Vanillin derived a carbonate dialdehyde and a carbonate diol: novel platform monomers for sustainable polymers synthesis

Insight into the hydrophobic functionalization of cellulose microfibrils using the Passerini three-component reaction

The aqueous catalyst-free one-pot Passerini 3-component reaction (P-3CR) was employed for the functionalization of dialdehyde cellulose (DAC) derived from the periodate oxidation of microfibrillated cellulose (MFC) with insights provided by 13C and 15N CP-MAS NMR and FTIR analyses. The kinetics of the P-3CR revealed rapid progress within the initial 2 h, reaching a plateau between 6 and 18 h. The reaction achieved a maximum degree of substitution (DS) with only 1 equivalent of carboxylic acid and isocyanide with respect to the number of aldehydes, therefore demonstrating the atom economy character of the P-3CR performed on MFC. Variable DS values (0.08 to 0.37) were achieved by altering the degree of oxidation of DAC (ranging from 0.48 to 1.1) when reacted with heptanoic acid and tert-butyl isocyanide. Additionally, aliphatic chain lengths of carboxylic acids from C4 to C11 were successfully used for the functionalization of DAC with distinct hydrophobic chains. Furthermore, while cosolvents negatively affected the DS when using heptanoic acid, a significant increase was observed in the case of undecanoic acid due to an improved solubility of the reagent. The aqueous medium P-3CR can thus be considered a versatile tool to tailor the functionalization of MFC and provide it with hydrophobicity.

Introducing the Reversible Reaction of CO2 with Diamines into Nonisocyanate Polyurethane Synthesis

Nonisocyanate polyurethanes (NIPUs) are considered greener alternatives to traditional polyurethanes, and the preparation of NIPUs considerably depends on the design and synthesis of suitable monomers. Herein, we propose a toolbox for in situ capturing and conversion of CO2 into α,ω-diene-functionalized carbamate monomers by taking advantage of the facile reversible reaction of CO2 with diamines in the presence of organic superbases. The activation of CO2 into carbamate intermedia was demonstrated by NMR and in situ FTIR, and the optimal conditions to prepare α,ω-diene-functionalized carbamate monomers were established. Thiol-ene and acyclic diene metathesis (ADMET) polymerization of these monomers under mild conditions yielded a series of poly(thioether urethane)s and unsaturated aromatic-aliphatic polyurethanes with high yield and glass transition temperatures ranging from -26.8 to -1.1 °C. These obtained NIPUs could be further modified via postpolymerization oxidation or hydrogenation to yield poly(sulfone urethane) and saturated polyurethane with tunable properties.

Synthesis of Functional Isosorbide-Based Polyesters and Polyamides by Passerini Three-Component Polymerization

Environmental issues are becoming more and more prominent, and bio-based polymers are essential to alleviate environmental degradation by replacing traditional polymers. With this context, a new family of functional isosorbide-based polyesters and polyamides with high glass transition temperature are prepared via Passerini-Three component polymerization (P-3CP). To optimize the P-3CP conditions, the influence of the polymerization solvent, temperature, feed ratio on the molar mass of final polymers are investigated. The higher molar mass (up to 10100 g/mol) and yield (>70 %) are achieved under very mild conditions (30 °C, standard atmosphere). Functional side groups, such as alkenyl, alkynyl and methyl ester, were introduced into polymer structure via P-3CP by using functional isocyanides. The obtained polyesters and polyamides are characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopies, differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). All polymers are thermal stable and amorphous with variable glass transition temperatures (Tg ). The obtained polyester has Tg up to 87.5 °C, while the Tg of polyamides (ISPA-2) is detected to be 97.5 °C depending on the amide bonds in the polymer backbone and the benzene ring side groups. The cytotoxicity is investigated by the CCK-8 assay against mBMSC cells to confirm the biological safety. Overall, this novel strategy provides an efficient approach to produce functional isosorbide-based polyesters and polyamides, which are promising prospect for being applied to biodegradable materials.

Eugenol-derived organic liquids as an in situ CO2 capturing and conversion system for Eugenol-based polycarbonate synthesis

The significant development of catalytic biomass conversion has provided a large library of chemicals ready for subsequent upgrading to polymerisable monomers for the design and preparation of sustainable polymers. In this study, hydroxyethylation of eugenol by using green ethylene carbonate as alkylation reagent and cheap tetrabutylammonium iodide ionic liquids as green solvents and catalysts produced 2-(4-allyl-2-methoxyphenoxy)ethan-1-ol with a 85% yield,  which could be used to construct an in situ CO 2 capture and conversion system by taking the reversible chemistry of alcoholic compounds with CO 2 in the presence of superbases, on which α,ω-diene functionalized carbonate monomers were successfully prepared and were applied in  thiol-ene click and acyclic diene metathesis polymerisation (ADMET), producing a series of poly(thioether carbonate)s and unsaturated aromatic aliphatic polycarbonates with moderate molecular weights and satisfactory thermal properties. The structures of the formed CO 2 reversible ILs, the polymerisable monomers and the corresponding polymers were fully characterized by various technologies.

