Isocyanate-Free Synthesis and Characterization of Renewable Poly

Research Article pubs.acs.org/journal/ascecg

Isocyanate-Free Synthesis and Characterization of Renewable Poly(hydroxy)urethanes from Syringaresinol Marine Janvier,*,†,‡ Paul-Henri Ducrot,*,‡ and Florent Allais*,†,§ †

Chaire ABI, AgroParisTech, CEBB 3 rue des Rouges Terres 51110 Pomacle, France Institut Jean-Pierre Bourgin, INRA/AgroParisTech/CNRS/Université Paris-Saclay, Route de Saint-Cyr 78026 Versailles, France § UMR 782 GMPA, INRA/AgroParisTech/CNRS/Université Paris-Saclay, Avenue Lucien Brétignières 78850 Thiverval-Grignon, France ‡

S Supporting Information *

ABSTRACT: In the context of replacement of petro-sourced and toxic bisphenol A (BPA), syringaresinol, a naturally occurring bisphenol deriving from sinapic acid, has been proposed as a greener and safer alternative. This work focuses on its applications for nonisocyanate polyurethane (NIPU) synthesis. A fivemembered cyclic carbonate SYR-CC has been prepared by carbon dioxide addition to bis-epoxy monomer SYR-EPO derived from syringaresinol. Upon polyaddition of SYR-CC with different biosourced and petrosourced diamines, the resulting polyhydroxyurethanes were fully characterized by structural (Fourier transform infrared, 1H nuclear magnetic resonance, high performance liquid chromatography size exclusion chromatography) and thermal analyses (thermogravimetric analysis, differential scanning calorimetry). These thermoplastics displayed high molar mass ( M n = 5.4 kg mol−1), excellent thermal stabilities (Td5% = 267− 281 °C) and glass transition temperatures (Tg) ranging from 63 to 98 °C. The coupling of SYR-CC with a triamine gave a thermoset material with interesting Tg (62 °C) and high thermal stability (Td5% = 225 °C). KEYWORDS: Chemo-enzymatic synthesis, Renewable bisphenol, Syringaresinol, Biobased NIPU, Thermoplastics, Thermosets

■

catalysts, such as metal salts19,21 or complexes,22,23 silicasupported amines,24 is necessary to achieve good yields. Recently, an efficient synthesis of cyclic carbonates under mild conditions in bulk under atmospheric pressure of CO2 was described, using a bifunctional quaternary phosphonium iodide as catalyst.25 In this alternative, poly(hydroxyl)urethanes are obtained via step growth polymerization of diamine and dicarbonate. The presence of pendant hydroxyl moiety, differing from classical PUs, offers a new range of properties: the resulting NIPUs generally display an increased polarity,5 higher glass transition temperature (Tg) due to interchain hydrogen bonds,26 better thermal stability, lower solubility in organic media, and higher water uptake.27 Their major drawbacks are the lower reactivity of cyclic carbonate toward amine8 and generally the lower degree of polymerization ( DPn). In addition to the replacement of isocyanate, the substitution of petro-based monomers by renewable synthons attracted the attention of the polymer community. Javni et al. described the curing of carbonated soybean oil with different diamines

INTRODUCTION Since the first examples of polyurethanes (PU) described in the 1940s, the PU market has reached about 5% of the global polymer market, with an estimated global market of 14 Mt in 2010 (according to research and markets).1 The adaptable properties of PU materials offer a wide development in various fields such as thermoplastics, thermosets or elastomers, for foams, coatings, adhesives, or isolation materials.2,3 Despite their interesting properties, PUs suffer from a major drawback, namely the use of harmful isocyanates as monomers. Indeed, isocyanates are toxic compounds and their synthesis involves the use of very harmful phosgene. Moreover, several isocyanates are now listed in the restriction list of annex XVII of REACH.4 For the development of safer alternatives, an increasing interest emerged toward new strategies for nonisocyanate polyurethanes (NIPUs) synthesis. Thus, the polymer community has been particularly interested in the ring opening polymerization of polyfunctional cyclic carbonates as a greener alternative.5−18 Cyclic carbonate monomers avoid both the use of isocyanate and the production of byproducts. Moreover, the addition of carbon dioxide to oxirane rings constitutes an easy and green access to cyclic carbonates.19,20 Nevertheless, the use of © 2017 American Chemical Society

Received: April 24, 2017 Revised: August 7, 2017 Published: August 24, 2017 8648

DOI: 10.1021/acssuschemeng.7b01271 ACS Sustainable Chem. Eng. 2017, 5, 8648−8656

Research Article

ACS Sustainable Chemistry & Engineering

Figure 1. General structures of studied bisphenols (BPA, IDF, and SYR) and their corresponding epoxy and cyclic carbonate derivatives.

leading to thermoset NIPUs with Tg ranging from 0 to 40 °C.28 Bähr et al. studied soy and linseed carbonated oil with high cyclic carbonate functionalities, exhibiting Tg values up to 60 °C upon curing.29 The authors also evaluated cyclic terpene (limonene) for NIPU application with similar Tg (62 °C).16 Similarly, Avérous’ team recently described a sebacic acid-based cyclic carbonate and its bulk catalyst-free polymerization with, however, lower molar mass than conventional PU (up to 22 kg mol−1).30,31 These studies highlighted a better reactivity of terminal cyclic carbonates compared to internal ones.16,32 Most examples of such biobased NIPUs were based on vegetable oils, with high functionality and varied structures of triglycerides, leading to low Tg thermosets or thermoplastics with low DPn . Higher mechanical properties could be obtained by using more rigid aromatic biosourced compounds as a competitive alternative to bisphenol A (BPA), a widespread monomer in polymer industry. In fact, high concern has been recently raised toward BPA toxicity. Due to its structure similar to estrogens, BPA is recognized as an endocrine disruptor, inducing a reduced fertility and potentially cancers.33,34 Recently, the use of BPA-based packaging for child products has been prohibited by the United States Food and Drug Administration.35 Despite the excellent properties obtained for BPA-based materials, its toxicity has raised a demand for BPA-free products and therefore increased the research of a safer and greener alternative.36 In this context, an interesting alternative envisaged is the valorization of lignin, the main bioresource for aromatic compounds, highly abundant (30% of the organic carbon in the biosphere37) and available as a byproduct of the paper industry without competition with food production. Nevertheless, to the best of our knowledge, published works on biophenol-based NIPUs are very scarce. Creosol based bisphenols were glycidylated, carbonated, and cured with various diamines ( M n up to 30 kg mol−1 and Tg ranging from 44 to 90 °C).38 Vanilin was also studied as a biophenol precursor for cyclic carbonate synthesis but has not been engaged yet in the synthesis of NIPUs.39 Our teams recently developed some biosourced bisphenols as an alternative to bisphenol A (BPA), describing first ferulic

