Polyesters and Poly(ester-urethane)s from Biobased Difuranic Polyols

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Polyesters and Poly(ester-urethane)s from Bio-based Difuranic Polyols Zehuai Mou, and Eugene Y.-X. Chen ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.6b02007 • Publication Date (Web): 12 Oct 2016 Downloaded from http://pubs.acs.org on October 18, 2016

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ACS Sustainable Chemistry & Engineering

Polyesters and Poly(ester-urethane)s from Bio-based Difuranic Polyols Zehuai Mou and Eugene Y.-X. Chen* Department of Chemistry, Colorado State University, 1301 Center Avenue, Fort Collins, Colorado 80523-1872, -United State ABSTRACT: This contribution investigates the impact of rigid and flexible difuranic polyols on the resulting polyester (PE) and poly(ester-urethane) (PEU) properties. Three bio-based difuranic polyol monomers, 5,5’-bihydroxymethyl furil (BHMF), 5,5’-dihydroxymethyl furoin (DHMF), and bis[5-(hydroxymethyl)furan-2-yl)methyl]adipate (BHFA), all derived from the biomass platform chemical 5-hydroxymethylfurfural (HMF), were employed for the synthesis of a series of new linear and cross-linked PEs as well as amorphous and semicrystalline PEUs. The polycondensations of diols (rigid BHMF and flexible BHFA) with various diacyl chlorides afford linear PEs, whereas the rigid triol (DHMF) reacts with diacyl chlorides to form crosslinked PEs. Among these difuranic PEs, the most intriguing PE is the one containing C=C double bonds, derived from BHFA and fumaryl chloride, which exhibits the unique self-curing ability via the Diels-Alder reaction. Furthermore, the catalyzed polyaddition of BHFA with various diiscyanates produces novel PEUs, the most interesting of which is the one derived from BHFA and hexamethylene diisocyanate, a semicrystalline material displaying a high melting-transition temperature of 135.8 oC.

KEYWORDS:

5-hydroxymethylfurfural,

polycondensation,

polyaddition,

polyester,

polyurethane, poly(ester-urethane)

ACS Paragon Plus Environment

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INTRODUCTION There has been an increasing interest in developing more environmentally friendly and renewable polymeric materials from biomass-based monomers as alternatives to petroleumbased polymers because of depleting fossil resources and environmental concerns.1,2 Among such biomass resources, 5-hydroxymethyl furfural (HMF) is considered as one of the most promising biofuran-based platform chemical, which is readily derived from carbohydrates such as fructose, glucose, sucrose and cellulose.3-8 Numerous efforts have been made to convert HMF into

bifunctional

monomers,

especially

2,5-furandicarboxylic

acid9-14

and

2,5-

bis(hydroxymethyl)furan.15-19 The former is a promising alternative to terephthalic acid for polyesters (PEs),20-24 and poly(ethylene 2,5-furandicarboxylate) has been reported, which possessed comparable properties with poly(ethylene terephthalate) (PET).25 The latter has also been widely employed to prepare PEs and polyurethanes (PUs).26-28 Moreover, etherification of two HMF molecules afforded difuranic dialdehyde, 5-oxy(bis-methylene)-2-furaldehyde, which was used to prepare imine-based polymers with high thermal and electrical conductivity.29 In organic synthesis, furan-based compounds are widely used as a diene to react with an appropriate dienophile via Diels-Alder reaction.30-37 In the polymeric materials field, by using the thermal reversible Diels-Alder cycloaddition between furan rings and maleimides,38, 39 polymers with recyclability,40 shape memory41-44 or healing ability were exploited.45-47 For example, Wudl and co-workers employed a four-furan based monomer as a multi-diene and a three-maleimide compound as a multi-dienophile to develop a self-remendable polymeric material under mild conditions.48 Yoshie and co-workers prepared 2,5-bis(hydroxymethyl)furan based (co)polyesters and systematically investigated the self-healing ability in the presence of a series of maleimides.27,49,50 Our group reported a novel furan-based unsaturated PE bearing C=C bonds,


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prepared by the proton-transfer polymerization of furfural dimethacrylate, which showed the unique self-curing ability (without any additional curing agents) to cross-linked material.51 We have been particularly interested in rigid difuranic compounds such as 5,5’dihydroxymethyl furoin (DHMF)52 and 5,5’-bihydroxymethyl furil (BHMF),53 conveniently prepared from self-condensation coupling of HMF and selective oxidation, as building blocks for diesel and jet fuels8, 54, 55 and polymeric materials such as PUs,53 respectively. In this contribution, we report the synthesis of a series of linear and cross-linked PEs derived from difuranic polyol monomers, the diol BHMF and the triol DHMF, respectively. In addition, a new difuranic diol, bis[5-(hydroxymethyl)furan-2-yl)methyl]adipate (BHFA), was synthesized from HMF, and subsequently employed to produce unsaturated PEs bearing C=C double bonds as well as amorphous and semicrystalline poly(ester-urethane)s (PEUs). Among these difuranic polyol monomers, two of them (BHMA and DHMF) contain a rigid difuranic moiety, while the third (BHFA) has two furan rings separated by a flexible linker, thereby providing a specifically designed platform to investigate the effects of both rigid and flexible difuranic polyols on the properties of the resulting PEs and PEUs.

EXPERIMENTAL SECTION Materials. All the synthesis and manipulations of air- and moisture-sensitive materials were carried out in flamed Schlenk-type glassware on a high-vacuum line or in a dry inert gas (N2 or Ar) filled glovebox. Hexamethylenediisocyanate (HDI), isophoronediisocyanate (IPDI), 2,4-toluenediisocyanate (TDI), diphenylmethanediisocyanate (MDI), anddibutyltindilaurate (DBTDL) were purchased from Sigma-Aldrich and used as received. Succinyl chloride (SC), adipoyl chloride (AC), terephthaloyl chloride (TC), fumaryl chloride (FC), activated manganese


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dioxide (MnO2), and sodium borohydride (NaBH4) were purchased from Alfa Aesar; liquid diacyl chlorides (SC, AC and FC) were freshly distilled before use, while other chemicals were used as received. 5-Hydroxymethylfurfural (HMF) was purchased from Ark Pharm and used as received. Triol 5,5’-dihydroxymethyl furoin (DHMF)52 and diol 5,5’-bihydroxymethyl furil (BHMF)53 were prepared from HMF according to their respective literature procedures. HPLCgrade dichloromethane (DCM) was sparged extensively with nitrogen during filling of the solventreservoir and then dried by passage through activated alumina stainless steel columns.Tetrahydrofuran (THF) was dried by distillation over sodium with benzophenone as indicator under a nitrogen atmosphere, while N,N-dimethyl formamide (DMF) and deuterated dimethyl sulfoxide (DMSO-d6) were degassed, dried over CaH2, filtered, vacuum-distilled, and stored in a glovebox over activated Davison 4 Å molecular sieves. Methods. NMR spectra ware recorded on a Varian Inova spectrometer (400 MHz for 1H NMR and 100 MHz for 13C NMR). Chemical shifts for 1H and 13C NMR spectra were referenced in ppm relative totetramethylsilane with the solvent residual resonances as the internal standard (DMSO-d6: δ 2.50 ppm for 1H NMR and 39.52 ppm for NMR and 77.16 ppm for

13

C NMR; CDCl3: δ7.26 ppm for 1H

13

C NMR). High-resolution mass spectrometry (HRMS) data were

collected on an Agilent 6220 Accurate time-of-flight LC/MS spectrometer. Fourier transform infrared (FTIR) spectroscopy was performedon a Thermoscientific (Nicolet iS50) FT-IR spectrometer equipped with a diamond attenuated totalreflectance (ATR) at room temperature in the range of 550–4000 cm-1. Polymer number-average molecular weight (Mn) and dispersity (Đ = Mw/Mn) were measured by gel permeation chromatography (GPC) analyses carried out at 40 ºC and a flow rate of 1.0 mL/min, with DMF as the eluent on a Waters University 1500 GPC instrument equipped with one PLgel 5 µm guard and three PLgel 5 µm mixed-C columns


