Tris(2-aminoethyl)amine-based ferrocene-terminated dendrimers as burning rate catalysts for ammonium perchlorate-based propellant decomposition

Article abstract of DOI:10.1002/aoc.4268

Ferrocene-based derivatives show potential application as burning rate catalysts (BRCs) for solid composite propellants. However, migration problems of simple ferrocene-based derivatives limit their application as BRCs in solid composite propellants. To o

Full text of DOI:10.1002/aoc.4268

Received: 11 October 2017
DOI: 10.1002/aoc.4268
Revised: 14 December 2017
Accepted: 15 December 2017
F U L L P A P E R
Tris(2‐aminoethyl)amine‐based ferrocene‐terminated
dendrimers as burning rate catalysts for ammonium
perchlorate‐based propellant decomposition
Zain‐ul‐Abdin | Li Wang
| Haojie Yu | Rizwan Ullah Khan | Raja Summe Ullah |
Muhammad Haroon
State Key Laboratory of Chemical
Engineering, College of Chemical and
Biological Engineering, Zhejiang
University, Hangzhou 310027, China
Ferrocene‐based derivatives show potential application as burning rate cata-
lysts (BRCs) for solid composite propellants. However, migration problems of
simple ferrocene‐based derivatives limit their application as BRCs in solid com-
posite propellants. To overcome the migration problems of ferrocene‐based
BRCs and to enhance the burning rate of ammonium perchlorate (AP)‐based
propellants, zero‐ to second‐generation tris(2‐aminoethyl)amine‐based ferro-
cene‐terminated dendrimers (G0, G1 and G2) were synthesized. The structures
Correspondence
Li Wang or Haojie Yu, State Key
Laboratory of Chemical Engineering,
College of Chemical and Biological
Engineering, Zhejiang University,
Hangzhou 310027, China.
1
of G0, G1 and G2 were confirmed using H NMR, Fourier transform infrared
Email: opl_wl@dial.zju.edu.cn;
hjyu@zju.edu.cn
and UV–visible spectroscopies. The electrochemical behavior of G0, G1 and
G2 was investigated using cyclic voltammetry. It was found that G0, G1 and
G2 showed redox behavior due to the presence of ferrocene and this redox
behavior was diffusion controlled over the investigated scan range. The burning
rate catalytic effect of G0, G1 and G2 on thermal decomposition of AP was
investigated using thermogravimetry and differential thermogravimetry. G0,
G1 and G2 showed good catalytic effect on the thermal decomposition of AP.
Anti‐migration studies showed that migration of G0, G1 and G2 was much
slower than that of 2,2‐bis(ethylferrocenyl)propane (catocene) and ferrocene.
Funding information
National Natural Science Foundation of
China, Grant/Award Numbers: 21272210,
21372200, 21472168 and 21411130187;
International Science and Technology
Cooperation Project of Ministry of Science
and Technology of China, Grant/Award
Number: (2009 DFR 40640); Science and
Technology Program of Zhejiang Province,
Grant/Award Number: (2013C24001); Sci-
ence and Technology Innovation Team of
Ningbo, Grant/Award Number:
KEYWORDS
(2011B82002); the Fundamental Research
Funds for the Central Universities, Grant/
Award Number: (2015FZA4025)
anti‐migration behavior, burning rate catalysts, dendrimers, ferrocene, synthesis
1 | INTRODUCTION
based derivatives have also been used as burning rate cat-
alysts (BRCs) for ammonium perchlorate (AP)‐based pro-
Ferrocene is an organometallic compound consisting of
ferrous ion sandwiched by two cyclopentadienyl
rings.[1] Ferrocene‐based derivatives have been used
in many scientific fields such as medicine,[2] electro-
chemical sensing,[3] memory storage,[4] catalysis,[5–10]
nanomaterials[11,12] and ion recognition[13–15] due to their
reversible redox behavior, high thermal stability and
chemical modification opportunities in their struc-
tures.[16–18] In addition to these applications, ferrocene‐
pellants.[1,19] There are various kinds of BRCs such as
nanometal particles, transition metal oxides, metal che-
lates (organic metal chelates) and ferrocene‐based com-
pounds that have been used to enhance the burning rate
of AP‐based propellants. Among these BRCs, ferrocene‐
based compounds have received much attention due to
their microscopic homogeneities in distribution, low pres-
sure exponents and good compatibility with organic
binders.[3,20,21]
Appl Organometal Chem. 2018;e4268.
wileyonlinelibrary.com/journal/aoc
Copyright © 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4268

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ZAIN‐UL‐ABDIN ET AL.
