Synthesis by different methods and characterization of hyperbranched polyurethane

Article abstract of DOI:10.14233/ajchem.2013.oh8

Hyperbranched polyurethane (HBPU) samples are synthesized by two different methods from isophorone diisocyanate, 1,4-dihydroxybutane and diethanolamine generation by generation. And two series of samples are marked HBPU1s and HBPU2s. FTIR measurement is u

Full text of DOI:10.14233/ajchem.2013.oh8

Asian Journal of Chemistry; Vol. 25, No. 10 (2013), 5527-5531
http://dx.doi.org/10.14233/ajchem.2013.OH8
Synthesis by Different Methods and Characterization of Hyperbranched Polyurethane†
*
GUANGMEI CHEN , CHAO LIU and DONGFENG HU
College of Materials and Chemical Engineering, Anhui Key Laboratory of Advanced Building Materials, Anhui University of Architecture,
Hefei 230022, Anhui Province, P.R. China
*Corresponding author: E-mail: chen_gm168@yahoo.com.cn
AJC-13251
Hyperbranched polyurethane (HBPU) samples are synthesized by two different methods from isophorone diisocyanate, 1,4-dihydroxybutane
and diethanolamine generation by generation. And two series of samples are marked HBPU1s and HBPU2s. FTIR measurement is used
to characterize the structure of the samples. DSC and TG measure the thermal properties of the samples. The results indicate that the
hyperbranched structure of the polyurethane is consistent with theoretical design through controlling the feed ratio. The intensity of
hydrogen-bonded interaction in HBPU1s is stronger than that in HBPU2s. Two series samples have same thermal stability.
Key Words: Hyperbranched polyurethane, Generation by generation, Hydrogen-bonded interaction, Thermal stability.
the non-equal reactivity of different functional groups8. The
INTRODUCTION
preparation of hyperbranched polyurethane (HBPU) belongs
During the latest decades a new series of the materials-
hyperbranched polymers have been created. Hyperbranched
polymers are highly branched macromolecules with three-
dimensional dentritic architecture. Due to their unique physical
and chemical properties and potential applications in various
fields such as coatings, additives, drug and gene delivery,
macromolecular building blocks, nanotechnology and supra-
molecular science, interest in hyperbranched polymers is
growing rapidly1-4. Generally, the synthetic techniques used
to prepare hyperbranched polymers can be divided into two
major categories5. The one category is the single-monomer
methodology, in which hyperbranched macromolecules are
polymerized by an ABn or a latent ABn monomer. The other
category includes methods of the double-monomer methodo-
logy, in which direct polymerization of two types of mono-
mers generates hyperbranched polymers. Double-monomer
methodology can be divided into two main subclasses based
on the selected monomer pairs and different reaction pathways.
The one, polymerization of A2 and B3 (or Bn, n ≥ 3) mono-
mers, can be called the 'A2 + B3' methodology and was first
adopted intentionally to prepare soluble hyperbranched
polymers by Kakimoto and Frechet6,7. The other, combination
of the basic single-monomer methodology synthetic principle
and the multimonomer character of 'A2 + B3' methodology, is
called couple-monomer methodology based on in situ forma-
tion of ABn intermediates from specific monomer pairs due to
to couple-monomer methodology.
Because of the high reactivity of isocyanato groups against
the nucleophile, it is hard to obtain an AB2 monomer with an
isocyanato group. Therefore, hyperbranched polyurethanes
cannot be directly synthesized from AB2 monomers. Through
theA2+ BB'n approach, HBPU can be easily prepared by direct
polymerization of commercially available diisocyanates and
multi-hydroxyl amines9.
Recently, HBPU has attracted much attention because of
its special hyperbranched structure, its large amount of terminal
groups and the properties of low viscosity, non-chain entangle-
ment, good solubility etc.10,11. Hyperbranched polyurethane
has good potential prospects in coatings, biological materials,
polymer mixture, compound materials and many other fields.
Up to now, the HBPU is synthesized by one-pot method
usually8. It is very difficult to apply the prepared hyperbranched
polyurethanes owing to the complexity of the synthesis and
the purification procedures. And the sample purity is too low
to study its structure in depth. So in order to research its structure
and properties further, it's important to synthesize HBPU with
a new method which can obtain high purity samples.
In this work, according to couple-monomer methodology,
HBPUs are synthesized from isophorone diisocyanate, 1,4-
dihydroxybutane (BDO) and diethanolamine (DEOA) gene-
ration by generation. In each generation, the feed ratios are in
accordance with the stoichiometric ratio strictly. The structures
†Presented to the 6th China-Korea International Conference on Multi-functional Materials and Application, 22-24 November 2012, Daejeon, Korea

