Robust amidation transformation of plant oils into fatty derivatives for sustainable monomers and polymers

Article abstract of DOI:10.1021/acs.macromol.5b00091

Sustainable fuels, chemicals, and materials from renewable resources have recently gained tremendous momentum in a global scale, although there are numerous nontrivial hurdles for making them more competitive with petroleum counterparts. We demonstrate a

Full text of DOI:10.1021/acs.macromol.5b00091

Article
pubs.acs.org/Macromolecules
Robust Amidation Transformation of Plant Oils into Fatty Derivatives
for Sustainable Monomers and Polymers
Liang Yuan, Zhongkai Wang, Nathan M. Trenor, and Chuanbing Tang*
Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
S
* Supporting Information
ABSTRACT: Sustainable fuels, chemicals, and materials from
renewable resources have recently gained tremendous
momentum in a global scale, although there are numerous
nontrivial hurdles for making them more competitive with
petroleum counterparts. We demonstrate a robust strategy for
the transformation of plant oils into polymerizable monomers
and thermoplastic polymer materials. Specifically, triglycerides
were converted into N-hydroxyalkyl fatty amides with the aid
of amino alcohols via a mild base-catalyzed amidation process
with nearly quantitative yields without the use of column
chromatography and organic solvents. These fatty amides were further converted into a variety of methacrylate monomers, cyclic
norbornene monomers and imino ether monomers. Representative polymers from selected monomers exhibit drastic different
physical properties with subtle structural variations, highlighting the potential of this particular amidation reaction in the field of
biomass transformation.
fatty-derived thermoplastic polymers with high atom effi-
ciency.41
INTRODUCTION
■
With the depletion of fossil oil reserves, the utilization of plant-
based materials is becoming increasingly important for
sustainable development.1−17 As feedstock for the chemical
industry, plant oils stand out as one of the most important
renewable resources among rich raw materials and have been
widely used for the preparation of surfactants, intermediates,
paints and resins, and polymers and for the production of
biofuels.5,18−25 Thus, efficient and economical transformation
of their major components, triglycerides, into simple fatty
derivatives is highly sought for further preparation of
sustainable monomers, polymers, and materials.
Functional groups in triglycerides offer versatile organic
reactions for derivatization, such as hydrolysis,26 transester-
ification27 and amidation28 for ester groups, hydrogenation,29
oxidation,30,31 polymerization,32,33 epoxidation,34 addi-
tion,9,35,36 and metathesis37 for double bonds. Among these
reactions, the most successful reaction in commercialization of
triglycerides is their transesterification into fatty esters, mostly
in the presence of methanol.38 On the other hand, polymeric
materials based on these derivatives are mostly thermosets, like
alkyd resins, epoxy resins and polyurethane resins, resulting
from their inherent multifunctional properties. Non-cross-
linked linear polymers from plant oils have been much less
reported. Plant oil based 2-oxazoline monomer has been
prepared and polymerized via microwave promoted cationic
ring-opening polymerization.39 Recently, a soy-derived vinyl
ether monomer was prepared through the transesterification
reaction with 2-vinyloxy ethanol and polymerized by cationic
polymerization to afford linear polymers.40 Such monomers are
desirable as they can eventually transform triglycerides into
In synthetic organic chemistry, amidation of unactivated
esters with amino alcohols assisted by a catalyst (e.g.,
lipases,42,43 inorganic base,44 organic base45,46) has been widely
explored to form N-hydroxyalkyl amides, partially because of
the importance of amide group in many areas, like drug
development,47 polymers,48,49 and asymmetric catalysis.50 It is
generally believed that the reaction between esters and amino
alcohols follows consecutive transesterification and rearrange-
ment via O−N intramolecular acyl migration to form
amides.51−53 The choice of an appropriate base is critical for
obtaining high yield for this reaction. Both inorganic and
organic bases were used to promote the catalytic amidation
with over 80% yields. Naturally derived surfactants and
lubrication additives have been prepared through the amidation
of triglycerides with amino alcohols using both homogeneous
and solid base catalysts.54,55
Inspired by the above-mentioned pioneer work, herein we
report strategies for the preparation of oil based monofunc-
tional monomers and thermoplastic polymers using derivatives
from the base-catalyzed amidation of plant oils. Specifically,
various amino alcohols were utilized in converting triglycerides
into N-hydroxyalkyl fatty amides with the aid of sodium
methoxide to provide precursors for further derivatization
(Scheme 1). The amidation process was achieved with nearly
quantitative yields in the absence of column chromatography,
Received: January 15, 2015
Revised: February 10, 2015
© XXXX American Chemical Society
A
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a
Scheme 1. Derivatization of Triglycerides into N-Hydroxyalkyl Fatty Amides and Corresponding Monomers
a
The fatty structure was represented by the oleic group only for the purpose of simplification.