Simple ferrocene‐based derivatives are neutral and
in excellent anti‐migration properties of these
dendrimers. The dendrimers with special topology and
containing polar elements (oxygen and nitrogen) show
excellent anti‐migration behavior in AP‐based propel-
lants. So, at first, we synthesized tris(2‐aminoethyl)
amine‐based dendrimers and then modified them to
afford tris(2‐aminoethyl)amine‐based ferrocene‐terminated
dendrimers. The structures of G0, G1 and G2 were con-
firmed using 1H NMR and Fourier transform infrared
(FT‐IR) spectroscopies. The electrochemical properties of
the synthesized dendrimers were analyzed using cyclic volt-
ammetry (CV). The thermal behavior and catalytic perfor-
mance of these synthesized dendrimers for the thermal
decomposition of AP were investigated using
thermogravimetry (TG) and differential thermogravimetry
(DTG). The anti‐migration behavior of G0, G1 and G2
was studied in comparison with catocene and ferrocene.
volatile,[22] which migrate to the surface of a propellant
on prolonged storage and sublime during curing and
processing.[23–25] The migration of BRCs to the surface
of propellants reduces life, changes particular burning
parameters and causes explosions.[22] The properties of
ferrocene‐based derivatives depend on their chemical
structure, solubility and iron contents. To overcome
migration problems, to reduce pressure exponents of solid
propellants and to enhance burning rate catalytic activity
of AP‐based propellants, many researchers have tried to
design high‐molecular‐weight ferrocene‐based BRCs[22]
but migration problems still need to be overcome in a
low‐cost and more efficient way.
Ferrocene‐terminated dendrimers are functionalized
materials that have attracted much attention in the past
few years, due to the special three‐dimensional structures
and high molecular weight of dendrimers[26,27] and the
unique electron‐rich potential and electrochemical revers-
ibility of ferrocene.[28] The use of ferrocene‐terminated
dendrimers containing large numbers of nitrogen or oxy-
gen atoms is an effective way to enhance the burning rate
of AP‐based propellants and to overcome migration prob-
lems. The introduction of large numbers of polar elements
in ferrocene‐terminated dendrimers strengthens the
attractive forces between BRC and propellant, which
reduces migration problems.[19]
The burning rate catalytic activity of BRCs can be
assessed by the thermal decomposition of AP.[29] The
faster AP decomposition results in better performance of
a solid composite propellant.[28] The best BRCs show
excellent anti‐migration property, low pressure exponents
and high burning rate catalytic activity.[19] With an
increase in BRC content, the number of active sites
increases and therefore the burning rate of AP‐based pro-
pellants increases, but, above a certain BRC content, the
propellant performance decreases and no increase in the
burning rate is observed due to the large amount of inert
ingredients.[30] The efficacy of BRCs can be increased by
increasing their surface area. As surface area increases,
the number of active sites increases, and so the burning
rate of AP‐based propellants increases.[30]
2 | EXPERIMENTAL
2.1 | Materials
Tris(2‐aminoethyl)amine, methyl acrylate, ethylenediamine,
methanol, pyridine, chloroform and petroleum ether
were purchased from Sinopharm Chemical Reagent Co.
Ltd, and were used after drying with 4A‐type molecular
sieves. Dichloromethane (DCM) was also purchased
from Sinopharm Chemical Reagent Co. Ltd, and was
used after drying with 4A‐type molecular sieves followed
by reflux. Oxalyl chloride, ferrocenecarboxylic acid and
NaHCO3 were purchased from Sinopharm Chemical
Reagent Co. Ltd, and were used without further purification.
Tetrabutylammonium tetrafluoroborate (Bu4NBF4) was
purchased from J&K Co. Ltd, and was used as received.
2.2 | Syntheses
2.2.1 | Ferrocenecarbonyl chloride
Ferrocenecarbonyl chloride was synthesized by the con-
densation reaction of ferrocenecarboxylic acid with oxalyl
chloride in freshly distilled DCM using pyridine as a cata-
lyst. In a typical procedure, ferrocenecarboxylic acid
(20.7140 g, 83.92 mmol) was dried at 40 °C under reduced
pressure for 4 h. Then the dried ferrocenecarboxylic acid
was dissolved in 150 ml of DCM. Pyridine (14.5 ml) was
added to the ferrocenecarboxylic acid solution. The
resulting solution was stirred under moisture‐free condi-
tions using a Schlenk line argon system at room tempera-
ture (25 °C) for about 15 min. Oxalyl chloride (15.5 ml,
180.72 mmol) was added dropwise to the solution at room
temperature. The resulting reaction mixture was stirred at
room temperature for about 30 min and then it was
In the study reported here, in continuation of our
interest in ferrocene‐based BRCs,[31] we synthesized zero‐
to second‐generation tris(2‐aminoethyl)amine‐based fer-
rocene‐terminated dendrimers (G0, G1 and G2) contain-
ing oxygen and nitrogen, to reduce the migration
problems of ferrocene‐based BRCs and to enhance the
burning rate of AP‐based propellants. The presence of
oxygen and nitrogen in these dendrimers resulted in
dipole–dipole interactions and the presence of N―H
groups resulted in strong hydrogen bonding of these
dendrimers with AP and also with binder, which resulted

ZAIN‐UL‐ABDIN ET AL.