5528 Chen et al.
Asian J. Chem.
NCO
OH
CH2NCO
H3C
+
HO
CH3
H3C
O
HN
O
OCNH2C
CH2NCO
O
HO
OH
O
NH
NH
CH CH OH
2 2
O
HOH CH
2
C
O
2
N
N
10
C13H CH OH15
2 14
2
O
NH
12
HO H CH
2
C
NH
O
2
11
8
9
1
O
O
4
5
2
NH
3
NH
7
6
HOH2CH2C
HOH2CH2C
CH2CH2OH
OCHN
NHCO
N
R
N
CH2CH2OH
Scheme-I: Synthesis routes and structures of the first generation HBPU1-G1
11.1 g of isophorone diisocyanate dissolved in 10 mL
dimethyl formamide was taken in a reaction vessel. All of
HBPU1-G1 dissolved in 15 mL dimethyl formamide was
added in the vessel and kept the temperature at 85 ºC for 6 h.
Then the temperature was reduced to 0 ºC. 5.26 g of diethanol-
amine in 20 mL dimethyl formamide was dropped to the vessel
and kept the reaction for 4 h at 0 ºC. The solvent was distilled
in vacuum. The second generation was obtained and marked
HBPU1-G2 (Scheme-II). The rest generations can be done in
the same manner.
Another preparation method of HBPU is based on
HBPU1-G1. 11.1 g of isophorone diisocyanate dissolved in
10 mL DMF was taken in a reaction vessel. 2.25 g of BDO
was added to the vessel and kept the temperature at 85 ºC for 6
h. 4.66 g of HBPU1-G1 dissolved in 15 mL dimethyl formamide
was dropped in the vessel and kept the temperature at 85 ºC
for 8 h. Then the temperature was reduced to 0 ºC. 2.63 g of
diethanolamine in 10 mL dimethyl formamide was dropped
to the vessel and kept the reaction for 4 h at 0 ºC. The solvent
was distilled in vacuum. The another second generation was
obtained and marked HBPU2-G2 (Scheme-III).
of the HBPU samples are characterized by FTIR. The thermo
properties of the HBPUs are analyzed by thermogravimetric
analyzer (TG) and differential scanning calorimeter. The
results show the hyperbranched structure of the polyurethane
is consistent with theoretical design.
EXPERIMENTAL
Isophorone diisocyanate was procured fromAldrich, 1,4-
dihydroxybutane (BDO), dimethylformamide (DMF) and
diethanolamine (DEOA) were obtained from Huipu Chemical
Agents Co. Ltd. (Hangzhou China).All the solvents were used
as received and freed from moisture by adding 4 Å molecular
sieves before use.
Hyperbranched polyurethanes (HBPUs) were synthesized
generation by generation. 5.55 g of isophorone diisocyanate
was taken in a reaction vessel. 10 mL dimethylformamide
contained 1.13 g of BDO were added to the vessel. The reaction
time was 6h at 85 ºC. Then the temperature was reduced to 0 ºC.
-NCO content was determined by dibutyl amine method which
was found to be close to the expected theoretical value12. 2.63
g of diethanolamine dissolved in 10 mL dimethylformamide
was added in the vessel. The reaction kept 3 h at 0 ºC and the
solvent was distilled in vacuum. The first generation sample
was obtained which marked HPU1-G1 (Scheme-I).
FTIR spectra (Nicolet Nexus 870, USA) of samples were
obtained by the KBr pellet method. Each sample was scanned
32 times with a resolution setting of 2 cm-1 and spectra were