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(Polymer Laboratories; linear range of MW = 200–2,000,000). The instrument was calibrated with 10 PMMA standards, and chromatograms were processed with Waters Empower software (version 2002). Thermal properties of the polymers were measured by a TA Q50 thermal gravimetric analyzer (TGA), a TA Q20 differential scanning calorimetry (DSC) analyzer under dry nitrogen flow of 40 mL/min. For TGA analysis, polymer samples were heated from ambient temperature to 750 oC at a heating rate of 10 oC/min under anitrogen atmosphere. For DSC analysis, polymer samples were first heated from room temperature to 150 oC at 10 oC/min, equilibrated at this temperature for 3 min, then cooled down to –50 oC at 10 oC/min, held at this temperature for 3 min, and reheated to 200 oC at 10 oC/min. The glass transition temperature (Tg), crystallization temperature (Tc) and melting temperature (Tm) were obtained from the second heating cycle, after removing the thermal history of the samples. Synthesis of bis[5-(hydroxymethyl)furan-2-yl)methyl]adipate (BHFA): In a 500 mLSchlenk flask, HMF (3.78 g,30 mmol) and pyridine (2.45 g, 31 mmol) were dissolved in 150 mL of DCM, and the flask was placed in an ice water bath. To this mixture, adipoyl chloride (15 mmol, 2.74 g) was added dropwise at 0 oC, and then the ice water bath was removed and the resulting solution was stirred at room temperature for 12 h, after which time 200 mL of distilled water was added, and the organic phase was separated. The aqueous phase was extracted with DCM twice (30 mL × 2), and the combined organic phase was evaporated to give a light yellow solid. The solid was redissolved in 150 mL of THF, to which an aqueous solution of NaBH4 (30 mmol, 1.14 g) was added dropwise at room temperature, and the resulting mixture was stirred for 12 h. The solvent was removed by rotary evaporation, and then 150 mL of ethyl acetate and 200 mL of distilled water were added. The organic phase was separated, and the aqueous phase was extracted with ethyl acetate (30 mL × 3). The organic solutions were combined and dried over


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anhydrous MgSO4. Removing the MgSO4 by filtration and the volatile by rotary evaporation afforded the crude product, which was further purified by column chromatograph on silica gel (ethyl acetate/hexane: 2/1). The yield was 4.56 g (83%). 1H NMR (400 MHz, DMSO-d6): δ 6.43 (d, J = 3.04 Hz, 2H; furan-H), 6.25 (d, J = 3.04 Hz, 2H; furan-H), 5.23 (t, J = 5.75 Hz, 2H; -OH), 5.00 (s, 4H; furan-CH2), 4.36 (d, J = 5.75 Hz, 4H; furan-CH2-OH), 2.32 (m, 4H; -CH2-), 1.52 ppm (m, 4H; -CH2-). 1H NMR (400 MHz, CDCl3): δ 6.34 (d, J = 2.80 Hz, 2H; furan-H), 6.25 (d, J = 2.80 Hz, 2H; furan-H), 5.03 (s, 4H; furan-CH2), 4.36 (s, 4H; furan-CH2-OH), 2.33 (m, 4H; CH2-), 2.08 (s, 2H; -OH), 1.63 ppm (m, 4H; -CH2-). 13C NMR (100 MHz, DMSO-d6): δ 172.34, 156.21, 148.48, 111.42, 107.73, 57.60, 55.64, 32.92, 23.77 ppm. HRMS calculated for C18H26O8N [M + NH4]+: 384.1653;found: 384.1648. Synthesis of Linear PEs. A typical procedure for the synthesis of linear PEs is described as follows. To a stirred THF solution of BHMF or BHFA (1.0 mmol) and diacyl chloride (1.0 mmol) was added dropwise a THF solution of pyridine or triethylamine (TEA) (2.2 mmol) at room temperature under nitrogen atmosphere. After 24 h, the suspension was poured into 100 mL methanol, and the resulting PE (PE-1 from BHMF or PE-2 from BHFA) was collected by centrifugation and dried in vacuo for 24 h. PE-1a: Succinyl chloride (1.0 mmol, 0.155 g), isolated yield (0.278 g, 83%). 1H NMR (400 MHz, DMSO-d6): δ 7.63 (m, 2H; furan-H), 6.83 (m, 2H; furan-H), 5.20 (s, 4H; furan-CH2), 2.67 ppm (s, 4H; -CH2CH2-).

13

C NMR (100 MHz, DMSO-d6): δ 176.94, 171.40, 157.02, 148.50,

125.83, 113.32, 57.75, 28.33 ppm. PE-1b: Adipoyl chloride (1.0 mmol, 0.183 g), isolated yield (0.305g, 84%). 1H NMR (400 MHz, CDCl3): δ 7.60 (d, J = 3.6 Hz, 2H; furan-H), 6.60 (d, J = 3.6 Hz, 2H; furan-H), 5.15 (s, 4H;


6

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furan-CH2), 2.39 (m, 4H; -CH2-), 1.67 ppm (m, 4H; -CH2-).

13

C NMR (100 MHz, CDCl3): δ

176.42, 172.50, 157.06, 149.27, 125.70, 112.95, 57.82, 33.51, 24.15 ppm. PE-1c: Terephthaloyl chloride (1.0 mmol, 0.203 g), isolated yield (0.342 g, 90%). 1H NMR (400 MHz, DMSO-d6): δ 8.11~8.07 (m, 4H; Ph-H), 7.66 (s, 2H; furan-H), 6.95 (s, 2H; furan-H), 5.50 ppm (s, 4H; furan-CH2). PE-2a: Succinyl chloride (1.0 mmol, 0.155 g), isolated yield (0.306 g, 68%). 1H NMR (400 MHz, CDCl3): δ 6.38 (s, 4H; furan-H), 5.04 (s, 4H; furan-CH2), 5.03 (s, 4H; furan-CH2), 2.66 (s, 4H; -CH2-), 2.34 (m, 4H; -CH2-), 1.65 ppm (m, 4H; -CH2-).

13

C NMR (100 MHz, CDCl3):

δ172.87, 171.84, 150.34, 150.04, 111.73, 111.61, 58.44, 58.06, 33.74, 28.99, 24.29 ppm. PE-2b: Fumaryl chloride (1.0 mmol, 0.152 g), isolated yield (0.304 g, 68%). 1H NMR (400 MHz, CDCl3): δ 6.88 (s, 2H; CH=CH), 6.40 (d, J = 3.05 Hz, 2H; furan-H), 6.37 (d, J = 3.05 Hz, 2H; furan-H), 5.15 (s, 4H; furan-CH2), 5.02 (s, 4H; furan-CH2), 2.34 (m, 4H; -CH2-), 1.65 ppm (m, 4H; -CH2-). 13C NMR (100 MHz, CDCl3): δ172.85, 164.38, 150.62, 149.43, 133.77, 112.22, 111.54, 58.88, 58.02, 33.74, 24.29 ppm. Synthesis of Cross-linked PEs. A typical procedure for the synthesis of cross-linked PEs from DHMF is described as follows. A suspension of DHMF (1.0 mmol) and diacyl chloride in THF (7 mL) was heated to 50 oC to obtain a clear solution, and then cooled down to room temperature. To this solution was added dropwise under nitrogen atmosphere while stirring a THF (3 mL) solution of pyridine. Upon mixing of the above two solutions, precipitates formed immediately. After 24 h, the resulting suspension was poured into 100 mL methanol, and the PE product was collected by centrifugation and dried in vacuo for 24 h. Synthesis of Linear PEUs. A typical procedure is shown as follows. BHFA (0.183 g,0.5 mmol) and a diisocyanate (0.5 mmol) were dissolved in 5 mL THF in a 25 mL vial, to which


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DBTDL (3 mol%) was added. The reaction mixture was placed in a temperature-controlled orbit shaker (30 oC, 250 rpm) for 24 h and quenched with methanol (1.0 mL). The resulting PEU was precipitated into 100 mL methanol, collected by centrifugation, and dried at 50 oC under vacuum for 12 h. PEU-1: HDI (0.5 mmol, 0.084 g), isolated yield (0.208 g, 78%). 1H NMR (400 MHz, DMSO-d6): δ 7.23 (t, J = 5.15 Hz, 2H; -NH-), 6.47 (d, J = 2.99 Hz, 2H; furan-H), 6.44 (d, J = 2.99 Hz, 2H; furan-H), 5.01 (s, 4H; furan-CH2), (s, 4H; furan-CH2), 2.96 (m, 4H, NH-CH2), 2.33 (s, 4H; -CH2-), 1.52 (s, 4H; -CH2-), 1.36 (s, 4H; -CH2-), 1.21 ppm (s, 4H; -CH2-). 13C NMR (100 MHz, DMSO-d6): δ 172.33, 155.63, 150.99, 149.76, 111.58, 111.09, 57.50, 57.30, 40.23, 32.89, 29.31, 25.92, 23.76 ppm. PEU-2: IPDI (0.5 mmol, 0.111 g), isolated yield (0.182 g, 62%).

