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Supercritical CO2 induced phase transition of Form III in isotactic poly-1-butene.

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ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING
Asia-Pac. J. Chem. Eng. 2009; 4: 800–806
Published online 7 July 2009 in Wiley InterScience
(www.interscience.wiley.com) DOI:10.1002/apj.341
Special Theme Research Article
Supercritical CO2 induced phase transition of Form III
in isotactic poly-1-butene
Lei Li, Tao Liu,* Ling Zhao* and Wei-kang Yuan
State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai, People’s Republic of China
Received 27 October 2008; Revised 19 March 2009; Accepted 20 March 2009
ABSTRACT: The effect of supercritical or high-pressure CO2 on the recrystallization of Form II in isotactic poly-1butene (iPB-1) during the melting of Form III was investigated using high-pressure differential scanning calorimetry
(DSC). The results showed that the recrystallization of Form II was inhibited by CO2 . The crystal–crystal transition
of Form III to I in ambient nitrogen and supercritical CO2 was studied using fourier transform infrared spectroscopy
(FTIR) and DSC. The results showed that CO2 promoted the phase transition and the transition proportion of Form
III increased with the CO2 pressure increasing. Form III completely transformed into Form I at 18 MPa. Moreover,
supercritical CO2 could induce the amorphous region to transit into Form I . The probable mechanism of the CO2
effects on Form III multiple transitions was also proposed.  2009 Curtin University of Technology and John Wiley
& Sons, Ltd.
KEYWORDS: isotactic poly-1-butene; supercritical carbon dioxide; phase transformation; crystal form III
INTRODUCTION
Isotactic poly-1-butene (iPB-1) with many outstanding
properties is one of the major commodity polymers.[1,2]
Depending on the formation conditions, it may exist in
four different crystal structures designated as forms I, II,
III, and I .[3 – 5] Unstable Form II is usually obtained by
crystallization from the melt under atmospheric pressure
and it slowly transforms to stable Form I.[6,7] Form III
and I can be generated from certain dilute solutions.[8]
Form I is also obtained by crystallization from the
melt of Form III under high hydrostatic pressure or by
annealing above 90 ◦ C.[9] Densities, crystal structure,
helix conformation, and melting points of four iPB-1
crystal forms are listed in Table 1.
The multiple phase transition of Form III has been
widely studied.[14 – 17] Clampitt et al . studied the melting behavior of Form III by differential thermal analysis
(DTA) measurement and found that Form II was generated during heating.[18] Geacintov et al . suggested that
the presence of an exothermal peak in the DTA thermogram peak may indicate that the recrystallization
involves a short-lived molten state.[19] Form III also
can transform into Form I under certain processes.
Miles et al . pointed out that Form III undergoes a
*Correspondence to: Tao Liu and Ling Zhao, State Key Laboratory
of Chemical Engineering, East China University of Science and
Technology, 200237 Shanghai, People’s Republic of China.
E-mail: liutao@ecust.edu.cn; zhaoling@ecust.edu.cn
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
crystal-crystal transition to Form I during Form III melt
at a very slow heating rate.[20] Form I was yielded after
a solid-state coextrusion of Form III at a lower temperature of 70 ◦ C by Nakamura et al .[21]
Supercritical CO2 [22] (Tc = 31.8 ◦ C, Pc = 7.37 MPa)
is widely used in polymer processing, such as polymerization, extraction, foam generation, impregnation, and
grafting.[23 – 31] The absorbed CO2 in polymers swells
and plasticizes those polymers, which reduces the melting temperature and glass-transition temperature.[32,33]
The plasticization of amorphous region increases the
chain mobility and thus promotes the rearrangement
of chains into a denser packing resulting in crystallization.[26,34] The absorbed CO2 in the polymers
can also influence the phase transition of different crystal structures.[27] The solid-solid phase transition of sPS
under supercritical CO2 has been widely reported.[35,36]
The special interaction between supercritical CO2 and
the polymer chains significantly influences the polymer structure and the conformation.[32] Thus, the phase
transition of iPB-1 Form III under supercritical CO2
must be different from those without it. This paper
is devoted to investigating the multiple phase transition of Form III under supercritical CO2 . The effect of
supercritical or high-pressure CO2 on Form II recrystallization process is studied by high-pressure differential scanning calorimetry (DSC). Fourier transform
infrared (FTIR) measurement is applied to analysis of
the crystal-crystal transition of Form III into I . The
influence of supercritical CO2 on the melting behavior
Asia-Pacific Journal of Chemical Engineering
CO2 INDUCED PHASE TRANSITION IN iPB-1
Table 1. Densities, crystal structure, helix conformation, and melting points of crystal forms of iPB-1.