Vol. 25, No. 10 (2013)
Synthesis by Different Methods and Characterization of Hyperbranched Polyurethane 5529
NCO
CH2NCO
H3C
HOH2CH2C
HOH2CH2C
CH2CH2OH
CH3
H3C
OCHN
NHCO
N
R
N
CH2CH2OH
O
O
C
CH2NCO
OCNH2C
OH2CH2C
OH2CH2C
CH2CH2O
CH2CH2O
C
OCHN
NHCO
R
N
N
C
O
C
O
CH2NCO
OCNH2C
HN
HO
OH
O
O
CH2CH2OH
HOH2CH2C
O
C
O
C
CH2NHCN
NCHNH2C
HOH2CH2C
OH2CH2C
OH2CH2C
CH2CH2O
CH2CH2O
CH2CH2OH
CH2CH2OH
OCHN
NHCO
R
N
N
C
C
O
HOH2CH2C
HOH2CH2C
NCHNH2C
CH2NHCN
O
CH2CH2OH
O
O
Scheme-II: Synthesis routes and structure of the second generation HBPU1-G2
determined over the range of 4000-400 cm-1. Perkin-Elmer
Pyris-1 TGA was used to study the thermal decomposition
profile of hyperbranched polyurethane samples at a constant
rate of 10 ºC/min in inert nitrogen atmosphere from 20 ºC to
500 ºC. Differential scanning calorimeter was performed on a
TA-50 instrument. The samples were heated from 20 ºC to
200 ºC, cooled rapidly to -20 ºC and reheated to 200 ºC under
nitrogen atmosphere. The heating rate was 20 ºC /min.
HBPU1-G8
HBPU1-G5
HBPU1-G2
HBPU1-G1
RESULTS AND DISCUSSION
FTIR analysis: Fig. 1 shows the representative FTIR
spectra of HBOU1 series in the range 4000-400 cm-1. In the
spectra, the characteristic absorption band of -NCO groups at
2270 cm-1 was not displayed. The results show the all isocyanate
groups reacted. From HBPU1-G1 to HBPU1-G8, a strong and
broad absorption band exists in the range of 3100-3800 cm-1,
but the absorption peak shifts to higher wavenumber gradually,
from 3336 cm-1 to 3382 cm-1. Comparing to the absorption
band at 1700 cm-1, the intensity of the peak at 1635 cm-1
enhances gradually. According to the references13, the peak
values at 3600, 3520, 3350 and 3300 cm-1 are assigned to free
-OH, -NH, bonded -OH and bonded -NH, while the peaks at
1708, 1705, 1648 and 1635 cm-1 are due to free urethane, urea,
4000 3500 3000 2500 2000 1500 1000
500
Wavenumber (cm-1)
Fig. 1. FTIR spectra for HBPU1s samples
bonded urethane and bonded urea, respectively. Enhancement
of the absorption peak at 1635 cm-1 indicates the hydrogen
bonded between urethane and urea increases. The C=O groups
for the urethane and urea can form the hydrogen-bonded

