Spectroscopic characterization of model urea, urethane compound, and diamine extender for polyurethane-urea

Article abstract of DOI:10.1021/ma011316+

During the reaction injecting molding process of polyurethane-urea (PUU) based on 4,4′-methylenebisphenyl diisocyanate (MDI), urethane as well as urea linkages are produced when a highly fluorescent aromatic diamine is used as a chain extender. To explore intrinsic fluorescence as a cure characterization technique, model urethane and urea compounds with similar chemical structures to MDI-based PUU were synthesized. Their fluorescence behavior were compared with that of diethyltolunediamine (DETDA), which is often employed as a chain extender. The emission maxima for DETDA in polypropylene oxide (PPO) polyol occurred at 336 nm, while the urea (diphenylurea) and the urethane (ethyl N-phenylcarbamate) model compounds showed emission maxima at 301 and 303 nm, respectively. The relative quantum yield for DETDA was determined to be 57 times greater than the urea compound, while the urethane compound possessed a relative quantum yield 11 times greater than the urea compound. The viscosity effect increased DETDA fluorescence intensity greater than the observed fluorescence intensity decrease associated with a temperature increase of 55°C. DETDA was found to be an effective collisional quencher for the urea and the urethane model compounds. The urea compound does not appear to quench the urethane compound's fluorescence significantly. Study of FT-IR spectra of model urea, urethane compounds, and DETDA provided characteristic peaks for each compound: 1727 cm^-1 for urethane, 1647 cm^-1 for urea, and 1623.7 cm^-1 for DETDA, which were also proportional to their concentration in PPO. NIR spectra of model compounds and DETDA indicate characteristics peaks for the urea, the urethane compounds, and DETDA. However, the urea peak absorbance was difficult to use for quantitative analysis, while the urethane and DETDA peaks could be readily applied for such analysis.

Full text of DOI:10.1021/ma011316+

Macromolecules 2002, 35, 877-882
877
Spectroscopic Characterization of Model Urea, Urethane Compound,
and Diamine Extender for Polyurethane-Urea
Sh i-Kw u n Wa n g a n d Ch on g Sook P a ik Su n g*
Polymer Program, Department of Chemistry, Institute of Materials Science, University of Connecticut,
9
7 North Eagleville Road, Storrs, Connecticut 06269-3136
Received J uly 24, 2001; Revised Manuscript Received November 19, 2001
ABSTRACT: During the reaction injecting molding process of polyurethane-urea (PUU) based on 4,4′-
methylenebisphenyl diisocyanate (MDI), urethane as well as urea linkages are produced when a highly
fluorescent aromatic diamine is used as a chain extender. To explore intrinsic fluorescence as a cure
characterization technique, model urethane and urea compounds with similar chemical structures to
MDI-based PUU were synthesized. Their fluorescence behavior were compared with that of diethyltolu-
enediamine (DETDA), which is often employed as a chain extender. The emission maxima for DETDA in
polypropylene oxide (PPO) polyol occurred at 336 nm, while the urea (diphenylurea) and the urethane
(ethyl N-phenylcarbamate) model compounds showed emission maxima at 301 and 303 nm, respectively.
The relative quantum yield for DETDA was determined to be 57 times greater than the urea compound,
while the urethane compound possessed a relative quantum yield 11 times greater than the urea
compound. The viscosity effect increased DETDA fluorescence intensity greater than the observed
fluorescence intensity decrease associated with a temperature increase of 55 °C. DETDA was found to be
an effective collisional quencher for the urea and the urethane model compounds. The urea compound
does not appear to quench the urethane compound’s fluorescence significantly. Study of FT-IR spectra of
model urea, urethane compounds, and DETDA provided characteristic peaks for each compound: 1727
-
1
-1
-1
cm for urethane, 1647 cm for urea, and 1623.7 cm for DETDA, which were also proportional to
their concentration in PPO. NIR spectra of model compounds and DETDA indicate characteristic peaks
for the urea, the urethane compounds, and DETDA. However, the urea peak absorbance was difficult to
use for quantitative analysis, while the urethane and DETDA peaks could be readily applied for such
analysis.
In tr od u ction
as by the changes in viscosity and temperature during
cure.