Crystal form
ρ (g/cm3 )
Crystal structure
Helix conformation
Melting points (◦ C)
Reference
0.914
Hexagonal
Untwined hexagonal
Tetragonal
Orthorhombic
3/1
3/1
11/3
4/1
120–135
90–100
110–120
90–100
[3–5,10,11]
[3–5,10,11]
[6–8,12,13]
[6–8,12,13]
I
I
II
III
0.889
0.797
of Form I generated after supercritical CO2 treatment
is also studied by DSC measurement.
EXPERIMENTAL
Materials and sample preparation
Poly-1-butene pellets (PB 0110M) were acquired from
Basell Polyolefins. Before used, they were purified by
Soxhlet extraction in acetone for at least 24 h and
then dried in a vacuum oven at 40 ◦ C for 2 days.
Then, iPB-1 was dissolved in carbon tetrachloride at
a weight concentration of 3%. iPB-1 film with Form
III was obtained by evaporating the solvent completely
in the iPB-1 solution at room temperature. CO2 (purity:
99.9%) was purchased from Air Products Co., Shanghai.
Treatment of iPb-1
Isothermal treatments of iPB-1 films in ambient nitrogen and supercritical CO2 were performed in a highpressure vessel made of stainless steel. The vessel was
placed in a homemade oil bath with temperature electronically controlled. After the desired time, the vessel
was cooled to the ambient temperature in the atmosphere, and then the gas in the vessel was released.
Before characterized, the samples after treatments were
placed in a vacuum oven at ambient temperature for
24 h to completely evacuate the CO2 in it.
was used for DSC measurements of iPB-1 under N2
and high-pressure CO2 . The calorimeter was calibrated
by carrying out the measurement of the melting points
and the heat of fusion of In, Bi, Sn, Pb, and Zn under
ambient and high CO2 pressure conditions, respectively.
For each DSC measurement, about 5–10 mg of the iPB1 was heated from 30 to 170 ◦ C at a rate of 10 ◦ C min−1 .
RESULTS AND DISCUSSION
CO2 effect on Form II recrystallization
Figure 1 shows the effect of CO2 on the Form III melting process. At low CO2 pressures (0.1 and 0.5 MPa)
the DSC thermogram of Form III showed two endothermic peaks: The one at a lower melting temperature
corresponds to the melting of Form III and the other
corresponds to the melting of Form II recrystallization
during the heating up. CO2 has no significant influence
on the melting process of Form III at low pressure.
When the pressure reached 2 MPa, the second peak at
a higher temperature decreased with CO2 . At 4 MPa
and above, no melting peak of Form II was observed.
It is claimed that the recrystallization of Form II is
suppressed by high-pressure CO2 . Further, the melting
temperature of Form III decreased with increased CO2
pressure. This phenomenon might be ascribed to the
plasticization of CO2 .
FTIR measurement
Infrared spectra were recorded with a BRUKER FTIR
spectrometry (EQUINOX 55, Bruker Co., Germany).
The spectra were recorded at a resolution of 4.0 cm−1
and a rate of 1 spectrum per 32 s. The IR intensity
referred to the peak height. The scanned wave number
range was 4000-400 cm−1 .
DSC measurement
A high-pressure differential scanning calorimeter of
type NETZSCH DSC 204 HP (Selb, Bavaria, Germany)
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Figure 1. The effect of CO2 on Form III melting
process.
Asia-Pac. J. Chem. Eng. 2009; 4: 800–806
DOI: 10.1002/apj
801
802
L. LI ET AL.
Figure 2. DSC curves of Form III annealed at 80 ◦ C
and ambient nitrogen for various time periods.
Asia-Pacific Journal of Chemical Engineering
Figure 3. IR spectra of Form III annealed at 80 ◦ C
and ambient nitrogen for various time periods.
Phase transformation of Form III to I
in ambient nitrogen
Figure 2 compares the melting behavior of the virgin
iPB-1 Form III film with those annealed at 80 ◦ C
and ambient nitrogen at different time periods. On the
thermogram of the treated sample, there was one more
small endothermic peak which was confirmed to be the
melting of Form I by the following FTIR analysis.
