Co- and Terpolyesters Based on Isosorbide and Succinic Acid for Coating Applications: Synthesis and Characterization

Recyclable and (Bio)degradable Polyesters in a Circular Plastics Economy

Polyesters carrying polar main-chain ester linkages exhibit distinct material properties for diverse applications and thus play an important role in today's plastics economy. It is anticipated that they will play an even greater role in tomorrow's circular plastics economy that focuses on sustainability, thanks to the abundant availability of their biosourced building blocks and the presence of the main-chain ester bonds that can be chemically or biologically cleaved on demand by multiple methods and thus bring about more desired end-of-life plastic waste management options. Because of this potential and promise, there have been intense research activities directed at addressing recycling, upcycling or biodegradation of existing legacy polyesters, designing their biorenewable alternatives, and redesigning future polyesters with intrinsic chemical recyclability and tailored performance that can rival today's commodity plastics that are either petroleum based and/or hard to recycle. This review captures these exciting recent developments and outlines future challenges and opportunities. Case studies on the legacy polyesters, poly(lactic acid), poly(3-hydroxyalkanoate)s, poly(ethylene terephthalate), poly(butylene succinate), and poly(butylene-adipate terephthalate), are presented, and emerging chemically recyclable polyesters are comprehensively reviewed.

Overcoming the low reactivity of biobased, secondary diols in polyester synthesis

Shifting away from fossil- to biobased feedstocks is an important step towards a more sustainable materials sector. Isosorbide is a rigid, glucose-derived secondary diol, which has been shown to impart favourable material properties, but its low reactivity has hampered its use in polyester synthesis. Here we report a simple, yet innovative, synthesis strategy to overcome the inherently low reactivity of secondary diols in polyester synthesis. It enables the synthesis of fully biobased polyesters from secondary diols, such as poly(isosorbide succinate), with very high molecular weights (M_n up to 42.8 kg/mol). The addition of an aryl alcohol to diol and diacid monomers was found to lead to the in-situ formation of reactive aryl esters during esterification, which facilitated chain growth during polycondensation to obtain high molecular weight polyesters. This synthesis method is broadly applicable for aliphatic polyesters based on isosorbide and isomannide and could be an important step towards the more general commercial adaption of fully biobased, rigid polyesters.

Bio-Based 2K PU Coating for Durable Textile Applications

Polyurethane (PU) coatings are often applied on high added value technical textiles. To date, most PU textile coatings are solvent based or water based. Recent advances are made in applying high solid and two-component (2K) PU on textiles. Currently, polymers made from renewable raw materials are experiencing a renaissance, owing to the trend to reduce CO2 emissions and switch to CO2-neutral renewable products. There is also the tendency towards the “bio, eco, natural” consciousness-awakening of the end consumer and the market-driven question to implement renewable materials. However, the application of bio-based coatings on textiles is limited. In this regard, the present study is conducted to develop bio-based 2K PU coating specifically designed for waterproof textiles. A 2K PU coating formulation, composed of bio-based polyol and bio-based isocyanate Desmodur Eco N7300, was made and directly applied on a polyester fabric prior to thermal curing in an oven. The coating was characterized via Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The coatings were not thermoplastic and had a glass transition temperature of approximately 50 °C. Since a bio-based pentamethylene diisocyanate trimer (PDI-trimer), Desmodur Eco N7300 was used as an isocyanate source and not a diisocyanate derivative, and the resulting bio-based 2K coating was a thermoset instead of a thermoplastic. The effect of the additives and content of isocyanate on the elongation and stress at break was studied by performing tensile tests (ISO 13934-1) on 50 µm 2K PU films and comparing the obtained values. The performance of the coating was studied by evaluating the resistance to hydrostatic pressure initially and after washing, the Q-panel Laboratory UltraViolet (QUV) aging and the hydrolysis test. The developed bio-based 2K PU coating had excellent hydrostatic pressure, QUV aging resistance, hydrolysis resistance and wash fastness at 60 °C.