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SCHEME 1 Routes for synthesis of ferrocene‐terminated dendrimers

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ZAIN‐UL‐ABDIN ET AL.
refluxed for 6 h. The excess amount of oxalyl chloride, pyr-
idine and solvent were evaporated under vacuum and then
the obtained residue was extracted with petroleum ether
(200 ml) at 90 °C to afford ferrocenecarbonyl chloride.
The product was stored under argon atmosphere.
with ferrocenecarbonyl chloride in freshly distilled
DCM. The synthetic procedure for G0, G1 and G2 was
the same. So, the synthesis of G0 is taken as an exam-
ple. In a typical procedure, tris(2‐aminoethyl)amine
(1.20 ml, 8.01 mmol) was dried under vacuum. The
dried tris(2‐aminoethyl)amine was dissolved in 35 ml
of freshly distilled DCM. A solution of ferrocenecarbonyl
chloride (5.9700 g, 24.03 mmol) prepared in 35 ml of
DCM was added dropwise to the solution. The resulting
solution was stirred at 25 °C for 12 h. Solvent was
evaporated using a rotary evaporator. The obtained
residue was dissolved in 200 ml of CHCl3. The
resulting solution was washed (five times) with 2%
NaHCO3 solution prepared in distilled water and
then it was further washed (four times) with distilled
water. The organic layer was separated, anhydrous
Na2SO4 (2.0000 g) was added and the obtained
mixture was left overnight. The mixture was filtered to
separate Na2SO4 and the resulting filtrate was dried using
a rotatory evaporator to afford the product. The crude
product was purified by column chromatography using
DCM as eluent. The product was dried in a vacuum oven
at 40 °C for 2 days. The experimental details for the
synthesis of the dendrimers are given in Table S1.
2.2.2 | Tris(2‐aminoethyl)amine‐based
amine‐terminated dendrimers
Tris(2‐aminoethyl)amine‐based
amine‐terminated
dendrimers (G0.75 and G1.75) were synthesized by
Michael addition reaction followed by reaction with
ethylenediamine.[32] The synthetic procedure for G0.5
and G1.5 was the same. So, the synthesis of G0.5 is taken
as an example. In a typical procedure, tris(2‐aminoethyl)
amine (3.0000 g, 20.02 mmol) was dissolved in 20 ml of
methanol in an ice bath under argon gas. Methyl acrylate
(54.44 ml, 600.70 mmol) was added dropwise to the solu-
tion. The resulting solution was stirred at 0 °C for 1 h.
Afterwards, the resulting solution was stirred at 25 °C
for 2 days. The solvent and excess amount of methyl acry-
late were evaporated using a rotary evaporator at 50 °C.
The synthetic procedure fir G0.75 and G1.75 was the
same. So, the synthesis of G0.75 is taken as an example.
In a typical procedure, G0.75 (13.3800 g, 20.19 mmol)
was dissolved in 20 ml of methanol in an ice bath under
argon gas. Ethylenediamine (12.14 ml, 181.80 mmol)
was added dropwise to the solution. The resulting solu-
tion was stirred at 0 °C for 1 h. Afterwards, the resulting
solution was stirred at 25 °C for 2 days. The solvent and
excess amount of ethylenediamine were evaporated using
a rotary evaporator at 70 °C.
2.3 | Characterization
1H NMR spectra of the dendrimers of various genera-
tions were recorded with an AVANCE NMR spectrome-
1
ter (600 MHz, model DMX‐400). For H NMR spectra of
G0, G1 and G2, CDCl3 was used as a solvent and chem-
ical shifts were related to tetramethylsilane at δ = 0 ppm;
for G0.5, G0.75, G1.5 and G1.75, D2O was used as a
solvent.