Hoyle and Kim investigated the emission spectra of
Recently, our laboratory has been involved in devel-
oping intrinsic fluorescence, phosphorescence, and UV-
vis spectroscopic techniques for the characterization of
8
model urethane or amine compounds to follow the
photolysis mechanism of MDI-based polyurethanes in
solution. They assigned the fluorescence peak at 301(
2 and 335( 2 nm to urethane and aromatic amine,
respectively, in dimethylformamide. Nevertheless, there
is little information published on the effects of their
interactions on the fluorescence emission spectra.
In this study, we report on the fluorescence behavior
of three model compounds representing the urea and
the urethane compounds as well as DETDA. Possible
interactions between the three model compounds and
their effects on the fluorescence characteristics were
investigated in addition to the effect of changes in
viscosity or temperature during cure. FT-IR and N IR
studies are also reported in an attempt to identify the
characteristic peaks for these three model compounds
and to evaluate whether such peaks can be used for
quantitative analyses.
1
cure in several polymers and composites such as epoxy,
2
3
4
polyimide, bis(maleimide), polyurethane, vinyl poly-
5
6
mers, and polycyanurate.
In polyurethanes based on nonfluorescent 4,4′-p-
methylenebisphenyl diisocyanante (MDI), fluorescence
intensity at the emission maxima of 314 nm was found
to increase about 87 times when MDI was converted to
diurethane, following reaction with 1-butanol or hy-
droxy-terminated poly(propylene oxide).4b The rate con-
stants and the activation energies for the model reaction
(
MDI with 1-butanol) and polyurethane formation (MDI
with hydroxy terminated polyol) were obtained from the
fluorescence results, which were correlated to the extent
of reaction determined by IR.
In polyurethane-ureas (PUU) which are often the
polymers made by reaction injection molding (RIM), the
chain extender is usually a highly fluorescent aromatic
diamine such as diethyltoluenediamine (DETDA), with
Exp er im en ta l Section
7
MDI and polyol as the other components. Thus, during
cure to form PUU, urethane linkage is formed from the
MDI-polyol reaction, while urea linkage is formed from
the MDI-DEDTA reaction. To explore intrinsic fluo-
rescence for cure characterization in PUU, we first
needed to characterize the fluorescence behavior of the
three fluorophores present in PUU: the urethane
derivative of MDI, the urea derivative of MDI, and
DETDA, individually. Furthermore, the fluorescence
intensities of these fluorophores may be influenced by
the interaction with each other (e.g., quenching) as well
Mod el Com p ou n d s. Diethyltoluenediamine (DETDA) with
a 80/20 isomer ratio as shown in Scheme 1 was received from
Ethyl Corp. and was purged with argon before storage in a
refrigerator. For the model compound representing mono-
urethane, ethyl N-phenylcarbamate was synthesized from the
reaction of excess ethanol with phenyl isocyanate from Aldrich
Chemical Co. by refluxing in ethanol at 70 °C in an oil bath
for 16 h under an argon gas purge. After removing unreacted
ethanol and phenyl isocyanate via vacuum distillation at 10
mmHg, the products were dissolved in cyclohexane at 50 °C,
followed by recrystallization upon slow cooling. The urea model
1
0.1021/ma011316+ CCC: $22.00 © 2002 American Chemical Society
Published on Web 01/04/2002

8
78 Wang and Sung
Macromolecules, Vol. 35, No. 3, 2002
Sch em e 1. Ch em ica l Str u ctu r es of Mod el Com p ou n d s
F igu r e 1. Emission fluorescence spectra of DETDA (1), ethyl
N-phenylcarbamate (2), and diphenyl urea (3) in ethylene oxide
terminated PPO (MW 2800) (4). Concentration at mole ratios
of 2/8, 8/8, and 2/8, respectively, when excited at 275 nm.
Ta ble 1. F lu or escen ce Em ission Ma xim a a n d Rela tive
F lu or escen ce Qu a n tu m Yield s (Of) of Mod el Com p ou n d s
in P P O
λmax, nm
relative φf
DETDA
ethyl N-phenylcarbamate
diphenylurea
336
303
301
57
11
1
background emission from PPO, when excited at 275
nm where all three models have UV absorption. Table
1
lists the emission maxima when excited at 275 nm
and the relative quantum yields according to eq 1,
If
(
)
)
A
If
(A
rel
(
φ )
)
(1)
f rel
compound, diphenylurea, also shown in Scheme 1, was syn-
thesized from the reaction of phenyl iscocyanate with aniline,
using a procedure similar to that described for the preparation
of ethyl N-phenylcarbamate. Diphenylurea was recrystallized
by cooling in dry ice from hot ethyl acetate solution, to yield
long needle-shaped fine crystals. Purity of ethyl N-phenyl-
carbamate and diphenylurea model compounds were confirmed
by FT-IR, DSC, and NMR.
