Synthesis of ferrocene-based saccharides and their anti-migration and burning rate catalytic properties

Article abstract of DOI:10.1039/c6ra16017d

In the search for ferrocene-based burning rate catalysts (BRCs) with good burning rate catalytic properties and low migration, we synthesized four ferrocene-based saccharides (S-Fcs). The synthesis of S-Fcs was confirmed by energy-dispersive X-ray (EDX), nuclear magnetic resonance (¹H NMR), Fourier transform infra-red (FT-IR) and ultraviolet-visible (UV-Vis) spectroscopy. The electrochemical behavior of ferrocene-based BRCs is important to investigate the electron transfer burning rate catalytic mechanism. Therefore, the electrochemical behavior of the S-Fcs was investigated by cyclic voltammetry. The burning rate catalytic properties of the S-Fcs on thermal disintegration of ammonium perchlorate (AP) were determined by TG and DTG techniques. Thermal analysis results showed that the S-Fcs were thermally stable and showed good burning rate catalytic effects on thermal disintegration of AP. The S-Fcs were also analyzed in anti-migration studies in comparison with the most commonly used ferrocene-based burning rate catalyst (catocene) and ferrocene. It was found that S-Fcs showed excellent anti-migration behavior in AP-based propellant as compared to catocene and ferrocene.

Full text of DOI:10.1039/c6ra16017d

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Synthesis of Ferrocene-based Saccharides and Their Anti-migration and
Burning Rate Catalytic Properties
∗
*
ZainꢀulꢀAbdin, Li Wang , Haojie Yu , Muhammad Saleem, Nasir M. Abbasi, 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
Abstract
In view of ferroceneꢀbased burning rate catalysts (BRCs) with good burning rate catalytic
properties and least migration, we synthesized four ferroceneꢀbased saccharides (S-Fcs). The
synthesis of S-Fcs was confirmed by energyꢀdispersive Xꢀray (EDX), nuclear magnetic
1
resonance ( H NMR), Fourier transform infraꢀred (FTꢀIR) and ultravioletꢀvisible (UVꢀVis)
spectroscopy. The electrochemical behavior of ferroceneꢀbased BRCs is important to investigate
electron transfer burning rate catalytic mechanism. Therefore, electrochemical behavior of S-Fcs
was investigated by cyclic voltammetry. Burning rate catalytic properties of S-Fcs on thermal
disintegration of ammonium perchlorate (AP) were determined by TG and DTG techniques.
Thermal analysis results showed that S-Fcs were thermally stable and showed good burning rate
catalytic effect on thermal disintegration of AP. S-Fcs were also analyzed for antiꢀmigration
studies in comparison with most commonly used ferroceneꢀbased burning rate catalyst (catocene)
and ferrocene. It was found that S-Fcs showed excellent antiꢀmigration behavior in APꢀbased
propellant as compared to catocene and ferrocene.
∗
Correspondence to Li Wang. Eꢀmail: opl_wl@dial.zju.edu.cn and Haojie Yu. Eꢀmail: hjyu@zju.edu.cn
Tel: +86ꢀ571ꢀ8795ꢀ3200; Fax: +86ꢀ571ꢀ8795ꢀ1612.
1

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Key words
Ferroceneꢀbased saccharides, electrochemistry, catalysis, antiꢀmigration behavior.
Introduction
1
Burning rate catalyst is one of the important components of the composite solid rocket
1
propellants, which play a key role in increasing burning rate of the composite solid propellant .
To achieve stable burning rate of the propellant and low pressure exponent, several burning rate
2
, 3
catalysts (BRCs) have been synthesized, such as transition metal oxides , nanometal particles
4
ꢀ6
7
8ꢀ10
,
metal chelates , ferroceneꢀbased derivatives and compounds
, etc. Among all BRCs,
ferroceneꢀbased derivatives and compounds have attracted much attention due to their good
catalytic performance on combustion of the solid propellant and homogenous distribution in the
1
, 8, 11, 12
propellant
. Although, ferroceneꢀbased derivatives and compounds are considered as
good ferroceneꢀbased BRCs for the propellants, but simple ferroceneꢀbased derivatives result in
1
, 13, 14
migration problems
. When solid propellant containing ferrocene or simple ferroceneꢀ
based derivatives are stored, these ferroceneꢀbased BRCs migrate to the interface of the
1
5ꢀ17
18ꢀ20
21
propellant
, which in turn results in poor aging
, reduces service life, changes designed
1
4
burning parameters and damages propellant system .