FT‐IR spectra of G0, G1 and G2 were recorded with a
Nicolet 5700 infrared spectrometer using the KBr pellet
technique. Each sample of G0, G1 and G2 (2%) and KBr
2.2.3 | G0, G1 and G2
G0, G1 and G2 were synthesized by the condensation
reaction of tris(2‐aminoethyl)amine, G0.75 and G1.75
FIGURE 1 (a) FT‐IR spectra and (b) UV–visible spectra of G0, G1 and G2

ZAIN‐UL‐ABDIN ET AL.
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was crushed to a powder, mixed together and a KBr pellet
prepared. UV–visible absorption spectra of G0, G1 and G2
were recorded with a 3802 UV‐Vis Unico spectrophotom-
eter. The details of sample preparation for UV–visible
spectroscopic studies are given in Table S2.
3 | RESULTS AND DISCUSSION
3.1 | Synthesis of G0, G1 and G2
Ferrocenecarbonyl chloride was synthesized from
ferrocenecarboxylic acid following a reported procedure
(Scheme 1).[31]
Dendrimers G0.75 and G1.75 were synthesized by
Michael addition reaction followed by reaction with
ethylenediamine. Dendrimers G1 and G2 were
CV curves of G0, G1 and G2 were recorded with a
CHI‐630A electrochemical analyzer (CH Instruments,
Inc., Austin, Texas) using a three‐electrode cell. The
working electrode was a Teflon‐shrouded platinum disc
electrode with a diameter of 2 mm for the solution test.
The working electrode was polished to a mirror finish
with 0.05 μm Al2O3 paste on felt, cleaned by
ultrasonication successively in 0.1 M NaOH and HNO3
(1,1), anhydrous ethyl alcohol and doubly distilled water,
then dried and used for the electrochemical measure-
ments. A platinum wire electrode was used as the
counter electrode. The reference electrode was an Ag
wire electrode for solution test. Every CV experiment
was performed two times to get an average result, and
in every experiment the concentration of electrolyte
(Bu4NBF4) was 0.1 M, the potential scan rates were 0.1
to 0.5 V s−1 and concentration of G0, G1 and G2 was
0.5 mM. The details of sample preparation for CV studies
are given in Table S3.
The samples for migration studies consisted of three
adjacent parts: loaded part, interface and unloaded part
(blank). The unloaded part consisted of AP (7.0530 g,
71.93%), hydroxyl‐terminated polybutadiene (HTPB;
2.0872 g, 21.28%) and isophorone diisocyanate (IPDI;
0.6655 g, 6.79%) and it was prepared by mixing AP,
HTPB and IPDI for 30 min. The resulting mixture was
cast into a mold and cured at room temperature for
3 days before undergoing accelerated aging. The loaded
part consisted of AP, HTPB, IPDI and a BRC (G0, G1,
G2, catocene or ferrocene). Typically, a sample (G0)
was prepared by mixing AP (1.9200 g, 70.00%), HTPB
(0.5555 g, 20.24%), IPDI (0.1859 g, 6.77%) and G0
(0.0822 g, 2.99%) for approximately 1 h. The resulting
mixture was subsequently cast on an unloaded layer that
had been cured for 3 days. After curing for 3 days
at room temperature, the sample was aged in an
oven at 50 °C and atmospheric pressure for 30 days.
The details of sample preparation for anti‐migration
studies are given in Table S4.
The burning rate catalytic studies of thermal decom-
position of AP were conducted with a PerkinElmer Pyris
1 thermogravimetric instrument at a heating rate of 5 °C
min−1 under nitrogen in the range 50–600 °C. To investi-
gate the catalytic performance of G0, G1 and G2 in the
thermal decomposition of AP, a specific amount of ferro-
cene‐terminated dendrimer and AP was mixed and
ground. The details of sample preparation for burning
rate catalytic studies are given in Table S5.
FIGURE 2 CV curves in DCM at various scan rates: (a) G0, (b)
G1 and (c) G2

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ZAIN‐UL‐ABDIN ET AL.
synthesized by the condensation reaction of G0.75 and
G1.75 with ferrocenecarbonyl chloride, respectively. The
synthetic routes for the synthesis of the dendrimers of var-
ious generations are shown in Scheme 1 and experimental
details are given in Table S1.
stretching vibrations of N―H of secondary amine of G0, G1
and G2 appeared at around 2960 cm−1. The stretching vibra-
tions of carbonyl groups of amide were observed at around
1690 cm−1. The vibrational and deformational bands of fer-
rocene of G0, G1 and G2 appeared at 1023–1040, 801–840
and 494–503 cm−1.[33] FT‐IR spectra of G0, G1 and G2 are
shown in Figure 1(A).