Sp ectr oscop ic Ch a r a cter iza tion of Mod el Com p ou n d s.
For UV-vis and fluorescence measurements, all model com-
pounds were dissolved in hydroxyl terminated poly(propylene
oxide), PPO (MW 2000 g/mol or MW 2800 g/mol, used as
received from Aldrich Chemical Co.). The UV-vis, NIR, and
fluorescence emission measurements were obtained using a 3
mm path length, fused silica cuvette. A Perkin-Elmer Lambda
ref
where (φf)rel is the relative quantum yield, If the
fluorescence intensity, and A the absorbance at 275 nm.
The subscript “ref” represents the diphenylurea com-
pound, since it had the lowest fluorescence intensity.
The emission maximum of ethyl N-phenylcarbamate (at
3
03 nm) was similar to that previously reported by
8
Hoyle and Kim, while the emission maximum of
DEDTA (at 336 nm) was close to that reported for
aniline in dimethylformamide. The results in Table 1
indicate that DEDTA is most fluorescent (about 57
times) followed by ethyl N-phenylcarbamate (about 11
times) than the urea model compound, which has
emission maximum at 301 nm. Thus, the emission
maxima for ethyl N-phenylcarbamate and diphenylurea
are quite close.
Sim u la tion of P h ysica l Ch a n ges d u r in g RIM
P olym er iza tion of P UU. During the RIM process to
make PUU, both temperature and viscosity can rise
sharply. In general, an increase in temperature will
lower the fluorescence intensity, while an increase in
viscosity will raise the fluorescence intensity. To evalu-
ate these effects, we measured the fluorescence behavior
of DETDA in various temperature/viscosity environ-
ments, since it possessed the strongest fluorescence.
Fluorescence emission spectra of DETDA in 2000 MW
PPO at a concentration of 0.05 mol of DETDA in 1 mol
of PPO was studied as a function of temperature. The
fluorescence emission intensity decreased about 25%
without a change in the peak position when the tem-
perature increased from 25 to 80 °C in a fairly linear
fashion, as shown in Figure 2a. To mimic the viscosity
6
UV-vis spectrometer, a Perkin-Elmer Lambda 900UV-vis
NIR spectrometer, and a Perkin-Elmer LS50B luminescence
spectrometer were used to obtain the UV-vis, NIR, and
fluorescence emission spectra of the model compounds, re-
spectively. FT-IR studies were performed using a Nicolet
6
80DSP Spectral workstation. NMR spectra were collected in
deuterated DMSO or CDCI using a Bruker AC-270 or DMX-
00 NMR spectrometer.
3
5
Resu lts a n d Discu ssion
F lu or escen ce Ch a r a cter istics of Mod el Com -
p ou n d s. For simulating the urethane portion in PUU,
ethyl N-phenylcarbamate was used, while diphenylurea
synthesized from phenyl isocyanate and aniline was
used as the model compound for urea portion in PUU.
Poly(propylene oxide) (PPO) was used as a solvent to
obtain the UV and fluorescence spectra, since it is often
the soft segment used in PUU. Figure 1 shows the
fluorescence emission spectra of ethyl N-phenylcarbam-
ate, diphenylurea, and DETDA as well as the low

Macromolecules, Vol. 35, No. 3, 2002
Polyurethane-Urea 879
F igu r e 2. (a) Fluorescence intensity of DETDA at 336 nm in
PPO 2000 at 0.05/1 mole ratio as a function of temperature,
when excited at 275 nm. (b) Fluorescence intensity of DETDA
at 336 nm in PPO at 0.05/1 mol ratio as a function of molecular
weight of PPO, when excited at 275 nm.
F igu r e 3. (a) Changes in fluorescence spectra of ethyl
N-phenylcarbamate in PPO 2000 as a function of added
DETDA, when excited at 275 nm. (b) Stern-Volmer plot for
the quenching of ethyl N-phenylcarbamate by DETDA.
changes, at least during the early stages of cure, varying
molecular weights of PPO were used to observe the
fluorescence of DETDA. As the molecular weight of PPO
increases from 750 to 4000 g/mol, the fluorescence
intensity increased approximately 60% without a change
in the emission peak maxima, as shown in Figure 2b.