Many researchers have tried to synthesize ferroceneꢀbased BRCs with good catalytic activity and
2
2
least migration . nꢀButylferrocene (NBF), tertꢀbutylferrocene (TBF) and 2,2ꢀbis(ethylꢀ
ferrocenyl)propane (catocene) are wellꢀknown ferroceneꢀbased BRCs for APꢀbased propellants
2
3, 24
.
NBT and TBF exhibited migration problems due to shorter carbon chain on ferrocene and
1
, 14, 25ꢀ29
lower molecular weight. Catocene was then developed to reduce migration problems
.
However, migration problems have not been reduced obviously and after longꢀtime storage,
2

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24
significant migration of catocene to the interface of the propellant was still observed
.
Therefore, study on migration problems of ferroceneꢀbased BRCs is still being continued to find
3
0
effective and cheap approach .
Two main approaches have been applied to design and develop new ferroceneꢀbased BRCs. First
approach is the grafting of ferrocene on main chain or side chain of the polymer and second
approach is the synthesis of ferroceneꢀbased derivatives with polar groups such as carbonyl
3
1
groups . Saccharides have large number of oxygen in their structures, which results in the
increase in their polarity and dipoleꢀdipole interactions between saccharides and APꢀbased
2
2
30
propellant . Ferrocene shows good burning rate catalytic properties . So, by grafting ferrocene
on saccharides, we can get ferroceneꢀbased saccharides, which may have good burning rate
catalytic and antiꢀmigration properties. Thermal decomposition of AP directly affects
32
performance of APꢀbased propellant . So, the burning rate catalytic activity of BRCs in APꢀ
3
3, 34
based propellant is usually assessed by thermal decomposition of AP
. With the increase in
BRCs percentage, number of active sites increases and therefore, burning rate of APꢀbased
propellant increases, but after certain BRCs percentage, propellant performance decreases or no
increase in the burning rate is observed due to the presence of high percentage of inert
3
5
ingredients . BRCs efficiency can be increased by increasing surface area of BRCs.
In this study, to reduce migration problems of ferroceneꢀbased BRCs in the propellant and to
increase burning rate of APꢀbased propellant, we synthesized four ferroceneꢀbased saccharides
(S-Fcs). The synthesis of S-Fcs was confirmed by energyꢀdispersion Xꢀray (EDX), nuclear
1
magnetic resonance ( H NMR), Fourier transform infraꢀred (FTꢀIR) and ultravioletꢀvisible (UVꢀ
Vis) spectroscopy. The electrochemical properties of S-Fcs were investigated by cyclic
voltammetry (CV). Burning rate catalytic performance of S-Fcs on thermal decomposition of AP
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was examined by thermogravimetry (TG) and differential thermogravimetry (DTG) techniques.
Antiꢀmigration behavior of S-Fcs was studied in comparison with catocene and ferrocene.
2
Experimental
.1 Materials
2
Glucose, maltose, maltotriose and amylose (M , ca = 15,000 and n = 92.5) were purchased from
W
SigmaꢀAldrich. Dichloromethane (DCM), tetrahydrofuran (THF), petroleum ether, pyridine,
chloroform (CHCl ), dimethyl sulfoxide (DSMO), oxalyl chloride, ferrocenecarboxylic acid and
3
NaHCO were purchased from Sinopharm Chemical Reagent Co., Ltd. Sodium hydride (NaH)
3
and tetrabutylammonium tetrafluoroborate (Bu NBF ) were purchased from J&K Co., Ltd.
4
4
Ammonium perchlorate (AP), hydroxylꢀterminated polybutadiene (HTPB) and isophorone
diisocyanate (IPDI) were purchased from Aladdin Co., Ltd. DCM and THF were dried with 4Åꢀ
type molecular sieves followed by reflux prior to use. Petroleum ether and pyridine were dried
with 4Åꢀtype molecular sieves and all other chemicals were used as received.
2.2 Synthesis
2.2.1 Ferrocenecarbonyl chloride
3
0
Ferrocenecarbonyl chloride was prepared by following the reported procedure . The obtained
product was stored under Ar atmosphere.
2.2.2 Ferrocene-based saccharides
Ferroceneꢀbased saccharides (S-Fcs) were prepared by the condensation reaction of
corresponding saccharides with ferrocenecarbonyl chloride using sodium hydride as a catalyst.
