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RSC Advances
DOI: 10.1039/C6RA15200G
ARTICLE
RSC Advances
the preparation of epoxy thermosets together with several acid Scheme 1. Molecular representations of reagents used for the
resin manufacturing process (hardeners: MA, PA, THPA, HHPA,
FDCA, MPA; catalyst: EMID).
derivatives hardeners. Although amines are the most used
hardeners, this family of curing agents was preferentially selected
because they also can be efficiently prepared from biorenewable
22
resources. DGE-isoEu was fully characterized by nuclear magnetic
resonance (NMR), mass spectrometry (MS) and Fourier transform
infrared spectroscopy (FT-IR). The polymerization and the resulting
materials were monitored and analysed by differential scanning
calorimetry (DSC), thermogravimetric analyses (TGA), and
nanoindentation. Finally, the curing properties of DGE-isoEu,
directly derived from lignin, are compared to those of
diglycidylether of eugenol (DGE-Eu), derived from clove, and
2
.2.
Methods
2
.2.1. Synthesis of diglycidylether of iso-eugenol (DGE-isoEu).
A solution of NaOH (4.5 mL, 14 M, 63 mmol) was slowly added to
iso-eugenol (10 g, 61 mmol) and epichlorohydrin (19 mL, 242 mmol)
o
and heated to 80 C. After three hours, the reaction mixture was
cooled down and the product was extracted with toluene (70 mL),
washed with water (20 mL) and brine (20 mL), dried with MgSO4,
filtered. After evaporation the resulting yellowish oil was purified by
column chromatography to yield the intermediate as a white solid
23
recently reported by Zhang et al.
(
9.35 g, 42 mmol) in 70% yield. This intermediate (0.30 g, 1.3 mmol)
2
. Materials and methods
was dissolved in 5 mL water and 5 mL dichloromethane (DCM) and
o
cooled to 0 C. NaHCO (0.57 g, 6.7 mmol), Bu NHSO (23 mg, 0.068
3
4
4
2.1.
Materials
mmol), acetone (1 mL, 1.3 mmol), and Oxone (aq) (10 mL, 0.4 M, 4
mmol) were slowly added. The reaction mixture was let to reach
room temperature and stirred for 3 hours. The reaction was
worked-up by adding DCM (5 mL), the organic phase was washed
2
.1.1. Synthesis
of
DGE-isoEu.
2-Methoxy-4-(1-
propenyl)phenol (isoEu) was prepared according to published
18
procedures. Epichlorohydrine (> 99% purity), Bu
4 4
NHSO (97%
purity), and Oxone were purchased from Sigma-Aldrich and were
with water 10 mL and brine 10 mL, dried using MgSO , filtered, and
4
used without any further purification. NaHCO
was obtained from Fisher Scientific.
3
(Analytical grade)
the solvents were evaporated to yield the product (280 mg, 1.2
mmol) as a transparent oil in 92% yield.
1
2.1.2. Thermosetting polymerization. Maleic anhydride (MA,
H NMR (400 MHz, CDCl ) δ 6.87 (m, 1H, Ar), 6.81 (m, 1H, Ar),
3
99% purity), phthalic anhydride (PA, 99% purity), 3,4,5,6-
6.73 (m, 1H, Ar), 4.21 (dd, J = 11.4 and 3.5 Hz, 1H, CH O), 4.00
2
tetrahydrophthalic anhydride (THPA, 95% purity), 1,2-
cyclohexanedicarboxylic anhydride (HHPA, 95% purity), 2,5-
furandicarboxylic acid (FDCA, 97% purity), and 2-ethyl-4-
methylimidazole (EMID, 95% purity) were purchased from Sigma-
Aldrich and were used without any further purification.
Maleopimaric acid (MPA) was prepared according to a published
(
dd, J = 11.4 and 5.6 Hz, 1H, CH O), 3.84 (s, 3H, Me), 3.51 (d, J =
2
2
.1 Hz, 1H, CH(O)CHMe), 3.35 (m, 1H), 2.99 (qd, J = 5.1 and 2.1
Hz, 1H, CH(O)CHMe), 2.86 (dd, J = 4.9 and 4.2 Hz, 1H), 2.70 (dd,
J = 4.9 and 2.7 Hz, 1H), 1.41 (d, J = 5.1 Hz, 3H, Me); cis isomer
(incomplete): 3.85 (s, 3H, Me), 3.28 (m, 1H), 1.07 (d, J = 5.5 Hz,
1
H, Me); C{ H} NMR (100 MHz, CDCl ) δ 149.8, 147.8, 131.4,
3
1
3
1
3
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procedures. Molecules are described in Scheme 1.
18.2, 114.0, 108.6, 70.3, 59.4, 58.8, 55.8, 50.1, 44.8, 17.7; MS
(EI) (m/z) (rel. intensity): 236 (M+, 45%), 207 (18%), 193 (55%),
1
51 (14%), 137 (100%), 122 (10%), 107 (8%), 91 (10%), 77
-1
(
10%); IR (neat, cm ): ν 3000, 2964, 2930, 1609, 1593, 1515,
max
1
1
461, 1417, 1378, 1352, 1319, 1269, 1247, 1229, 1195, 1162,
137, 1081, 1022, 971, 928, 912, 862, 840, 803, 757, 720.
2
.2.2. Curing of the epoxy monomers. A comparable protocol
as previously depicted by Zhang et al. was repeated for each sample
2
3
of this study. DGE-isoEu prepolymer and curing agents (MA, PA,
THPA, HHPA, FDCA, MPA) in a 1:0.8 molar ratio were first ground in
a mortar at room temperature until an homogeneous mixture is
obtained. EMID used as catalyst (ratio 0.08 eq or 0.12 eq with
respect to curing agent (see details in table 1) was then added and
intimately ground. The 1:0.8 molar ratio instead of a 1:1 was used
to take into account the possible reaction involving hydroxyl groups
formed and epoxy functions, leading to polyether.
A few milligrams of this homogeneous mixture was placed
in a DSC pan in order to study polymerisation reaction. The
remaining mixture was transferred in an aluminium pan and
cured in an oven at 150 °C during 1h.
2
| RSC Adv., 2016, 00, 1-3
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