912 Biomacromolecules, Vol. 11, No. 4, 2010
Hojabri et al.
for 20 h. The reaction mixture was precipitated into a large excess of
warm distilled water. After removing water, the resulting polymer was
dissolved in 70 mL of chloroform, then precipitated in 800 mL of
methanol and stirred for 1 h at room temperature. The resulting white
solid was filtered and washed in methanol. The samples were coded as
ODEDO-HDI-NDO and ODEDO-HPMDI-NDO for TPUs produced
from ODEDO with HDI and HPMDI, respectively, with NDO used as
a chain extender. The yield for ODEDO-HDI-NDO was 83% and for
ODEDO-HPMDI-NDO was 78%. The detailed reaction procedure for
ODEDO-HPMDI-NDO system is illustrated in Scheme 2 as an example.
Experimental Section
Materials. Oleic acid (90% purity), triethylamine, sodium azide,
1,3-bis-(2,4,6-trimethylphenyl)-2-
(imidazolidinylidene)(dichlo-
rophenylmethylene)-(tricyclohexylphosphine)ruthenium (Grubbs cata-
lyst, second generation), ethyl vinyl ether, dibutyltin dilaurate (DBTDL),
tin(II) 2-ethylhexanoate (Sn(OCT)2), lithium aluminum hydride (Li-
AlH4), anhydrous DMF, and anhydrous THF were purchased from
Sigma-Aldrich. Ethylchloroformate was obtained from BDH Ltd.
Methanol, chloroform, ethyl acetate, and hexane were purchased from
Fisher. Aliphatic 1,6-hexamethylene diisocyanate (HDI, Desmodur H)
was sourced from Bayer Corporation. 1,7-Heptamethylene diisocyanate
(HPMDI)17 was synthesized from oleic acid according to the reported
procedure.
1,18-Octadec-9-enedioic acid 2. Oleic acid [28.2 g (90%), 0.1 mol]
was transferred into a 250 mL three-necked round-bottomed flask and
stirred at 45 °C under nitrogen gas for 0.5 h. Grubbs catalyst, second
generation (89 mg, 0.01 mmol), was then added. The reaction mixture
was stirred with a stirrer bar and kept at 45 °C. After approximately 5
min, the diacid began to precipitate from the reaction mixture. The
reaction was kept at this temperature for 24 h and then it was quenched
with ethyl vinyl ether (6.5 mL), and excess ether was removed under
reduced pressure. The residue was purified by column chromatography
using a hexane/ethyl acetate eluting solvent (4:1, 3:1, 2:1, 1:1, 1:0) to
give 10.0 g of pure 1,18-octadec-9-enedioic acid 2 as a white solid
(64%).25 1H NMR: δ 1.28-1.34 (m, 16H, 8CH2), 1.61-1.66 (m, 4H,
2CH2), 1.95-1.98 (m, 4H, 2CH2), 2.35 (t, J ) 7.2 Hz, 4H, 2 CH2COO),
5.35-5.37 (m, 2H, CHdCH).
1,18-Octadec-9-endiol (ODEDO) 3. The diacid compound 2 (5 g,
16 mmol) was dissolved in 50 mL of anhydrous THF. The reaction
flask was kept at 0 °C in an ice bath, and LiAlH4 (1.5 g, 38.4 mmol)
was added slowly over 30 min. The ice bath was removed, and the
mixture was stirred at room temperature for 4 h, followed by refluxing
for 0.5 h. Distilled water (40 mL) was added followed by 80 mL of 2
N HCl. The organic layer was extracted by 2 × 100 mL of ethyl acetate,
washed with brine (2 × 40 mL), and dried over MgSO4. The solvent
was evaporated by reduced pressure and residue was purified by flash
chromatography to afford 4.1 g (90%) of diol 3 as a white solid. Purity
of the compound (99%) was determined by GC-FID. 1H NMR: δ
1.25-1.37 (m, 20H, 10CH2), 1.41 (brS, 2OH), 1.53-1.59 (m, 4H,
2CH2), 1.94-1.98 (m, 4H, 2CH2), 3.63 (t, J ) 6.5 Hz, 4H, 2OCH2),
5.36-5.38 (m, 2H, CHdCH); 13C NMR: δ 25.7 (CH2), 29.0 (CH2),
29.4 (CH2), 29.5 (CH2), 29.6 (CH2), 32.6 (CH2), 32.8 (CH2), 63.0
(O-CH2), 130.3 (CHdCH).
1,9-Nonanediol (NDO) 5. The diacid compound 4 (9.4 g, 50 mmol)
was dissolved in 200 mL of anhydrous THF. The reaction flask was
kept at 0 °C in an ice bath, and LiAlH4 (4.69 g, 120 mmol) was added
slowly over 30 min. The ice bath was removed, and the mixture was
stirred at room temperature for 3 h, followed by refluxing for 0.5 h.
Distilled water (250 mL) was added, followed by 500 mL of 2 N HCl.
The organic layer was extracted by 2 × 150 mL of ethyl acetate, washed
with brine (2 × 20 mL), then dried over MgSO4. The solvent was
evaporated by reduced pressure, and the residue was purified by flash
chromatography to afford 7.3 g (91%) of diol 5 as a white solid. Purity
of the compound (99%) was determined by GC-FID. 1H NMR: δ 1.29
(m, 10H, 5CH2), 1.51-1.55 (m, 4H, 2CH2), 3.58-3.61 (m, 4H, 2CH2);
13C NMR: δ 25.7 (CH2), 29.3 (CH2), 29.4 (CH2), 32.7 (CH2), 63.0
(O-CH2).