The synthetic procedure of all S-Fcs was same. Therefore, synthesis of S-Fc-1 is taken as an
4

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example. In typical procedure, glucose (1.2000 g, 6.66 mmol) was dried under reduced pressure
and then dried glucose was dissolved in 15 mL THF. A suspension of NaH (0.7996 g, 33.33
mmol) in 15 mL THF was prepared. The glucose solution prepared in THF was dropwise added
to NaH suspension. The resulting mixture was stirred for 10 h at 15 °C. Thereafter,
ferrocenecarbonyl chloride solution (11.5880 g, 46.63 mmol) prepared in 40 mL THF was
dropwise added to previous glucose solution. The resulting solution was then refluxed for 10 h.
Solvent was evaporated on rotary evaporator. The obtained residue was dissolved in 200 mL
ethyl acetate The resulting solution was washed with 2 % NaHCO solution prepared in distilled
.
3
water (four times) and then it was further washed with distilled water (three times). Organic
phase was separated, Na SO anhydrous (2.0000 g) was putted to organic phase and then
2
4
resulting mixture was left overnight. The mixture was filtered to separate Na SO and then
2
4
resulting filtrate was dried to get product. The product was further dried in vacuum oven at 45 °C
for 2 days. The experimental detail is given in Table S1.
2.3 Characterization
1
H NMR spectra of S-Fcs were recorded on AVANCE NMR spectrometer (600 MHz, Model
DMXꢀ600) in DMSO and chemical shifts were correlated with tetramethyl silane (TMS) at δ=0
ppm. FTꢀIR spectra of glucose, maltose, maltotriose, amylose and S-Fcs were taken from Nicolet
5700 infrared spectrometer by KBr pellet technique. 2 % sample (S-Fcs) and KBr were mixed
together, crushed and KBr pellets were prepared.
UVꢀVis spectra of S-Fcs were reordered on 3802 UVꢀVis unico spectrophotometer. CV curves
of S-Fcs were recordered on a CHIꢀ630A electrochemical analyzer (CH Instruments, Inc., Austin,
Texas) in an undivided threeꢀelectrode cell. The electrodes used were from CH instruments.
Teflonꢀshrouded platinum disk was used as working electrode with diameter about 2 mm for test
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solution. The working electrode was polished to a mirror finish with 0.05 µm Al O paste on felt,
2
3
washed by ultraꢀsonication in 0.1 M NaOH and HNO (1:1), anhydrous ethyl alcohol, doubly
3
distilled water and then dried prior to electrochemical measurements. A platinum wire electrode
was used as counter electrode. Ag wire electrode was used as reference electrode for test solution.
Every CV experiment was performed two times to get an average result and in every experiment,
concentration of electrolyte (Bu NBF ) was 0.1 M, potential scan rates were 0.1 to 0.5 V/s and
4
4
concentration of S-Fcs was 0.5 mM.
The samples for migration studies were consisted of three adjacent parts: loaded part, interface
and unloaded part (blank). The loaded part was consisted of AP, HTPB, IPDI and a burning rate
catalyst (S-Fcs or catocene or ferrocene). Typically, sample (S-Fc-1) was prepared by mixing
AP (1.9149 g, 69.08 %), HTPB (0.5820 g, 20.99 %), IPDI (0.1930 g, 6.96 %) and S-Fc-1
(0.0820 g, 2.95 %) for approximately 1 h. The obtained mixture was cured at 25 °C for 3 days.
The unloaded part was comprised of AP (21.1605 g, 71.93 %), hydroxylꢀterminated
polybutadiene (HTPB) (6.2619 g, 21.28 %) and isophorone diisocyanate (IPDI) (1.9971 g,
6.79 %) and it was prepared by mixing AP, HTPB and IPDI for 30 min. The migration tubes
(including loaded and unloaded parts) were cured for 3 days at 25 °C and then samples were
putted in oven at 50 °C and 1 atmospheric pressure for 30 days for aging process.
Thermal analysis was done on a PerkinꢀElmer Pyris 1 thermogravimetric instrument in range of
5
0ꢀ600 °C under N at heating rate of 5 °C/min. Burning rate catalytic performance of S-Fcs on
2
thermal disintegration of AP was done by mixing specific amount of ferroceneꢀbased saccharides
with AP.