The increase in fluorescence intensity with PPO molec-
ular weight appears to approximate a linear relation-
ship. Since the viscosity is approximately proportional
to the molecular weight, we may assume fluorescence
intensity increases with viscosity. However, the viscosity
range investigated is relatively small compared to the
viscosity changes which occur throughout the cure
reaction. Therefore, the viscosity effect during cure is
expected to be greater than the temperature effect on
the fluorescence intensity.
In ter a ction s a m on g Mod el Com p ou n d s. During
PUU cure, all three fluorophores (DETDA, urea, and
urethane model compounds) can contribute to the
fluorescence. Furthermore, in the early stages of cure,
DETDA may be able to diffuse so as to quench the
fluorescence of the urea or the urethane fluorophores,
since aromatic amines are generally known to be good
quenchers.9b Before we can relate fluorescence charac-
teristics to the specific reactions (urea formation vs
urethane formation), we need to investigate the interac-
tions of these fluorophores.
Collisional quenching can be described by the Stern-
Volmer eq 9 as shown in eq 2.
F /F ) 1 + k τ [Q] ) 1 + K [Q]
(2)
0
q
0
D
where F0 is the fluorescence intensity in the absence of
quencher and F is the fluorescence intensity in the
presence of quencher. The terms kq, τ0, and KD represent
the biomoleuclar quenching constant, the fluorophore
lifetime in the absence of quencher, and the Stern-
Volmer quenching constant, respectively. Figure 3b
shows a Stern-Volmer plot, which is fairly linear with
an intercept of 1 as predicted by the Stern-Volmer
equation. Therefore, it is likely that the quenching may
be collisional. Since the fluorescence from urethane
compound can be reabsorbed by DETDA due to its UV
absorption characteristics, the observed quenching may
in part be caused by such an energy transfer.
(b) Qu en ch in g of Dip h en ylu r ea by DETDA. Fig-
ure 4 shows the quenching effect of DETDA on diphen-
ylurea fluorescence. When DETDA is added to diphen-
ylurea in PPO2000, urea fluorescence at 303 nm dis-
appears. Therefore, we can conclude that DETDA is an
effective quencher of urea fluorescence.
(c) In ter action of Eth yl N-P h en ylcar bam ate with
Dip h en ylu r ea . During PUU formation, urea linkages
may be formed earlier than urethane linkage, since
DETDA may react faster than the OH group of PPO.
Therefore, we tried to study the interaction between the
urethane and the urea model compound by fixing the
urea concentration, followed by adding increasing
amounts of the urethane model compound, ethyl N-
phenylcarbamate. Since the emission maxima for the
urea and the urethane model compounds are very close,
we cannot distinguish one compound from the other.
(
a) Qu en ch in g of Eth yl N-P h en ylcar bam ate Flu o-
r escen ce by DETDA. Ethyl N-phenylcarbamate, the
urethane model compound, shows a strong emission at
3
0l nm when excited at 275 nm in PPO. When succes-
sively greater amounts of DETDA were added, the
fluorescence intensity at 301 nm due to ethyl N-
phenylcarbamates decreased sharply, as illustrated in
Figure 3a. This behavior suggests quenching by
DETDA, which can be caused by energy transfer,
complex formation, and collisional encounters.

8
80 Wang and Sung
Macromolecules, Vol. 35, No. 3, 2002
F igu r e 4. Changes in emission fluorescence spectra of diphen-
ylurea in PPO 2000 as a function of added DETDA, when
excited at 275 nm.
F igu r e 6. FTIR spectra of ethyl N-phenylcarbamate in PPO
2000 at varying mole ratios (0.1, 0.2, 0.5, and 1 from bottom
to top curves).
F igu r e 7. FTIR spectra of diphenylurea in PPO 2000 at
varying mole ratios (0.005, 0.008, 0.01, 0.02, 0.04, 0.08, 0.1,
0
.25 from bottom to top spectra).
stretching band was free from hydrogen bonding in PPO
solutions at lower molar ratios, since it appears at 1727
F igu r e 5. Changes in emission fluorescence spectra of diphen-
ylurea in PPO (mole ratio: 0.2/0.8) as a function of added ethyl
N-phenylcarbamate (mole ratios of ethyl N-phenylcarbamate/
diphenyl urea, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 from bottom
to top spectra).