Table 1. Amidation of HOSO with Amino Alcohols and Further Preparation of Fatty Monomers
thus much appealing for sustainability. N-hydroxyalkyl fatty
amides were further converted into noncyclic methacrylate
monomers, and cyclic norbornene monomers and imino ether
monomers (oxazoline and oxazine). Selected monomers were
polymerized to validate the feasibility toward versatile
polymers. The subtle structural variation in N-hydroxyalkyl
amides led to polymers with drastically different properties,
highlighting the opportunities for the amidation process in the
preparation of biorenewable polymers and materials from plant
oils.
B
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Figure 1. (A) 1H NMR spectra of HOSO and N-hydroxyalkyl fatty amides 1, 2, and 3. (B) Proposed mechanism for the amidation of triglycerides
with amino alcohols, ethanol amine used as an example. (C) Photos of HOSO, 1, 2, and 3 at room temperature.
compound 3, corresponding to methylene protons in the N-
hydroxyalkyl groups. Peaks for the proton on nitrogen
(−NH−) were found at 5.8 ppm in 1 and 5.9 ppm in 2. A
peak for the methyl group on nitrogen (−N−CH3−) was
shown at 3.0 ppm in 3. The amidation process was also
monitored by FTIR, which observed the diminishing ester
carbonyl peak at ∼1763 cm−1 and the increasing amide
carbonyl group at ∼1640 cm−1 (Figure S1). The complete
disappearance of the ester group accompanied by the formation
of amide bond demonstrated a quantitative conversion. As
shown in many reports, a proposed mechanism of the above
transformation is probably involved with cascade trans-
esterification and acyl migration (Figure 1B). Transesterifica-
tion of esters with alcohol under basic conditions is very
common. The acyl migration subsequently led to more stable
amides via a possible cyclic intermediate, which could be
confirmed with the formation of cyclic imino ether, as described
in a later section of this paper.
These fatty derivatives have quite different physical
appearance. Both compounds 1 and 2 are secondary amides
and are solid at room temperature, while tertiary amide
compound 3 is a liquid (Figure 1C). The difference in their
physical states is certainly due to the difference in their
molecular structures. The presence of N−H group in 1 and 2
promotes the formation of H-bonds.
From N-Hydroxyalkyl Fatty Amides to Fatty Mono-
mers. We attempted to convert these N-hydroxyalkyl fatty
amides into a variety of noncyclic and cyclic monomers using
facile reactions (Scheme 1). We first prepared methacrylate
monomers.56 Initially methacryloyl chloride was used for direct
RESULTS AND DISCUSSION
■
From Triglycerides to Fatty Amide Derivatives. High
oleic soybean oil (HOSO), which contains an average of three
double bonds per triglyceride, was used as the representative
plant oil in this study. Amidation of unactivated esters into N-
hydroxyalkyl amides is typically carried out via a base-catalyzed
reaction, which involves transesterification and subsequent
rearrangement via O−N intramolecular acyl migration. A
variety of bases have been explored, including inorganic
hydroxides and organic bases such as N-heterocyclic
carbenes.44,46 Sodium methoxide was chosen as the base in
consideration of a homogeneous reaction media and facile
purification process.