The melting temperature of the transformed Form I
generated after annealment increased with time. For the
sample annealed for 5 days, the endothermic peak of
Form I superposed the melting peak of Form III. Thus,
only one endothermic peak was observed. The increase
of the melting temperature of Form I should be due
to the increase of the average crystallite size or better
crystal packing structure.
The phase transformation of Form III into I was
also detected by FTIR. Figure 3 shows the IR spectra of Form III annealed for various time periods.
There are distinct differences in the IR spectra range
of 750–950 cm−1 . The intense band at 905 cm−1 is the
characteristic band of Form III of iPB-1, while the weak
IR band at 925 cm−1 is known to be the characteristic
band of Form I .[37 – 41] The intensity of Form I characteristic band did not change as the annealing time
was increased, which revealed that the phase transition
was time independent. The results are close to those
obtained by Gtacintov.[20] The form transition is a thermodynamic selection process and only a certain amount
of Form III can transform to I at a certain annealing
temperature.
Phase transformation of Form III to I under
supercritical CO2
However, the phase transformation in supercritical CO2
will be different from that in ambient N2 . Figure 4
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Figure 4. DSC curves of Form III or I and the
samples annealed under supercritical CO2 .
compares the melting behavior of Form III or I and
those of Form III samples annealed at 60 and 80 ◦ C
under 15 MPa for 48 h. No supercritical CO2 aging
effect was observed. But, for the sample treated at 80 ◦ C
and 15 MPa for 48 h, there was only one endothermic
peak in its DSC curve, which was supposed to be the
melting of Form I . As shown in Fig. 5, a weak band at
925 cm−1 of the sample treated at 60 ◦ C and 15 MPa
suggested that a small fraction of Form III transformed
to Form I during the annealing process. And the
intense band at 925 cm−1 on the IR spectra of the
sample annealed at 80 ◦ C and 15 MPa confirmed that
all of Form III transformed to Form I . Compared with
the phase transition in ambient nitrogen at 80 ◦ C and
atmospheric pressure, the application of supercritical
CO2 substantially promoted the phase transition process
and the Form I that was generated under supercritical
CO2 at 80 ◦ C and 15 MPa showed unique melting
behavior in comparison with normal Form I . No Form
II recrystallization was detected during Form I melting
Asia-Pac. J. Chem. Eng. 2009; 4: 800–806
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
Figure 5. IR spectra of the samples annealed at 80
and 60 ◦ C under 15 MPa for 48 h.
Figure 6. IR spectra of form III annealed at 15 MPa
and 60 ◦ C as a function of the aging time.
process. It might be ascribed to the increase of the
melting temperature of Form I or the change in the
polymer chain packing.
Figure 6 shows the IR spectra of samples annealed
at 60 ◦ C and 15 MPa for 5, 15, and 48 h. The intensity
of Form I characteristic band at 925 cm−1 also showed
no significant change during the annealing. Since 48 h
is a relatively long time, it also indicates that the phase
transformation from Form III to I is a thermodynamic
selection process at 60 ◦ C and 15 MPa.
The melting behaviors of Form III annealed at 80 ◦ C
and 15 MPa for different time periods are shown in
Fig. 7. The melting temperature and the melting peak
area of Form III decreased with increase in annealing
time. When the annealing time was longer than 24 h,
no endothermic peak for Form III was observed which
indicated that all of Form III transformed into I when
the annealing time was long enough. The IR results
(Fig. 8) confirmed that Form III was transformed into
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
CO2 INDUCED PHASE TRANSITION IN iPB-1
Figure 7. DSC patterns of Form III anneal at 15 MPa
and 80 ◦ C as a function of the aging time.
Figure 8. IR spectra of Form III annealed at 15 MPa
and 80 ◦ C as a function of the aging time.
Form I completely. Moreover, in the DSC curves, the
endothermic peak of Form II disappeared. It indicates
that supercritical CO2 has a substantial effect on the
structure of Form I .
The melting temperatures and fusion enthalpies of
Form I obtained under supercritical CO2 are shown in
Table 2. The melting temperature and fusion enthalpies
of Form I increased with increased annealing time. The
increase in the enthalpy indicated that more and more
Form I was generated as the annealing time increased.
Meanwhile, the dissolved CO2 in the polymer can
accelerate the motion of polymer chain in amorphous
region with increase of free volume fraction of the
polymer, and induce the crystallization of amorphous
region in Form I . The melting temperature increased
with annealing time by a better rearrangement of the
polymer chain.