UV–visible absorption spectra of G0, G1 and G2 (c =
0.012 mM) in DCM showed absorption bands with λmax
at around 250 and 275 nm which can be assigned to
π–π* transitions, while absorption bands with λmax at
around 325 and 450 nm can be assigned to the charge
transfer (CT) band and d–d transitions, respectively.[3]
In the case of G1 and G2, strong absorption bands cor-
responding to CT and d–d transitions were observed,
while strong absorption bands corresponding to π–π*
transitions of G0, G1 and G2 were observed. As ferro-
cene units in these dendrimers increased, the CT
absorption band become more intense. UV–visible
The structures of the synthesized dendrimers were
confirmed using 1H NMR and FT‐IR spectroscopies.
1
On comparing H NMR spectra of G0, G1 and G2 with
those of tris(2‐aminoethyl)amine, G0.75 and G1.75,
three new peaks attributed to ferrocene protons were
observed in the region 4.00–5.00 ppm. The intensity of
all the peaks including signals of protons of ferrocene
and the rest of the protons was according to the struc-
tures, which confirmed the synthesis of G0, G1 and
G2.1H NMR spectra of the synthesized dendrimers are
shown in Figure S1.
The structures of G0, G1 and G2 were further confirmed
from their FT‐IR spectra. The stretching and bending vibra-
tions of N―H of amide appeared at around 3100 cm−1. The
FIGURE 3 (a) (1) View of the migration tube and (b) schematic procedure for the fabrication of migration tubes used for anti‐migration
studies: (2) blank migration tubes, (3) migration tubes filled with loaded part and (4) migration tubes filled with loaded and unloaded parts

ZAIN‐UL‐ABDIN ET AL.
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FIGURE 4 Anti‐migration study photos for G0, G1, G2, catocene (C) and ferrocene (Fc) on days 1, 7, 15 and 30 at 50 °C
absorption spectra of G0, G1 and G2 are shown in
Figure 1(B).
In DCM, well‐defined and sharp peaks with high
current were observed. Lowest peak‐to‐peak potential
separation (ΔEp) was observed in DCM. The diffusion rate
of the charge was faster and resistance of G0, G1 and G2
solutions was smaller in DCM than in CHCl3, which
shows that redox reaction was more favorable in DCM.
CV data for G0, G1 and G2 in different organic solvents
at 0.1 V s−1 are presented in Table S5.
3.2 | Electrochemical Properties
The combustion of ferrocene‐terminated dendrimers with
AP‐based propellant can be explained in terms of electro-
chemical properties (gain and loss of electrons). There-
fore, the electrochemical properties of G0, G1 and G2
are important for investigating their potential application
as BRCs. Among various methods of electrochemical
measurements, CV is considered as an effective one for
determining electrochemical properties.[34] So, the elec-
trochemical properties of G0, G1 and G2 (0.5 mM) were
analyzed in DCM, CHCl3 and dimethylsulfoxide (DMSO)
using Bu4NBF4 (0.10 M) as a supporting electrolyte at var-
ious potential scan rates with CV. It was found that the
CV curves of G0, G1 and G2 were affected by both solvent
polarity and potential scan rate.[35–39] An increase in
polarity of the solvent resulted in the deformation of the
peak shapes. The peak shape was found to be more
compact in a polar solvent like DMSO. Both oxidation
and reduction peak potentials were decreased with an
increase in solvent polarity, which showed that the polar-
ity of the solvent was proportional to the reduction and
oxidation processes for G0, G1 and G2.[40] CV curves of
G0, G1 and G2 in DCM at various potential scan rates
are shown in Figure 2.
CV curves of G0, G1 and G2 were sensitive to potential
scan rate. Additionally, peak current values (ipa and ipc)
FIGURE 5 Anti‐migration study results for G0, G1, G2, catocene
and ferrocene on days 7, 15 and 30 at 50 °C

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ZAIN‐UL‐ABDIN ET AL.
increased with an increase in potential scan rate and
showed a linear relationship with the square root of the
potential scan rate (ν1/2). Furthermore, the rate of
increase in reduction peak current (ipc) was higher than
that in oxidation peak current (ipa).
Figures S2–S4, respectively, while electrochemical data are
given in Tables S6–S9.