1

H NMR (400 MHz,

DMSO-d6): δ7.30 (t, J = 6.22 Hz, 1H; -NH-), 7.17 (m, 1H; NH), 6.47 (m, 4H; furan-H), 5.01 (s, 4H; furan-CH2), 4.93 (m, 4H; furan-CH2), 3.60 (br, 1H; NH-CH), 2.72 (m, 2H; NH-CH2), 2.33 (t, J = 7.36 Hz, 4H; -CH2-), 1.52 (m, 4H; -CH2-), 1.47~0.78 ppm (m, 15H; -CH2- and -CH3).

13

C

NMR (100 MHz, DMSO-d6): δ 172.48, 156.48, 155.00, 151.05, 149.86, 111.72, 111.28, 57.61, 54.47, 46.65, 45.50, 44.18, 41.39, 36.35, 35.81, 35.04, 33.01, 31.49, 27.57, 23.86, 23.24 ppm. PEU-3: TDI (0.5 mmol, 0.087 g), isolated yield (0.221 g, 82%).

1

H NMR (400 MHz,

DMSO-d6): δ 9.72 (s, 1H; NH), 8.99 (s, 1H; -NH-), 7.52 (s, 1H; Ph-H), 7.14 (d, J = 8.58 Hz, 1H; Ph-H), 7.05 (d, J = 8.58 Hz, 1H; Ph-H), 6.53 (m, 2H; furan-H), 6.50 (m, 2H; furan-H), 5.06 (d, J = 4.40 Hz, 4H; furan-CH2), 5.03 (d, J = 2.13 Hz, 4H; furan-CH2), 2.33 (s, 4H; -CH2-), 2.09 (s, 3H; Ph-CH3), 1.52 ppm (s, 4H; -CH2-).

13

C NMR (100 MHz, DMSO-d6): δ 172.38, 153.78,

152.92, 150.56, 150.44, 150.07, 150.01, 136.99, 136.31, 130.34, 125.89, 115.16, 114.81, 111.69, 111.60, 57.87, 57.70, 57.53, 32.92, 23.79, 17.12 ppm.


8

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PEU-4: MDI (0.5 mmol, 0.125 g), isolatedyield (0.249 g, 81%). 1H NMR (400 MHz, DMSO-d6): δ 9.69 (s, 2H; -NH-), 7.34 (d, J = 8.19 Hz, 4H; Ph-H), 7.08 (d, J = 8.19 Hz, 4H; PhH), 6.52 (d, J = 2.81 Hz, 2H; furan-H), 6.48 (d, J = 2.81 Hz, 2H; furan-H), 5.06 (s, 4H; furanCH2), 5.02 (s, 4H; furan-CH2), 3.77 (s, 2H; Ph-CH2), 2.32 (m, 4H; -CH2-), 1.51 (m, 4H; -CH2-). 13

C NMR (100 MHz, DMSO-d6): δ 172.32, 152.94, 150.40, 150.04, 136.85, 135.63, 128.88,

118.36, 111.62, 57.67, 57.48, 39.80, 32.87, 23.74 ppm.

RESULTS AND DISCUSSION Difuranic Polyol Monomers from HMF. DHMF was readily prepared by selfcondensation coupling of HMF,52 while BHMF was synthesized by subsequently selective oxidation of the α-hydroxyketone DHMF53 (Scheme 1).The new diol monomer BHFA was synthesized in two steps. First, adipoyl chloride reacted with 2 equivalents of HMF (in DCM) in the presence of pyridine to prepare the corresponding difuranic dialdehyde with the ester group linkage. Next, the resulting dialdehyde was reduced with aqueous NaBH4 solution in THF to afford the desired diol BHFA (Scheme 1). The 1H NMR spectrum in DMSO-d6 (Figure 1) showed that the resonance of the hydroxyl group (-OH) appeared at 5.23 ppm, splitting into a triplet as a result of spin-coupling with the methylene protons (-CH2-) at 4.37 ppm, while in CDCl3, the chemical shift of -OH was observed at 2.08 ppm as a broad singlet (Figure 2A). In the 13C NMR spectrum (Figure S2, see the SI), the carbonyl carbon of the ester linkage appeared at 172.34 ppm.


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Ph N N

2

Ph

O

HO

O

OMe

OH

N Ph

HO

O DHMF O

Cl

4

O O

MnO2 THF

O

HMF

Pyridine DCM

O OH

O

DCM

2 HMF + O O

O

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HO

O O BHMF

O 4

O O

O O

NaBH4 THF/H2O

HO

OH

O

O

O

O 4

O

O

OH

BHFA

Cl

Scheme 1. Synthetic routes to triol monomer DHMF as well as diol monomers BHMF and BHFA, all starting from HMF.

Figure 1. 1H NMR spectrum (DMSO-d6, 2.50 ppm) of BHFA.


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Linear PEs Derived from BHMF and BHFA. The polycondensation of diols and diacyl chlorides was usually conducted in THF or DCM using organic bases (such as pyridine and TEA) as the HCl-acceptor.56 Accordingly, linear PEs were synthesized by polycondensations of BHMF and BHFA with various diacyl chlorides, including succinyl chloride (SC), adipoylcholoride (AC), terephthaloyl chloride (TC), and fumaryl chloride (FC) (Scheme 2). In a typical procedure, the base was added dropwise into a mixture of the diol and the diacyl chloride. The diol BHMF is soluble in THF but insoluble in DCM; accordingly, the polymerization was firstly conducted in THF, and pyridine was used as the HCl-acceptor (Table 1, runs 1-3). High isolated PE yields (83–90%) were achieved, while the molecular weights of the resulting PEs were rather low (Mn = 3.2–5.5 kg/mol), largely limited by precipitation of the resulting PEs during the polycondensation due to their poor solubility in THF. As these PEs are soluble in DCM and chloroform, a solvent mixture of THF/DCM (3 mL/7 mL) was then used as the polymerization media (Table 1, runs 4 and 5). Compared with the PEs obtained in THF (Table 1, runs 1 and 2), the molecular weights of PE-1a and PE-1b synthesized in THF/DCM was increased by 47–69%, from 5.3 to 7.8 kg/mol for PE-1a and from 3.2 to 5.4 kg/mol for PE-1b (Table 1, runs 4 and 5); the polymer yields were enhanced to 88–92% as well. Changing the order of addition for the preparation of PE-1b, where a mixture of BHMF and pyridine in THF (3 mL) was added into a DCM (7 mL) solution of AC, resulted in a lower molecular weight PE of 4.2 kg/mol (Table 1, run 6). Although high molecular weight BHMF-based polyesters were not obtained by optimizing the polymerization conditions, these difuranic PEs may be used for self-healing and shape memory materials via the Diels-Alder reaction with bismaleimides.27,57,58


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O HO

OH

O O

O

O

O

pyridine

+ Cl

O

R

Cl

R = (CH2)2 (SC), (CH2)4 (AC), Ph (TC)

BHMF

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∗

O

O

O

∗

R

O

O O n O R = (CH2)2 (PE-1a), (CH2)4 (PE-1b), Ph (PE-1c)

O HO

O

O

O

O

OH

O

BHFA + O O

O base THF

∗

O

O

O

O

O

O

O

Cl R Cl R = (CH2)2 (SC), CH=CH (FC)

∗

R O

O

n

R = (CH2)2 (PE-2a), CH=CH (PE-2b)

Scheme 2. Synthesis of linear PEs based on BHMF and BHFA.

As BHFA and BHFA-based PEs are both soluble in THF, these polycondensations were conducted in THF (Table 1, runs 7 and 8). Compared with BHMF, the polycondensation of BHFA afforded lower polymer yields (PE-2a, 68%; PE-2b, 56%), and the Mn values of the resulting PEs were 8.6 kg/mol for PE-2a and 5.8 kg/mol for PE-2b, which were comparable to those of 2,5-bis(hydroxymethyl)furan-based PEs.26-28 Noteworthy here is that using pyridine as the HCl-acceptor for the polycondensation of BHFA and FC afforded the PE-2b in black color (Table 1, run 8), but when TEA was employed instead, the polycondensation afforded the PE-2b in off-white color also with higher yield and higher thermal stability (Table 1, run 9 vs. 8). Accordingly, the sample of PE-2b prepared with TEA was used for the self-crosslinking investigation (vide infra). Table 1.Polycondensation of BHMF and BHFA with diacylchloridesa Run # 1 2 3

Sample # PE-1a PE-1b PE-1c

BHMF BHMF BHMF

Diacyl chloride SC AC TC

4

PE-1a

BHMF

SC

5

PE-1b

BHMF

AC

Diol

Solvent (mL) THF (10) THF (10) THF (10) THF (3) DCM (7) THF (3)

