Polymer Reviews easily be epoxidized, leading to reactive epoxide groups. Secondly, triglycerides double bonds could undergo a wide range of reaction to yield polyols. Finally, the carbonyl group could also be used as a reactive group to yield various polyols. In a second part, the present review is dedicated to the commercial biobased polyols, and, based on the patent literature; focus on the industrial synthetic routes.
In recent years, the sustainability is becoming increasingly important for the chemical industry; thus, the use of renewable resources has gained interest in polymer applications. Vegetable oils are extracted primarily from the seeds of oilseed plants. Their competitive cost, worldwide availability, and built-in functionality (ester functions and insaturations) make them attractive. The development of oleochemicals has been carried out from two distinct ways. The first one corresponds to the double-bond modification 1 of crude oils or fatty acid derivatives. The second one is the carboxylic acid group modification of vegetable oils. 2 The chemical functionalizations of unsaturated oils to produce polyols have been widely developed to prepare new polyurethane structures, which depend on triglyceride and isocyanate reagents used. 3À5 These polyols are mainly obtained from intermediate epoxy oil either in one or two steps. The onestep reaction consists of the in-situ epoxidation followed by hydroxylation using acetic and sulfuric acids and hydrogen peroxide. 6 The two-step reaction deals with the triglyceride epoxidation followed by the ring-opening of oxirane, based on the use of difunctional molecules such as alcohols 7 or amines, 8 obtaining polyols from vegetable oils. Moreover, vegetable oil double bonds were converted into primary alcohols through hydroformylation followed by hydrogenation. 9 Eventually, ozonolysis was used to obtain polyols with terminal primary hydroxyl groups and different functionalities from natural vegetable oil and synthetic triglycerides. 10 Those functionalization processes usually require at least two-step reaction and sometimes expensive catalysts.Radical additions, such as thiolÀene coupling (TEC), are very attractive. A lot of unsaturated polymers were thus functionalized 11À14 from thiolÀene addition. So far, TEC reactions have mainly been used both to polymerize and to cross-link fatty acids 15À17 and triglycerides 18 by using polyfunctional thiols. 19 In addition, from TEC reaction, an effective optimization of vegetable oils lubricating property was performed either in one step or after grafting of mercaptosilanes on metallic surfaces. 20 Recently, Meier et al. synthesized polyols by TEC from methyl 10-undecenoate and thiol alcohol without initiator. These polyols were used as polyester precursors. 21 TEC reaction belongs to a set of reactions named "click" reactions 22À24 characterized by high yields, simple reaction ABSTRACT: A model study of the radical addition of 2-mercaptoethanol onto oleic acid was performed under mild conditions (generation of radicals under UV light at room temperature without any photoinitiator). To evaluate the efficiency and the robustness of thiolÀene reaction, experimental parameters were varied, such as the irradiation intensity (ranging from 0.5 to 15.0 W/cm 2 ), the thiol/double bond ratio (ranging from 1.2/1 to 5.0/1), the solvent/double bond ratio (ranging from 0/1 to 500/1), and the number of double bonds per chain. It was especially shown...
Biobased polyols were synthesized from reaction between epoxidized soybean oil and lactic, glycolic, or acetic acids. Polyols were characterized by NMR, alcohol and acid titration, and SEC. These analyses allowed to determine an average hydroxyl functionality between 4 and 5, with an oligomer content close to 50 wt%. Synthesized polyols were formulated with isocyanate to yield polyurethanes (PUs). Thermal and mechanical properties of obtained materials showed that synthesized polyols lead to rigid and brittle material with Young moduli higher than 900 N/mm2 at RT and with Tg values around 50°C.Practical application: The products of the chemistry described in this contribution, i.e.: polyol from vegetable oils and lactic, glycolic, or acetic acids, provide biobased building blocks for further PUs syntheses by reaction with diisocyanates. The obtained PUs are partially biobased and may be applied as binders and coatings.