3.3 | Anti‐migration Studies
According to CV theory,[41] these results show that
charge transport of the electrode processes obeyed Fick's
law and also the electrode processes were diffusion con-
trolled over the investigated scan rate range for G0, G1 and
G2. CV curves of G0, G1 and G2 in CHCl3 and DMSO at
various potential scan rates (0.1, 0.2, 0.3, 0.4 and 0.5 V s−1)
and in DCM, CHCl3 and DMSO at 0.1 V s−1 are shown in
Catocene is a commonly used ferrocene‐based BRC. So,
G0, G1 and G2 were analyzed for their anti‐migration
behavior in comparison with catocene and ferrocene.
The procedure for the fabrication of migration tubes used
for anti‐migration studies is shown schematically in
Figure 3. Anti‐migration study photos are shown in
Figure 4 and anti‐migration results for G0, G1 and G2 in
FIGURE 6 Migration mechanism of G1 in AP‐based propellant

ZAIN‐UL‐ABDIN ET AL.
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comparison with catocene and ferrocene are shown in
Figure 5.
behavior in AP‐based propellant which might be due to
the presence of less ferrocene. The migration mechanism
of G1 in AP‐based propellant is shown in Figure 6.
It was found that migration of G0, G1 and G2 was
slower than that of catocene and ferrocene. The slower
migration of G0, G1 and G2 was due to the presence of
polar elements (oxygen and nitrogen) in the structures.
The presence of oxygen and N―H groups resulted in
dipole–dipole forces and hydrogen bonding of these
dendrimers with AP and also with binder (HTPB).
It was also found that migration tendency was
increased with an increase in ferrocene.[31] Among the
three dendrimers, G0 showed excellent anti‐migration
3.4 | Catalytic Performance and Possible
Burning Rate Catalytic Mechanism
Thermal stability is an important parameter for BRCs. It
was found that G0, G1 and G2 were stable up to 265 °C.
A catalyst having thermal stability is advantageous for
its use in the combustion of AP‐based propellants. The
catalytic performance of BRCs for the combustion of AP‐
FIGURE 7 (a) TG curves and (b) DTG curves of pure AP and AP with 5 wt% of G0, G1 and G2. (c) TG curves and (d) DTG curves of pure AP
and AP with various contents of G2
FIGURE 8 Possible burning rate catalytic mechanism for thermal decomposition of AP catalyzed by G2

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ZAIN‐UL‐ABDIN ET AL.
based propellants is usually determined via the activity in
the thermal decomposition of AP.[42] The catalytic activity
of G0, G1 and G2 in the thermal decomposition of AP was
investigated using TG and DTG.
4 | CONCLUSIONS
Zero‐ to second‐generation tris(2‐aminoethyl)amine‐
based ferrocene‐terminated dendrimers (G0, G1 and G2)
have been successfully synthesized. The dendritic struc-
tures and presence of oxygen and N―H groups in these
dendrimers resulted in excellent anti‐migration behavior
in AP‐based propellant and the presence of ferrocene
contributed to the catalytic performance. UV–visible
absorption spectra indicated that G1 and G2 showed pho-
toinduced CT effect and this effect was more prominent in
G2. CV results indicated that G0, G1 and G2 showed
redox processes which were diffusion controlled over the
investigated scan rate range. TG and DTG results
confirmed the good catalytic activity of G0, G1 and G2
in the thermal decomposition of AP. On the basis of the
experimental results, we found that these ferrocene‐termi-
nated dendrimers have a good catalytic effect on the
thermal decomposition of AP and show excellent anti‐
migration behavior in AP‐based propellant.
The catalytic activity of G0, G1 and G2 in the thermal
decomposition of AP was investigated using 5 wt% of G0,
G1 and G2, as shown in Figure 7(a,b). The catalytic activ-
ity of G2 in the thermal decomposition of AP was also
investigated by varying the content (1–5 wt%) of G2, as
shown in Figure 7(c,d). On addition of 5 wt% G0, G1
and G2, the thermal decomposition temperature of AP
was significantly decreased, as shown in Figure 7(a). Sim-
ilarly, as the content of G2 was increased, the thermal
decomposition temperature decreased, as shown in
Figure 7(c). Among the three dendrimers, G2 showed bet-
ter catalytic activity for thermal decomposition of AP and
the thermal decomposition temperature of AP was
decreased to 328.25 °C as shown in Figure 7(a), which
might be due to the presence of relatively large amount
of ferrocene. With an increase in ferrocene units from
G0 to G2, the number of iron atoms per molecule
increased. Iron atoms per molecule in G0, G1 and G2
were 3, 6 and 12, respectively.
ACKNOWLEDGMENTS
It was found that pure AP and mixtures of AP
with G0, G1 and G2 were decomposed in two stages.