Yieldb (%) 83 84 90

Mnc (kg/mol) 5.3 3.2 5.5

Ðc (Mw/Mn) 1.84 1.51 1.81

Tg(DSC) (oC) 52.7 26.9 101.3

Td(5%)d (oC) 281 295 284

Chard (%) 28.4 28.6 26.6

92

7.8

2.04

-

-

-

88

5.4

1.66

-

-

-


12

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DCM (7) THF (3) PE-1b BHMF AC 89 4.2 1.75 6 DCM (7) 7 PE-2a BHFA SC THF (10) 68 8.6 1.70 -0.7 247 9.2 8 PE-2b BHFA FC THF (10) 56 5.8 1.96 11.2 203 21.5 9f PE-2b BHFA FC THF (10) 68 6.1 1.79 10.6 229 19.0 a Conditions: diol (1.0 mmol), diacyl chloride (1.0 mmol), pyridine (2.2 mmol), T = 25 oC, t = 24 h. b Isolated yield via precipitation into excess methanol. c Determined by gel permeation chromatograph (GPC) in DMF relative to PMMA standards. d Obtained from TGA (% stable residue at 700 oC as char yield). e Mixture of BHMF and pyridine in THF was added into a DCM solution of AC. f TEA (2.2 mmol) was used as base. e

Cross-linked PEs Derived from DHMF. The polycondensations of triol DHMF and diacyl chlorides (SC and AC) in 1:1 and 1:1.5 molar ratios were also investigated in THF (Scheme 3). In this polycondensation, when 2.2 equivalents of pyridine were added dropwise into the mixture of DHMF and a diacyl chloride in a 1:1 molar ratio, yellow solid precipitated gradually from the reaction solution, affording moderate isolated polymer yields (PE-3a, 59%; PE-3b, 53%; Table 2, runs 1 and 2). The resulting PEs are insoluble in common organic solvents (THF, DCM, DMF, DMSO, etc.), due to the crosslinking because all of the three hydroxyl groups can react with the diacyl chloride. In addition, even after changing the order of addition, where 1 equivalent of the diacyl chloride (AC) was added slowly into the mixture of DHMF and pyridine in THF (Table 2, run 3), the resulting PE-3b had similar isolated yield and thermal properties to that obtained under normal procedures (Table 2, run 3 vs. 2), suggesting that the three hydroxyl groups present in DHMF display no notable reactivity difference for the reaction with the high active diacyl chlorides. As anticipated, the polycondensation of DHMF with 1.5 equivalents of diacyl chlorides also produced cross-linked PEs, but with higher isolated yields (PE-4a, 85%; PE-4b, 89%; Table 2, runs 4 and 5), due to achieving more complete conversions of both monomers under the stoichiometric ratio of the functional groups.


13


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O Cl

O R 1.0

HO

∗

O

O

O O

OH

O

R

O

O O O OH R = (CH2)2 (PE-3a), (CH2)4 (PE-3b) O

pyridine THF

OH

O

O Cl

Page 14 of 36

O

O O O

∗ n

R

O O DHMF

O Cl

O R 1.5

pyridine THF

O ∗

Cl

O

O

O

∗

R

O O

O

On

R = (CH2)2 (PE-4a), (CH2)4 (PE-4b)

Scheme 3. Synthesis of cross-linked PEs based on DHMF. Table 2.Polycondensation of DHMF with diacyl chlorides in the presence of pyridinea Run Sample Acyl chloride Pyridine Yieldb Tg(DSC) Td(5%)c Charc o o # # (loading) (mmol) (%) ( C) ( C) (%) 1 PE-3a SC (1.0 eq.) 2.2 59 67.2 192 25.2 2 PE-3b AC (1.0 eq.) 2.2 53 33.0 226 26.8 3d PE-3b AC (1.0 eq.) 2.2 54 32.0 226 26.8 4 PE-4a SC (1.5 eq.) 3.3 85 89.1 188 25.0 5 PE-4b AC (1.5 eq.) 3.3 89 52.5 215 27.3 a Conditions: DHMF (1.0 mmol), solvent: THF (10 mL), T = 25 oC, t = 24 h. b Isolated yield via precipitation into excess methanol. c Obtained from TGA (% stable residue at 700 oC as char yield). d THF solution of AC was added into the mixture of DHMF and pyridine in THF.

Characterization of Linear and Cross-linked PEs. (1) Characterization by NMR. Although the triol DHMF-based PEs are insoluble, the diol BHMF- and BHFA-based PEs are soluble in DMSO and chloroform, enabling their characterizations in solution by NMR. As shown by the overlay of the 1H NMR spectra of BHFA and PE-2 in Figure 2 (for BHMF-based PEs, see the SI), the resonance of the hydroxyl group of BHFA at 2.08 ppm disappeared completely, while new sharp peaks were observed at 2.66 ppm and 6.88 ppm, which were attributed to the saturated succinyl (PE-2a) moiety and the unsaturated fumaryl (PE-2b) moiety, respectively. Moreover, the CH2OH resonance (4.59 ppm) in BHFA shifted downfield (PE-2a, 5.04 ppm; PE-2b, 5.14 ppm) in the resulting PEs. In the 13C NMR spectra, the carbonyl carbons of the newly formed ester linkage in the PEs appeared at 171.84 (PE-2a) and 164.38 ppm (PE-


14

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2b), while those of the ester linkages from the adipoyl moieties were observed at 172.87 (PE-2a) and 172.85 ppm (PE-2b), similar to the values observed in the monomer (172.34 ppm).

Figure 2. Overlay of 1H NMR spectra (CDCl3) of BHFA and representative linear PEs (PE-2a and PE-2b). (2) Characterization by FTIR. Figure 3 shows the FTIR spectra of BHMF and DHMF and their representative resulting PEs. The broad absorption bands at 3259 and 3309 cm-1 are the stretching vibration of the hydroxyl groups (-OH) of BHMF and DHMF, respectively. The strong absorption bands centered at 1633 and 1681cm-1 were attributed to the carbonyl group (C=O) stretching vibration. After the polymerization, new strong absorption bands appeared at about 1733 and 1135 cm-1, due to the newly formed carbonyl group (C=O) and ether group (CO-C) in the ester linkage (C-O-CO), confirming that PEs were formed. For cross-linked PE-3b,


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Page 16 of 36

there was a weak absorption band at 3451 cm-1, due to the excess hydroxyl group when the stoichiometric ratio of the hydroxyl and acyl chloride groups was not used in the polycondensation (vide supra).

Figure 3. FTIR spectra of BHMF and DHMF and representative resulting PEs.

(3) Characterization by TGA. The thermal degradation profiles of the synthesized PEs were monitored by thermal gravimetric analysis (TGA) (Figure 4). For the linear PEs, the difuranic BHMF-based PEs displayed higher thermal stability than the BHFA- and DHMF-based ones, as evidenced by the onset decomposition temperatures (Td at 5% weight loss) of above 280 o

C, with PE-1b (obtained from AC) exhibiting the highest Td of 295 oC. The BHFA-based PEs

displayed lower thermal stability, with PE-2b (obtained from unsaturated FC) exhibiting a much lower Td of 229 oC, as compared with that of PE-2a (247 oC, obtained from SC). For the DHMFderived cross-linked PEs, the ones obtained from AC (PE-3b, 226 oC and PE-4b, 215 oC) displayed higher Td’s than those obtained from SC (PE-3a, 192 oC and PE-4a, 188 oC), but the


16

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thermal stabilities of all these cross-linked PEs were considerably lower than those of the linear PEs. This observation can be explained by the reasoning that there are fewer amounts of ester linking groups in the PEs having similar molecular weights.26 Consistent with this reasoning, the PEs having a higher degree of crosslinking (PE-4a and PE-4b) resulted in somewhat lower thermal stability (188 oC and 215 oC), compared with PE-3a and PE-3b (192 oC and 226 oC).

Figure 4. TGA traces of linear (a) and cross-linked (b) PEs. (4) Characterization by DSC. Based on the differential scanning calorimetry (DSC) curves of these PEs (Figure 5), PE-1b bearing a longer soft segment [-(CH2)4-] has a lower glass transition temperature (Tg) of 26.9 oC, compared with that of PE-1a having a short linker of -


17


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(CH2)2- (52.7 oC). Noteworthy is that the Tg’s of these BHMF-based PEs are much higher than those of the 2,5-bis(hydroxymethyl)furan-based PEs bearing the same dicarboxylic segments (52.7 vs. 4 oC; 26.9 vs.–19oC),26 which is attributed to the more rigid difuranic BHMF moiety present in the polymer chain. As anticipated, PE-1c containing the hard segment (-Ph-) in the main chain displayed the highest Tg (101.3 oC). As compared to the BHMF-based PEs, BHFAbased ones displayed lower Tg’s (PE-2a, –0.7 oC; PE-2b, 10.6 oC) because the two furan rings were connected by the softer segment. Relative to the linear PE-1a and PE-1b, DHMF-based cross-linked PE-3a and PE-3b exhibited slightly higher Tg’s (67.2 vs.52.7oC; 33.0 vs. 26.9 oC), attributable to the crosslinking by the DHMF moiety bearing three hydroxyl groups. By increasing the diacyl chloride/DHMF ratio from 1:1 to 1.5:1 (the stoichiometric ratio of the acyl chloride and hydroxyl groups), the resulting cross-linked PE-4a and PE-4b showed higher Tg’s (89.1 vs. 67.2; 52.5 vs. 33.0 oC), in accordance with the enhanced degree of crosslinking.