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3
3
Results and discussion
.1 Synthesis of S-Fcs
3
0
Ferrocenecarbonyl chloride was prepared by following the reported procedure . The synthesis of
ferrocenecarbonyl chloride is shown in Scheme 1.
Ferroceneꢀbased saccharides (S-Fcs) were prepared by the condensation reaction of glucose,
maltose, maltotriose and amylose with ferrocenecarbonyl chloride. The synthetic routes for the
synthesis of S-Fcs are displayed in Scheme 1 and experimental detail is given in Table S1.
Scheme 1. The synthetic routes for the synthesis of S-Fcs.
1
The synthesis of S-Fcs was confirmed by EDX, H NMR, FTꢀIR and UVꢀVis spectroscopy. The
elemental percentage composition of S-Fc-1 (C = 60%, O = 21% and Fe = 19%), S-Fc-2 (C = 56%,
O = 28% and Fe = 16%), S-Fc-3 (C = 55%, O = 26% and Fe = 19%) and S-Fc-4 (C = 61%, O = 22%
and Fe = 17%) confirmed the synthesis of S-Fcs. From S-Fc-1 to S-Fc-4, chain length of the
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saccharides was increased, but %age composition of Fe was almost same, which supported the
1
formation of S-Fcs. EDX spectra of S-Fcs are shown in Figure S1. On comparing H NMR
1
spectra of S-Fcs with H NMR spectra of corresponding saccharides, three new peaks attributed
to ferrocene protons were observed in the region 4.00ꢀ5.00 ppm. The intensity of all the peaks
including protons of ferrocene and rest of the protons was according to the structures, which
1
confirmed the synthesis of S-Fcs. H NMR spectra of the synthesized S-Fcs are shown in Figure
1.
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1
Figure 1. H NMR spectra of the synthesized S-Fcs.
The synthesis of S-Fcs was further confirmed by FTꢀIR spectroscopy. On comparing FTꢀIR
spectra of S-Fcs with corresponding saccharides, we found that OꢀH stretching and bending
vibrations of saccharides disappeared and vibrational and deformational bands of ferrocene
appeared in FTꢀIR spectra of S-Fcs. The stretching vibrations of carbonyls esters of S-Fcs were
ꢀ1
observed around 1710 cm . The stretching vibrations of (CꢀO) esters of S-Fcs were observed
ꢀ1
ꢀ1 36
around 1120 cm . The (CꢀH) bending vibrations of S-Fcs were observed around 1458 cm
.
The vibrational and deformational bands of ferrocene of S-Fcs were observed around 1020, 820
ꢀ1 37
and 480 cm
. FTꢀIR spectra of S-Fcs, glucose, maltose, maltotriose and amylose are shown in
Figure 2(A).
UV–Vis absorption studies of S-Fcs (c = 0.012 mM) were done in DCM. The detail of samples
preparation is given in Table S2. It was found that S-Fcs exhibited absorption bands with λmax
around 260 and 230 nm, which were attributed to πꢀπ* transitions, while absorption bands with
λmax around 310 and 450 nm were attributed to charge transfer band (CT) and dꢀd transitions,
1
1, 30
respectively
. For all S-Fcs, intense bands (πꢀπ* transitions) were observed. For S-Fc-2,
absorption bands of dꢀd transitions and for S-Fc-1, absorption bands of dꢀd transitions and CT
were not observed. With the increase in ferrocene in S-Fcs, CT absorption bands become more
intense. UVꢀVis spectra of S-Fcs are shown in Figure 2(B).
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(
a)
b)
(
A)
(B)
(
π−π∗ transition
(a)
(
a)
S-Fc-1
S-Fc-2
S-Fc-3
S-Fc-4
1
.6
(
(
b)
c)
(c)
1.4
(
d)
(
d)
1
1
0
0
0
0
0
.2
.0
.8
.6
.4
.2
.0
π−π∗ transition
(d)
(
e)
f)
(c)
(
(b)
(g)
(a)
(h)
Charge transfer band
d-d transition
4000
3500
3000
2500
2000
1500
1000
500
200
300
400
500
600
700
-
1
Wavenumber (cm )
Wavelength (nm)
Figure 2. (A) FTꢀIR spectra of: (a) glucose, (b) S-Fc-1, (c) maltose, (d) S-Fc-2, (e) maltotriose, (f)
S-Fc-3, (g) amylose and (h) S-Fc-4 and (B) UVꢀVis absorption spectra of: (a) S-Fc-1, (b) S-Fc-2,
(c) S-Fc-3 and (d) S-Fc-4.