The first stage corresponds to low‐temperature decom-
position (LTD), while the second stage corresponds to
high‐temperature decomposition (HTD). In the case of
pure AP, LTD was observed at 302.94 °C and HTD
was observed at 398.15 °C, while in the case of AP with
the ferrocene‐terminated dendrimers, LTD was observed
at around 260 °C and HTD was observed at around
330 °C, as shown in Figure 7(b). As the amount of G2
with AP was increased, the thermal decomposition
temperature of AP was decreased, as shown in
Figure 7(d). The addition of G0, G1 and G2 in AP
significantly decreased both LTD and HTD stages of
AP. These results show that G0, G1 and G2 have good
catalytic activity in lowering the thermal decomposition
temperature of AP.
Financial support by the National Natural Science Foun-
dation of China (21272210, 21372200, 21472168,
21411130187), International Science and Technology
Cooperation Project of Ministry of Science and Technol-
ogy of China (2009 DFR 40640), Science and Technology
Program of Zhejiang Province (2013C24001), Science
and Technology Innovation Team of Ningbo
(2011B82002) and the Fundamental Research Funds for
the Central Universities (2015FZA4025) is gratefully
acknowledged.
ORCID
Li Wang http://orcid.org/0000-0001-9356-9930
REFERENCES
In the case of AP‐based propellant combustion, ther-
mal decomposition of AP is considered as a first step.[43]
On combustion of ferrocene‐terminated dendrimers along
with AP‐based propellant, the distance between Cp rings
and iron atom increases and then ferrocene starts
to degrade, which results in the oxidation of Cp rings to
produce CO2. At the same time, iron atom of ferrocene
moiety reacts with oxygen to form nanoscale hematite.
The nanoscale hematite particles have larger surface area
and show excellent catalytic activity for the thermal
decomposition of AP. A possible burning rate catalytic
mechanism for the decomposition of AP catalyzed by G2
is shown in Figure 8.
[1] X. Gao, J. Li, Y. Luo, C. Li, F. Bi, W. Zhang, G. Zhang, Z. Gao, Z.
Anorg. Allg. Chem. 2015, 641, 475.
[2] S. S. Braga, A. M. S. Silva, Organometallics 2013, 32, 5626.
[3] Z. M. Lai, H. M. Ye, Q. Wan, L. L. Xie, S. Bai, Y. F. Yuan, J. Mol.
Struct. 2014, 1059, 33.
[4] H. Khalid, H. Yu, L. Wang, W. A. Amer, M. Akram, N. M.
Abbasi, Zain‐ul‐Abdin, M. Saleem, Polym. Chem. 2014, 5, 6879.
[5] M. Drusan, R. Sebesta, Tetrahedron 2014, 70, 759.
[6] D. J. Young, S. W. Chien, T. S. A. Hor, Dalton Trans 2012, 41,
12655.
[7] D. Schaarschmidt, H. Lang, Organometallics 2013, 32, 5668.

ZAIN‐UL‐ABDIN ET AL.
11 of 11
[8] V. H. Purecha, N. S. Nandurkar, B. M. Bhanage, J. M. Nagarkar,
[30] S. Isert, L. J. Groven, R. P. Lucht, S. F. Son, Combust. Flame
2015, 162, 1821.
Tetrahedron Lett. 2008, 49, 5252.
[9] Z. Cheng, G. Zhang, X. Fan, F. Bi, F. Zhao, W. Zhang, Z. Gao,
[31] Zain‐ul‐Abdin, L. Wang, H. Yu, M. Saleem, M. Akram, N. M.
Abbasi, H. Khalid, R. Sun, Y. Chen, New J. Chem. 2016, 40, 3155.
Inorg. Chim. Acta 2014, 421, 191.
[10] R. Kurane, V. Gaikwad, J. Jadhav, R. Salunkhe, G. Rashinkar,
[32] M. Senel, C. Nergiz, E. Cevik, Sens. Actuators B 2013, 176, 299.
Tetrahedron Lett. 2012, 53, 6361.
[33] F. Xiao, M. Shi, L. Peng, Y. Luo, J. Zhao, J. Inorg. Organometal.
Polym. Mater. 2011, 21, 175.
[11] A. W. Orbaek, N. Aggarwal, A. R. Barron, J. Mater. Chem. A
2013, 1, 14122.
[34] N. G. Tsierkezos, J. Solution Chem. 2007, 36, 289.
[12] G. Huang, J. Weng, Curr. Org. Chem. 2011, 15, 3653.