-
1
-1
cm . A shoulder at 1715 cm appearing at high ethyl
carbamate concentrations suggests that some hydrogen
-1
bonding may be occurring. The absorbance at 1727 cm
due to urethane was fairly linear with concentration,
-
1
when ratioed with the absorbance at 1373 cm due to
CH2 wagging mode, which is only present in PPO.10 On
the basis of these results, we selected the band at 1727
Figure 5 shows the fluorescence emission spectra of
diphenylurea in PPO as a function of added ethyl
N-phenylcarbamate. At lower molar ratios, the increase
in intensity was proportional to the molar concentration
of ethyl N-phenylcarbamate, which is about 11 times
more fluorescent than diphenylurea. Therefore, it ap-
pears that the urea compound does not seem to quench
the fluorescence of the urethane compound (ethyl N-
phenylcarbamate) significantly.
-
1
cm to represent the urethane group to correlate its
absorbance with fluorescence emission in the following
1
2
paper.
Dip h en ylu r ea in P P O. Figure 7 shows the FTIR
spectral changes associated with varying concentrations
of diphenylurea in PPO. Characteristic peaks in diphen-
ylurea are the CdO stretching band at 1647 cm , the
amide II combination band (at 1559 cm ), and the
-
1
F T-IR Sp ectr a of Mod el Com p ou n d s. Even though
the IR spectra of other urethane, urea compounds, and
aromatic amines have been extensively reported in the
-1
-1
amide III combination band at 1237 cm , while the
-1
band at 1596 cm
aromatic ring.
is due to C-H bending in the
1
0
literature, it was desirable to obtain IR spectra of these
three model compounds in a PPO environment as a
function of increasing concentration in order to properly
identify these functional groups during the formation
of PUU and to assess whether their characteristic IR
absorbances were proportional to their concentration.
11
11
According to the assignment made by Priester, free
urea appeared at 1715 cm and loosely H-bonded urea
appeared at 1700-1650 cm , while hydrogen-bonded
urea appeared at 1640 cm . From Figure 7, there
appears to be little free urea observed at any concentra-
tion. Urea appears hydrogen bonded as indicated by a
strong peak at 1647 cm . This trend may indicate
aggregation of urea in PPO. The absorbance at 1647
cm is proportional to its concentration, when refer-
-1
-1
-1
Eth yl N-P h en ylca r ba m a te in P P O. Figure 6 shows
the FTIR spectral changes observed with varying con-
centration of ethyl N-phenylcarbamate in PPO. Char-
acteristic peaks are the CdO stretching band at 1727
-1
-1
-
1
-1
cm , the amide II combination band at 1542 cm , and
-1
enced to the 1373 cm band due to PPO. Therefore,
we selected to use this urea band for subsequent
-1
the amide III combination band at 1223 cm , while the
band at 1601 cm
aromatic ring.
According to the assignment made by Priester,11 the
-
1
is due to C-H bending in the
12
correlation with fluorescence emission.
1
1
DETDA in P P O. Figure 8 shows the concentration
dependence of aromatic amine chain extender, DETDA
in PPO. The only characteristic peak in the 2000-1200
cm range is the band at 1623.7 cm , which can be
assigned to C-N stretching. Its absorbance is propor-
CdO stretching of the free urethane appeared at 1730
-
1
-1
-1
cm , while the H-bonded urethane appeared at 1715
-
1
cm . It seems that most of the ethyl carbamate CdO

Macromolecules, Vol. 35, No. 3, 2002
Polyurethane-Urea 881
F igu r e 8. FTIR spectra of DETDA in PPO 2000 at varying
mole ratios (0.05, 0.1, 0.15, 0.25 from bottom to top spectra).
F igu r e 10. NIR difference spectra of diphenylurea in PPO
2000 at varying mole ratios (0.001, 0.004, and 0.008 from
bottom to top) after subtracting PPO 2000 spectra.
F igu r e 9. NIR difference spectra of ethyl N-phenylcarbamate
in PPO 2000 at varying mole ratios (0.05, 0.1, 0.2, 0.5, 0.8, 1,
1
2
.6, and 2 from bottom to top spectra), after subtracting PPO
000 spectra.