Asia-Pac. J. Chem. Eng. 2009; 4: 800–806
DOI: 10.1002/apj
803
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L. LI ET AL.
Asia-Pacific Journal of Chemical Engineering
Table 2. The melting temperatures and enthalpies of
Form I as a function of annealing time at 80 ◦ C and
18 MPa.
Annealed time (h)
0.5
1
2
24
48
TmI (◦ C)
Enthalpy (J/g)
104.3
105.2
105.6
105.3
107.6
27.06
29.14
33.42
43.98
44.62
Figure 10. IR spectra of the samples annealed at
80 ◦ C and under 8 and 6 MPa CO2 for 1 and 24 h.
Figure 9. DSC thremogram of the samples
annealed at 80 ◦ C, and under 8 and 6 MPa CO2
for 1 and 24 h.
The effect of supercritical CO2
on the generated Form I
As stated above, supercritical CO2 significantly influenced the melting behavior of Form I . In order to
demonstrate whether the suppression of Form II recrystallization was caused by the increase of melting temperature of Form I , the samples were annealed at 80 ◦ C
under 8 and 6 MPa for 1 and 24 h, respectively. The
DSC thremogram of the samples annealed after supercritical CO2 treatments exhibited a single endothermic
peak (Fig. 9). The IR spectra of the sample annealed at
80 ◦ C and 6 MPa for 24 h, as shown in the top curve
in Fig. 10, exhibited two intensity bands at 925 and
905 cm−1 . The intensity of Form III characteristic band
at 905 cm−1 was stronger than that of Form I characteristic band at 905 cm−1 . It reveals that the major
form of the sample after CO2 treatment is Form III.
Meanwhile, as shown in the bottom curve in Fig. 8, the
proportion of Form III of the sample after annealing at
80 ◦ C and 8 MPa for 1 h was still large. In these two
conditions, the melting temperatures of Form I generated after CO2 treatments were similar to the Form III
melting temperatures. In these temperatures, Form II
could be recrystallized from the melt during the melting process of Form III and I . But, the recrystallization
was also inhibited.
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
These results indicate that the suppression of Form
II recrystallization from melt during the heating up of
Form I is not ascribed to the increase of the melting
temperature but the change in the polymer chains
packing. Therefore it is supposed that Form I generated
under supercritical CO2 has a better polymer chain
packing than that obtained under normal condition.
These polymer chains have high interchain cohesive
forces that do not allow the Form I chain to obtain
enough energy to convolute the chain segment and
recrystallize into Form II.
The nature of Form III transition under
supercritical CO2
The melting behavior of Form III under high-pressure
or supercritical CO2 is different from that under atmospheric pressure. As shown in Fig. 11(a), the melting
process of Form III under atmospheric pressure consists of two steps. Firstly, Form III melts into a shortlived intermediate molten state. Second, the molten state
recrystallizes into Form II at elevated temperatures.
During the recrystallization process, the polymer chain
in the short-lived intermediated molten state undergoes
a sudden convolution of a chain segment into the 11/3
helix of Form II. Fig. 11(b) shows the Form III melting
process under high-pressure or supercritical CO2 . Form
III directly melts without recrystallizing into Form II.
The CO2 increases the polymer chain mobility in the
amorphous region and in the molten state. The mobility of the molten state polymer chain under supercritical
CO2 is higher than at atmosphere pressure. The polymer
chain cannot acquire sufficient energy at the transition temperature to break interchain cohesive forces to
recrystallize into Form II.
Form I and I have the same unit cell. The transition
of Form III to I involves a change in the chain
Asia-Pac. J. Chem. Eng. 2009; 4: 800–806
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
CO2 INDUCED PHASE TRANSITION IN iPB-1
Figure 11. Mechanism of Form III melting process; (a)under atmosphere;
(b)under high-pressure CO2 .
Figure 12. Mechanism of form transformation from Form
III to I under supercritical CO2 .
conformation and requires an elongation of the helix
from 1.89 to 2.17 Å.[13] The polymer chain in the
amorphous region might play a substantial role in
the phase transition.[42,43] The absorbed CO2 increases
the free volume fraction of polymer as well as the
motion of polymer chains in the amorphous region. As
shown in Fig. 12, the extended chains in the amorphous
region induce the tensile stress on the molecule parts
that belong to the crystalline lattice. The extra stress
on the crystalline will cause the elongation of the
chain helix and increase the phase transition rate.