1
ODEDO-HDI-NDO. H NMR: δ 1.27-1.32 (m, CH2), 1.47-1.48
(m, CH2), 1.57-1.58 (m, CH2), 1.93-2.04 (m, CH2), 3.14-3.15 (m,
NCH2), 4.01-4.03 (m, OCH2), 4.76 (bs, NH), 5.36-5.38 (m, CHdCH);
13C NMR: δ 25.81 (CH2), 25.87 (CH2), 26.30 (CH2), 29.08 (CH2),
29.14 (CH2), 29.28 (CH2), 29.39 (CH2), 29.61 (CH2), 29.94 (CH2),
32.57 (CH2), 40.77 (N-CH2), 64.84 (O-CH2), 130.32 (CHdCH),
156.84 (CdO); IR (cm-1): 1258, 1535, 1682 (CdO), 2853, 2921
(C-H), 3057()C-H), 3315 (NH).
ODEDO-HPMDI-NDO. 1H NMR: δ 1.23-1.30 (m, CH2), 1.46-1.49
(m, CH2), 1.57-1.59 (m, CH2), 1.93-2.04 (m, CH2), 3.13-3.15 (m,
NCH2), 4.01-4.05 (m, OCH2), 4.73 (bs, NH), 5.36-5.37 (m, CHdCH);
13C NMR: δ 25.86 (CH2), 25.92 (CH2), 26.66 (CH2), 28.92 (CH2),
29.12 (CH2), 29.19 (CH2), 29.32 (CH2), 29.44 (CH2), 29.65 (CH2),
29.98 (CH2), 32.62 (CH2), 40.94 (N-CH2), 64.88 (O-CH2), 130.38
(CHdCH), 156.89 (CdO); IR (cm-1): 1253, 1536, 1684 (CdO), 2852,
2921 (C-H), 3067 (dC-H), 3328 (NH).
Gas Chromatograph-Flame Ionization Detector (GC-FID)
System. Gas chromatograms were obtained on an Agilent 6890N
capillary GC (Santa Clara, CA) equipped with a flame ionization
detector and Agilent 7683B auto sampler. A 30 m × 0.32 mm × 0.1
µm DB-5HT column was used for the determination of diisocyanate
compound purity. The temperature of the column was initially set at
85 °C then increased to 250 °C at a rate of 10 °C/min and held for 5
min.
FTIR and NMR. FTIR spectrum of diisocyanate was measured with
a Mattson Galaxy series 3000 FTIR spectrophotometer. The analysis
of polymer specimens was performed using a Bruker Vertex 70 FTIR
main bench with an attached Hyperion FTIR microscope using OPUS
software. The spectra were obtained using a micro-ATR objective with
an analysis area approximately 100 µm in diameter. The spectra were
acquired using 128 scans at a resolution of 4 wavenumbers. 1H and
13C NMR were recorded at larmor frequencies of 500 and 125 MHz,
respectively, using a Varian UNITY 500 NMR spectrometer (Varian,
Inc., CA). Deuterated chloroform (CDCl3) was used as solvent.
Molecular Weight Measurements by Gel Permeation
Chromatography (GPC). The number and weight-average molecular
weights (Mn and Mw, respectively) were determined by GPC (Santa
Clara, CA). The tests were carried out using a GPC with an Agilent
G1311A quaternary pump, G1362A refractive index detector, and a
PL gel column (5 µm mixed-D). Chloroform and DMSO (1:1) was
used as the eluent at a flow rate of 0.8 mL/min. Sample concentrations
of 0.4% (w/v) and injection volumes of 10 µL were used. Polystyrene
standards were used to generate a calibration curve.
Wide Angle X-ray Diffraction (WAXD). A Bruker AXS X-ray
diffractometer (Madison U.S.A.) equipped with a filtered Cu KR
radiation source (λ ) 0.1542 nm) and a 2D detector was used to record
the WAXD patterns. The procedure was automated and controlled by
the Bruker AXS’s “GADDs V 4.1.08” software. The frames were
processed using GADDS software and the resulting spectra were
analyzed using Bruker AXS’s “Topas V 2.1” software.
Thermal Properties. MDSC measurements were carried out on a
DSC Q100 (TA Instruments, DE, U.S.A.), equipped with a refrigerated
cooling system. The samples were heated at a rate of 10 °C/min from
25 to 160 °C to erase thermal history, then cooled down to -50 °C at
a cooling rate of 5 °C/min. MDSC measurements were performed with
a modulation amplitude of 1 °C/min and a modulation period of 60 s
at a heating rate of 3 °C/min to 160 °C. The second heating stage was
selected for the analysis of heating data. All the DSC measurements
Polymerization. An excess amount of HDI (12 mmol) or HPMDI
(12 mmol) was dissolved in 4 mL of anhydrous DMF. The solution
was added to a three-neck flask and stirred. ODEDO (1.14 g, 4 mmol)
and four drops of Sn(Oct)2 were dissolved in 20 mL of anhydrous DMF
and added through an addition funnel fitted to the three-neck flask.
ODEDO and catalyst solution was in this manner slowly (within 30
min) added to the diisocyanate solution. The reaction mixture was then
stirred at 65 °C for 3 h to form the prepolymer. The prepolymer was
then chain extended to form a high molecular weight polymer by adding
NDO (1.28 g, 8 mmol) to the reaction mixture and stirring at 85 °C