F igu r e 11. NIR difference spectra of DETDA in PPO 2000
at varying mole ratios (0.0005, 0.0008, 0.002, 0.02, 0.03, 0.07,
0.1, 0.15, and 0.25 from bottom to top) after subtracting PPO
Ta ble 2. IR Ba n d P osition s (in cm -1) for Eth yl
N-P h en ylca r ba m a te a n d Dip h en ylu r ea in P P O
2
000 spectra.
ethyl
N-phenylcarbamate
were observed. From the band assignment by Miller,13b
the 1672 and 2155 nm bands might originate from the
overtone of aromatic CH, 1735 nm from the overtone of
CH group in the PPO soft segment, and 2045 nm from
the urethane N-H stretching combination band. From
the results of the model compounds study, the NIR
spectra seemed very sensitive to changes in the ure-
thane concentration. The absorbance values of all three
bands at 1672, 2045, and 2155 nm showed linear
correlations with concentration up to a very high molar
ratio, greater than the usual urethane concentration in
PUU. This result indicates that the urethane chro-
mophore can be quantified by NIR by tracking the band
at 2045 nm due to N-H group, if the sample thickness
is thick enough to obtain an accurate absorbance.
Dip h en ylu r ea in P P O. For the NIR spectra of
diphenylurea in PPO, as illustrated in Figure 10, only
the band at 2038 nm showed linear changes with
concentration at very low ratios. This band position
coincides with the urea overtone band for free CdO
vibration modes
diphenylurea
CdO stretching
amide II
amide III
1727
1542
1223
1601
1647
1559
1237
1596
aromatic C-H bending
tional to its concentration when referenced to 1373 cm-1
band due to PPO.
Table 2 compares the band positions for the urethane
and the urea model compounds for several characteristic
vibration modes. We can see from Table 2 that the Cd
O stretching bands are well-separated (∆v ) 81 cm ),
thus making them good choices to be used for distin-
guishing the urethane group from the urea group.
NIR Sp ectr a of Mod el Com p ou n d s. The absorption
spectral range of the model compounds was extended
to the NIR region to explore its applicability in cure
monitoring. Previous research demonstrated the poten-
-
1
1
3
tial of NIR spectroscopy on polyurethane ureas and
polyurethanes. Dittman and Siesler also reported on
NIR monitoring of the syntheses of diphenylurethane.
1
4
1
5
13b
stretching reported by Miller. At molar ratios above
Miller has studied aliphatic urea model compound for
NIR band assignments.13 It appears that careful NIR
studies using model compounds whose structures are
similar to PUU based on MDI and DETDA are not
available in the literature, especially with regards to
whether NIR bands can be used for quantitative analy-
ses. Therefore, we varied the concentrations of model
urea, urethane compounds, or DEDTA in PPO and
investigated their NIR spectra.
Eth yl N-P h en ylca r ba m a te in P P O. Figure 9 shows
the NIR difference spectra for the PPO solutions of ethyl
N-phenylcarbamate at varying molar ratios, after sub-
tracting the NIR spectra of PPO. Three positive absor-
bance changes and one negative absorbance change
the range of 0.001-0.008 mol of diphenyl urea per 1 mol
of PPO, the mixture becomes turbid, probably due to
urea aggregation, making NIR absorbance meaningless.
This phenomenon makes it difficult, if not impossible,
to use the 2038 nm peak to quantify the urea group in
PUU where the urea concentration is typically in the
range of 0.2 mol of urea per 1 mol of PPO.
DETDA in P P O. Three positive NIR difference bands
were observed for the NIR spectra of DETDA in PPO
solutions as shown in Figure 11. The peak at 1496 nm
1
3b
was not assigned by Miller, but it possibly originates
from the overtone of free aromatic amine N-H stretch-
ing while the 1974 nm band might be from the H-bonded
aromatic amine N-H stretching overtone band. The

8
82 Wang and Sung
Macromolecules, Vol. 35, No. 3, 2002
Ta ble 3. Ch a r a cter istic Ba n d s in NIR Sp ectr a of Mod el
Com p ou n d s in P P O
(3) (a) Phelan, J . C.; Sung, C. S. P. Macromolecules 1997, 30,
6837. (b) Phelan, J . C.; Sung, C. S. P. Macromolecules 1997,
3
0, 6845.
4) (a) Huang, X. Y.; Yu, W. C.; Sung, C. S. P. Macromolecules
990, 23, 390. (b) Sun, X. D.; Sung, C. S. P. Macromolecules
characteristic NIR absorption
(
model compounds
bands (nm)
1
ethyl N-phenylcarbamate
diphenylurea
DETDA
1672, 2045, 2155
1919, 2038, 2165
1496, 1974, 2165
1996, 29, 3198. (c) Wang, S. K.; Sung, C. S. P. ACS Polym.