Reductive Hydroformylation of Isosorbide Diallyl Ether

Isosorbide and its functionalized derivatives have numerous applications as bio-sourced building blocks. In this context, the synthesis of diols from isosorbide diallyl ether by hydrohydroxymethylation reaction is of extreme interest. This hydrohydroxymethylation, which consists of carbon-carbon double bonds converting into primary alcohol functions, can be obtained by a hydroformylation reaction followed by a hydrogenation reaction. In this study, reductive hydroformylation was achieved using isosorbide diallyl ether as a substrate in a rhodium/amine catalytic system. The highest yield in bis-primary alcohols obtained was equal to 79%.

Searching potential antiviral candidates for the treatment of the 2019 novel coronavirus based on DFT calculations and molecular docking

In the present work, the succinic acid (SA), L-pyroglutamic acid (L-PGA), N-phenyl-thioacetamide (N-NPTA), 2-amino-5-chloropyridine hydrogen succinate (ACPS), epigallocatechine Gallate (EGCG) or KDH and, selenomethionine (SeM) compounds have been proposed as potential antiviral candidates to treatment of COVID-19 based on B3LYP/6-311++G∗∗ calculations and molecular docking. Solvation energies, stabilization energies, topological properties have been evaluated as function of acceptors and donors groups present in their structures. ACPS presents the higher reactivity in solution possibly because has the higher nucleophilicity and elecrophilicity indexes while KDH evidence the higher solvation energy probably due to the higher quantity of donors and acceptors groups. NBO studies show that KDH is the most stable in solution. Mapped MEP surfaces have evidenced stronger nucleophilic and electrophilic sites in ACPS, in agreement with the three C=O and two N-H and O-H groups present in this species while KDH has only a C=O group but a total of 19 acceptors and donors groups. From the above studies for six species we can propose that the better potential antiviral candidate to treatment of COVID-19 is ACPS and then, KDH. For a better prediction of the antiviral and anti-inflammatory properties of the proposed compounds, molecular docking calculations were performed by using four structures of COVID-19. Docking results were discussed basing on binding affinities and the interaction types among ligands and different amino acid residues, indicating the powerful ability of KDH and then ACPS ligands on front of the novel coronavirus disease especially for the first and the fourth species (6LU7, 7BTF).

Properties of Novel Polyesters Made from Renewable 1,4-Pentanediol

Novel polyester polyols were prepared in high yields from biobased 1,4-pentanediol catalyzed by non-toxic phosphoric acid without using a solvent. These oligomers are terminated with hydroxyl groups and have low residual acid content, making them suitable for use in adhesives by polyurethane formation. The thermal behavior of the polyols was studied by differential scanning calorimetry, and tensile testing was performed on the derived polyurethanes. The results were compared with those of polyurethanes obtained with fossil-based 1,4-butanediol polyester polyols. Surprisingly, it was found that a crystalline polyester was obtained when aliphatic long-chain diacids (>C12 ) were used as the diacid building block. The low melting point of the C12 diacid-based material allows the development of biobased shape-memory polymers with very low switching temperatures (<0 °C), an effect that has not yet been reported for a material based on a simple binary polyester. This might find application as thermosensitive adhesives in the packaging of temperature-sensitive goods such as pharmaceuticals. Furthermore, these results indicate that, although 1,4-pentanediol cannot be regarded as a direct substitute for 1,4-butanediol, its novel structure expands the toolbox of the adhesives, coatings, or sealants formulators.

Balancing the transesterification reactivity of isosorbide with diphenyl carbonate: preferential activation of exo-OH

Exo-OH on ISB has long been asserted as a highly reactive moiety compared with endo-OH. Herein, we report that the nucleophilic attack surmounts steric hindrance in rendering endo-OH more reactive than exo-OH in case of transesterification with DPC.

Utilizing Furfural-Based Bifuran Diester as Monomer and Comonomer for High-Performance Bioplastics: Properties of Poly(butylene furanoate), Poly(butylene bifuranoate), and Their Copolyesters

