In this commentary, we will explain why, for many years, manufacturers and researchers have been trying to replace polyurethane chemistry with a new isocyanate-free chemistry, which will be described in detail. The limitations of this new chemistry for forming isocyanate-free polyurethanes will also be discussed.

The mono epoxy methacrylate and the diepoxy of vanillyl alcohol (DGEVA) are products already known and reported in literature. However, their respective synthesis processes lead to mixtures of products and side-products. Hence, the final reaction yields are low, mainly due to the purification steps. The mixture of by-products obtained is due to the presence of phenol and methylol in raw vanillin. In this article, we have proposed selective synthesis methods avoiding the formation of these by-products, which allows to consider the industrialization of these synthetic routes. Thanks to the difference in reactivity and the basicity of the catalysts used, we were able either to propose a two-step synthesis of the mono-epoxy vanilin, or to epoxidize the two hydroxyl groups to obtain the diepoxy in a single step. Finally, a toxicology study of pure vanillyl alcohol and pure DGEVA was carried out to demonstrate the interest of vanillyl alcohol as a potential substituent of bisphenol A.

High oleic sunflower oil-based polyol was obtained by thiol-ene coupling and applied in the preparation of flexible polyurethane foams. The photochemically initiated thiol-ene click reaction was carried out under UV irradiation using 2-mercaptoethanol. Bio-based polyol with hydroxyl value of 201.4 mg KOH/g was used as 30 wt% substituent of petrochemical polyether polyol in the formulations of flexible foams. Both reference foams, as well as foams modified with bio-based polyol, were formulated to have various isocyanate indices (0.85, 0.95, 1.05). Flexible foams were compared in terms of their thermomechanical properties and analyzed using FT-IR and SEM microscopy. Modification with bio-based polyol resulted in foams with superior compression properties, higher support factor, and lower resilience than reference foams. TGA and FT-IR curves confirmed the presence of urethane/urea and ether linkages in the polyurethane matrix. Moreover, double glass transition temperature corresponding to soft and hard segments of polyurethane was observed by DSC proving the phase-separated morphology.

Poly(meth)acrylates are well-known commodity polymers widely used for coating applications due to easy production, low cost and interesting properties such as their relatively high thermal stability, resistance to breakage and transparency. Some of these properties can be improved by cross-linking, therefore an additional functionalization is necessary. Carbonate group allowed reaction with amines to generate a urethane linkage without the use of toxic and harmful isocyanates. We have synthesized (meth)acrylic copolymers functionalized with cyclic carbonates groups using butyl acrylate (BA), methyl methacrylate (MMA) and glycerol carbonate methacrylate (GCMA) as comonomers to obtain cross-linkable polymers. Different ratios of BA and MMA have been used in order to evaluate the effect on the thermo-mechanical properties. The cross-linking was performed with tris(2-aminoethyl)amine at 80 degrees C during 2 h and was quantitative. The cross-linked hydroxyurethane acrylate copolymers were fully characterized and were used as coatings on glass and steel. The ease of the application and curing process as well as the adhesion strength tests showed that these cross-linked copolymers are promising materials as coating on glass and steel.

The synthesis of polymers from renewable resources is largely investigated in a context of sustainable development. Polyepoxide networks, widely used in many applications, constitute a major class of thermosetting polymers synthesized from bisphenol A (BPA), a substance identified as chemical estrogen. Moreover, epichlorohydrin used to graft a glycidyl ether group onto BPA to yield diglycidyl ether of BPA (DGEBA) is very toxic. This review proposes to demonstrate that eugenol represents an asset in the development of sustainable epoxy thermosets, by giving a general approach of the researches on the use of eugenol and its isomers for the synthesis of epoxidized precursors. The syntheses of precursors with hetero atoms (nitrogen, phosphorus or silicon) used in specific applications in electrochemistry or as flame-retardants is compared to DGEBA materials.

This study focuses on the synthesis of new liquid aromatic bismaleimide monomers in order to improve self-curing on demand (SCOD) systems previously based on aliphatic bismaleimides. These SCOD systems are based on Diels-Alder (DA)/retro-DA reactions. The syntheses of new different aromatic bismaleimides with ester and amide bonds are presented. These maleimides have been protected using DA reaction and characterized by 1H NMR analysis to determine protection rate and diastereomer ratios. The retro-DA reactions of both aromatic and aliphatic DA adducts in presence of thiol molecules were studied. Kinetic analysis was monitored by 1H NMR and compared to model study. Finally, both aromatic and aliphatic bismaleimides-based polymers were synthesized with 2-mercaptoethyl ether and thermal properties of polymers were compared. The glass transition temperature values ranged from −20 °C to 14 °C and very good thermal stabilities were observed (up to 300 °C).