acid-based bis- and trisphenols as potential substitutes to BPA (for example isosorbide dihydroferulate IDF shown in Figure 1).40 Interestingly the endocrine activity assay showed no endocrine disruption for these phenols. These bis- and trisphenols were used to synthesize linear (thermoplastics) or cross-linked (thermoset) non-isocyanate polyurethanes with a wide range of Tg (17−72 °C).41 Unfortunately, the aliphatic chain of the ester moiety of IDF is flexible and provides lower mechanical properties to the resulting polymers compared to those obtained from BPA. Moreover IDF exhibits higher sensibility toward acido-basic treatments, due to the polyester nature of the polymers. Committed to offering a genuine renewable alternative to BPA (with comparable thermomechanical properties), we are now taking into consideration syringaresinol (SYR) (Figure 1), a naturally occurring bisphenol present in plants such as Syringa patula42 or Magnolia Thailandica,43 as a promising candidate. Our team indeed recently reported on an efficient selective chemoenzymatic process for the synthesis of syringaresinol, resulting from the oxidative coupling of two molecules of sinapyl alcohol, obtained from syringaldehyde.44 With cis-fused tetrahydrofuranic moieties and two aromatic rings providing high stiffness (Figure 1), syringaresinol shows interesting structural similarities with BPA but revealed no endocrine disruption. SYR has been used as a precursor for the synthesis of novel α,ωdienes monomers for ADMET polymerization45 and, when derived as diglycidyl ether (SYR-EPO), for the formulation of epoxy-amine resins46 with high mechanical properties almost competing with BPA. In this study, we explored the potential of syringaresinol as a precursor for the synthesis of new biobased aromatic NIPUs. Cyclic carbonate SYR-CC is readily obtained via carbonation of SYR-EPO. After polyaddition of different diamines with SYRCC, the resulting NIPUs were structurally (Fourier transform infrared (FT-IR), 1H and 13C nuclear magnetic resonance (NMR), high performance liquid chromatography size exclusion chromatography (HPLC-SEC)) and thermally (thermogravimetric analysis (TGA), differential scanning calorimetry (DSC)) characterized. NIPU thermosets obtained 8649


Research Article


anhydrous MgSO4, filtered, and concentrated to give SYR-CC as a white amorphous solid (4.75 g, 81% crude yield).

by coupling with triamine were characterized by FT-IR, TGA, and DSC. The resulting syringaresinol-based thermoplastics and thermoset properties were compared with previously described IDF- and widely used BPA-based counterparts.

■

EXPERIMENTAL SECTION

Material and Methods. Syringaldehyde, malonic acid, aniline, pyridine, diisobutylaluminum hydride (DIBAL-H), Trametes versicolor laccase, ferulic acid, Pd/C, benzyltriethylammonium chloride (TEBAC), lithium bromide, and tris(2-aminoethyl)amine (TREN) were purchased from Sigma-Aldrich; epichlorohydrin and decane diamine (DA10) were purchased from Acros Organics; isophorone diamine (IPDA) was purchased from Chemical Industry Co; furfurylamine, isosorbide, and diglycidyl ether of bisphenol A were purchased from Alfa Aesar. All reagents were used as received. CO2 was purchased from Linde. Solvents were purchased from ThermoFisher Scientific, dimethylformamide was dried on a mBraun SPS 800 system. Deuterated chloroform (CDCl3) and dimethyl sulfoxide (DMSO-d6) were purchased from Euriso-top. Evaporations were conducted under reduced pressure at temperature below 40 °C for usual solvent and at 60 °C for dimethylformamide. Column chromatographies were carried out with an automated flash chromatography (PuriFlash 4100, Interchim) and prepacked INTERCHIM PF-30SI-HP (30 μm silica gel) columns using a gradient of cyclohexane and ethyl acetate for the elution. Carbonations were made in a 100 mL Paar autoclave equipped with magnetic stirring. FT-IR analyses were performed on Cary 630 FT-IR with attenuated total reflectance (ATR). UV analyses were performed on Cary 60 UV−vis from Agilent technologies, by dissolving the samples in acetonitrile. Melting points were measured on a Mettler Toledo MP50 melting point system at 2 °C·min−1. NMR analyses were recorded on a Bruker Fourier 300. 1H NMR spectra of samples were recorded in CDCl3 at 300 MHz, chemicals shifts were reported in parts per million (CDCl3, CHCl3 residual signal at δ = 7.26 ppm ; DMSO-d6, DMSO residual signal at δ = 2.50 ppm). 13C NMR spectra of samples were recorded at 75 MHz (CDCl3 signal at δ = 77.16 ppm; DMSO residual signal at δ = 39.52 ppm). HRMS were recorded by the PLANET platform at URCA on a Micromass GC-TOF. Thermogravimetric analyses (TGA) were recorded on a Q500, from TA. About 10 mg of each sample was heated at 10 °C·min−1 from 30 to 800 °C under nitrogen flow (60 mL·min−1) or compressed air (20 mL·min−1). Differential scanning calorimetry (DSC) thermograms were obtained using a DSC TA Q20, under an inert atmosphere (N2), with a calibration using indium, n-octadecane and n-octane standards. For each sample, about 10 mg were weighed in a pan which was then sealed and submitted to 3 heat/cool/heat cycles: heating from 30 to 250 °C at 10 °C·min−1, cooling from 250 °C to −50 °C at 20 °C· min−1. Glass transition temperatures (Tg) were determined at the inflection value in the heat capacity jump. High pressure chromatography by size exclusion (HPLC-SEC) was performed at 70 °C on an Infinity 1260 system from Agilent Technologies with a quadruple detection (IR, UV, MALS, viscosimetry) and two PL-gel 5 mm mixed-D columns (300 mm × 7.5 mm) in DMF (flow rate 1 mL· min−1) using polyethylene glycol/poly(ethylene oxide) (PEG/PEO) calibration and toluene as the internal standard. Synthesis of Monomers. The syntheses of ethyl sinapate,46−49 sinapyl alcohol,44 syringaresinol (SYR),44 bis-epoxy-syringaresinol (SYR-EPO),46 ethyl dihydroferulate (IDF),50 IDF-EPO,50 IDFCC,50 and difurfurylamine (DIFFA)46 have been carried out following procedures previously described in the literature. Detailed procedures are available in the Supporting Information (SI). Carbonation Procedure. A solution of epoxy precursor SYR-EPO (5.05 g, 9.52 mmol), lithium bromide (41 mg, 0.476 mmol, 0.05 equiv) in DMF (20 mL) was sealed in a 100 mL autoclave. The system was stirred at 80 °C under 20 bar of carbon dioxide for 24 h. The solvent was removed by distillation and the crude product was solublized in ethyl acetate (150 mL) and washed with water (3 × 60 mL) to remove DMF traces. The organic phase was dried over