Two homopolyesters and a series of novel random copolyesters were synthesized from two bio-based diacid esters, dimethyl 2,5-furandicarboxylate, a well-known renewable monomer, and dimethyl 2,2'-bifuran-5,5'-dicarboxylate, a more uncommon diacid based on biochemical furfural. Compared to homopolyesters poly(butylene furanoate) (PBF) and poly(butylene bifuranoate) (PBBf), their random copolyesters differed dramatically in that their melting temperatures were either lowered significantly or they showed no crystallinity at all. However, the thermal stabilities of the homopolyesters and the copolyesters were comparable. Based on tensile tests from amorphous film specimens, it was concluded that the elastic moduli, tensile strengths, and elongation at break values for all copolyesters were similar as well, irrespective of the furan:bifuran molar ratio. Tensile moduli of approximately 2 GPa and tensile strengths up to 66 MPa were observed for amorphous film specimens prepared from the copolyesters. However, copolymerizing bifuran units into PBF allowed the glass transition temperature to be increased by increasing the amount of bifuran units. Besides enhancing the glass transition temperatures, the bifuran units also conferred the copolyesters with significant UV absorbance. This combined with the highly amorphous nature of the copolyesters allowed them to be melt-pressed into highly transparent films with very low ultraviolet light transmission. It was also found that furan-bifuran copolyesters could be as effective, or better, oxygen barrier materials as neat PBF or PBBf, which themselves were found superior to common barrier polyesters such as PET.

Lipasas en síntesis de polímeros: avances y contribución a la química verde de polímeros

Las lipasas han sido usadas en las últimas décadas como catalizadores eficientes en la síntesis enzimática de polímeros y gracias a características como alta selectividad, reciclabilidad, inocuidad y fácil separación/purificación se han convertido en una herramienta importante en el campo de los polímeros. En este trabajo se recopilan los desarrollos más importantes en el área y a su vez se muestra la tendencia actual de este campo de investigación.

New bio-based monomers: tuneable polyester properties using branched diols from biomass

A family of monomers, including 2,5-hexandiol, 2,7-octandiol, 2,5-furandicarboxylic acid (FDCA), terephthalic acid (TA), and branched-chain adipic and pimelic acid derivatives, all find a common derivation in the biomass-derived platform molecule 5-(chloromethyl)furfural (CMF). The diol monomers, previously little known to polymer chemistry, have been combined with FDCA and TA derivatives to produce a range of novel polyesters. It is shown that the use of secondary diols leads to polymers with higher glass transition temperatures (T_g) than those prepared from their primary diol equivalents. Two methods of polymerisation were investigated, the first employing activation of the aromatic diacids via the corresponding diacid chlorides and the second using a transesterification procedure. Longer chain diols were found to be more reactive than the shorter chain alternatives, generally giving rise to higher molecular weight polymers, an effect shown to be most pronounced when using the transesterification route. Finally, novel diesters with high degrees of branching in their hydrocarbon chains are introduced as potential monomers for possible low surface energy materials applications.

Effects of Isosorbide Incorporation into Flexible Polyurethane Foams: Reversible Urethane Linkages and Antioxidant Activity

Isosorbide (ISB), a nontoxic bio-based bicyclic diol composed from two fuzed furans, was incorporated into the preparation of flexible polyurethane foams (FPUFs) for use as a cell opener and to impart antioxidant properties to the resulting foam. A novel method for cell opening was designed based on the anticipated reversibility of the urethane linkages formed by ISB with isocyanate. FPUFs containing various amounts of ISB (up to 5 wt%) were successfully prepared without any noticeable deterioration in the appearance and physical properties of the resulting foams. The air permeability of these resulting FPUFs was increased and this could be further improved by thermal treatment at 160 °C. The urethane units based on ISB enabled cell window opening, as anticipated, through the reversible urethane linkage. The ISB-containing FPUFs also demonstrated better antioxidant activity by impeding discoloration. Thus, ISB, a nontoxic, bio-based diol, can be a valuable raw material (or additive) for eco-friendly FPUFs without seriously compromising the physical properties of these FPUFs.

Fully Biobased Aliphatic Anionic Oligoesters: Synthesis and Properties

Biobased aliphatic sulfonated oligoesters with 10 to 30% of sulfonated units were synthesized by melt polycondensation of biobased monomers such as diethyl succinate, z-octadec-9-enedioic acid, dimer fatty acid, sodium (sulfonated dimethyl succinate), and various diols like 1,4-butane diol and isosorbide. Structural characterization of the resulting oligoesters was determined by 1H NMR spectroscopy and MALDI-TOF MS technique. Showing a regular structure, the nature of the different expected species present in the macromolecular structure allowed the detection of etherification and cyclisation side reactions. The study of the thermal properties indicates that the resulting oligoesters are amorphous or semicrystalline that essentially depend on the nature of monomers. Films of oligoesters treated in acidic, basic, and natural media at 37°C indicate that the remaining weight depends essentially on the composition of oligoesters. Finally, sulfonated oligoester was used to prepare a biobased poly(ester-urethane) thermoset, a material having tunable properties.