In a typical procedure, an amino alcohol was mixed with
HOSO, followed by the addition of sodium methoxide to
promote the amidation process (Scheme 1). After the reaction,
N-hydroxyalkyl fatty amides were obtained by simply washing
the reaction mixture with brine water to remove catalysts and
glycerol, a side product from amidation. Using different amino
alcohols, three fatty derivatives, labeled as 1, 2, and 3, were
prepared with yields nearly 100% (Table 1). A typical structure
of N-hydroxyalkyl fatty amide based on the oleic group is
shown in Scheme 1, as 75% of the fatty acid chains in HOSO
were composed of oleic acid. The fatty amide structures were
confirmed by 1H NMR, as presented in Figure 1A. The spectra
show the complete disappearance of protons at 5.2 ppm
(−CH−) and 4.1−4.3 ppm (−CH2−), associated with the
glycerol core of HOSO. New peaks appeared at 3.4 ppm
(-NH−CH2−) and 3.7 ppm (−O−CH2−) in compound 1, 3.4
and 3.6 ppm in compound 2, and 3.5 and 3.8 ppm in
C
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halide displacement to form esters. However, it was found later
that such-prepared monomers often led to the formation of
cross-linked polymers. One possible reason was associated with
the formation of dimethacrylate between methacryloyl chloride.
Thus, column chromatography must be needed to make highly
pure monomers. We then employed a much more efficient
transesterification reaction with the aid of methacrylic
anhydride and catalytic DMAP. The reaction was very smooth
and went to nearly 100% conversion with a ratio of 1:1 between
N-hydroxyalkyl fatty amides and methacrylic anhydride without
the use of any organic solvent.
We also prepared norbornene monomers from these N-
hydroxyalkyl fatty amides for ring-opening metathesis polymer-
ization (ROMP) to make poly(norbornene)s. In order to
eliminate the influence of double bonds from the fatty chains
that could interfere in ring-opening metathesis polymerization,
epoxidation of 1, 2, and 3 was done with the aid of mCPBA to
transform the double bonds into oxirane rings (Figure S4).
Hydrogen peroxide could also be used to perform epoxidation
in a more environment-benign process.57,58 Esterification
between epoxidized N-hydroxyalkyl fatty amides and exo-5-
norbornenecarboxylic acid resulted in norbornene monomers
containing oxirane groups, labeled as 7, 8, and 9. The coupling
reaction, catalyzed by DMAP with the assistance of trimethyl
acetic anhydride that would form mixed anhydride with exo-5-
norbornenecarboxylic acid,56 was more efficient than an EDC/
DMAP-assisted reaction. Almost 100% conversion was
obtained after 12 h at 60 °C, when the acid and anhydride
were both used in 1.1 equiv to the hydroxyl group. As shown in
Figure 2B, the peak for the methylene protons (−O−CH2−)
shifted completely to 4.1−4.3 ppm with the formation of ester
bonds. Also, new peaks from the carbonyl group and double
bond were observed in 13C NMR spectra of norbornene
monomers (Figure S5).
Figure 2A shows 1H NMR spectra of methacrylate
monomers 4, 5, and 6. The methylene group (−O−CH2−)
Next, we explored the possibility to prepare cyclic monomers
from N-hydroxyalkyl fatty amides. Cyclic imino ethers of five or
six-membered systems are reactive monomers for making
poly(N-acylalkylenimine),59−61 which has numerous applica-
tions such as thermoresponsive hydrogels and polymer
surfactants.62,63 Such cyclic monomers are generally prepared
through a condensation process between alkyl acids or nitriles
with amino alcohols, which involves a high temperature
catalytic system.41 Specifically, cyclic imino ethers derived
from fatty acids need high vacuum distillation for purification.