The radical telomerisation of vinylidene fluoride (VDF) with 2-mercaptoethanol as chain transfer agent (CTA) was studied to synthesise fluorinated telomers which bear a hydroxy end-group, such as H(VDF)nS(CH2)2OH, under thermal (di-tert-butyl peroxide as the initiator) or photochemical initiations. A careful structural study of a typical H-VDF-S(CH2)2OH telomer was performed by 1H and 19F NMR spectroscopy. These analytical methods allowed us to explore the selective addition of the thiyl radical onto the hydrogenated side of VDF, and the telomer containing one VDF unit was obtained selectively. Surprisingly, for higher [VDF]o initial concentrations, a monoadduct telomer was produced as well as PVDF homopolymer. This feature was related to the fast consumption of the CTA. The kinetics of radical telomerisation led to a quite high transfer constant of the CTA (40 at 140 °C) that evidences the formation of a monoadduct as the only telomer formed.

The Diels-Alder (DA) reaction is regarded as quite a useful strategy in organic and macromolecular syntheses. The reversibility of this reaction and the advent of self-repair technology, as well as other applications in controlled macromolecular architectures and crosslinking, have strongly boosted the research activity, which is still attracting a huge interest in both academic and industrial research. The DA reaction is a simple and scalable toolbox. Though it is well-established that furan/maleimide is the most studied diene/dienophile couple, this perspective article reports strategies using other reversible systems with deeper features on other types of diene/dienophile pairs being either petro-sourced (cyclopentadiene, anthracene) or bio-sourced (muconic and sorbic acids, myrcene and farnesene derivatives, eugenol, cardanol). This review is composed of four sections. The first one briefly recalls the background on the DA reactions involving cyclodimerizations, dienes, and dienophiles, parameters affecting the reaction, while the second part deals with the furan/maleimide reaction. The third one deals with petro-sourced and bio-sourced (or products becoming bio-sourced) reactants involved in DA reactions are also listed and discussed. Finally, the authors' opinion is given on the potential future of the crosslinking-decrosslinking reaction, especially regarding the process (e.g., key temperatures of decrosslinking) or possibly monocomponents. It presents both fundamental and applied research on the DA reaction and its applications.

The discovery of huge petroleum reserves in the 19th century was a golden opportunity that promoted the industrial revolution, by offering a wide variety of cheap raw materials and a reliable source of energy. This caused an unprecedented increase of commodity and production of specialty chemicals in order to fulfill the needs of the global markets. However, as global warming and environmental issues have become a hazardous and worried situation, researchers are looking for biorenewable monomers with low toxicity in order to produce more sustainable polymers. This policy was applied to epoxy resin materials because of their high volume production in industry for a wide range of applications. This review highlights the recent advances in the preparation of diamines and diepoxy monomers for the synthesis of epoxy resins, mainly from 2-furfural, 5-(hydroxymethyl)furfural (5-HMF), and 2,5-furandicarboxylic acid (FDCA), obtained from natural cellulose and hemicellulose feedstocks, respectively, and able to replace phthalic moieties in polyethylene terephthalate. In addition, the processes involved in the monomer preparations, such as reductive amination, etherification, esterification, and carbonatation, are listed. This review, reporting quasi-exhaustive synthetic pathways of epoxy precursors containing furanic moieties and describing the resulting resins, is composed of seven main parts, based on the synthesis of glycidyl derivatives containing one or two or four furan nuclei bearing or not a spacer between the furan ring and the function. The influence of the substituents on furan moieties (O, CO, CH2) and the spacer between these groups have also been evaluated. Finally, thermal and a few mechanical properties of the obtained biosourced epoxy resins were compared to their fossil fuel analogues (from bisphenol A), featuring the high potential of biobased monomers as substituents for nonrenewable ones.

The observation and influence of hydrogen bonds in epoxy-system curing and material properties is also discussed through a state of the art of literature. Epoxy-amine systems are widely used polymers for various industrial applications, such as composites, adhesives, paints and coatings due to their high thermal and mechanical properties. The reactivity of epoxy-amine system is crucial for both academic and industrial communities and is dramatically influenced by H bonds. In addition, the ring opening reaction of epoxy system yields hydroxyl groups, which can form hydrogen bonds and thus influence the curing kinetic and the material properties. Those formed hydroxyl groups have also an influence on the properties of cured materials due to their H bond sites. Hence, this article focuses on the description of an amine reactivity scale and on the gathering of literature data mentioning the hydrogen bond observation and study in epoxy-amine system. First, this article presents an amine reactivity scale clarification due to our team expertise and knowledge. Then, all external factors influencing the hydrogen bond formation are described based on several studies. Finally, the influence of hydrogen bond in epoxy-amine system was summarized.