A synthetic strategy toward isosorbide polycarbonate with a high molecular weight: the effect of intermolecular hydrogen bonding between isosorbide and metal chlorides

Isosorbide polycarbonate (ISB-PC) was prepared by melt transesterification and polycondensation reaction by employing ISB and diphenyl carbonate (DPC) as monomers.

Highly Cross-Linked Shape Memory Polymers with Tunable Oxidative and Hydrolytic Degradation Rates and Selected Products Based on Succinic Acid

Minimally invasive medical devices are of great interest, with shape memory polymers (SMPs) representing one such possibility for producing these devices. Previous work with low density, highly porous SMPs has demonstrated oxidative degradation, while attempts to incorporate hydrolytic degradation have resulted in rapidly decreasing glass transition temperature (T _g ), ultimately preventing strain fixity of the materials at clinically relevant temperatures. Through esterification of the amino alcohol triethanolamine, an alcohol containing network was synthesized and incorporated into SMPs. These ester networks were used to control the bulk morphology of the SMP, with the T _g remaining above 37 °C when 50% of the alcohol was contributed by the ester network. This methodology also yielded SMPs that could degrade through both hydrolysis and oxidation; by oxidation, the SMPs degrade at a similar rate as the control materials (0.2%/day mass) for the first 30 days, at which point the rate changes to 3.5%/day until the samples become too fragile to examine at 80 days. By comparison, control materials have lost approximately 30% of mass by 140 days, at a constant rate of degradation, demonstrating that the ester SMPs are a promising material system for producing more rapidly degradable, soft, porous biomaterials.

Biotic and Abiotic Synthesis of Renewable Aliphatic Polyesters from Short Building Blocks Obtained from Biotechnology

Biobased polymers have seen their attractiveness increase in recent decades thanks to the significant development of biorefineries to allow access to a wide variety of biobased building blocks. Polyesters are one of the best examples of the development of biobased polymers because most of them now have their monomers produced from renewable resources and are biodegradable. Currently, these polyesters are mainly produced by using traditional chemical catalysts and harsh conditions, but recently greener pathways with nontoxic enzymes as biocatalysts and mild conditions have shown great potential. Bacterial polyesters, such as poly(hydroxyalkanoate)s (PHA), are the best example of the biotic production of high molar mass polymers. PHAs display a wide variety of macromolecular architectures, which allow a large range of applications. The present contribution aims to provide an overview of recent progress in studies on biobased polyesters, especially those made from short building blocks, synthesized through step-growth polymerization. In addition, some important technical aspects of their syntheses through biotic or abiotic pathways have been detailed.

Isosorbide as Core Component for Tailoring Biobased Unsaturated Polyester Thermosets for a Wide Structure-Property Window

Biobased unsaturated polyester thermosets as potential replacements for petroleum-based thermosets were designed. The target of incorporating rigid units, to yield thermosets with high thermal and mechanical performance, both in the biobased unsaturated polyester (UP) and reactive diluent (RD) while retaining miscibility was successfully achieved. The biobased unsaturated polyester thermosets were prepared by varying the content of isosorbide, 1,4-butanediol, maleic anhydride, and succinic anhydride in combination with the reactive diluent isosorbide-methacrylate (IM). Isosorbide was chosen as the main component in both the UP and the RD to enhance the rigidity of the formed thermosets, to overcome solubility issues commonly associated with biobased UPs and RDs and volatility and toxicity associated with styrene as RD. All UPs had good solubility in the RD and the viscosity of the mixtures was primarily tuned by the feed ratio of isosorbide but also by the amount of maleic anhydride. The flexural modulus and storage modulus were tailorable by altering the monomer composition The fabricated thermosets had superior thermal and mechanical properties compared to most biobased UP thermosets with thermal stability up to about 250 °C and a storage modulus at 25 °C varying between 0.5 and 3.0 GPa. These values are close to commercial petroleum-based UP thermosets. The designed tailorable biobased thermosets are, thus, promising candidates to replace their petroleum analogs.