Figure 5. DSC curves of linear (a) and cross-linked (b) PEs (second heating cycles; heating rate: 10 oC/min).


18

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Self-Curing of Furan-based PEs via the Diels-Alder Reaction. We were interested in introducing C=C double bonds into the furan-based PEs, which can endow the resulting unsaturated furan-containing polymers with the unique self-curing property via the Diels-Alder (DA) reaction.51 To this end, we first performed the polycondensation of BHMF with unsaturated FC in the presence of pyridine, which afforded an insoluble black solid. When TEA was used as the HCl acceptor, a light yellow product (PE-1d) was obtained, but its solubility was very poor in common organic solvents (DCM, chloroform, DMF, DMSO, etc.), presumably due to in-situ crosslinking via the DA reaction. Next, the obtained PE-1d was treated with heating in bulk at 150 oC or in DCM suspension in the presence of a Lewis acid catalyst (AlCl3) to further enhance the degree of crosslinking. Based on the DSC curves (Figure S21), the Tg’s of the resulting samples after both types of treatment did not change appreciably (84.5 oC and 86.0 oC vs. 85.1 o

C). On the other hand, PE-2b, obtained from the polycondensation of BHFA and unsaturated

FC (vide supra), demonstrated more controlled and apparent self-curing property (Scheme 4). In this context, four different conditions were applied to form cross-linked PE-2b: heating in bulk, heating in solution, microwave irradiation (MI), and Lewis-acid catalysis. As shown in Figure 6a, the cross-linked PE-2b after heating in bulk at 150 oC for 3 h displayed a Tg of 13.8 oC, which is higher than that the Tg (12.6 oC) via heating in solution (DMF, 3 h). The MI-treatment (150 oC in DMF, 3 h) produced a product with a Tg of 13.9 oC. A higher degree of crosslinking between the furan ring and the unsaturated double bond in PE-2b was achieved via Lewis-acid (AlCl3 in DCM) catalyzed DA reaction, which afforded a product displaying no apparent Tg.


19


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O ∗

O

O

Page 20 of 36

O O

O

O

O

O

∗ n

O

O

DA reaction O

O ∗

O

O

O O

O

O

O

O O

∗ n

O

O O

O O

O O

Scheme 4. Schematic representation of self-curing of PE-2b through the Diels-Alder reaction.

TGA traces of the resulting network polymers (Figure 6b) showed that the cross-linked PE2b prepared by heating in bulk (Td, 221 oC), heating in solution (Td, 224 oC), and microwave irradiation (Td, 225 oC) exhibited slightly lower thermal stability, but a higher amount of highly stable carbonaceous residue produced at 700 oC (char yield), as compared with the as-prepared PE-2b (only dried in vacuo at room temperature; Td, 229 oC). The AlCl3-treated sample exhibited the lowest Td of 174 oC but with the highest char yield (32.5%). In sharp contrast, treating PE-2a, obtained from BHFA and SC, with heating in bulk at 150 oC did not noticeably change the Tg of the resulting sample (Figure S23) (–0.7 oC vs. –1.1 oC, before and after heating treatment). This comparative example provided further evidence for the self-curing property of the furan-based PE (PE-2b) bearing the unsaturated double bond.


20

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Figure 6. (a) DSC curves of PE-2b (dried in vacuo at room temperature) and cross-linked PE-2b prepared by different methods (all from second heating cycles, with a heating rate of 10 oC/min). (b) TGA traces of PE-2b (dried in vacuo at room temperature) and cross-linked PE-2b prepared by different methods (treatment time: 3 h): PE-2b, Td = 229 oC, char yield = 19.0%; by heating in bulk at 150 oC, Td = 221 oC, char yield = 19.7%; by heating in DMF at 150 oC, Td = 224 oC, char yield = 22.1%; by MI in DMF at 150 oC, Td = 225 oC, char yield = 20.5%; by AlCl3 catalysis at 30 oC, Td = 174 oC, char yield = 32.5%. Synthesis and Characterization of Linear PEUs from BHFA. PEUs are the copolymers produced by the polyadditon of (poly)ester diols and diisocyanates. There has been an extensive interest in the synthesis of bio-based PEUs59-61 and their shape memory applications.62-65 With the ester-linked diol BHFA in hand, we investigated the influence of rigid and flexible difuranic polyols on the resultant polymer properties, compared with the BHMF based PUs we reported previously.53 Polyadditions of BHFA with diisocyanates (Scheme 5), including hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 2,4-toluenediisocyanate (TDI), and diphenylmethane diisocyanate (MDI), were conducted in THF at 30 oC using dibutyltindilaurate (DBTDL) (3 mol%) as catalyst, and the corresponding PEUs were obtained as off-white solids after precipitation from methanol. The polymerization data are summarized in Table 3. Unlike the polycondensation of BHMF with diacyl chlorides, this polyaddition with diisocyanates afforded PEUs with much higher molecular weights (Mn = 13.1–31.4 kg/mol) and moderate dispersity (Ð =1.72–2.46). These novel PEUs were first characterized by NMR in DMSO-d6. Taking the 1H NMR spectra of aliphatic HDI-based PEU-1 and aromatic MDI-based PEU-4 for example (Figure 7), there were no peaks for the hydroxyl group at around 5.23 ppm, while new peaks at 7.23 (PEU-1)


21


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Page 22 of 36

and 9.69 ppm (PEU-4) were observed, which were assigned to the amide proton of the newly produced urethane linkage [-OC(=O)-NH-]. The formation of these PEUs was further confirmed with FTIR (Figure S25), where the broad stretching vibration absorption band of O-H (3311 cm-1) in BHFA was superseded by the stretching vibration absorption bands of N-H (centered at 3320 cm-1) in the resulting PEUs, and the stretching vibration absorption bands of C=O, in the ester groups and urethane groups, appeared at around 1720 cm-1 and 1690 cm-1, respectively, or overlapped at about 1710 cm-1, accounting for the free and hydrogen-bonded carbonyl groups.6668

Furthermore, the N-H bending vibrations were observed at 1530 cm-1. Next, the thermal

properties of the resulting PEUs were characterized with TGA and DSC. The TGA traces (Figure 8a) indicated that these PEUs displayed two apparent stages of thermal decomposition accompanied by two maximum rate decomposition temperatures (Tmax, Figure S26 for DTG curves), in which the Tmax1 varied in the range of 229~290 oC, and the Tmax2 appeared in the range of 410~460 oC, depending on the diisocyante units. The first stage, where the PEU weight lost sharply (weight loss: around 40% for PEU-1,3,4; 50% for PEU-2), was attributed to the rupture of the weakest C(O)-NH urethane bonds, and the second stage was due to the pyrolysis of the CC bonds, while the scission of the alkoxy oxygen bond (C-O) in the ester linkage did not show a segregated decomposition stage or Tmax.66 The weight decreased very slowly above 500 oC, and upon heating to 700 oC, these polymers produced a significant amount of highly stable carbonaceous residue with 13–21% (derived from aliphatic diisocyanates) and 35–41% (derived from aromatic diisocyanates) char yields (Figure 8a). PEU-4 exhibited lower thermal stability (Td = 214 oC) than the previously reported BHMF-based PU (Td = 234 oC).53 On the other hand, the other three PEUs exhibited higher thermal stability (Td > 230 oC) than those corresponding BHMF-based PUs (Td < 227 oC).53 Within the current PEUs, the ones derived from the aliphatic


22

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diisocyanates exhibited higher Td, with the IPDI-based PEU-2 displaying the highest Td of 264 o

C. As shown in Figure 8b, the HDI-based PEU-1 containing a soft segment [-(CH)6-] displayed

a lower Tg (13.3 oC), compared to other PEUs (PEU-2, 55.5 oC; PEU-3, 63.4oC; PEU-4, 62.8 oC) bearing the rigid diisocyanate moieties, and all Tg’s of the BHFA-based PEUs were lower by 50 o