Aza-Michael addition on acrylated linseed oil (AELO) is performed to synthetize biobased bulk thermosets without any catalyst. First, acrylation of epoxidized linseed oil (ELO) allows to obtain acrylate functions with vicinal hydroxyl groups which enhance the reactivity of acrylates. The autocatalytic effect of hydroxyl groups on acrylate monomers is highlighted by kinetic studies monitored by NMR and FTIR analyses on model molecules. Then, Priamine 1071, amine terminated poly(propyleneoxide) (PPO) and meta-xylylenediamine (MXDA) are used as cross-linkers with AELO. Curing kinetics are studied by DSC analyses to compare the reactivity of these structures. Priamine 1071 shows the highest reactivity; curing at room temperature is performed and high conversion is reached. Two enthalpies are observed with MXDA and only one at high temperature for PPO-based materials. Thermosets with a large range of mechanical properties are finally obtained from soft materials with PPO-diamine to hard materials with MXDA. Practical Applications: Thermosets are obtained by curing AELO with various diamines via aza-Michael reaction. Model reaction allows to demonstrate catalytic effect of hydroxyl groups on Aza-Michael reaction of acrylated oil with amines. Hence, linseed oil is a promising resource in terms of sustainable development in polymer science.

Most of the current amine hardeners are petro-sourced and only a few studies have focused on the research of bio-based substitutes. Hence, in an eco-friendly context, our team proposed the design of bio-based amine monomers with aromatic structures. This work described the use of the reductive amination with imine intermediate in order to obtain bio-based pluri-functional amines exhibiting low viscosity. The effect of the nature of initial aldehyde reactant on the hardener properties was studied, as well as the reaction conditions. Then, these pluri-functional amines were added to petro-sourced (diglycidyl ether of bisphenol A, DGEBA) or bio-based (diglycidyl ether of vanillin alcohol, DGEVA) epoxy monomers to form thermosets by step growth polymerization. Due to their low viscosity, the epoxy-amine mixtures were easily homogenized and cured more rapidly compared to the use of more viscous hardeners (<0.6 Pa s at 22 °C). After curing, the thermo-mechanical properties of the epoxy thermosets were determined and compared. The isophthalatetetramine (IPTA) hardener, with a higher number of amine active H, led to thermosets with higher thermo-mechanical properties (glass transition temperatures (Tg and Tα) were around 95 °C for DGEBA-based thermosets against 60 °C for DGEVA-based thermosets) than materials from benzylamine (BDA) or furfurylamine (FDA) that contained less active hydrogens (Tg and Tα around 77 °C for DGEBA-based thermosets and Tg and Tα around 45 °C for DGEVA-based thermosets). By comparing to industrial hardener references, IPTA possesses six active hydrogens which obtain high cross-linked systems, similar to industrial references, and longer molecular length due to the presence of two alkyl chains, leading respectively to high mechanical strength with lower Tg.

Most of the current amines are issued from petrochemical resources and only a few of them are derived from biomass. Hence, there are increasing expectations for bio-based amines, particularly for aromatic ones. We have designed and synthesized new bio based amines containing aromatic moieties from cardanol, an aromatic nonedible co-product from agri-food industry of cashew nut. We used green amination reaction of epoxy monomers with ammonia under microwave irradiations, from two commercial epoxidized cardanol monomers with different epoxy functions: NC-514 and GX-2551 (Cashew, nutshell liq., polymer with epichlorohydrin). We studied the efficiency of our amination route onto both glycidyl and epoxy functions at the middle of the chain and the reactivity of synthesized amines toward ring opening of epoxy function, The synthesized bio-based amines were further evaluated as curing agents for epoxy resins. The thereto-mechanical properties of final bio-based thermosets synthesized there from are almost similar (T-g = 51 degrees C, T-d 5% = 332 degrees C and T-a = 64 degrees C for T-NC thermoset, T-g = 58 degrees C, T(d)5% = 340 degrees C and T-a = 78 degrees C for T-GX thermoset). Moreover, another aim of this study was to reduce the viscosity of hardeners compared to DHAVA hardener (400 000 mPa sat 50 degrees C), which was synthesized in previous work. Lower viscosities were observed in the case of cardanol-based hardener (362 000 and 33 000 mPa s at 50 degrees C for respectively NC-A and GX-A hardener).