From D-sorbitol to five-membered bis(cyclo-carbonate) as a platform molecule for the synthesis of different original biobased chemicals and polymers

Bis(cyclo-carbonate) was successfully synthesized from D-sorbitol (Sorb-BisCC) through an environmentally friendly process with dimethyl carbonate (DMC) as a reactant. In agreement with green chemistry principles, solvent free reactions were catalyzed and took place at low temperature. The reaction yield was increased until 50%, with the use of 1.3.5-triazabicyclo[4.4.0]dec-5-ene as catalyst and a continuous DMC feed to limit the side-reactions or the loss of reactant by azeotropic flux with a reactional subsidiary product. The obtained Sorb-BisCC is a remarkable platform molecule which could compete with others polycyclic platform molecules (isosorbide). Sorb-BisCC can be e.g., used to synthesize different chemicals such as short and long polyols, or novel biobased non-isocyanate polyurethanes (NIPU). Two Sorb-BisCC molecules have been coupled to obtain novel cyclic diols with pendant side chains. Polyether polyols were also obtained by anionic ring opening polymerization. According to the synthesis conditions, these synthetized polyether polyols range from partially to highly cross-linked materials. Finally, NIPU were synthesized with short and biobased fatty diamines. These different modifications and synthesis highlight the versatility of the Sorb-BisCC and demonstrated its high potential as building block. Sorb-BisCC can be considered as a platform molecule to open the way to different original and biobased chemical architectures.

Synthesis and Characterization of Renewable Polyester Coil Coatings from Biomass-Derived Isosorbide, FDCA, 1,5-Pentanediol, Succinic Acid, and 1,3-Propanediol

Biomass-derived polyester coatings for coil applications have been successfully developed and characterized. The coatings were constituted by carbohydrate-derived monomers, namely 2,5-furan dicarboxylic acid, isosorbide, succinic acid, 1,3-propanediol, and 1,5-pentanediol, the latter having previously been used as a plasticizer rather than a structural building unit. The effect of isosorbide on the coatings is widely studied. The inclusion of these monomers diversified the mechanical properties of the coatings, and showed an improved performance against common petrochemical derived coatings. This research study provides a range of fully bio-derived polyester coil coatings with tunable properties of industrial interest, highlighting the importance of renewable polymers towards a successful bioeconomy.

Novel copolyimides containing 1,4:3,6-dianhydro-d-mannitol unit Preparation, characterization, thermal, mechanical, soluble, and optical properties

In order to obtain colorless and soluble polyimide films, a dianhydride containing 1,4:3,6-dianhydro-d-mannitol unit, 2,5-bis(3,4-dicarboxyphenoxy)-1,4:3,6-dianhydromannitol dianhydride (IMDA) was synthesized. And a series of copolyimides were prepared from IMDA, 1,2,4,5-benzenetetracarboxylic anhydride (PMDA), and 4,4′-oxydianiline by adjusting the mole fraction (between IMDA and PMDA) of IMDA from 0% to 100%. It was found that the solubility as well as the transmittance of the copolyimide films enhanced with the increased content of IMDA. Especially, when the content of IMDA was 60% or more, the copolyimides were readily soluble in common polar solvents and could afford flexible, tough, and colorless films with transparency up to 84% at 450 nm, which may be ascribed to the incorporation of the relatively twisted and flexible 1,4:3,6-dianhydro-d-mannitol units into the backbone of copolyimides. Additionally, the influence of IMDA on the thermal, mechanical, and morphological properties of copolyimides was investigated.

Microwave-assisted synthesis of isosorbide-derived diols for the preparation of thermally stable thermoplastic polyurethane

In order to prepare thermally stable isosorbide-derived thermoplastic polyurethane, the synthesis of two new chiral exo-exo configured diols, prepared from isosorbide, and two types of diphenols (bisphenol A and thiodiphenol) was described. The synthesis conditions were optimized under conventional heating and microwave irradiations. To prove their suitability in polymerization, these monomers were successfully polymerized using 4,4'-diphenylmethane diisocyanate (MDI) and hexamethylene diisocyanate (HDI). Both monomers and polymers have been studied by NMR, FT-IR, TGA, DSC; intrinsic viscosity of polymers has also been determined. The results showed the effectiveness of the synthetic strategy proposed; moreover, a dramatic reduction of the reaction time and an important improvement of the monomers yield using microwave irradiation have been demonstrated. The monomers, as well as the polymers, showed excellent thermal stability both in air and nitrogen. It was also shown that the introduction of sulphur in the polyurethane backbone was effective in delaying the onset of degradation as well as the degradation rate.