One example of plant oil-derived cyclic imino ethers was a
soybean oil based 2-oxazoline monomer,39 which was prepared
under a harsh condition with the use of a titanium catalyst
under 200 °C. We carried out a direct dehydration of N-
hydroxyalkyl fatty amides 1 and 2 to make cyclic imino ethers
10 and 11 in a milder condition (Scheme 1). The dehydration
was assisted with p-toluenesulfonyl chloride, triethylamine and
DMAP in a solution of DCM at room temperature.50 Complete
1
conversion was observed within 12 h. Both H NMR (Figure
3A) and 13C NMR (Figure S6) confirmed the structures of 10
and 11. The peak from the N−H proton at around 6.2 ppm
disappeared with the formation of the cyclic structure. The
reaction followed a possible mechanism of in situ tosylation and
subsequent base-catalyzed cyclization (Figure 3B). The current
process provides a facile and milder strategy to obtain plant oil
based cyclic imino ethers when compared with the traditional
condensation method.
Representative Polymers from Fatty Monomers. To
validate the impact of versatile N-hydroxyalkyl fatty amides on
the properties of soy oil-derived polymers, we first selected
methacrylate monomers for free radical polymerization
(Scheme 2).
Figure 2. 1H NMR spectra of (A) methacrylate monomers; (B)
norbornene monomers from N-hydroxyalkyl fatty amides by anhydride
assisted esterification.
at around 3.5 ppm shifted to 4.2 ppm after the formation of the
ester group. New peaks at 6.1 ppm (−CH2C−), 5.6 ppm
(−CH2C−) and 2.0 ppm (C−CH3) corresponded to
vinyl and methyl protons next to the ester group. The
successful synthesis of monomers 4−6 was also confirmed by
13C NMR (Figure S3). This process was superior to other
methacrylation methods, as it only required aqueous solution
wash for the purification of monomers.
As shown in Table 2, all methacrylate monomers were
polymerized to achieve conversions >90%. The N−H
containing monomers 4 and 5 were found to be polymerized
much faster than 6. Over 90% conversion was obtained at 70
°C after 6 h for 4 and 5, while it took 20 h for 6 to reach similar
conversion at 80 °C. These polymers are very soluble in many
organic solvents (e.g., DCM, THF, toluene), without noticeable
1
formation of any cross-linked materials. Figure 4 shows the H
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Table 2. Properties of Polymers P1−P6 Prepared by Free
Radical Polymerization of Methacrylate Monomers (4−6)
and ROMP of Norbornene Monomers (7−9)
polymer
monomer
Đ
Mn (g/mol)
Tg (°C)
P1
P2
P3
P4
P5
P6
4
5
6
7
8
9
1.5
2.2
1.8
1.2
1.1
1.2
15 300
49 100
63 000
22 300
22 900
89 100
45.5
30.0
−6.2
−27.0
−30.7
−32.7
transition temperatures (Tg) are 45 and 30 °C, respectively, for
P1 and P2 (Figure 4), while P3 displayed a much lower Tg
around −6 °C.
Compared with P3, the higher Tg of P1 and P2 could be
explained by the presence of hydrogen bonding from the
secondary amide group. As shown in Figure 2 and Figure 4, the
signal for the amide proton underwent a low-field shift from a
narrow peak at 5.8 ppm to a broadened peak around 7.0 ppm
after the polymerization, indicating the formation of hydrogen
bonding between pendant amide groups.64 Thermogravimetric
analysis (TGA) indicated that polymer P1 shows two
degradation stages. According to the derivative TGA curves
of P1−P3, the two maximum degradation temperature of P1
was calculated to be 320.7 and 465.2 °C, while P2 and P3 show
better thermal stability with maximum degradation temper-
atures of 378.2 °C, 412.5 °C, 465.2 °C, and 388.5 °C, 432.2 °C
respectively (Figure S8). These results demonstrated that
methacrylate polymers P1−P3 have high thermal stability.
Due to the intermolecular hydrogen bonding and thus high
Tg, P1 and P2 may exhibit mechanical properties like
thermoplastics. Moreover, due to the facile preparation, we
carried out the synthesis of polymer P2 at a one pound scale.
Figure 3. (A) 1H NMR spectra of cyclic imino ethers derived from N-
hydroxyalkyl fatty amides; (B) proposed mechanism for the formation
of cyclic imino ethers.