C than that of the BHMF-based PUs,53 which indicated that the flexibility of the difuranic diol

had a significant impact on the thermal property of the resultant polymer. Most interestingly, PEU-1 displayed a high Tm of 135.8 oC (heat of fusion, ∆H = 43.5 J/g) in the second heating cycle after eliminating the thermal history, which was attributed that the long methylene segments in the difuranic diol (-(CH2)4-) and HDI (-(CH2)6-) enabled the resulting PEU-1 more flexible and better chain packing capability, thus easier to rotate and/or undergo conformational rearrangements. Furthermore, a cold crystallization peak (Tc: 71.6 oC) was observed, suggesting that the crystallization speed of PEU-1 was slow.69 For PEU-2-4, no Tc and Tm were observed from the second heating curves, because the rigid and/or asymmetric units introduced from those diisocyanates (IPDI, TDI and MDI) rendered these polymers difficult to crystallize. Based on the chemical structures (ester and urethane groups) and thermal properties, the difuranic PEUs would be suitable for some biological and engineering applications.69-71

O HO

O

O

O

O

O BHFA + R OCN NCO Diisocyanates

OH O DBTDL THF, 30 oC

∗

O

O

O

O

O

H N

O

O

R

O

H N

∗ O n

NCO OCN Diisocyanate:

OCN

NCO 6

HDI (PEU-1)

NCO

IPDI (PEU-2)

NCO

OCN

NCO IPDI (PEU-3)

IPDI (PEU-4)

Scheme 5. Synthesis of PEUs based on BHFA.


23


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Table 3.Polyaddition of BHFA with diisocyanates in the presence of DBTDLa Run Sample DiisoYieldb Mnc Ðc Tg(DSC) Tm(DSC) Td(5%)d Char d # # cyanate (%) (kg/mol) (Mw/Mn) (oC) (oC) (oC) (%) 1 PEU-1 HDI 78 13.1 2.18 13.3 135.8 257 21.1 2 PEU-2 IPDI 62 23.9 1.72 55.5 264 13.2 3 PEU-3 TDI 82 31.4 2.46 63.4 231 40.9 4 PEU-4 MDI 81 20.0 2.25 62.8 214 35.9 a Conditions: BHFA (0.5 mmol), diisocyanate (0.5 mmol), DBTDL (3 mol%), THF (5 mL), T = 30 oC, t = 24 h. b Isolated yield via precipitation into excess methanol. c Determined by gel permeation chromatograph (GPC) relative to PMMA standards in DMF. d Obtained from TGA (% stable residue at 700 oC as char yield).

Figure 7. Overlay of 1H NMR spectra (DMSO-d6) of representative PEUs.


24

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Figure 8. TGA traces (a) and DSC curves (b) of linear PEUs (second heating cycles; heating rate: 10 oC/min).

CONCLUSIONS We utilized three bio-based difuranicpolyol monomers, including diols BHMF and BHFA as well as triol DHMF, for the synthesis of a series of new linear (saturated and unsaturated) and cross-linked PEs as well as PEUs containing either rigid (BHMF and DHMF) or flexible (BHFA) difuranic moieties. The polycondensations of the diols and various diacyl chlorides afforded linear PEs of relatively low molecular weights with Mn in the range of 3.2–8.6 kg/mol, depending on the solvent, diol and diacyl chloride. The triol DHMF reacted with diacyl chlorides to produce cross-linked PEs, regardless of whether the molar ratio of 1:1 or 1:1.5 was used, although the latter (stoichiometric) ratio afforded the PE with much higher isolated yield (85– 89%) and a higher degree of crosslinking. For the linear PEs, the ones containing the rigid difuranic moiety (i.e., derived from BHMF) exhibited much higher Tg’s, as compared to those containing either a single furan ring or two furan rings but separated by a flexible linker, highlighting the impact of the nature of the difuranic moiety on the polymer properties. The


25


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Page 26 of 36

cross-linked PEs based on the rigid difuranic DHMF showed further enhanced Tg values, but at the expense of thermal stability. The unsaturated difuranic PE derived from the polycondensation of BHFA and FC displayed the unique self-curing phenomenon via the Diels-Alder reaction between the furan ring and the C=C double bond. Treatment of this as-prepared PE with four different methods, including heating in bulk, heating in solution, microwave-irradiation, and Lewis acid catalysis, produced more robust, cross-linked PE materials. Among these methods, the AlCl3 catalysis produced the material with the highest degree of crosslinking and also the highest amount (32.5%) of stable carbonaceous residue at 700oC. The catalyzed polyaddition between BHFA and various diiscyanates produced novel PEUs with considerably higher molecular weights of Mn = 13.1–31.4 kg/mol, compared with those of the BHFA-based PEs obtained by polycondensation. The PEUs derived from aliphatic diisocyanates (HDI and IPDI) exhibited higher thermal stability than those derived from aromatic diisocyanates (TDI and MDI), while the latter afforded a larger amount of stable carbonaceous residue at 700 oC (up to 41%). Among these BHFA-based PEUs, the one derived from HDI is most interesting, as it is a semicrystalline material that displays a low Tg of 13.3 oC but a high Tm of 135.8 oC and a high ∆H of 43.5 J/g.

ASSOCIATED CONTENT Supporting information. Additional 1H,

13

C, and 1H-13C HSQC NMR spectra, TGA traces,

DSC curves, and FTIR spectra (PDF). This information is available free of charge via the Internet at http://pubs.acs.org.


26

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AUTHOR INFORMATION Corresponding Author *

Eugene Y.-X. Chen. Email: [email protected]

Notes The authors declare no competing financial interest.

ACKNOWLEDGEMENTS This work was supported by the US Department of Energy Office of Basic Energy Sciences, grant DE-FG02-10ER16193.

REFERENCES (1)

Gandini, A.; Lacerda, T. M.; Carvalho, A. J.; Trovatti, E. Progress of Polymers from Renewable Resources: Furans, Vegetable Oils, and Polysaccharides. Chem. Rev. 2016,116, 1637-1669.

(2)

Galbis, J. A.; Garcia-Martin Mde, G.; de Paz, M. V.; Galbis, E. Synthetic Polymers from Sugar-Based Monomers. Chem. Rev. 2016,116, 1600-1636.

(3)

Mirzaei, H. M.; Karimi, B. Sulphanilic Acid as ARecyclable Bifunctional Organocatalyst in the Selective Conversion of Lignocellulosic Biomass to 5-HMF. Green Chem.2016,18, 2282-2286.

(4)

Wrigstedt, P.; Keskivali, J.; Leskela, M.; Repo, T. The Role of Salts and Bronsted Acids in Lewis Acid-Catalyzed Aqueous-Phase Glucose Dehydration to 5-Hydroxymethylfurfural. ChemCatChem 2015, 7, 501-507.


27


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(5)

Page 28 of 36

Wang, T.; Nolte, M. W.; Shanks, B. H. Catalytic Dehydration of C6 Carbohydrates for the Production of Hydroxymethylfurfural (HMF) as AVersatile Platform Chemical. Green Chem. 2014, 16, 548-572.

(6) Teong, S. P.; Yi, G.; Zhang, Y. Hydroxymethylfurfural Production from Bioresources: Past, Present and Future. Green Chem.2014, 16, 2015-2026. (7)

He, J.; Zhang, Y.; Chen, E. Y. X. Chromium(0) Nanoparticles as Effective Catalyst for the Conversion of Glucose into 5-Hydroxymethylfurfural. ChemSusChem 2013, 6, 61-64.

(8)

Liu, D.; Chen, E. Y. X. Integrated Catalytic Process for Biomass Conversion and Upgrading to C12Furoin and Alkane Fuel. ACS Catal. 2014, 4, 1302-1310.

(9)

Zuo, X.; Venkitasubramanian, P.; Busch, D. H.; Subramaniam, B. Optimization of Co/Mn/Br-Catalyzed

Oxidation

of

5-Hydroxymethylfurfural

to

Enhance

2,5-

Furandicarboxylic Acid Yield and Minimize Substrate Burning. ACS Sustainable Chem. Eng.2016, DOI: 10.1021/acssuschemeng.6b00174. (10) Zhang, Z. H.; Zhen, J. D.; Liu, B.; Lv, K. L.; Deng, K. J. Selective Aerobic Oxidation of the Biomass-Derived Precursor 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid under Mild Conditions over AMagnetic Palladium Nanocatalyst. Green Chem.2015, 17, 1308-1317. (11) Wang,

S.;

Zhang,

Z.;

Liu,

B.

Catalytic

Conversion

of

Fructose

and

5-

Hydroxymethylfurfural into 2,5-Furandicarboxylic Acid over a Recyclable Fe3O4– CoOxMagnetite Nanocatalyst. ACS Sustainable Chem.Eng.2015, 3, 406-412. (12) Han, X.; Geng, L.; Guo, Y.; Jia, R.; Liu, X.; Zhang, Y.; Wang, Y. Base-Free Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid over a Pt/C–O–Mg catalyst. Green Chem. 2016, 18, 1597-1604.