3.2 Electrochemical properties of ferrocene-based saccharides
The electron transfer catalytic mechanism of ferroceneꢀbased BRCs on APꢀbased propellant can
be explained in term of their electrochemical properties (gain and loss of electron). Therefore,
electrochemical properties of S-Fcs are important to investigate their potential application as
ferroceneꢀbased BRCs. Among various methods of electrochemical measurements, CV is
3
8
considered as an effective method . So, electrochemical properties of S-Fcs were analyzed by
CV. The detail of samples preparation is given in Table S3.
The electrochemical properties of S-Fcs (0.5 mM) were investigated in DCM, CHCl and DMSO
3
using Bu NBF (0.10 M) as an electrolyte at different potential scan rates. It was found that CV
4
4
3
9ꢀ43
curves of S-Fcs were affected by both solvent polarity and potential scan rate
. The increase
in solvent polarity resulted in the deformation of peaks shape. The peaks shape was found more
compact in high polar solvent like DMSO. The peak potential of reduction process was
decreased with the increase in polarity of the solvent, which showed that reduction of S-Fcs was
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proportional to the polarity of the solvent and oxidation of S-Fcs was inversely proportional to
4
4
the polarity of solvent .
Sharp and wellꢀdefined CV curves of S-Fcs with high current were observed in DCM. The small
peak to peak potential separation (ꢁE ) was observed in DCM and large ꢁE values were
p
p
observed in CHCl . It was found that rate of electrode reaction was faster in DCM than CHCl3.
3
The resistance offered by DCM was small and charge diffusion rate was fast, while in CHCl3,
vice versa results were obtained. It was found that redox reactions of S-Fcs occurred more easily
in DCM in comparison with CHCl . CV curves of S-Fcs in different organic solvents and at
3
different potential scan rates are shown in Figure 3 to Figure 6.
Figure 3. CV curves of S-Fc-1 in: (a) DCM, (b) CHCl and (c) DMSO at different scan rates and
3
(d) different solvents at 0.1 V/s.
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Figure 4. CV curves of S-Fc-2 in: (a) DCM, (b) CHCl and (c) DMSO at different scan rates and
3
(d) different solvents at 0.1 V/s.
Figure 5. CV curves of S-Fc-3 in: (a) DCM, (b) CHCl and (c) DMSO at different scan rates and
3
(d) different solvents at 0.1 V/s.
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Figure 6. CV curves of S-Fc-4 in: (a) DCM, (b) CHCl and (c) DMSO at different scan rates and
3
(d) different solvents at 0.1 V/s.
It was found that CV curves of S-Fcs were also sensitive to potential scan rate. In addition, peak
current values (i and i ) were increased with the increase in potential scan rate. Additionally,
pc
pa
reduction peak current rate (i ) was increased faster than oxidation peak current rate (i ). On the
pc
pa
4
5
basis of electrochemical theory , above results showed that charge transport of the electrode
processes followed Fick’s law and electrode reactions were controlled by mass diffusion.
Additionally, it was concluded that the electrode processes of S-Fcs were neither simple
reversible nor totally irreversible.
3.3 Anti-migration studies of ferrocene-based saccharides
Catocene is the most commonly used ferroceneꢀbased burning rate catalyst. So, S-Fcs were
analyzed for antiꢀmigration studies by comparing with catocene and also with ferrocene. The
detail of samples preparation is given in Table S4. It was found that S-Fcs showed better antiꢀ
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migration behavior than catocene and ferrocene. S-Fcs have high molecular weight and contain
large number of oxygen atoms. The presence of large number of oxygen in S-Fcs resulted in
dipoleꢀdipole interactions of S-Fcs with propellant and low pressure exponent due to their high
molecular weight of S-Fcs resulted in better antiꢀmigration properties of S-Fcs. The main reason
for excellent antiꢀmigration properties of S-Fcs was the formation of dipoleꢀdipole forces and
hydrogen bonding between S-Fcs and the propellant, which retard the migration of S-Fcs in the
propellant. Saccharides show good antiꢀmigration behavior and ferrocene shows burning rate
catalytic properties. So, we grafted ferrocene on saccharides to enhance burning rate of APꢀbased
propellant and to overcome migration problems. The least migration was observed for S-Fc-4,
which might be due to the existence of comparatively large number of oxygen and high
molecular weight. The schematic procedure for the fabrication of migration tubes is shown in
Figure 7. Antiꢀmigration studies photos of S-Fcs, catocene and ferrocene at 50 °C are shown in
Figure 8. Antiꢀmigration studies result of S-Fcs in comparison with catocene and ferrocene is
shown in Figure 9 and migration mechanism of S-Fc-1 is shown in Figure 10.