SYR-CC. White amorphous solid, 81% yield. 1H NMR (300 MHz, DMSO-d6) δ 3.07 (m, 2H, Hβ, Hβ′), 3.78 (s, 12H, H5, H5′), 3.84 (dd, 2H, J = 3.3 and 9.1 Hz, Hγ1, Hγ1′), 3.98 (dd, 4H, J = 3.5 and 11.9 Hz, H6), 4.14 (dd, 4H, J = 2.5 and 11.9 Hz, H6′), 4.21 (m, 2H, Hγ2, Hγ2′), 4.58 (m, 4H, H8, H8′), 4.69 (m, 2H, Hα, Hα′), 4.98 (m, 2H, H7, H7′), 6.66 (s, 4H, H2, H2′). 13C NMR (75 MHz, DMSO-d6) δ 53.8 (Cβ, Cβ′), 56.0 (C5, C5′), 65.8 (C8, C8′), 71.4 and 71.5 (C6, C6′ and Cγ, Cγ′), 75.6 (C7, C7′), 85.1 (Cα, Cα′), 102.9 (C2, C2′), 135.2 (C4, C4′), 137.8 (C1, C1′), 152.6 (C3, C3′), 155.0 (C = O). m.p. 63 °C. UV (nm, λmax): 270. FT-IR (neat, cm−1): νmax 2937 (C−Harom), 1786 (CO) 1400−1600 (CCarom), 1000−1300 (C−O−C). HRMS (TOF MS, ES+): m/z calcd for C30H34O14Na 641.1841; found 641.1838.

BPA-CC. White solid, 92% yield. 1H NMR (300 MHz, DMSO-d6) δ 1.58 (s, 6H, H2), 4.16 (dd, 2H, J = 4.5 and 11.3 Hz, H7), 4.24 (dd, 2H, J = 2.7 and 11.3 Hz, H7′), 4.38 (dd, 2H, J = 5.9 and 8.4 Hz, H9), 4.62 (t, 2H, J = 8.4 Hz, H9′), 5.13 (m, 2H, H8), 6.85 (d, 4H, H4), 7.12 (d, 4H, H5). 13C NMR (75 MHz, DMSO-d6) δ 30.7 (C2), 41.3 (C1), 66.1 (C9), 67.4 (C7), 74.9 (C8), 114.1 (C4), 127.6 (C5), 143.3 (C3), 154.9 (C10), 155.8 (C6). m.p.: 166 °C. UV(nm, λmax): 275. FT-IR (neat, cm−1): νmax 2980 (C−Harom), 1783 (COcarbonate), 1400−1600 (C Carom), 1000−1300 (C−O−C). HRMS (TOF MS, ES+): m/z calcd for C23H24O8Na: 451.1363; found: 451.1376. General Procedures for NIPU Syntheses. The cyclic carbonate precursor SYR-CC was melted around 80 °C, and the adequate amount of diamine (DA10, DIFFA, and IPDA) or triamine (TREN) was added. An equimolar ratio was chosen, considering that one fivemembered ring cyclic carbonate reacts only once with a primary amine. The system was then manually homogenized, transferred to a rubbery mold and cured. In order to avoid freezing of the system and to ensure optimal conversion, a temperature program was established. For example, for SYR-CC, the oven temperature was gradually increased by 10 °C.h−1 from 80 to 160 °C, then maintained at 160 °C for 18 h (temperature superior to the exothermic reaction peak observed in DSC scan). The different compositions and corresponding temperature programs are depicted in Table 1.

Table 1. Composition and Temperature Program of the Formulated Thermoplastics

8650

cyclic carbonate precursor (wt %)

curing agent (wt %)

BPA-CC (72) BPA-CC (75) IDF-CC (80) IDF-CC (83) SYR-CC (78) SYR-CC (73) SYR-CC (78) SYR-CC (81)

IPDA (28) TREN (25) IPDA (20) TREN (17) DA10 (22) DIFFA (27) IPDA (22) TREN (19)

temperature program 165 °C (5 h) 180 °C (18 h) 80 °C (5 h) 100 °C (10 h) 80 to 160 °C (10 °C·h−1) 160 °C (18 h)


Research Article

ACS Sustainable Chemistry & Engineering Scheme 1. Synthesis of Dicarbonate from Syringaresinol (SYR-CC)

a Three step procedure described by Jaufurally et al.44 and Janvier et al.46 bTEBAC (0.2 equiv), epichlorhydrin (20 equiv), 80 °C, 2 h, then NaOH (8 equiv), rt, 2 h (88%).46 cCO2 (40 bar), LiBr (0.1 equiv), DMF, 80 °C, 24 h (81%).