[35] L. Ma, L. Wang, Q. Tan, H. Yu, J. Huo, Z. Ma, H. Hu, Z. Chen,
[13] P. Molina, A. Tarraga, M. Alfonso, Dalton Trans. 2014, 43, 18.
Electrochim. Acta 2009, 54, 5413.
[14] M. Alfonso, A. Espinosa, A. Tarraga, P. Molina, Chem.
Commun. 2012, 48, 6848.
[36] Q. Tan, L. Wang, L. Ma, H. Yu, Q. Liu, A. Xiao, Macromolecules
2009, 42, 4500.
[15] S. R. Beeren, J. K. M. Sanders, J. Am. Chem. Soc. 2011, 133,
[37] C. Li, L. Wang, L. Deng, H. Yu, J. Huo, L. Ma, J. Wang, J. Phys.
Chem. B 2009, 113, 15141.
3804.
[16] H. D. Li, Z. H. Ma, K. Yang, L. L. Xie, Y. F. Yuan, J. Mol. Struct.
2012, 1024, 40.
[38] Q. Tan, L. Wang, L. Ma, H. Yu, J. Ding, Q. Liu, A. Xiao, G. Ren,
J. Phys. Chem. B 2008, 112, 11171.
[17] B. Wei, Y. Gao, C. X. Lin, H. D. Li, L. L. Xie, Y. F. Yuan,
[39] H. Yu, L. Wang, J. Huo, C. Li, Q. Tan, Des. Monom. Polym. 2009,
12, 305.
J. Organometal. Chem. 2011, 696, 1574.
[18] M. Saleem, H. Yu, L. Wang, Zain‐ul‐Abdin, H. Khalid, M.
Akram, N. M. Abbasi, J. Huang, Anal. Chim. Acta 2015, 876, 9.
[40] T. Chen, L. Wang, G. Jiang, J. Wang, X. J. Wang, J. Zhou, J.
Wang, C. Chen, W. Wang, H. Gao, J. Electroanal. Chem. 2006,
586, 122.
[19] Zain‐ul‐Abdin, H. Yu, L. Wang, M. Saleem, H. Khalid, N. M.
Abbasi, M. Akram, Appl. Organometal. Chem. 2014, 28, 567.
[41] A. Bard, L. Faulkner, Electrochemical Methods: Fundamentals
and Applications, John Wiley, New York 2001.
[20] J. Gao, L. Wang, H. Yu, A. Xiao, W. Ding, Propell. Explos. Pyrot.
2011, 36, 404.
[42] Q. Yang, S. Chen, G. Xie, S. Gao, J. Hazard. Mater. 2011, 197,
199.
[21] N. Dilsiz, A. Unver, J. Appl. Polym. Sci. 2006, 101, 2538.
[43] K. Fujimura, A. Miyake, J. Therm. Anal. Calorim. 2010, 99, 27.
[22] X. Liu, W. Zhang, G. Zhang, Z. Gao, New J. Chem. 2015, 39, 155.
[23] P. J. Swarts, M. Immelman, G. J. Lamprecht, S. E. Greyling, J.
C. Swarts, S. Afr. J. Chem. 1997, 50, 208.
SUPPORTING INFORMATION
[24] H. Yu, L. Wang, J. Huo, J. Ding, Q. Tan, J. Appl. Polym. Sci.
2008, 110, 1594.
Additional Supporting Information may be found online
in the supporting information tab for this article.
[25] F. Xiao, F. Feng, L. Li, D. Zhang, Propell. Explos. Pyrot. 2013, 38,
358.
[26] H. Dong, A. Qin, C. K. W. Jim, J. W. Y. Lam, M. Haeussler, B. Z.
How to cite this article: Zain‐ul‐Abdin, Wang L,
Yu H, Khan RU, Ullah RS, Haroon M. Tris(2‐
aminoethyl)amine‐based ferrocene‐terminated
dendrimers as burning rate catalysts for
Tang, J. Inorg. Organometal. Polym. Mater. 2008, 18, 201.
[27] R. Sun, L. Wang, H. Yu, Zain‐ul‐Abdin, Y. Chen, H. Khalid, N.
Abbasi, M. Akram, J. Inorg. Organometal. Polym. Mater. 2014,
24, 1063.
ammonium perchlorate‐based propellant
decomposition. Appl Organometal Chem. 2018;
e4268. https://doi.org/10.1002/aoc.4268
[28] H. Zhao, M. Chen, X. Zhu, S. Chen, Z. Bian, Chem. Intermed.
2015, 41, 3971.
[29] F. Xiao, X. Sun, X. Wu, J. Zhao, Y. Luo, J. Organometal. Chem.
2012, 713, 96.