3.4 Burning rate catalytic performance and possible mechanism
3
0
BRCs with high thermal stability are considered as excellent BRCs . The detail of samples
preparation is given in Table S5. It was found that S-Fcs were thermally stable up to 230 °C. The
burning rate catalytic activity of BRCs on combustion of APꢀbased propellant is commonly
4
6
checked by their catalytic activity on thermal disintegration of AP . Catalytic activity of S-Fcs
on thermal disintegration of AP was examined by TG and DTG using 5 wt.% of S-Fcs, as shown
in Figure 11(a) and 11(b).
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Figure 7. Schematic procedure for the fabrication of migration tubes: (a) Filling of the migration
tubes and (b) samples of the migration tubes. Migration tubes: (1) empty, (2) filled with loaded
part and (3) filled with loaded and unloaded part.
The catalytic activity of S-Fc-4 on thermal disintegration of AP was also studied by changing
contents (1ꢀ5 wt. %) of S-Fc-4, as shown in Figure 11(c) and 11(d). The maximum lower shift
was observed at 324.62 °C for 5 wt.% of S-Fc-4, as shown in Figure 11(a). Similarly, as wt.% of
S-Fc-4 was increased, thermal disintegration temperature of AP was obviously decreased, as
shown in Figure 11(c). It was found that pure AP and mixtures of AP with S-Fcs were
disintegrated in two stages. First stage disintegration attributes to lower temperature
disintegration (LTD) and second stage disintegration attributes to higher temperature
disintegration (HTD).
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Figure 8. Antiꢀmigration studies photos of S-Fc-1, S-Fc-2, S-Fc-3, S-Fc-4, catocene and
ferrocene on days 1, 7, 15 and 30 at 1 atmospheric pressure and at 50 °C.
S-Fc-1 (1)
(Fc)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
S-Fc-2 (2)
S-Fc-3 (3)
S-Fc-4 (4)
Catocene (C)
Ferrocene (Fc)
(
Fc)
(C)
(Fc)
(
C)
(3)
(C)
(2)
(1)
(2)
(4)
(1)
(3)
(4)
(2)
(1)
(3)
(4)
7
Days
15 Days
30 Days
Migration days
Figure 9. Antiꢀmigration studies of S-Fc-1, S-Fc-2, S-Fc-3, S-Fc-4, catocene and ferrocene on
days 7, 15 and 30 at 1 atmospheric pressure and at 50 °C.
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Figure 10. Migration mechanism: (a) S-Fc-4, (b) model of S-Fc-4, (c) catocene, (d) model of
catocene, (e) ferrocene and (f) model of ferrocene stored at 50 °C and 1 atmospheric pressure.
In case of pure AP, LTD appeared at 302.94 °C and HTD was observed at 398.15 °C, while in
case of AP with S-Fcs, LTD and HTD appeared around 280 °C and 350 °C, respectively, as
shown in Figure 11(b). It was found that addition of S-Fcs in AP significantly decreased both
LTD and HTD stages of AP. These results show that S-Fcs have good catalytic behavior on
thermal disintegration of AP. Among S-Fcs, S-Fc-4 showed better catalytic activity on thermal
disintegration of AP and this behavior might be due to the existence of comparatively large
number of ferrocene units. So, these S-Fcs can be used as ferroceneꢀbased BRCs for APꢀbased
17

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DOI: 10.1039/C6RA16017D
propellants due to their excellent antiꢀmigration properties in APꢀbased propellant and burning
rate catalytic activity on thermal disintegration of AP.