This is why the form transition could occur at a
temperature of 60 ◦ C at which Form III is stable under
atmospheric pressure. Higher temperature and pressure
favor the transition. It suggests that the conditions that
can promote the polymer chain mobility will enhance
the phase transition. The crystallinity increase in the
transformed Form I under supercritical CO2 is ascribed
to the rearrangement of the amorphous region into better
packing of Form I by the increased polymer chain
mobility.
CONCLUSIONS
The main results of the Form III transition under
supercritical CO2 can be summarized as follows:
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
1. The melting behavior of Form III under highpressure CO2 reveals that high-pressure or supercritical CO2 significantly influences Form II recrystallization process during Form III melting process. The
Form II recrystallization process is inhibited when
CO2 pressure is above 4 MPa.
2. The phase transition of Form III into I in ambient
nitrogen at 80 ◦ C reveals transformation is a thermodynamic selection process, and only a certain
proportion of Form III can transform into Form I .
3. The application of supercritical CO2 can promote the
transition of Form III to I . Supercritical CO2 induces
the phase transformation at 60 ◦ C. Meanwhile, the
transformation under supercritical CO2 but at a low
temperature is also a thermodynamic process.
4. At 80 ◦ C and 15 MPa, Form III completely transforms into Form I . As the annealing time increases,
supercritical CO2 induces the amorphous region to
transit into Form I .
5. The suppression of Form II recrystallization from
Form I generated under supercritical CO2 is ascribed
to the change in the polymer chains packing of
Form I .
6. Supercritical CO2 has a substantial effect on the
motion of Form III chains both in the short-lived
molten state and the amorphous region in the solid
state. Increased motion in the short-lived molten
state suppresses the Form II recrystallization. The
increased motion of the polymer chains in the
amorphous region supply extra stress on the polymer
chains in Form III crystal region chains and promotes
the the transition of Form III into I .
Acknowledgements
The authors are grateful to the National Science Foundation of China and PetroChina for the support of a joint
Asia-Pac. J. Chem. Eng. 2009; 4: 800–806
DOI: 10.1002/apj
805
806
L. LI ET AL.
Asia-Pacific Journal of Chemical Engineering
project on multiscale methodologies (20490204), the
National Science Foundation of China (50703011), and
for the Shanghai Rising-Star Program (08QA1402200),
Shanghai Shuguang Project, Program for Changjiang
Scholars and Innovative Research Team in University
(IRT0721); and the 111 Project (B08021).
REFERENCES
[1] A. Marigo, C. Marega, G. Cecchin, G. Collina, G. Ferrara.
Eur. Polym. J., 2000; 36, 131–136.
[2] F. Azzurri, A. Flores, G.C. Alfonso, F.J.B. Calleja. Macromolecules, 2002; 35, 9069–9073.
[3] L. Luciani, J. Seppala, B. Lofgren. Prog. Polym. Sci., 1988;
13, 37–62.
[4] F. Azzurri, G.C. Alfonso, M.A. Gomez, M.C. Marti, G. Ellis,
C. Marco. Macromolecules, 2004; 37, 3755–3762.
[5] M. Kaszonyiova, K. Rybnikar, P.H. Geil. J. Macromol. Sci.,
2005; B44, 377–396.
[6] R.J. Schaffhauser. Polym. Lett., 1967; 5, 839–841.
[7] G.C. Alfonso, F. Azzurri, M. Castellano. J. Therm. Anal.
Calorim., 2001; 66, 197–207.
[8] C. Nakafuku, T. Miyaki. Polymer, 1983; 24, 141–148.
[9] R.L. Miller, V.F. Holland. Polym. Lett., 1964; 2, 519–521.
[10] D. Maring, M.W.H.W. Spiess, B. Meurer, G. Weill. J. Polym.
Sci., 2000; B38, 2611–2624.
[11] V. Causin, C. Marega, A. Marigo, G. Ferrara, G. Idiyatullina,
F. Fantinel. Polymer, 2006; 47, 4773–4780.
[12] T. Miyoshi, S. Hayashi, F. Imashiro, A. Kaito. Macromolecules, 2002; 35, 6060–6063.
[13] G. Cojazzi, V. Malta, G. Celotti, R. Zannetti. Makromol.
Chem., 1976; 177, 915–926.