Figure 2. Structures of cyclic carbonates (BPA-CC, IDF-CC, SYR-CC), amines (DA10, DIFFA, IPDA, TREN), and resulting NIPU.

■

spectrum.46 This bisepoxy was then carbonated in the presence of a metallic salt catalyst (lithium bromide) under high pressure of carbon dioxide (PCO2 = 20 bar) at 80 °C. A complete

RESULTS AND DISCUSSION

Synthesis of Bisphenol SYR and Functionalization to Cyclic Carbonate. Syringaresinol (SYR) was prepared from syringaldehyde with a 62% overall yield via a three-step process (Scheme 1) including as key step the oxidative enzymatic dimerization of sinapyl alcohol.44 The enzyme-catalyzed dimerization was carried out under mechanical stirring combined with O2 bubbling for a better efficiency of the enzyme. SYR was engaged in the following step without further purification. Functionalization of bisphenol SYR toward epoxy precursor SYR-EPO was carried out in epichlorohydrin with a catalytic amount of triethylbenzylammonium chloride as phase transfer catalyst. A basic treatment with sodium hydroxide gave SYR-EPO with a functionality of 2.0 according to 1H NMR

conversion of oxiran rings was observed within 20 h, and SYRCC was obtained with a high purity and a functionality of 2.0 according to the 1H NMR spectrum. Similarly, IDF was obtained in a three-step procedure from ferulic acid, then glycidylated and carbonated to obtain IDFCC with a 48% overall yield.41 The same procedure was applied on commercially available DGEBA to obtain BPA-CC with a 92% yield. SYR-CC, IDF-CC, and BPA-CC were fully characterized by 1H and 13C NMR, UV, FT-IR and HRMS (see the Experimental Section and SI). 8651


Research Article


Figure 3. FT-IR analyses of (left) syringaresinol-based NIPU (right) BPA-based NIPU at different temperatures

Table 2. RI/II, Conversion, and Degree of Polymerization Estimated by 1H NMR primary OH

a

secondary OH

CH cyclic carbonate

NIPU composition

δ (in ppm)

integration

δ (in ppm)

integration

RI/II

δ (in ppm)

integration

conva(%)

DPn

BPA-CC IPDA IDF-CC IPDA SYR-CC DA10 SYR-CC DIFFA SYR-CC IPDA

5.23 5.20 4.90 4.97 4.98

0.70 0.67 0.95 0.43 0.99

4.94 3.57 3.55 3.38 3.57

0.57 1.57 1.11 1.88 1.87

1.22 0.20 0.86 0.23 0.53

5.13 5.09 4.98 4.9 4.98

0.30 0.26 0.34 0.21 0.27

85 87 83 90 87

6 7 5 9 6

Conversion is calculated via the formula: 100 −

I(1Hcyclo) I(1Harom)

× 100.

and/or chain scission may occur.2 Inversely, for both SYR-CC and BPA-CC, more robust, a higher temperature program was chosen (160 and 180 °C, respectively). Structural Analysis of the Polymers. FT-IR Analysis. The structures of the linear and cross-linked prepared NIPUs were first confirmed through FT-IR (Figure 3). The conversion was monitored by observing the disappearance of the carbonate signal (νCO,carbonate ≈ 1800 cm−1) and the appearance of that of the carbamate (νCO,carbamate ≈ 1700 cm−1, νNH ≈ 3400 cm−1) (Figure 3, left). This simple analysis allows a qualitative estimation of the conversion, very useful to adjust the polymerization temperature. For example, the FT-IR analysis of BPA-CC polymerized at different temperature showed an improvement of the conversion at higher temperature (Figure 3, right): the cyclic carbonate peak (γCO at 1783 cm−1) is more intense after polymerization at 100 °C than 180 °C. NMR Analyses. For all the linear NIPU synthesized, NMR analyses were carried out in DMSO-d6. The formation of urethane link was confirmed by 13C NMR spectroscopy, with the appearance of new peaks for the quaternary carbon of the

Synthesis of NIPU Thermoplastics and Thermosets in Bulk. For the preparation of NIPU thermoplastics (or thermosets), an equimolar ratio of dicarbonate and diamine (or triamine) was mixed, considering that one primary amine group will react with one cyclic carbonate (Figure 2). Different carbonates were chosen, allowing the comparison between oilsourced widely used BPA-CC, flexible biobased IDF-CC, and rigid biobased SYR-CC. For the choice of diamine, petro-based cycloaliphatic IPDA was chosen as reference, aliphatic DA10 (from castor oil) and aromatic DIFFA (from furfural) were used to synthesize fully biosourced NIPUs. For the thermosets curing, triamine TREN was chosen. Polyaddition were carried out in bulk in the molten state, following a temperature program adapted to each cycliccarbonate. IDF-CC was cured at the lower temperature (100 °C), to both ensure the homogeneity of the reaction media and avoid degradation of the fragile ester bond. A higher temperature curing is known to reduce the viscosity of the system and enhance the conversion. Nevertheless, higher temperature was not applied on IDF-CC as transamidation 8652


Research Article


Figure 4. Regioselectivity of the addition of amine on cyclic carbonate

Table 3. HPLC-SEC Analyses of NIPU NIPU composition

Mrepeat unit (g·mol−1)

conversion (%)

M n (kg·mol−1)

M w (kg·mol−1)