AP
AP
(
a) AP + 5 Wt.% S-Fc-1
(b)
302.94
°
C
398.35 °C
AP + 5 Wt.% S-Fc-2
AP + 5 Wt.% S-Fc-1
4
06.42 °C
AP + 5 Wt.% S-Fc-3
2
99.41 °C
3
44.54
°
C
AP + 5 Wt.% S-Fc-2
AP + 5 Wt.% S-Fc-3
AP + 5 Wt.% S-Fc-4
3
33.32
°
C
3
49.70
°C
2
89.96 °C
1
71.99
°
C
3
42.01
°C
2
83.03 °C
3
29.79
°
C
AP + 5 Wt.% S-Fc-4
3
33.32 °C
1
64.18
°
C
3
24.62
°
C
266.52 °C
3
21.97 °C
1
00
200
300
400
500
600
100
200
300
400
500
600
Temperature (
°
C)
Temperature (°C)
AP
AP
(
c) AP + 1 Wt.% S-Fc-4
(d)
3
02.94 °C
3
98.35 °C
AP + 2 Wt.% S-Fc-4
AP + 1 Wt.% S-Fc-4
AP + 2 Wt.% S-Fc-4
AP + 3 Wt.% S-Fc-4
244.84
°
C
346.29 °C
4
06.42 °C
AP + 4 Wt.% S-Fc-4
AP + 5 Wt.% S-Fc-4
1
56.37
AP + 3 Wt.% S-Fc-4
59.77
AP + 4 Wt.% S-Fc-4
60.65
AP + 5 Wt.% S-Fc-4
°
C
2
57.83
°
C
340.25 °C
1
°C
3
50.58
45.41
40.25
34.96
24.62
°
C
260.47
°
C
334.20 °C
3
°C
1
°C
2
62.11
°
°
C
C
3
°
C
330.67 °C
3
°C
1
64.18
°
C
2
66.52
3
°
C
321.97
°
C
1
00
200
300
400
500
600
100
200
300
400
500
600
Temperature (
°
C)
Temperature (
°
C)
Figure 11. (a) TG curves of pure AP and 5 wt. % of S-Fcs with AP, (b) DTG curves of pure AP
and 5 wt. of % S-Fcs with AP (c) TG curves of pure AP and different wt. % of S-Fc-4 with AP
and (d) DTG curves of pure AP and different wt. % of S-Fc-4 with AP.
In case of APꢀbased propellant combustion, thermal disintegration of AP is considered as first
4
7
step . On combustion of APꢀbased propellant containing S-Fcs, S-Fcs decompose and produce
nanoscale hematite particles, which catalyze thermal disintegration of AP. On combustion of S-
Fcs, Cp rings and iron atom distance increases and then ferrocene starts to disintegrate, which
leads to Cp rings oxidation. Meanwhile, Fe of ferrocene reacts with oxygen either from air or
produced by the thermal disintegration of AP to form Fe O particles. The nanoscale particles
2
3
have large surface area and show excellent catalytic activity on thermal disintegration of AP. The
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possible catalytic mechanism of thermal disintegration of AP catalyzed by S-Fc-4 is shown in
Figure 12.
Figure 12. The possible burning rate catalytic mechanism of thermal decomposition of AP
catalyzed by S-Fc-4.
4
Conclusion
In this paper, four ferroceneꢀbased saccharides (S-Fcs) were successfully synthesized. The
1
structures of S-Fcs were confirmed by EDX, H NMR, FTꢀIR and UVꢀVis spectroscopy. It was
found that S-Fcs showed excellent antꢀmigration properties and good catalytic activity on
thermal decomposition of APꢀbased propellant. UV–Vis absorption studies of S-Fcs showed
photoꢀinduced charge transfer effect. Cyclic voltammetry results of S-Fcs exhibited reversible
redox behavior due to the presence of ferrocene. It was also found that electrode reactions were
controlled by mass diffusion. The burning rate catalytic studies confirmed their good catalytic
behavior on thermal disintegration of AP. We concluded that S-Fcs have excellent antiꢀmigration
and burning rate catalytic properties for APꢀbased propellant and can be used as ferroceneꢀbased
BRCs for APꢀbased propellant.
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Acknowledgments
Financial support by National Natural Science Foundation of China (21272210, 21372200,
1472168, 21411130187), International Science and Technology Cooperation Project of
2
Ministry of Science and Technology of China (2009 DFR 40640), Science and Technology
Program of Zhejiang Province (2013C24001) and Science and Technology Innovation Team of
Ningbo (2011B82002), the Fundamental Research Funds for the Central Universities
(2015FZA4025) are gratefully acknowledged.
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3
31x165mm (300 x 300 DPI)