Bio-Based Degradable Poly(ether-ester)s from Melt-Polymerization of Aromatic Ester and Ether Diols

Vanillin, as a promising aromatic aldehyde, possesses worthy structural and bioactive properties useful in the design of novel sustainable polymeric materials. Its versatility and structural similarity to terephthalic acid (TPA) can lead to materials with properties similar to conventional poly(ethylene terephthalate) (PET). In this perspective, a symmetrical dimethylated dialkoxydivanillic diester monomer (DEMV) derived from vanillin was synthesized via a direct-coupling method. Then, a series of poly(ether-ester)s were synthesized via melt-polymerization incorporating mixtures of phenyl/phenyloxy diols (with hydroxyl side-chains in the 1,2-, 1,3- and 1,4-positions) and a cyclic diol, 1,4-cyclohexanedimethanol (CHDM). The polymers obtained had high molecular weights (M_w = 5.3–7.9 × 10⁴ g.mol⁻¹) and polydispersity index (Đ) values of 1.54–2.88. Thermal analysis showed the polymers are semi-crystalline materials with melting temperatures of 204–240 °C, and tunable glass transition temperatures (T_g) of 98–120 °C. Their 5% decomposition temperature (T_d,5%) varied from 430–315 °C, which endows the polymers with a broad processing window, owing to their rigid phenyl rings and trans-CHDM groups. These poly(ether-ester)s displayed remarkable impact strength and satisfactory gas barrier properties, due to the insertion of the cyclic alkyl chain moieties. Ultimately, the synergistic influence of the ester and ether bonds provided better control over the behavior and mechanism of in vitro degradation under passive and enzymatic incubation for 90 days. Regarding the morphology, scanning electron microscopy (SEM) imaging confirmed considerable surface degradation in the polymer matrices of both polymer series, with weight losses reaching up to 35% in enzymatic degradation, which demonstrates the significant influence of ether bonds for biodegradation.

Bio-based Poly(hydroxy urethane)s: Synthesis and Pre/Post-Functionalization

New and emerging demand for polyurethane (PU) continues to rise over the years. The harmful isocyanate binding agents and their integrated PU products are at the height of environmental concerns, in particular PU (macro and micro) pollution and their degradation problems. Non-isocyanate poly(hydroxy urethane)s (NIPUs) are sustainable and green alternatives to conventional PUs. Since the introduction of NIPU in 1957, the market value of NIPU and its hybridized materials has increased exponentially in 2019 and is expected to continue to rise in the coming years. The secondary hydroxyl groups of these NIPU's urethane moiety have revolutionized them by allowing for adequate pre/post functionalization. This minireview highlights different strategies and advances in pre/post-functionalization used in biobased NIPU. We have performed a comprehensive evaluation of the development of new ideas in this field to achieve more efficient synthetic biobased hybridized NIPU processes through selective and kinetic understanding.

Biomass-derived chemical substitutes for bisphenol A: recent advancements in catalytic synthesis

Bisphenol A is an oil-derived, large market volume chemical with a wide spectrum of applications in plastics, adhesives and thermal papers. However, bisphenol A is not considered safe due to its endocrine disrupting properties and reproductive toxicity. Several functional substitutes of bisphenol A have been proposed in the literature, produced from plant biomass. Unless otherwise specified, the present review covers the most significant contributions that appeared in the time span January 2015-August 2019, describing the sustainable catalytic synthesis of rigid diols from biomass derivatives. The focus is thereupon on heterogeneous catalysis, use of green solvents and mild conditions, cascade processes in one-pot, and continuous flow setups. More than 500 up-to-date references describe the various substitutes proposed and the catalytic methods for their manufacture, broken down according to the main biomass types from which they originate.

Sustainable Aromatic Aliphatic Polyesters and Polyurethanes Prepared from Vanillin-Derived Diols via Green Catalysis

The design and preparation of polymers by using biobased chemicals is regarded as an important strategy towards a sustainable polymer chemistry. Herein, two aromatic diols, 4-(hydroxymethyl)-2-methoxyphenol and 2-(4-(hydroxymethyl)-2-methoxyphenoxy)ethanol, have been prepared in good yields through the direct reduction of vanillin and hydroxyethylated vanillin (4-(2-hydroxyethoxy)-3-methoxybenzaldehyde) using NaBH4, respectively. The diols were submitted to traditional polycondensation and polyaddition with acyl chlorides and diisocyanatos, and serials of new polyesters and polyurethanes were prepared in high yields with moderate molecular weight ranging from 17,000 to 40,000 g mol-1. Their structures were characterized by 1H NMR, 13C NMR and FTIR, and their thermal properties were studied by TGA and differential scanning calorimetry (DSC), indicating that the as-prepared polyesters and polyurethanes have Tg in the range of 16.2 to 81.2 °C and 11.6 to 80.4 °C, respectively.