5530 Chen et al.
Asian J. Chem.
NCO
OH
CH2NCO
CH3
H3C
H3C
+
HO
HOH2CH2C
HOH2CH2C
CH2CH2OH
CH2CH2OH
OCHN
NHCO
O
N
R
N
O
OCNH2C
CH2NCO
O
O
NH
NH
O
O
H
N
OCNRHNCOH2CH2C
CH2CH2OCNHRNCO
HO
OH
OCHN
NHCO
N
R
N
OCNRHNCOH2CH2C
CH2CH2OCNHRNCO
O
O
O
O
CH2CH2OH
HOH2CH2C
CH2CH2OCNHRNHCO
N
N
OCHNRHNCOH2CH2C
CH2CH2OH
CH2CH2OH
HOH2CH2C
HOH2CH2C
OCHN
NHCO
N
R
N
OCHNRHNCOH2CH2C
N
CH2CH2OCNHRNCO
N
HOH2CH2C
O
CH2CH2OH
O
Scheme-III: Synthesis routes and structure of the second generation HBPU2-G2
interaction with -NH and -OH. It is obvious that the enhance-
ment of the hydrogen-bonded interaction for C=O groups can
not be ascribed to the content -NH groups. The content ratio
of -NH/--OH decreases generation by generation in HBPU1
series, as shown in Scheme-I and II. The content of -OH groups
plays the impotant role on the hydrogen-bonded interaction
in HBPU1s. Shift to higher wavenumber of the peak in the
range 3800-3100 cm-1 approves the result.
Thermal property study: Fig. 3 gives the differential
scanning calorimeter curves for HBPU1-G5 and HBPU2-G5.
HBPU2-G5
HBPU2-G4
HBPU2-G3
HBPU2-G2
Interesting result appears in FTIR spectra of HBPU2
series, as shown in Fig. 2. The strong and broad absorption
band displays in the range from 3800-3100 cm-1. But the peak
values hold at 3335 cm-1. Meanwhile, compare to the absor-
ption band at 1700 cm-1, the intensity of the peak at 1635 cm-1
decreased generation by generation in HBPU2 series. Accor-
ding to the synthesis routes as shown in Scheme-III, the
content ratio of -NH/-OH in HBPU2s is higher than that in
HBPU1s.And the arm of each generation in HBPU2s is longer.
Free curl of the chain segment for HBPU2s is difficult. So
intensity of the hydrogen-bonded interaction for HBPU2s
reduces.
HBPU2-G1
4000 3500 3000 2500 2000 1500 1000
500
Wavenumber (cm-1)
Fig. 2. FTIR spectra for HBPU2s samples

Vol. 25, No. 10 (2013)
Synthesis by Different Methods and Characterization of Hyperbranched Polyurethane 5531
A broad dispersion endothermal peak displays in each curve.
For two differential scanning calorimeter curves, endothermal
range is from 20 to 120 ºC. The glass transition temperatures
for two samples can not be observed distinctly. But it is obvious
that the broad endothermal peaks are not attributed to crystal-
line melt. It can be deduced the broad endothermal peaks are
relevant to the disassembly of the hydrogen-bonded interaction.
On the other hand, it can be observed that the endothermal
enthalpy of HBPU1-G5 is bigger than that of HBPU2-G5 from
the curves. Intensity of the hydrogen-bonded interaction for
HBPU1-G5 exceeds that for HBPU2-G5. The results are
consistent with FTIR.
Conclusion
Hyperbranched polyurethane samples were synthesized
by two different methods and marked HBPU1s and HBPU2s,
respectively. FTIR measurement revealed that the hyperbranched
structure of the polyurethane is consistent with theoretical
design. Thermal properties studied by TG displayed HBPU1s
and HBPU2s have same thermal stability. However, only FTIR
measurement did not expatiate the structure of the hyper-
branched samples well and truly. More characterization
methods will be applied in our future work.
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3
2
1
0
0
40
80
120
160
200
Temperature (ºC)
Fig. 3. DSC curves for HBPU1-G5 and HBPU2-G5
The relative thermal stability of HBPU1-G5 and HBPU2-
G5 is evaluated from the thermal gravimetric ananlysis in N2
environment (Fig. 4). The decomposition curves for two
samples are identical. The characteristic thermal decomposition
temperatures such as onset decomposition temperature, tempe-
rature corresponding to maximum rate of weight loss and endset
decomposition temperature for different samples are equal.
HBPU1-G5 and HBPU2-G5 have same thermal stability.
100
HBPU1-G5
80
HBPU2-G5
60
40
20
0
0
100
200
300
400
500
Temperature (ºC)
Fig. 4. TG curves for HBPU1-G5 and HBPU2-G5