NMR spectra of polymers P1−P3. The double bond in the
fatty side chain was found to be stable during the polymer-
ization process as the internal double bonds were not very
active in radical polymerization.
The influence of monomer structure on the polymer
properties was first observed from the physical appearance of
polymers P1, P2, and P3. Both P1 and P2 can form free-
standing films like thermoplastics, while P3 is very tacky and
could not form free films. DSC curves showed that the glass
Scheme 2. (A) Free Radical Polymerization of Methacrylate Fatty Monomers and (B) ROMP of Norbornene Monomers
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the polymerization, which indicated no cross-linking occurred
in the absence of double bond in the side chain.
The Tg of P4−P6 was determined from the DSC
thermograms, as shown in Figure 6. The Tg of all polymers
prepared by ROMP was around −30 °C. The presence of
secondary amide groups in the side chains of P4 and P5 did not
lead to appreciable difference from polymer P6 with tertiary
amide group. It suggested that hydrogen bonds from the
pendant amide groups in P4 and P5 could be weaker than
those in polymers P1 and P2. Additional evidence can be found
1
by comparing H NMR spectra of these polymers (Figure 4
and Figure 6), the chemical shifts of amide proton in P4 and P5
were less than those in P1 and P2 after the polymerization. The
Tgs of P4−P6 are comparable with those of poly(norbornene)s
from saturated C18 fatty ester of norbornene methanol (Tg =
−32 °C and Tm = 5.9 °C), as reported by the Meier group.66
However, no melting point was observed for P4−P6, possibly
due to the presence of oxirane ring within the side chain. P4−
P6 showed good thermal stability with similar two stage
degradation behaviors to P1−P3 (Figure S10).
CONCLUSIONS
■
In conclusion, highly efficient catalytic amidation reactions
between plant oils with amino alcohols were utilized for the
preparation of fatty amide derivatives, which were then used as
a powerful chemical platform for further derivatization into a
variety of monomers and thermoplastic polymers. Most plant
oil derived intermediates and monomers (methacrylates,
norbornenes and cyclic imino ethers) were obtained with
nearly quantitative yields without laborious column separation.
Selected monomers were further polymerized to yield polymers
that exhibit appreciable structure-dependent properties. The
strategy developed in the current work might pave a path for
the facile preparation of renewable monomers and thermo-
plastic polymers with targeted properties from plant oils.
EXPERIMENTAL SECTION
Figure 4. 1H NMR spectra and DSC curves of polymers P1−P3
prepared by free radical polymerization.
■
Materials. Plenish high oleic soybean oil (HOSO) was provided by
Dupont. Ethanolamine (99%, Aldrich), 3-amino-1-propanol (99%,
Aldrich), N-methyl ethanolamine (98%, Aldrich), methacrylic
anhydride (94%, Aldrich), trimethylacetic anhydride (99%, Aldrich),
exo-5-norbornenecarboxylic acid (97%, Aldrich), 4-dimethylaminopyr-
idine (DMAP, 99%, Aldrich), Grubbs catalyst (2nd Generation,
Aldrich), sodium methoxide (5.4 M solution in methanol, 30 wt %,
Acros Organics), triethylamine (TEA, 99%, Alfa Aesar), p-
toluenesulfonyl chloride (TsCl, 98%, Alfa Aesar), 3-chloroperbenzoic
acid (mCPBA, 70−75%, Alfa Aesar), and 5-norbornene-2-methyl-
amine (mixture of isomers, 98%, TCI) were used as received. Grubbs
Catalyst (3rd generation) was prepared according to a previous
report.67 Azobis(isobutyronitrile) (AIBN, 98%, Aldrich) was recrystal-
lized from methanol. All other reagents were from commercial
resources and used as received unless otherwise mentioned.
Figure 5A presents a picture of ∼1 lb P2 in a 2 L beaker with a
free-standing film of P2. Dog-bone specimens were cut from
the film for tensile testing (Figure 5B). A photo of P3 was also
given in Figure 5C, and the polymer was too soft to form a film.
