, and the modification of bulky nonpolar DA SSs.