DPn

PDI

BPA-CC IPDA BPA-CC IPDA 100 °C IDF-CC IPDA SYR-CC DA10 SYR-CC DIFFA SYR-CC IPDA

599 599 873 791 853 789

88 81 88 78 93 90

3.0 2.0 3.0 5.4 5.3 4.6

8.4 3.0 4.5 26.7 16.8 13.4

5 3 3 6 6 6

2.9 1.5 1.5 4.9 3.2 2.9

flow marker. The molecular weights were determined according to polyethylene glycol/poly(ethylene oxide) (PEG/PEO) standards. The refractive index signal was used to create a calibration curve. The results are summed up in Table 3. For all the NIPU, high conversions were obtained (between 78 and 93%). In the case of IPDA, the degree of polymerization was slightly inferior for IDF-CC ( DPn = 3), but similar between BPA-CC and SYR-CC ( DPn = 5−6). In all cases, dispersity superior to 1.5 was obtained, as expected for polyaddition. In the case of BPA and SYR, higher dispersities were observed: these results seem to be correlated to the higher polymerization temperature. Indeed, polymerization of BPA-CC at lower temperature (100 °C instead of 160 °C) led to lower polydisperisty index (PDI 1.5 instead of 2.9). The differences of DPn values between NMR estimation and SEC are correlated to the choice of SEC calibration standard. Indeed, PEG does not have a similar molecular weight to NIPU, for a given hydrodynamic volume; the presence of hydrogen bonds in NIPU reduces the hydrodynamic radius compared to PEG. Thermal Characterization of the Polymers. The structural analyses of NIPU were completed with thermal characterization (TGA and DSC), and Table 4 sums up these results. Thermogravimetric Analyses. Thermal stability was assessed by TGA under inert atmosphere (N2) and oxidative atmosphere (air). Thermograms are depicted in Figure 5. Td5% is defined as the temperature at which the thermoplastic lost 5% w of its initial mass; w%char corresponds to the relative amount of stable residue at high temperature (700 °C). The behavior of NIPU prepared under heating showed a one-step degradation under inert atmosphere (Figure 5, top) and a twostep process under oxidative atmosphere (Figure 5, bottom). Table 4 sums up the values of Td5% and w%char of the NIPU prepared. The thermoplastics prepared from syringaresinol displayed good thermal stability, with a range of Td5% from 267 to 280 °C. This stability is similar to the stability of both IDFand BPA-based NIPUs. For the thermoset materials, similar Td5% were obtained for SYR-, IDF-, and BPA-based resins (ranging from 225 to 254 °C).

carbonyl moiety (at 156.0 and 156.4 ppm for SYR-CC-based NIPU, when resonance of the carbonyl group of the starting carbonates was observed at 155.0 ppm). In 1H NMR spectra, the appearance of peaks between 7.1 and 7.7 ppm corresponds to the NH of the urethane moiety obtained by ring opening. The 1H NMR gives access to an estimated conversion, calculated with the integration of the signal at 4.98 ppm corresponding to the residual unreacted SYR-CC (proton of the tertiary carbon of the cyclic carbonate group). Conversions are depicted in Table 2. NMR analyses also provide information on the regioselectivity of the ring opening polyaddition. As depicted in Figure 4, the nucleophilic attack of the primary amine on cyclic carbonate moiety gives access to both primary and secondary alcohols. The signal of primary alcohol at 4.8−5.0 ppm and that of secondary OH at 3.38−3.57 ppm in the case of SYR-CC were attributed thanks to 2D NMR (COSY, HSQC and HMBC) and hydrogen−deuterium exchange. The ratio of primary and secondary hydroxyl groups (RI/II) can thus be defined by the alcohols signals integrations ratio, as described in literature, and results are summed up in Table 2. RI/II values show the preferential formation of secondary alcohol compared to primary. This observation is in accordance with the literature,7,9,51 which established that the presence of an electro-withdrawing group (PhOCH2−) promotes a selectivity toward secondary alcohol. The careful examination of 1H NMR spectra shows no evidence of unreacted amine, so that we could assess that residual cyclic carbonates are end-chain groups. This hypothesis allows the calculation of the degree of polymerization. For instance, in the case of the NIPU SYR-CC DA10, the 83% conversion would be equivalent to 10 opened carbonates for 2 closed end-of-chain cyclic carbonates, corresponding to a DPn of 5. For all the NIPUs synthesized, similar DPn values were obtained (between 5 and 7), except for the couple DIFFA SYR-CC which offered a higher DPn of 9. Size Exclusion Chromatography. NMR analyses were then completed with SEC. For the SEC analyses, thermoplastic NIPUs obtained were solubilized in DMF, using toluene as a 8653


Research Article


(about 20 °C lower). Moreover, thermal degradation under air was total with the different materials, allowing full incineration for products end-life. Differential Scanning Calorimetry Analyses. To assess the glass transition temperatures (Tg) of the prepared NIPU, DSC analyses were carried out. DSC curves of prepared NIPUs are presented in ESI and results are summarized in Table 4. For the same cyclocarbonate precursor (SYR-CC), the choice of diamines offers a wide range of Tg, from 62 °C with flexible aliphatic DA10 to 98 °C for more rigid cyclic IPDA. For the same amine used (IPDA), IDF-based linear NIPU offered the lowest Tg (62 °C) due to the flexibility of the aliphatic chain of the esters. The same trend was previously observed for epoxyamine resins.46 Interestingly, in the case of NIPU thermoplasitcs, the rigidity of syringaresinol offered the highest Tg, 20 °C higher than BPA. For NIPU thermosets, IDF offered the lower Tg (47 °C) while SYR reached BPA value. Moreover, Miller et al.52 had already described a rise of Tg linked to the presence of methoxy groups on the aromatic monomer, due to an increase of conformational barriers for chain motion. Interestingly the same trend was observed in our study, showing higher Tg for SYR (two methoxy) compared to IDF (one methoxy). Unfortunately, both thermoplastics and thermosets prepared were too brittle for further mechanical analysis (by DMA).