A typical nominal stress-nominal strain curve of P2 obtained at
room temperature is shown in Figure 5D. The elongation at
break was found to be 140% with stress at break about 2.0 MPa.
The drastic difference between P2 and P3 probably results
from the chemical structure of the side chains as illustrated in
Figure 5E. Polymer chains of P2 can form strong interaction
with each other through hydrogen bonding with N−H bond on
the secondary amide group as the donor and carbonyl oxygen
as the acceptor, while no such significant interaction presents
between polymer chains of P3, which has tertiary amide group.
Ring-opening metathesis polymerization (ROMP) of nor-
bornene monomers 7, 8, and 9 were then carried out in the
presence of Grubbs III catalyst.65 The properties of norbornene
polymers P4−P6 were summarized in Table 2. The polymer-
ization went to nearly complete conversion in less than 20 min,
as confirmed by the disappearance of the double bond from
norbornene ring at 6.1−6.2 ppm and the appearance of double
bond in the polymer backbone at 5.1−5.5 ppm (Figure 6).
Peaks associated with the pendant chains were retained after
Characterizations. 1H NMR and 13C NMR spectra were recorded
on a Varian Mercury 300 spectrometer with tetramethylsilane (TMS)
as an internal reference. Molecular weights and distribution of
polymers were determined using a gel permeation chromatography
(GPC) equipped with a 2414 RI detector, a 1525 Binary Pump and
three Styragel columns. The columns consisted of HR 1, HR 3 and HR
5E in the effective molecular weight ranges of 100−5K, 500−30K, and
2K−4M respectively. THF was used as eluent at 35 °C with a flow rate
of 1.0 mL/min. The system was calibrated with polystyrene standards
obtained from Polymer Laboratories. GPC samples were prepared by
dissolving the sample in THF with a concentration of 3.0 mg/mL and
passing through microfilters with average pore size of 0.2 μm. Fourier
transform infrared spectrometry (FTIR) spectra were taken on a
F
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Figure 5. (A)Polymer P2 (1 lb) with a solvent-cast film; (B) specimens for tensile-stress test; (C) P3 in a mold; (D) stress−strain curve of P2; (E)
illustration of H-bonding in P2, in comparison with P3.
PerkinElmer spectrum 100 FTIR spectrometer. The glass transition
temperature (Tg) of polymers was tested through differential scanning
calorimetry (DSC) conducted on a DSC 2000 instrument (TA
Instruments). Samples were first heated from −70 to +200 °C at a rate
of 10 °C/min. After cooling down to −70 °C at the same rate, the data
were collected from the second heating scan. A 10 mg amount of each
sample was used for the DSC test with nitrogen gas at a flow rate of 50
mL/min. Thermogravimetric analysis (TGA) was conducted on a
Q5000 TGA system (TA Instruments), ramping from 25 to 600 °C
with a rate of 10 °C/min. Each test cost around 10 mg of the sample.
Tensile stress−strain testing was carried out with an Instron 5543A
testing instrument. The films were prepared by casting a DCM
solution of the polymer in a PTFE mold. After the evaporation of
solvent, the film was put under vacuum for 4 h at room temperature
and 4 h at 60 °C. Dog-bone shaped specimens were cut from the film
with a length of 20 mm and width of 5.0 mm before tested at room
temperature with the crosshead speed of 20 mm/min.
Synthesis of N-hydroxyalkyl Fatty Amides (1−3). HOSO (100 g,
around 0.344 mol ester group) was charged into a 500 mL round-
bottom flask and purged with nitrogen in an 100 °C oil bath for 1 h
before cooling down to 60 °C. For the preparation of compound 1,
ethanolamine (27 g, 0.443 mol) was added to the cooled HOSO.
Then, sodium methoxide dissolved in methanol (1.5 mL, 0.008 mol)
was added to the mixture. The solution was kept stirring at 60 °C until
the complete conversion of the ester bond as confirmed by FTIR.