In this study, various novel cyclic carbonate-siloxane monomers were synthesized by hydrosilylation and CO2 carbonation of allyl glycidyl ether and epoxy-eugenol functions. Different structures were obtained from cyclic siloxane (D4) or linear PMHS-PDMS polymers with dangling cyclic carbonate functions. This hybrid route gives access to highly functional and low viscous cyclic carbonate monomers. Cyclic siloxane-carbonate monomers were reacted with 1,5-diamino-2-methylpentane (DYTEK-A) and 1,3-cyclohexanebis(methylamine) (CBMA) to afford polyhydroxyurethane (PHUs) thermosets as non-isocyanate polyurethanes (NIPUs) with high conversions and good reactivity. PHU thermosets were characterized to compare the thermal and mechanical properties of those different structures. The impact of the functionality was highlighted with different functional oligomers playing on cross-linking density of materials. D4 structure led to short and functional star shape monomers and afforded polymers with the highest mechanical properties. Eugenol, with an aromatic moiety, increased the stiffness and the thermal stability of PHU thermosets. Such hybrid PHU-siloxanes polymers combined flexibility of siloxanes with high mechanical performances of urethane groups.

Generally, chemistry, and in particular polymer chemistry, faces the major challenge of finding solutions to ensure the sustainable and environmentally benign development of industry to meet consumer needs.

Chemistry in general, but polymer chemistry in particular has to face the major challenge of finding solutions to ensure a sustainable and environmental-benign development of industry to answer consumer needs. Aldehydes are very important chemical groups for polymer science of the synthesis of phenolic resins for example, however, most molecular aldehydes (such as formaldehyde) are toxic. Finding less toxic and sustainable aldehydes is not easy because this functional group is relatively scarce in nature. In consequence aldehydes-containing building blocks must be synthesized. The present review gives an overview of the different synthetic methods to prepare such aldehyde building blocks. It then focusses on the use of radically polymerizable aldehyde-containing monomers to prepare polymers and materials featuring available aldehyde pendent group. Indeed, owing to the rich reactivity and properties of aldehydes, such functional polymers will undoubtedly lead to the development of high-added value applications. This review also gives a brief overview of such potential applications.

The development of epoxy thermosets from renewable resources is of paramount importance in a sustainable development context. In this paper, a novel bio-based epoxy monomer derived from limonene was synthesized without epichlorohydrine and characterized. In fact, this paper depicts the synthesis of bis-limonene oxide (bis-LO). However, intern epoxy rings generally exhibit a poor reactivity and allow reaction with anhydride. Therefore, we used a reaction model with hexahydro-4-methylphthalic anhydride to compare reactivity of terminal and interepoxy functions. We also studied the influence of methyl group on intern epoxy functions. Furthermore, the influence of epoxy:anhydride stoichiometry and initiator amount was studied. These studies allow to propose an optimized formulation of bis-LO. Finally, a bis-LO-based thermoset was obtained and characterized.

In the scope of fully bio-based materials development, access to bio-based aromatic amine monomers is one of the main industrial challenges over the coming years.

The synthesis of polymers from renewable resources is a burning issue that is actively investigated. Polyepoxide networks constitute a major class of thermosetting polymers and are extensively used as coatings, electronic materials, and adhesives. Owing to their outstanding mechanical and electrical properties, chemical resistance, adhesion, and minimal shrinkage after curing, they are used in structural applications as well. Most of these thermosets are industrially manufactured from bisphenol A (BPA), a substance that was initially synthesized as a chemical estrogen. The awareness of BPA toxicity, combined with the limited availability and volatile cost of fossil resources and the nonrecyclability of thermosets, implies necessary changes in the field of epoxy networks. Thus, substitution of BPA has witnessed an increasing number of studies from both the academic and industrial sides. This chapter proposes to give an overview of the reported epoxide building blocks synthesized from biomass or from molecules that may be obtained from transformed biomass. After a reminder of the main glycidylation routes and mechanisms, this chapter will provide a brief description of the main natural sources of biobased epoxy molecules and the materials resulting therefrom.

The synthesis of polymers from renewable resources is a burning issue that is actively investigated. Polyepoxide networks constitute a major class of thermosetting polymers and are extensively used as coatings, electronic materials, adhesives. Owing to their outstanding mechanical and electrical properties, chemical resistance, adhesion, and minimal shrinkage after curing, they are used in structural applications as well. Most of these thermosets are industrially manufactured from bisphenol A (BPA), a substance that was initially synthesized as a chemical estrogen. The awareness on BPA toxicity combined with the limited availability and volatile cost of fossil resources and the non-recyclability of thermosets implies necessary changes in the field of epoxy networks. Thus, substitution of BPA has witnessed an increasing number of studies both from the academic and industrial sides. This review proposes to give an overview of the reported aromatic multifunctional epoxide building blocks synthesized from biomass or from molecules that could be obtained from transformed biomass. After a reminder of the main glycidylation routes and mechanisms and the recent knowledge on BPA toxicity and legal issues, this review will provide a brief description of the main natural sources of aromatic molecules. The different epoxy prepolymers will then be organized from simple, mono-aromatic di-epoxy, to mono-aromatic poly-epoxy, to di-aromatic di-epoxy compounds, and finally to derivatives possessing numerous aromatic rings and epoxy groups.