Table 4. Thermal Characterization of NIPU prepared from BPA-CC, IDF-CC, and SYR-CC Td5% (°C)

w%char (%)

NIPU composition

N2b

airc

N2b

airc

Tg (°C)d

BPA-CC IPDA BPA-CC TREN IDF-CC IPDA IDF-CC TREN SYR-CC DA10 SYR-CC DIFFA SYR-CC IPDA SYR-CC TREN

276 254 264a 228 280 267 273 225

274 243 260a 228 261 247 271 225

2 2 10a 15 19 28 21 24

0.20 0.32 0.17a 0.19 0.48 0.18 0.12 0.26

79 63 62a 47 62 73 98 62

a As described by Ménard et al.41 bDetermined by TGA (10 °C·min−1, N2 flow). cDetermined by TGA (10 °C·min−1, air flow). dDetermined by DSC on the second heat−cool−heat cycle (10 °C·min−1, N2 flow).

■

CONCLUSIONS

A renewable aromatic cyclic carbonate (SYR-CC) was synthesized in excellent yield and purity from syringaresinol, a bisphenol readily obtained at the multigram scale via an efficient chemo-enzymatic pathway from syringaldehyde. This nonendocrine disruptive biosourced bisphenol was studied as an interesting and genuinely safe alternative to BPA. In this purpose, SYR-CC was polymerized in bulk with different diamines, providing fully biobased linear NIPUs, with high conversion and average molar mass (4.6−5.4 × 103 g mol−1, corresponding to DPn = 6). The polyhydroxyurethane structures were confirmed by FT-IR and NMR analyses. For the thermal characterization, SYR-CC was compared to two other bisphenols: IDF-CC from biosourced ferulic acid and widely used BPA-CC from oil. The analyses of SYR-CC NIPUs demonstrated tunable glass transition and degradation temperatures by varying the diamine nature (up to Tg = 98 °C and Td5% = 280 °C) competing with that of BPA (Tg = 79 °C and Td5% = 276 °C). The stiffness of syringaresinol thus compensated for the low DPn observed to obtain high mechanical properties. In the case of DIFFA and DA10, the polymers were fully prepared from renewable feedstocks and could be envisaged as sustainable substitutes to conventional petro-based polyurethanes. Additionally, NIPU thermosets were obtained by coupling SYR-CC with the triamine TREN, showing thermal properties comparable to similar BPA-based resins. In addition to ADMET45 and epoxy amine resine46 applications, this study thus confirms the great potential of syringaresinol as a greener and safer alternative to BPA. To further explore the potential of syringaresinol use in polymers, α,ω-diene derivatives of syringaresinol are currently being investigated for thiol−ene coupling polymerization, and results will be reported in due course.

Figure 5. TGA analyses of NIPU prepared from BPA-CC, IDF-CC, SYR-CC: (top) under N2; (bottom) under air.

Concerning the high temperature char content w%char, the DIFFA containing NIPU offers the highest char content and the DA10 the lowest. This trend is in accordance with the structure of the amine: during the thermal degradation, aromatic moiety (e.g., furanic rings of DIFFA) is favorable to the charring mechanism, contrary to aliphatic chains. When comparing the NIPUs with regards to IPDA, BPA-CC exhibits the lowest char content (2%) whereas both IDF-CC and SYRCC display the highest (10 and 21%, respectively). The same trend is observed for the thermosets obtained with TREN. These high char contents could be interesting in the case of flame retardant applications. Interestingly, the TGA analyses under air revealed quiet similar thermal stability for both IPDA and TREN. In the case of DA10 and DIFFA, the presence of air implies lower Td5% 8654