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Page 29 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(13) Yi, G.; Teong, S. P.; Li, X.; Zhang, Y. Purification of Biomass-Derived 5Hydroxymethylfurfural and Its Catalytic Conversion to 2,5-Furandicarboxylic Acid. ChemSusChem 2014, 7, 2131-2135. (14) Yi, G.; Teong, S. P.; Zhang, Y.Base-Free Conversion of 5-Hydroxymethylfurfural to 2,5Furandicarboxylic Acid over a Ru/C Catalyst. Green Chem. 2016,18, 979-983. (15) Hao, W.; Li, W.; Tang, X.; Zeng, X.; Sun, Y.; Liu, S.; Lin, L. Catalytic Transfer Hydrogenation of Biomass-Derived 5-Hydroxymethyl Furfural to the Building Block 2,5Bishydroxymethyl Furan. Green Chem. 2016, 18, 1080-1088. (16) De, S.; Kumar, T.; Bohre, A.; Singh, L. R.; Saha, B. Furan-Based Acetylating Agent for the Chemical Modification of Proteins. Bioorg. Med. Chem. 2015, 23, 791-796. (17) Chatterjee,

M.;

Ishizaka,

T.;

Kawanami,

H.

Selective

Hydrogenation

of

5-

Hydroxymethylfurfural to 2,5-Bis-(hydroxymethyl)furan Using Pt/MCM-41 in An Aqueous Medium: ASimple Approach. Green Chem. 2014, 16, 4734-4739. (18) Cao, Q.; Liang, W.; Guan, J.; Wang, L.; Qu, Q.; Zhang, X.; Wang, X.; Mu, X. Catalytic Synthesis of 2,5-Bis-methoxymethylfuran: A Promising Cetane Number Improver for Diesel. Appl. Catal., A 2014, 481, 49-53. (19) Cottier, L.; Descotes, G.; Soro, Y. Heteromacrocycles from Ring-Closing Metathesis of Unsaturated Furanic Ethers.Synth. Commun.2003, 33, 4285-4295. (20) Jiang, M.; Liu, Q.; Zhang, Q.; Ye, C.; Zhou, G. Y. A Series of Furan-Aromatic Polyesters Synthesized via Direct Esterification Method Based on Renewable Resources. J. Polym. Sci., Part A: Polym. Chem. 2012, 50, 1026-1036.


29


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 36

(21) Ma, J. P.; Pang, Y.; Wang, M.; Xu, J.; Ma, H.; Nie, X. The Copolymerization Reactivity of Diols with 2,5-Furandicarboxylic Acid for Furan-Based Copolyester Materials. J. Mater. Chem.2012, 22, 3457-3461. (22) Wu, L. B.; Mincheva, R.; Xu, Y. T.; Raquez, J. M.; Dubois, P. High Molecular Weight Poly(butylene succinate-co-butylene furandicarboxylate) Copolyesters: From Catalyzed Polycondensation Reaction to Thermomechanical Properties. Biomacromolecules 2012, 13, 2973-2981. (23) Zhu, J.; Cai, J.; Xie, W.; Chen, P.-H.; Gazzano, M.; Scandola, M.; Gross, R. A. Poly(butylene 2,5-furan dicarboxylate), A Biobased Alternative to PBT: Synthesis, Physical Properties, and Crystal Structure. Macromolecules 2013, 46, 796-804. (24) Tsanaktsis, V.; Terzopoulou, Z.; Exarhopoulos, S.; Bikiaris, D. N.; Achilias, D. S.; Papageorgiou, D. G.; Papageorgiou, G. Z. Sustainable, Eco-Friendly Polyesters Synthesized from Renewable Resources: Preparation and Thermal Characteristics of Poly(dimethyl-propylene furanoate). Polym. Chem. 2015, 6, 8284-8296. (25) Gandini, A.; Silvestre, A. J. D.; Neto, C. P.; Sousa, A. F.; Gomes, M. The Furan Counterpart of Poly(ethylene terephthalate): An Alternative Material Based on Renewable Resources. J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 295-298. (26) Jiang, Y.; Woortman, A. J.; Alberda van Ekenstein, G. O.; Petrovic, D. M.; Loos, K. Enzymatic Synthesis of Biobased Polyesters Using 2,5-Bis(hydroxymethyl)furan as the Building Block. Biomacromolecules 2014, 15, 2482-2493. (27) Zeng, C.; Seino, H.; Ren, J.; Hatanaka, K.; Yoshie, N. Bio-Based Furan Polymers with Self-Healing Ability. Macromolecules 2013, 46, 1794-1802.


30

Page 31 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(28) Gomes, M.; Gandini, A.; Silvestre, A. J. D.; Reis, B. Synthesis and Characterization of Poly(2,5-furan dicarboxylate)s Based on AVariety of Diols. J. Polym. Sci., Part A: Polym. Chem. 2011, 49, 3759-3768. (29) Wang, H.; Wang, Y.; Deng, T.; Chen, C.; Zhu, Y.; Hou, X. Carbocatalyst in Biorefinery: Selective Etherification of 5-Hydroxymethylfurfural to 5,5 '(oxy-bis(methylene)bis-2furfural over Graphene Oxide. Catal. Commun. 2015, 59, 127-130. (30) Chang, C.-C.; Cho, H. J.; Yu, J.; Gorte, R. J.; Gulbinski, J.; Dauenhauer, P.; Fan, W. Lewis Acid Zeolites for Tandem Diels-Alder Cycloaddition and Dehydration of Biomass-Derived Dimethylfuran and Ethylene to Renewable p-Xylene. Green Chem.2016, 18, 1368-1376. (31) Foster, R. W.; Benhamou, L.; Porter, M. J.; Bucar, D.-K.; Hailes, H. C.; Tame, C. J.; Sheppard, T. D. Irreversible Endo-Selective Diels-Alder Reactions of Substituted Alkoxyfurans: A General Synthesis of Endo-Cantharimides. Chem. Eur. J. 2015, 21, 61076114. (32) Xue, Y.-P.; Li, W.-D. Z. Formal Total Synthesis of (+/-)-Estrone via the Furano Diene Approach. J. Org. Chem. 2011, 76, 57-64. (33) Shiramizu, M.; Toste, F. D. On the Diels-Alder Approach to Solely Biomass-Derived Polyethylene Terephthalate (PET): Conversion of 2,5-Dimethylfuran and Acrolein into pXylene. Chem. Eur. J. 2011, 17, 12452-12457. (34) Sim, J. Y.; Hwang, G.-S.; Kim, K. H.; Ko, E. M.; Ryu, D. H. Asymmetric Synthesis of (+)Cis-nemorensic Acid from AChiral Diels-Alder Adduct of 2,5-Dimethylfuran. Chem. Commun. 2007, 5064-5065.


31


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 36

(35) Griffith, G. A.; Hillier, I. H.; Moralee, A. C.; Percy, J. M.; Roig, R.; Vincent, M. A. Interplay of Structure and Reactivity in AMost Unusual Furan Diels-Alder Reaction. J. Am. Chem. Soc. 2006, 128, 13130-13141. (36) Petronijevic, F.; Timmons, C.; Cuzzupe, A.; Wipf, P. A Microwave Assisted Intramolecular-Furan-Diels-Alder Approach to 4-Substituted Indoles. Chem. Commun. 2009, 104-106. (37) Hayashi, Y.; Nakamura, M.; Nakao, S.; Inoue, T.; Shoji, M. The HfCl4-Mediated Diels– Alder Reaction of Furan. Angew. Chem., Int. Ed. 2002, 41, 4079-4082. (38) Gandini, A. The Furan/Maleimide Diels-Alder Reaction: A Versatile Click-Unclick Tool in Macromolecular Synthesis. Prog. Polym. Sci. 2013, 38, 1-29. (39) Liu, Y.-L.; Chuo, T.-W. Self-Healing Polymers Based on Thermally Reversible DielsAlder Chemistry. Polym. Polym. Chem. 2013, 4, 2194-2205. (40) Watanabe, M.; Yoshie, N. Synthesis and Properties of Readily Recyclable Polymers from Bisfuranic Terminated Poly(ethylene adipate) and Multi-Maleimide Linkers. Polymer 2006, 47, 4946-4952. (41) Yamashiro, M.; Inoue, K.; Iji, M. Recyclable Shape-Memory and Mechanical Strength of Poly(lactic acid) Compounds Cross-Linked by Thermo-Reversible Diels-Alder Reaction. Polym. J. 2008, 40, 657-662. (42) Defize, T.; Riva, R.; Thomassin, J. M.; Jerome, C.; Alexandre, M. Thermo-Reversible Reactions for the Preparation of Smart Materials: Recyclable Covalently-Crosslinked Shape Memory Polymers. Macromol. Symp. 2011, 309-310, 154-161.