Formic acid as a secondary substrate for succinic acid production by metabolically engineered Mannheimia succiniciproducens

There has been much effort exerted to reduce one carbon (C1) gas emission to address climate change. As one promising way to more conveniently utilize C1 gas, several technologies have been developed to convert C1 gas into useful chemicals such as formic acid (FA). In this study, systems metabolic engineering was utilized to engineer Mannheimia succiniciproducens to efficiently utilize FA. ¹³ C isotope analysis of M. succiniciproducens showed that FA could be utilized through formate dehydrogenase (FDH) reaction and/or the reverse reaction of pyruvate formate lyase (PFL). However, the naturally favored forward reaction of PFL was found to lower the SA yield from FA. In addition, FA assimilation via FDH was found to be more efficient than the reverse reaction of PFL. Thus, the M. succiniciproducens LPK7 strain, which lacks in pfl, ldh, pta, and ack genes, was selected as a base strain. In silico metabolic analysis confirmed that utilization of FA would be beneficial for the enhanced production of SA and suggested FDH as an amplification target. To find a suitable FDH, four different FDHs from M. succiniciproducens, Methylobacterium extorquens, and Candida boidinii were amplified in LPK7 strain to enhance FA assimilation. High-inoculum density cultivation using ¹³ C labeled sodium formate was performed to evaluate FA assimilation efficiency. Fed-batch fermentations of the LPK7 (pMS3-fdh2 meq) strain was carried out using glucose, sucrose, or glycerol as a primary carbon source and FA as a secondary carbon source. As a result, this strain produced 76.11 g/L SA with the yield and productivity of 1.28 mol/mol and 4.08 g/L/h, respectively, using sucrose and FA as dual carbon sources. The strategy employed here will be similarly applicable in developing microorganisms to utilize FA and to produce valuable chemicals and materials from FA.

Isohexide Dinitriles: A Versatile Family of Renewable Platform Chemicals

Building blocks of isohexides extended by one carbon atom at the 2- or 5-positions are now synthetically accessible by a convenient, selective, base-catalyzed epimerization of the corresponding dinitriles. Kinetic experiments using the strong organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) show that all three possible isohexide dinitrile isomers exist within a dynamic equilibrium. An epimerization mechanism based on density functional theory (DFT) calculations is proposed. Structural identification of all three possible isomers is based on NMR analysis and single crystal x-ray crystallography. DFT calculations confirm that the observed crystal structures are indeed the lowest energy conformers of these isohexide derivatives.

Structural deformation phenomenon of synthesized poly(isosorbide-1,4-cyclohexanedicarboxylate) in hot water

Water induced deformation phenomena of synthesized polyester including isosorbide shares analogous mechanism of solvent induced crystallization. This structural deformation is effected by pH, open-ring ISB and ester hydrolysis.

Sugar-based bicyclic monomers for aliphatic polyesters: a comparative appraisal of acetalized alditols and isosorbide

Three series of polyalkanoates (adipates, suberates and sebacates) were synthesized using as monomers three sugar-based bicyclic diols derived from D-glucose (Glux-diol and isosorbide) and D-mannose (Manx-diol). Polycondensations were conducted in the melt applying similar reaction conditions for all cases. The aim was to compare the three bicyclic diols regarding their suitability to render aliphatic polyesters with enhanced thermal and mechanical properties. The ensuing polyesters had molecular weights (M_w) in the 25,000–50,000 g mol⁻¹ range with highest values being attained for Glux-diol. All the polyesters started to decompose above 300 °C and most of them did not display perceivable crystallinity. On the contrary, they had glass transition temperatures much higher than usually found in homologous polyesters made of alkanediols, and showed a stress–strain behavior consistent with their T_g values. Glux-diol was particularly effective in increasing the T_g and to render therefore polyesters with high elastic modulus and considerable mechanical strength.