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8
Macromolecules, Vol. 44, No. 1, 2011
Chen et al.
0
to 140 °C. 1,3-Dimethyl-3-phospholene oxide (DMPO, 0.050 g)
and diphenyl carbodiimide 21 (2.02 g, 10.4 mmol) were added
into the solution and stirred for 5 min. N,N -Bis(2,6-diiso-
propylphenyl)carbodiimide 1 (3.77 g, 10.4 mmol) dissolved in
N -phenyl-N-(2,6-diisopropylphenyl) carbodiimide (PiPr-CDI)
20 and diphenyl carbodiimide 21 respectively before their
hydrolysis.
0
Synthesis of Polyamide 4a-3 with No iPr-CDI Initiator in
Regular SSRR (Figure 4c). Synthesis of Aromatic Polyamide
1
2 mL of dry NMP and was then added into the reaction
0
0
mixture at 140 °C. The reaction was monitored by FT-IR. The
peak absorption at 2107, 2137, and 2166 cm were converted
into new CDI absorption at 2156 cm in 240 min. The result-
ing mixture was quenched by concentrated H SO (1 mL) and
H O (4 mL) and poured into 200 mL of water, filtered and
dried, to yield 4.89 g of crude urea product. FT-IR analysis
of the crude product showed the new CDI peak absorption
at 2156 cm have been converted into urea absorption at
1
N-(2,6-diisopropylphenyl) urea, diphenyl urea, and N,N -bis-
(2,6-diisopropylphenyl) urea respectively were measured by HPLC
analysis. This ratio of 32:23:45 was assumed to be the ratio of
the corresponding CDIs for N -phenyl-N-(2,6-diisopropylphenyl)
carbodiimide (PiPr-CDI) 20, diphenyl carbodiimide 21 and
N,N -bis(2,6-diisopropylphenyl)carbodiimide 1 respectively
before their hydrolysis.
4a -3 with No iPr-CDI Initiator 1 (Figure 4c). Reaction of 4,4 -
methylenebis(phenylisocyanate) (MDI) 3 with isophthalic acid
(IA) 2a in the molar ratio of iPr-CDI/MDI/IA = 0/1/1 is given
here as a typical example. Into a 100 mL, three-necked, round-
bottomed flask equipped with a thermometer, a nitrogen gas
inlet tube, a reflux condenser, an oil bath, and a magnetic stirrer
was placed 10 mL of dry NMP, and the flask was heated to
180 °C. 1,3-Dimethyl-3-phospholene oxide (DMPO, 0.050 g) was
added into the hot NMP solution and stirred for 30 s. Freshly
distilled MDI 3 (2.500 g, 10 mmol) and IA 2a (1.660 g, 10 mmol)
were dissolved in 20 mL of dry NMP and were then added
dropwise into the NMP solution in 6 min at 180 °C. The reaction
was further heated to 202 °C for 3 h. The reaction was monitored
-
1
-1
2
4
2
-1
-1
0
643 cm . The urea product ratios of 32:23:45 for N -phenyl-
0
0
-
1
by FT-IR. The peak absorption at 2112 and 2136 cm dis-
appeared in 10 min. No CDI peak absorption was generated and
persisted to the rest of 170 min. The resulting product 4a-3
solution was poured into 500 mL of water, filtered and dried, to
0
Reaction of 2,6-Diisopropylphenyl Isocyanate (iPr-NCO) 7
with Diphenyl Carbodiimide (diphenyl CDI) 21 (Scheme 9b). Into
a 100 mL three-necked round-bottomed flask equipped with a
thermometer, a nitrogen gas inlet tube, and a magnetic stirrer
was placed 6 mL of dry NMP and was heated to 140 °C. 1,
0
yield 3.214 g (98%) of crude polyamide 4a -3 (light yellow solid).
FT-IR analysis of the crude product showed amide absorp-
-
1
tion at 1668 cm and no CDI peak absorption at 2112 and
-
1
2136 cm . A small portion of product (0.5 g) was further puri-
fied by dissolving in about 5 mL of NMP solvent, following by
precipitating from 50 mL of chloroform (78% yields). The detail
3-Dimethyl-3-phospholene oxide (DMPO, 0.050 g) and diphenyl
carbodiimide 21 (0.51 g, 2.64 mmol) were added into the
solution and stirred for 5 min. 2,6-Diisopropylphenyl isocya-
nate 7 (1.07 g, 5.28 mmol) was dissolved in 7 mL of dry NMP
and was then added into the reaction mixture at 140 °C.
The reaction was monitored by FT-IR. The peak absorption at
1
results of FT-IR, H NMR, and GPC for aromatic polyamides
0
4a -3 were described above.