A new synthesis of 4-[(prop-2-en-1-yloxy)methyl]-1,3-dioxolan-2-one (AGC) was performed by Williamson ether synthesis from 4-(hydroxymethyl)-1,3-dioxolan-2-one. Dicyclocarbonates were synthesized by UV thiol-ene coupling of allyl-cyclocarbonate with a 2,2 0 -oxydiethanethiol. This photochemical thiol-ene reaction was carried out under air, with neither solvent nor photoinitiator. The products, obtained with high yield, were characterized by 1 H NMR and FTIR analysis. The synthesized dicyclocarbonates were used without purification to synthesize polyhydroxyurethanes without isocyanate by step growth polyaddition with 1,10-diaminodecane. The synthesized polyhydroxyurethanes were characterized by 1 H NMR, FTIR, ATG and DSC analysis. These polyhydroxyurethanes exhibited glass transition temperatures from À31 Ct oÀ14 C, molecular weight from 7,000 g mol À1 to 9000 g mol À1 and degradation temperature for 5% of weight loss (T d 5%) between 227 C and 250 C. ; Tel: 05 40 00 27 34 † Electronic supplementary information (ESI) available. See
International audienceSoybean oil was modified into a novel biobased polyacid hardener by thiol-ene coupling with thioglycolic acid. The structure of the initial soybean oil and polyacid triglyceride was carefully analyzed using 1H NMR and titration. The thermal crosslinking reaction between acid hardener and epoxidized resin was studied by differential scanning calorimetry (DSC) and rheology. Then, the synthesized biobased acid hardener was employed as a novel curing agent for bisphenol A diglycidyl ether to elaborate new partially biobased materials. These materials, formulated in stoichiometry ratio, were characterized by DSC, thermogravimetry analyses, dynamic mechanical analyses and exhibit interesting properties for coatings
Transesterification of methyl esters of rapeseed oil with ethylene glycol in excess led to a v-hydroxy fatty ester with a yield of 90%. 2-Mercaptoethanol was grafted onto the double bonds of this v-hydroxy fatty ester by UV initiated thiol-ene coupling under mild conditions. Double bond conversion was found to be quantitative and yielded a polyol with average of two primary hydroxyl functions. This pseudo-diol was characterized by means of NMR spectroscopy, titration and mass spectroscopy (MS) and was used to synthesize polyurethane (PU) by step growth polyaddition with methylene diphenyl-4,4 0 -diisocyanate. The polymer, analyzed by thermogravimetric analysis (TGA) and DSC, showed a glass transition temperature of À38C, close to the one measured (88C) on a PU based on a commercial polyol, Desmophen 1150.Practical application: The products of the chemistry described in this contribution, i.e. polyol from vegetable oils derivatives, provide biobased building blocks for further PUs syntheses by reaction with diisocyanates. The obtained PUs are partially biobased and may be applied as binders and coatings.
Soybean vegetable oil was functionalized in a single step by addition of mercaptan with hydroxyl functions by ther-mal thiol-ene coupling. The synthesized biobased polyol was analyzed by nuclear magnetic resonance, titrations, size exclusion chromatography, and mass analyses to precisely determine its average functionality, thus allowing the use of the mixture of products without purification. This polyol was added to a prepolymer of 4, 4'-diisocyanate diphenylmethylene (MDI) with a ratio OH/NCO of 1, to synthesize partially bio-based polyurethane by step growth polymerization. The synthesized polyurethane was compared to polyurethane obtained from a commercial polyether polyol polyester, named desmophen 1150. Mixtures of these polyols were made to optimize the properties of the materials obtained. Polymerization was monitored by rheology. Polyurethanes were characterized by thermogravimetric analysis, differential scanning calorimetry, shore hardness, and tensile tests at different temperatures to determine their thermal and mechanical properties. Different materials present the characteristics of soft and ductile elastomers with thermal stability of polyurethanes.
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