Normally, it took around 4 h to obtain complete conversion for all the
amidation process. The crude product was poured into dichloro-
methane and washed twice with brine before being dried over
anhydrous magnesium sulfate. After filtration and removing the
solvent under reduced pressure, the product was obtained in yield
between 95%−97%. Compound 2 and 3 were prepared in the same
method using amino propanol and N-methyl ethanolamine as the
amidation agent.
state of liquid at room temperature. Compound 4 and 5 were prepared
in the same method.
Epoxidation of N-Hydroxyalkyl Fatty Amides. Compound 1 (10.2
g, 30 mmol) was dissolved together with mCPBA (9.0 g, 36 mmol) in
100 mL DCM and put into an ice−water bath. Na2CO3 (4.5 g, 42
mmol) was added into the solution. The solution was kept in ice−
water bath for 30 min and stirred at room temperature for 3 h. The
product was subsequently washed with Na2S2O3, NaHCO3, NaCl
before dried over anhydrous MgSO4. The dried solution was filtered
through a short column with basic Al2O3. With the evaporation of
DCM, the epoxidized product was obtained. The epoxidized
compound 1 and 2 were solid, while epoxidized compound 3 is a
liquid.
Synthesis of Norbornene-Functionalized Monomers (7−9).
Epoxidized compound 1 (1.0 g, 2.91 mmol), pivalic anhydride (0.6
g, 3.2 mmol, exo-5-norbornenecarboxylic acid (0.441 g, 3.2 mmol) and
DMAP (3.7 mg, 0.03 mmol) were dissolved in 3 mL THF and stirred
in an oil bath of 60 °C. After stirring for 20 h, 1.0 mL water was added
into the solution and stirred for 1 more hour. DCM was added to
dissolve the product and washed with NaHCO3 and NaCl aqueous
solution. The product 7 was obtained after drying the organic phase
and evaporation the solvent. Monomers 8 and 9 were prepared with
the same method.
Synthesis of Cyclic Imino Ethers (10 and 11). Compound 1 (3.25g,
10 mmol), DMAP (0.122g, 1 mmol), and TEA (3.3 mL, 22 mmol)
were dissolved within 40 mL of DCM in a 100 mL round-bottom flask.
The solution was put into an ice−water bath and stirred for 30 min
before TsCl (1.91g, 10 mmol) dissolved in DCM was added. The
reaction was stirred at room temperature for 20 h and the solution was
washed subsequently by aqueous solution of NH4Cl (twice),
NaHCO3, and water. The organic phase was dried by anhydrous
MgSO4 and flushed through silicone gel to get a liquid product 10.
Compound 11 was prepared in a similar way from compound 2.
Synthesis of Polymer P1 and P2 by Free Radical Polymerization.
Monomer 4 (5.0 g, 12.7 mmol) and AIBN (0.02 g, 0.12 mmol) were
dissolved in 10 mL toluene. The solution was purged with nitrogen for
15 min and put into a preheated oil bath set at 70 °C. After 6 h, the
solution was directly poured slowly into methanol at room
temperature under stirring. The polymer at the bottom was washed
twice with methanol and dried under vacuum at 60 °C to get P1.
Polymer P2 was prepared when monomer 5 was used.
Synthesis of Methacrylate Monomers (4−6). Compound 3 (102 g,
0.300 mol), methacrylic anhydride (49 g, 0.300 mol) and DMAP
(0.366g, 0.003 mol) were charged together into a 500 mL round-
bottom flask and put into an oil bate set at 60 °C. After stirring
overnight, 10 mL of deionized water was added into the reactor and
stirred for 1 h. The solution was then poured into DCM, washed with
brine for twice and dried with anhydrous magnesium sulfate. After
filtration and evaporation of DCM, compound 6 was obtained in a
G
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material is available free of charge via the Internet at http://
pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*(C.T.) E-mail: tang4@mailbox.sc.edu.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Support from the United Soybean Board (Project number
1440-612-6273) and National Science Foundation (DMR-
1252611) is acknowledged. We are grateful to Susan Knowlton
and David Tegeder from Dupont for providing Plenish high
oleic soybean oil.
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