Research Article


■

(12) Beniah, G.; Liu, K.; Heath, W. H.; Miller, M. D.; Scheidt, K. A.; Torkelson, J. M. Novel thermoplastic polyhydroxyurethane elastomers as effective damping materials over broad temperature ranges. Eur. Polym. J. 2016, 84, 770−783. (13) Tamami, B.; Sohn, S.; Wilkes, G. L. Incorporation of carbon dioxide into soybean oil and subsequent preparation and studies of nonisocyanate polyurethane networks. J. Appl. Polym. Sci. 2004, 92 (2), 883−891. (14) Mann, N.; Mendon, S. K.; Rawlins, J. W.; Thames, S. F. Synthesis of Carbonated Vernonia Oil. J. Am. Oil Chem. Soc. 2008, 85, 791−796. (15) Mahendran, A. R.; Aust, N.; Wuzella, G.; Müller, U.; Kandelbauer, A. Bio-Based Non-Isocyanate Urethane Derived from Plant Oil. J. Polym. Environ. 2012, 20, 926−931. (16) Bähr, M.; Bitto, A.; Mülhaupt, R. Cyclic limonene dicarbonate as a new monomer for non-isocyanate oligo- and polyurethanes (NIPU) based upon terpenes. Green Chem. 2012, 14 (5), 1447−1454. (17) Cornille, A.; Dworakowska, S.; Bogdal, D.; Boutevin, B.; Caillol, S. A new way of creating cellular polyurethane materials. Eur. Polym. J. 2015, 66, 129−138. (18) Samanta, S.; Selvakumar, S.; Bahr, J.; Wickramaratne, D. S.; Sibi, M.; Chisholm, B. J. Synthesis and Characterization of Polyurethane Networks Derived from Soybean-Oil-Based Cyclic Carbonates and Bioderivable Diamines. ACS Sustainable Chem. Eng. 2016, 4, 6551− 6561. (19) Rokicki, G.; Kuran, W. Cyclic carbonates obtained by reactions of alkali metal carbonates with epihalohydrins. Bull. Chem. Soc. Jpn. 1984, 57 (6), 1662−1666. (20) Reithofer, M. R.; Sum, Y. N.; Zhang, Y. Synthesis of cyclic carbonates with carbon dioxide and cesium carbonate. Green Chem. 2013, 15 (8), 2086−2090. (21) Liang, S.; Liu, H.; Jiang, T.; Song, J.; Yang, G.; Han, B. Highly efficient synthesis of cyclic carbonates from CO2 and epoxides over cellulose/KI. Chem. Commun. 2011, 47 (7), 2131−2133. (22) Paddock, R. L.; Nguyen, S. T. Chemical CO2 fixation: CR(III) salen complexes as highly efficient catalysts for the coupling of CO2 and epoxides. J. Am. Chem. Soc. 2001, 123 (46), 11498−11499. (23) Buchard, A.; Kember, M. R.; Sandeman, G.; Williams, C. K. A bimetallic iron (III) catalyst for CO2/epoxide coupling. Chem. Commun. 2011, 47, 212−214. (24) Yu, K. M. K.; Curcic, I.; Gabriel, J.; Morganstewart, H.; Tsang, S. C. Catalytic Coupling Of CO2 With Epoxide Over Supported And Unsupported Amines. J. Phys. Chem. A 2010, 114 (11), 3863−3872. (25) Liu, S.; Suematsu, N.; Maruoka, K.; Shirakawa, S. Design of bifunctional quaternary phosphonium salt catalysts for CO2 fixation reaction with epoxides under mild conditions. Green Chem. 2016, 18 (17), 4611−4615. (26) Ochiai, B.; Satoh, Y.; Endo, T. Nucleophilic polyaddition in water based on chemo-selective reaction of cyclic carbonate with amine. Green Chem. 2005, 7 (11), 765−767. (27) Ochiai, B.; Kojima, H.; Endo, T. Synthesis and properties of polyhydroxyurethane bearing silicone backbone. J. Polym. Sci., Part A: Polym. Chem. 2014, 52 (8), 1113−1118. (28) Javni, I.; Hong, D. P.; Petrovic, Z. S. Soy-Based Polyurethanes by Nonisocyanate Route. J. Appl. Polym. Sci. 2008, 108 (6), 3867− 3875. (29) Bähr, M.; Mülhaupt, R. Linseed and soybean oil-based polyurethanes prepared via the non-isocyanate route and catalytic carbon dioxide conversion. Green Chem. 2012, 14 (2), 483−489. (30) Carré, C.; Bonnet, L.; Avérous, L. Original biobased nonisocyanate polyurethanes: solvent- and catalyst-free synthesis, thermal properties and rheological behaviour. RSC Adv. 2014, 4, 54018−54025. (31) Carré, C.; Bonnet, L.; Avérous, L. Solvent- and catalyst-free synthesis of fully biobased nonisocyanate polyurethanes with different macromolecular architectures. RSC Adv. 2015, 5 (121), 100390− 100400. (32) Boyer, A.; Cloutet, E.; Tassaing, T.; Gadenne, B.; Alfos, C.; Cramail, H. Solubility in CO2 and carbonation studies of epoxidized

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.7b01271. Complementary procedures, 1H and 13C NMR spectra, FT-IR spectra, HPLC-SEC chromatograms, and DSC traces (PDF)

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (M.J.). *E-mail: [email protected] (P.-H.D.). *E-mail: fl[email protected] (F.A.). ORCID

Florent Allais: 0000-0003-4132-6210 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors are grateful to the Région Champagne−Ardenne, the Conseil Départemental de la Marne, and Reims Métropole for their financial support.

■

REFERENCES

(1) Nohra, B.; Candy, L.; Blanco, J.-F.; Guerin, C.; Raoul, Y.; Mouloungui, Z. From petrochemical polyurethanes to biobased polyhydroxyurethanes. Macromolecules 2013, 46 (10), 3771−3792. (2) Maisonneuve, L.; Lamarzelle, O.; Rix, E.; Grau, E.; Cramail, H. Isocyanate-Free Routes to Polyurethanes and Poly(hydroxy Urethane)s. Chem. Rev. 2015, 115 (22), 12407−12439. (3) Sardon, H.; Pascual, A.; Mecerreyes, D.; Taton, D.; Cramail, H.; Hedrick, J. L. Synthesis of polyurethanes using organocatalysis: A perspective. Macromolecules 2015, 48 (10), 3153−3165. (4) ECHA (European Chemical Agency). Methylenediphenyl diisocyanate (MDI) including−Substance Information−Restriction List (Annex XVII)−ECHA. https://echa.europa.eu/substanceinformation/-/substanceinfo/100.239.193 (accessed Feb 9, 2017). (5) Kihara, N.; Endo, T. Synthesis and properties of poly(hydroxyurethane)s. J. Polym. Sci., Part A: Polym. Chem. 1993, 31 (11), 2765−2773. (6) Kihara, N.; Kushida, Y.; Endo, T. Optically active poly(hydroxyurethane)s derived from cyclic carbonate and L-lysine derivatives. J. Polym. Sci., Part A: Polym. Chem. 1996, 34 (11), 2173−2179. (7) Tomita, H.; Sanda, F.; Endo, T. Structural analysis of polyhydroxyurethane obtained by polyaddition of bifunctional fivemembered cyclic carbonate and diamine based on the model reaction. J. Polym. Sci., Part A: Polym. Chem. 2001, 39 (6), 851−859. (8) Tomita, H.; Sanda, F.; Endo, T. Polyaddition behavior of bis(fiveand six-membered cyclic carbonate)s with diamine. J. Polym. Sci., Part A: Polym. Chem. 2001, 39 (6), 860−867. (9) Tomita, H.; Sanda, F.; Endo, T. Model reaction for the synthesis of polyhydroxyurethanes from cyclic carbonates with amines: Substituent effect on the reactivity and selectivity of ring-opening direction in the reaction of five-membered cyclic carbonates with amine. J. Polym. Sci., Part A: Polym. Chem. 2001, 39 (21), 3678−3685. (10) Figovsky, O. L.; Shapovalov, L. D. Features of reaction aminocyclocarbonate for production of new type nonisocyanate polyurethane coatings. Macromol. Symp. 2002, 187, 325−332. (11) Cornille, A.; Michaud, G.; Simon, F.; Fouquay, S.; Auvergne, R.; Boutevin, B.; Caillol, S. Promising mechanical and adhesive properties of isocyanate-free poly(hydroxyurethane). Eur. Polym. J. 2016, 84, 404−420. 8655