[14] Y.T. Shieh, M.S. Lee, S.A. Chen. Polymer, 2001; 42,
4439–4448.
[15] F. Danusso, G. Gianotti. Makromol. Chem., 1965; 88,
149–158.
[16] M. Kaszonyiova, F. Rybnikar, P.H. Geil. J. Macromol. Sci.,
2004; B43, 1095–1114.
[17] M. Kaszonyiova, F. Rybnikar, P.H. Geil. J. Macromol. Sci.,
2007; B46, 195–205.
[18] B.H. Clampitt, R.H. Hughes. J. Polym. Sci., 1964; C6, 43–51.
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
[19] C. Geacintov, R.S. Schotl, R.B. Miles. J. Polym. Sci., 1964;
C6, 197–207.
[20] C. Geacintov, R.B. Miles, H.J.L. Schuubmans. J. Polym. Sci.,
1966; C14, 283–290.
[21] K. Nakamura, T. Aoike, K. Usaka, T. Kanamoto. Macromolecules, 1999; 32, 4975–4982.
[22] M. Faisal, Y. Atsuta, H. Daimon, K. Fujie. Asia-Pac. J. Chem.
Eng., 2008; 3, 364–367.
[23] G.-S. Tong, T. Liu, G.-H. Hu, L. Zhao, W.-K. Yuan. J.
Supercrit. Fluids, 2007; 43, 64–73.
[24] B. Li, G.H. Hu, G.P. Cao, T. Liu, L. Zhao, W.K. Yuan.
J. Supercrit. Fluids, 2008; 44, 446–456.
[25] B. Li, L. Li, L. Zhao, W. Yuan. Eur. Polym. J., 2008; 44,
2619–2624.
[26] B. Li, X. Zhu, G.-H. Hu, T. Liu, G. Cao, L. Zhao, W. Yuan.
Polym. Eng. Sci., 2008; 48, 1608–1614.
[27] L. Li, T. Liu, L. Zhao, W.-K. Yuan. Macromolecules, 2009;
42, 2286–2290.
[28] G.-S. Tong, T. Liu, L. Zhao, H. Li-xia, Y. Wei-kang. J.
Supercrit. Fluids, 2009; 48, 261–268.
[29] J.L. Kendall, D.A. Canelas, J.L. Young, J.M. DeSimone.
Chem. Rev., 1999; 99, 543–564.
[30] Z.-M. Xu, X.-L. Jiang, T. Liu, G.-H. Hu, L. Zhao, Z.-N. Zhu,
W.-K. Yuan. J. Supercrit. Fluids, 2007; 41, 299–310.
[31] X.-L. Jiang, T. Liu, Z.-M. Xu, L. Zhao, G.-H. Hu,
W.-K. Yuan. J. Supercrit. Fluids, 2009; 48, 167–175.
[32] B. Bonavoglia, G. Storti, M. Morbidelli, A. Rajendran,
M. Mazzotti. J. Polym. Sci., 2006; B44, 1531–1546.
[33] P. Alessi, A. Cortesi, I. Kikic, F. Vecchione. J. Appl. Polym.
Sci., 2003; 88, 2189–2193.
[34] D. Wang, H. Gao, W. Jiang, Z. Jiang. J. Polym. Sci., 2007;
B45, 2927–2936.
[35] W.M. Ma, J. Yu, J.S. He. Macromolecules, 2004; 37,
6912–6917.
[36] X. Liao, J.S. He, J. Zhang, W.M. Ma. J. Polym. Sci, 2007;
B45, 1625–1636.
[37] K.W. Chau, Y.C. Yang, P.H. Geil. J. Mater. Sci., 1986; 21,
3002–3014.
[38] J.P. Luongo, R. Salovey. J. Polym. Sci., 1966; A4, 997–1008.
[39] G. Goldbach, G. Peitscher. J. Polym. Sci., 1968; B6, 783–788.
[40] K.H. Lee, C.M. Snively, S. Givens, D.B. Chase, J.F. Rabolt.
Macromolecules, 2007; 40, 2590–2595.
[41] J.P. Luongo, R. Salovey. J. Polym. Sci., 1965; B3, 513–515.
[42] G. Goldbach. Angew. Makromol. Chem., 1973; 29, 213–227.
[43] G. Goldbach. Angew. Makromol. Chem., 1974; 39, 175–188.
Asia-Pac. J. Chem. Eng. 2009; 4: 800–806
DOI: 10.1002/apj
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