Demonstration of the Importance of iPr-CDI to Control
The Molecular Weight in New SSRR (Scheme 10). First Step:
Synthesis of Polyamides 26 with Unhindered Poly-CDI Contain-
-
1
2
290 cm rapidly diminished and disappeared, while a new
-
1
0
CDI IR absorption at 2156 cm became the major absorption
in 60 min. The resulting mixture was quenched by the addition of
concentrated H SO (0.5 mL) and H O (2 mL) to convert all
CDIs in the solution into urea derivitives. The resulting solu-
tion was poured into 200 mL of water, filtered and dried, to yield
1
product showed the new CDI peak absorption at 2156 cm
have been converted into urea absorption at 1643 cm . The
composition of this urea product mixture was analyzed through
HPLC where the relative ratio of ureas were determined to be
83:17 for N -phenyl-N-(2,6-diisopropylphenyl) urea and diphenyl
urea. This ratio of 83:17 was assumed to be the ratio of the
corresponding CDIs for N -phenyl-N-(2,6-diisopropylphenyl)
carbodiimide (PiPr-CDI) 20 and diphenyl carbodiimide 21
respectively before their hydrolysis.
Reaction of 2,6-Diisopropylphenyl Isocyanate (iPr-NCO) 7
with Phenyl Isocyanate (Phenyl NCO) 25 (Scheme 9c). Into a
1
ing (Scheme 10a). Reaction of 4,4 -methylenebis(phenylisocyanate)
0
(MDI) 3 with 4,4 -sulfonyldibenzoic acid (SA) 2c in the molar ratio
of iPr-CDI/MDI/SA = 0/10/8 is given here. Into a 100 mL, three-
necked, round-bottomed flask equipped with a thermometer, a
nitrogen gas inlet tube, a reflux condenser, an oil bath, and a mag-
netic stirrer, was placed 6 mL of dry NMP, and the flask was heated
to 180 °C. 1,3-Dimethyl-3-phospholene oxide (DMPO, 0.050 g)
was added into the hot NMP solution and stirred for 30 s. Freshly
distilled MDI 3 (2.500 g, 10 mmol) and SA 2c (2.450 g, 8 mmol)
were dissolved in 15 mL of dry NMP and were then added dropwise
into the NMP solution in 10 s at 180 °C. The reaction was further
heated to 202 °C for 2 min. The resulting product solution became
viscous and sticky in the process. The resulting product solution was
monitored by FT-IR. The peak absorption was converted into
2
4
2
.22 g of crude urea product. FT-IR analysis of the crude
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1
-1
0
0
-
1
poly-CDI absorption at 2112 and 2136 cm in 2 min. Taking small
resulting product solution (about ∼2 mL) was quenched by 50 mL
of water, filtered and dried, to yield 0.008 g of high molecular weight
polyamide 26 product with unhindered poly-CDI containing
00 mL three-necked round-bottomed flask equipped with a
thermometer, a nitrogen gas inlet tube, and a magnetic stirrer
was placed 5 mL of dry NMP, and heated to 140 °C. 1,3-
Dimethyl-3-phospholene oxide (DMPO, 0.05 g) and phenyl
isocyanate 25 (0.29 g, 2.43 mmol) were added into the solution
and stirred for 5 min. 2,6-Diisopropylphenyl isocyanate 7 (0.50 g,
(yellow and viscous solid). GPC (DMF): dispersity = 2.15, M
114752, M = 52373.
n
w
=
Second Step: Synthesis of Aromatic Polyamide 4c-2 with
Adding iPr-CDI Initiator 1 and SA Diacids 2c To Control The
Molecular Weight and Finish The Reaction (Scheme 10b). Reac-
0
2
.43 mmol) dissolved in 5 mL of dry NMP was then added into
tion of N,N -bis(2,6-diisopropylphenyl)carbodiimide (iPr-CDI)
0
the reaction mixture at 140 °C. The reaction was monitored by
FT-IR. The peak absorption at 2260 and 2290 cm disappeared
1 and 4,4 -sulfonyldibenzoic acid (SA) 2c with the first step of
-
1
the resulting product in the overall molar ratio of iPr-CDI/
MDI/SA = 1/10/10 is given here. The first step of the resulting
product solution was carried onto the second step. Initiator iPr-
CDI 1 (0.363 g, 1 mmol) and residual SA 2c (0.612 g, 2 mmol)
were dissolved in 9 mL of dry NMP and were then added
dropwise into the NMP solution in 6 min at 202 °C. The reaction
was further heated to 202 °C for 3 h. The viscous resulting
product solution clarified immediately in the process. The
reaction was monitored by FT-IR. The peak absorption at
-
1
and was replaced by new CDI absorption at 2156 cm in
20 min. The resulting mixture was quenched by concentrated
H SO (0.5 mL) and H O (2 mL) and poured into 200 mL of
1
2
4
2
water, filtered, and dried, to yield 0.51 g of crude urea product.
FT-IR analysis of the crude product showed the new CDI peak
absorption at 2156 cm has been converted into urea absorp-
-
1
-
1
tion at 1643 cm . The composition of this urea product mixture
was analyzed through HPLC where the relative ratio of urea was
0
-1
determined to be 72:28 for N -phenyl-N-(2,6-diisopropylphenyl)
urea and diphenyl urea, respectively. This ratio of 72:28
was assumed to be the ratio of the corresponding CDIs for
2112, 2136, and 2290 cm disappeared and was replaced by the
new hindered-CDI of absorption at 2151 cm in 30 min. The
-
1
-
1
new peak absorption at 2151 cm was persisted to the rest of 2.5 h.