Research Article


(52) Nguyen, H. T. H.; Miller, S. A.; et al. Polyethylene ferulate (PEF) and congeners: polystyrene mimics derived from biorenewable aromatics. Green Chem. 2015, 17 (9), 4512−4517.

fatty acid diesters: towards novel precursors for polyurethane synthesis. Green Chem. 2010, 12 (12), 2205−2213. (33) Maffini, M. V.; Rubin, B. S.; Sonnenschein, C.; Soto, A. M. Endocrine disruptors and reproductive health: The case of bisphenolA. Mol. Cell. Endocrinol. 2006, 254−255, 179−186. (34) Chen, M.-Y.; Ike, M.; Fujita, M. Acute toxicity, mutagenicity, and estrogenicity of bisphenol-A and other bisphenols. Environ. Toxicol. 2002, 17 (1), 80−86. (35) Food Additives & Ingredients. Bisphenol A (BPA): Use in Food Contact Application. http://www.fda.gov/Food/ IngredientsPackagingLabeling/FoodAdditivesIngredients/ucm064437. htm. (36) Nelson, A. M.; Long, T. E. A perspective on emerging polymer technologies for bisphenol-A replacement. Polym. Int. 2012, 61 (10), 1485−1491. (37) Boerjan, W.; Ralph, J.; Baucher, M. Lignin biosynthesis. Annu. Rev. Plant Biol. 2003, 54 (1), 519−546. (38) Chen, Q.; Gao, K.; Peng, C.; Xie, H.; Zhao, Z. K.; Bao, M. Preparation of lignin/glycerol-based bis(cyclic carbonate) for the synthesis of polyurethanes. Green Chem. 2015, 17 (9), 4546−4551. (39) Fache, M.; Darroman, E.; Besse, V.; Auvergne, R.; Caillol, S.; Boutevin, B. Vanillin, a promising biobased building-block for monomer synthesis. Green Chem. 2014, 16 (4), 1987−1998. (40) Pion, F.; Reano, A. F.; Ducrot, P.-H.; Allais, F. Chemoenzymatic preparation of new bio-based bis- and trisphenols: new versatile building blocks for polymer chemistry. RSC Adv. 2013, 3 (23), 8988−8997. (41) Ménard, R.; Caillol, S.; Allais, F. Chemo-Enzymatic Synthesis and Characterization of Renewable Thermoplastic and Thermoset Isocyanate-Free Poly(hydroxy)urethanes from Ferulic Acid Derivatives. ACS Sustainable Chem. Eng. 2017, 5 (2), 1446−1456. (42) El-Desouky, S. K.; Gamal-Eldeen, A. M. Cytotoxic and antiinflammatory activities of some constituents from the floral buds of Syringa patula. Pharm. Biol. 2009, 47 (9), 872−877. (43) Monthong, W.; Pitchuanchom, S.; Nuntasaen, N.; Pompimon, W. (+)-Syringaresinol lignan from new species Magnolia thailandica. Am. J. Appl. Sci. 2011, 8 (12), 1268−1271. (44) Jaufurally, A. S.; Teixeira, A.; Hollande, L.; Allais, F.; Ducrot, P.H. Optimization of the laccase-catalyzed synthesis of (±)-syringaresinol and study of its thermal and antiradical activities. Chem. Sel. 2016, 1, 5165−5171. (45) Hollande, L.; Jaufurally, A. S.; Ducrot, P.-H.; Allais, F. ADMET polymerization of biobased monomers deriving from syringaresinol. RSC Adv. 2016, 6, 44297−44304. (46) Janvier, M.; Hollande, L.; Jaufurally, A. S.; Pernes, M.; Ménard, R.; Grimaldi, M.; Beaugrand, J.; Balaguer, P.; Ducrot, P.-H.; Allais, F. Syringaresinol: A Renewable and Safer Alternative to Bisphenol A for Epoxy-Amine Resins. ChemSusChem 2017, 10, 738−746. (47) Gaspar, A.; Martins, M.; Silva, P.; Garrido, E. M.; Garrido, J.; Firuzi, O.; Miri, R.; Saso, L.; Borges, F. Dietary phenolic acids and derivatives. Evaluation of the antioxidant activity of sinapic acid and its alkyl esters. J. Agric. Food Chem. 2010, 58 (21), 11273−11280. (48) Sakakibara, N.; Nakatsubo, T.; Suzuki, S.; Shibata, D.; Shimada, M.; Umezawa, T. Metabolic analysis of the cinnamate/monolignol pathway in Carthamus tinctorius seeds by a stable-isotope-dilution method. Org. Biomol. Chem. 2007, 5, 802−815. (49) Mouterde, L. M. M.; Flourat, A. L.; Cannet, M. M. M.; Ducrot, P.-H.; Allais, F. Chemoenzymatic total synthesis of a naturally occurring (5−5′)/(8′-O-4″) dehydrotrimer of ferulic acid. Eur. J. Org. Chem. 2013, 2013, 173−179. (50) Ménard, R.; Caillol, S.; Allais, F. Ferulic acid-based renewable esters and amides-containing epoxy thermosets from wheat bran and beetroot pulp: Chemo-enzymatic synthesis and thermo-mechanical properties characterization. Ind. Crops Prod. 2017, 95, 83−95. (51) Steblyanko, A.; Choi, W.; Sanda, F.; Endo, T. Addition of fivemembered cyclic carbonate with amine and its application to polymer synthesis. J. Polym. Sci., Part A: Polym. Chem. 2000, 38 (13), 2375− 2380. 8656


Isocyanate-Free Synthesis and Characterization of Renewable Poly

Recommend Documents