32

Page 33 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(43) Defize, T.; Riva, R.; Raquez, J. M.; Dubois, P.; Jerome, C.; Alexandre, M. Thermoreversibly Crosslinked Poly(epsilon-caprolactone) as Recyclable Shape-Memory Polymer Network. Macromol. Rapid Commun. 2011, 32, 1264-1269. (44) Zeng, C.; Seino, H.; Ren, J.; Yoshie, N. Polymers with Multishape Memory Controlled by Local Glass Transition Temperature. ACS Appl. Mater. Interfaces 2014, 6, 2753-2758. (45) Kavitha, A. A.; Singha, N. K. "Click Chemistry" in Tailor-Made Polymethacrylates Bearing Reactive Furfuryl Functionality: A New Class of Self-Healing Polymeric Material. ACS Appl. Mater. Interfaces 2009, 1, 1427-1436. (46) Peterson, A. M.; Jensen, R. E.; Palmese, G. R. Room-Temperature Healing of A Thermosetting Polymer Using the Diels−Alder Reaction. ACS Appl. Mater. Interfaces 2010, 2, 1141-1149. (47) He, J. H.; Zhang, Y. T.; Chen, E. Y. X. Anionic Polymerization of Biomass-Derived Furfuryl Methacrylate: Controlling Polymer Tacticity and Thermoreversibility. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2793-2803. (48) Chen, X. X.; Dam, M. A.; Ono, K.; Mal, A.; Shen, H. B.; Nutt, S. R.; Sheran, K.; Wudl, F. A Thermally Re-mendable Cross-Linked Polymeric Material. Science 2002, 295, 16981702. (49) Zeng, C.; Seino, H.; Ren, J.; Hatanaka, K.; Yoshie, N. Self-Healing Bio-Based Furan Polymers Cross-Linked with Various Bis-Maleimides. Polymer 2013, 54, 5351-5357. (50) Ikezaki, T.; Matsuoka, R.; Hatanaka, K.; Yoshie, N. Biobased Poly(2,5-furandimethylene succinate-co-butylene succinate) Crosslinked by Reversible Diels-Alder Reaction. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 216-222.


33


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 36

(51) Hong, M.; Tang, X.; Falivene, L.; Caporaso, L.; Cavallo, L.; Chen, E. Y. X. ProtonTransfer Polymerization by N-Heterocyclic Carbenes: Monomer and Catalyst Scopes and Mechanism for Converting Dimethacrylates into Unsaturated Polyesters. J. Am. Chem. Soc. 2016, 138, 2021-2035. (52) Liu, D. J.; Zhang, Y. T.; Chen, E. Y. X. Organocatalytic Upgrading of the Key Biorefining Building Block by ACatalytic Ionic Liquid and N-heterocyclic Carbenes. Green Chem. 2012, 14, 2738-2746. (53) Mou, Z. H.; Feng, S.; Chen, E. Y. X. Bio-Based Difuranic Polyol Monomers and Their Derived Linear and Cross-Linked Polyurethanes. Polym. Chem. 2016, 7, 1593-1602. (54) Liu, D.; Chen, E. Y. X. Organocatalysis in Biorefining for Biomass Conversion and Upgrading. Green Chem.2014, 16, 964-981. (55) Liu, D.; Chen, E. Y. Diesel and Alkane Fuels from Biomass by Organocatalysis and MetalAcid Tandem Catalysis. ChemSusChem 2013, 6, 2236-2239. (56) Yan, Y.; Siegwart, D. J. Scalable synthesis and derivation of functional polyesters bearing ene and epoxide side chains. Polym. Chem. 2014, 5, 1362-1371. (57) Canadell, J.; Fischer, H.; De With, G.; van Benthem, R. A. T. M. Stereoisomeric effects in thermo-remendable polymer networks based on Diels-Alder crosslink reactions. J. Polym. Sci., Part A: Polym. Chem. 2010, 48, 3456-3467. (58) Hager, M. D.; Bode, S.; Weber, C.; Schubert, U. S. Shape memory polymers: Past, present and future developments. Prog. Polym. Sci. 2015, 49-50, 3-33. (59) Genovese, L.; Soccio, M.; Gigli, M.; Lotti, N.; Gazzano, M.; Siracusa, V.; Munari, A. Gas permeability, mechanical behaviour and compostability of fully-aliphatic bio-based multiblock poly(ester urethane)s. Rsc Adv. 2016, 6, 55331-55342.


34

Page 35 of 36

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(60) Oulame, M. Z.; Pion, F.; Allauddin, S.; Raju, K. V. S. N.; Ducrot, P.-H.; Allais, F. Renewable alternating aliphatic-aromatic poly(ester-urethane)s prepared from ferulic acid and bio-based diols. Eur. Polym. J. 2015, 63, 186-193. (61) Yao, X.; Wu, G.; Xu, L.; Zhang, H.; Yan, Y. Enzyme-catalyzed preparation of dimeric acid polyester polyol from biodiesel and its further use in the synthesis of polyurethane. RSC Adv. 2014, 4, 31062. (62) Bothe, M.; Emmerling, F.; Pretsch, T. Poly(ester urethane) with Varying Polyester Chain Length: Polymorphism and Shape-Memory Behavior. Macromol. Chem. Phys. 2013, 214, 2683-2693. (63) Fritzsche, N.; Pretsch, T. Programming of Temperature-Memory Onsets in a Semicrystalline Polyurethane Elastomer. Macromolecules 2014, 47, 5952-5959. (64) Bothe, M.; Pretsch, T. Two-Way Shape Changes of a Shape-Memory Poly(ester urethane). Macromol. Chem. Phys. 2012, 213, 2378-2385. (65) Wang, W.; Jin, Y.; Ping, P.; Chen, X.; Jing, X.; Su, Z. Structure Evolution in Segmented Poly(ester urethane) in Shape-Memory Process. Macromolecules 2010, 43, 2942-2947. (66) Shetranjiwalla, S.; Li, S. J.; Bouzidi, L.; Narine, S. S. Imparting elastomeric properties to entirely lipid-derived thermoplastic poly(ester urethane)s: Molecular weight control. Polymer 2016, 92, 140-152. (67) Pretsch, T.; Jakob, I.; Müller, W. Hydrolytic degradation and functional stability of a segmented shape memory poly(ester urethane). Polym. Degrad. Stab. 2009, 94, 61-73. (68) Zha, L.; Wu, M.; Yang, J. Hydrogen bonding and morphological structure of segmented polyurethanes based on hydroquinone– bis(β-hydroxyethy)ether as a chain extender. J.Appl. Polym. Sci. 1999, 73, 2895-2902.


35


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 36

(69) Wang, Z.; Zhang, X.; Zhang, L.; Tan, T.; Fong, H. Nonisocyanate Biobased Poly(ester urethanes) with Tunable Properties Synthesized via an Environment-Friendly Route. ACS Sustainable Chem. Eng. 2016, 4, 2762-2770. (70) Zeng, J.-B.; Li, Y.-D.; Zhu, Q.-Y.; Yang, K.-K.; Wang, X.-L.; Wang, Y.-Z. A novel biodegradable multiblock poly(ester urethane) containing poly(l-lactic acid) and poly(butylene succinate) blocks. Polymer 2009, 50, 1178-1186. (71) Caracciolo, P. C.; Thomas, V.; Vohra, Y. K.; Buffa, F.; Abraham, G. A. Electrospinning of novel biodegradable poly(ester urethane)s and poly(ester urethane urea)s for soft tissueengineering applications. J.Mater. Sci.: Mater.Med. 2009, 20, 2129-2137.

For Table of Contents Use Only

Polyesters and Poly(ester-urethane)sfrom Bio-based Difuranic Polyols Zehuai Mou and EugeneY.-X. Chen* OH

OH O O OH

O DHMF OH

OH

O

Cross-linked Polyesters

O O

O

O OH

O BHMF

HMF OH

O O

O

OH

O 4

O

Linear Polyesters

O

BHFA

Bio-based Difuranic Polyols

Poly(ester urethane)s

Synopsis. Three bio-based difuranic polyol monomers, allderived from the biomass platform chemical 5-hydroxymethylfurfural (HMF), were utilized to synthesize a series of new linear and cross-linked polyesters as well as amorphous and semicrystalline poly(ester-urethane)s.


36

Polyesters and Poly(ester-urethane)s from Biobased Difuranic Polyols

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