Prepr. 1998, 40-1, 637.
(5) (a) Kim, Y. S.; Sung, C. S. P. J . Appl. Polym. Sci. 1995, 57,
63. (b) Grunden, B.; Kim, Y. S.; Sung, C. S. P. ACS Polym.
3
Prepr. 1996, 37, 477.
2
165 nm band was similar in all three model compounds
(
6) (a) Xu, Y. E.; Sung, C. S. P. ACS Polym. Prepr. 1996, 37-2,
and originates from the aromatic CH stretching over-
tone. The absorbance values of these three bands
appeared to be linear with DETDA concentration up to
high molar ratios.
Table 3 summarizes the characteristic bands found
in the NIR study of the urethane, the urea model
compounds, and aromatic amine chromophores. These
bands were well isolated from each other. With the
exception of diphenylurea, the bands for ethyl N-
phenylcarbamate and DETDA may be used for quanti-
tative analysis.
2
08. (b) Xu, Y. E.; Sung, C. S. P. ACS Polym. Prepr. 1995,
36-2, 356.
(7) (a) Macosko, C. W. RIM Fundamentals of Reaction Injection
Molding; Hanser: New York, 1989; Chapter 1. (b) Schlotter-
beck, D. G.; Matzke, G.; Horn, P.; Schmidt, H. U. Plast. Engr.
1
989, 1, 37.
8) Hoyle, C. E.; Kim, K. J . J . Polym. Sci., Part A: Polym. Chem.
986, 24, 1879.
(
(
1
9) (a) Doub, L.; Vanderbelt, J . M. J . Am. Chem. Soc. 1947, 69,
2714; 1949, 71, 2414. (b) Lakowicz, J . R. Principles of
Fluorescence Spectroscopy, 2nd ed.; Plenum: New York, 1999;
Chapter 8.
10) (a) Camargo, R. E.; Gonzalez, V. M.; Macosko, C. W.; Tirrell,
M. Rubber Chem. Technol. 1983, 56, 774. (b) Yokoyama, T.
Adv. Urethane Sci. Technol. 1978, 6, 1.
11) Priester, R. D., J r.; McClusky, J . V.; Cortelek, D. I.; Carleton,
P. S.; Porter, J . R.; DeHaseth, J . A. 34th Annual Polyurethane
Technical/Marketing Conference, 21, 1992.
(
Ack n ow led gm en t. We acknowledge the financial
support of this work by NSF (DMR-94-15385), ARO
(
(
Contract DAAL03-92-G-026), and the Office of Naval
Research. We also extend our gratitude to Dr. Bradley
Grunden for his excellent editorial help on the manu-
scripts.
(
(
12) Wang, S. K.; Sung, C. S. P. Macromolecules 2002, 35, 883.
13) (a) Miller, C. E.; Edelman, P. G.; Ratner, B. D.; Eichinger,
B. E. Appl. Spectrosc. 1990, 44, 581. (b) Miller, C. E.;
Edelman, P. G.; Ratner, B. D. Appl. Spectrosc. 1990, 44, 576.
Refer en ces a n d Notes
(
c) Miller, C. E.; Eichinger, B. E. J . Appl. Polym. Sci. 1991,
2, 2169.
14) DeThomas, F. A.; Hall, J . W.; Monfre, S. L. Talanta 1994,
1, 425.
4
(
1) (a) Song, J . C.; Sung, C. S. P. Macromolecules 1993, 26, 4818.
(
(
(
b) Song, J . C.; Sung, C. S. P. Macromolecules 1995, 28, 5581.
c) Yu, J . W.; Sung, C. S. P. Macromolecules 1995, 28, 2506.
4
(
2) (a) Pyun, E.; Mathisen, R.; Sung, C. S. P. Macromolecules
989, 22, 1174. (b) Dickinson, P.; Sung, C. S. P. Macromol-
(15) Dittman, K.; Siesler, H. W.; Fresenius, J . Anal. Chem. 1998,
363, 109.
1
ecules 1992, 25, 3758. (c) Kailani, M. H.; Sung, C. S. P.
Macromolecules 1998, 31, 5771. (d) Kailani, M. H.; Sung, C.
S. P. Macromolecules 1998, 31, 5779.
MA011316+