Reactive ladder-like poly(p-decyl anilino)silsesquioxane for functional material's precursor: Synthesis, characterization and functionalization

Article abstract of DOI:10.1016/j.reactfunctpolym.2012.05.003

A well-defined polysilsesquioxane with reactive Si-N bonds, poly(p-decyl anilino)silsesquioxane (PASQ), was successfully prepared using supramolecular template polymerization. The monomers 1,3-bis-(p-decyl anilino)-1,1,3,3- tetrachloro-disiloxanes first self-assembled into ladder superstructures (LSs) primarily through the synergistic interactions of hydrogen bonding and the van der Waals interactions, and then polymerized by adding water and triethylamine to produce a well-defined PASQ. The LSs was fully characterized using vapor pressure osmometry (VPO), UV-vis spectroscopy and X-ray diffraction (XRD). NMR and XRD measurements revealed that the PASQ was a ladder polymer. The reactivity of PASQ was confirmed by its SiN bond reacting with trimethylsilanol to form a ladder-like trimethylsiloxysilicate (LMQ). The ladder structure of LMQ was also thoroughly characterized, which further verified the ladder structural regularity of PASQ.

Full text of DOI:10.1016/j.reactfunctpolym.2012.05.003

Reactive & Functional Polymers 72 (2012) 503–508
Contents lists available at SciVerse ScienceDirect
Reactive & Functional Polymers
journal homepage: www.elsevier.com/locate/react
Reactive ladder-like poly(p-decyl anilino)silsesquioxane for functional
material’s precursor: Synthesis, characterization and functionalization
Zhize Chen a, Zhongjie Ren b, Jintao Zhang a, Wenxin Fu a, Zhibo Li a, Rongben Zhang a,
⇑
a Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
b State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A well-defined polysilsesquioxane with reactive Si–N bonds, poly(p-decyl anilino)silsesquioxane (PASQ),
was successfully prepared using supramolecular template polymerization. The monomers 1,3-bis-(p-
decyl anilino)-1,1,3,3-tetrachloro-disiloxanes first self-assembled into ladder superstructures (LSs) pri-
marily through the synergistic interactions of hydrogen bonding and the van der Waals interactions,
and then polymerized by adding water and triethylamine to produce a well-defined PASQ. The LSs was
fully characterized using vapor pressure osmometry (VPO), UV–vis spectroscopy and X-ray diffraction
(XRD). NMR and XRD measurements revealed that the PASQ was a ladder polymer. The reactivity of PASQ
was confirmed by its SiAN bond reacting with trimethylsilanol to form a ladder-like trimethylsiloxysili-
cate (LMQ). The ladder structure of LMQ was also thoroughly characterized, which further verified the
ladder structural regularity of PASQ.
Received 18 March 2012
Received in revised form 1 May 2012
Accepted 5 May 2012
Available online 14 May 2012
Keywords:
Ladder polymer
Macromonomers
Polysiloxanes
Self-assembly
SiAN bonds
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Much attention should be devoted to the reactive ladder poly-
siloxanes because they are important precursors for the functional
Considerable attention has been devoted to the preparation of
organic/inorganic hybrid polymers, such as polymers based on sils-
esquioxanes, because of their unique and attractive properties [1–
4]. Ladder polysilsesquioxanes, which are hybrid materials with
an inorganic double-chained backbone, have attracted considerable
interest because of their excellent thermo-resistant and mechanical
properties [5–7]. However, some common factors that affect the
regularity of the ladder are still difficult to control when synthesiz-
ing ladder polysilsesquioxanes. For instance, the unavoidable use of
multi-functional monomers may result in irregular cross-linking
and other side reactions [8]. Supramolecular template polymeriza-
tion is an effective method for synthesizing all types of polymers
with designed structures [9–12]. Based on the supramolecular tem-
plate polymerization technique, we proposed the ‘supramolecular
architecture-directed stepwise coupling/polymerization’ (SCP)
method for the synthesis of ladder polysilsesquioxanes [13].
Currently, a series of ladder organo-bridged polysiloxanes and lad-
der polysilsesquioxanes have been successfully obtained using SCP
[14–16]. In addition, these ladder polysiloxanes and poly-
silsesquioxanes contain many types of organic ladder rungs, such
as light-emitting 9,10-diphenylanthryl [17] or organic side groups
such as phenyl-Br [18], ACH2CH2OCOCH3 [19], ACH2CH2CH2OC6
H4NO2 [20] and ACH2CH2CH2OCH2(CHCH2O) [21].
ladder polymers that have special properties. Among the typical
reactive groups mentioned above, phenyl-Br and ACH2CH2OCOCH3
groups can react through the functional groups of the CABr and
C@O bonds, respectively, which results in the formation of SiAC-
based hybrid ladder polysiloxanes with low thermo-stability, as
previously reported [22–26]. Recently, we reported the synthesis
of reactive ladder polyhydrosilsesquioxane, which can be con-
verted to many types of functional ladder polysiloxanes primarily
with the use of hydrosilylation reactions. However, as a precursor
for functional ladder polymers, polyhydrosilsesquioxane has some
limitations: its synthesis is relatively complicated, resulting in a
low yield [27]; the very high reactivity of the SiAH bond makes
it difficult to store; and the inorganic nature results in extremely
poor solubility in organic solvents. Therefore, the pursuit of new
reactive ladder polysiloxanes that can act as an effective macromo-
lecular intermediate for introducing the polysiloxane-double-chain
structure is of importance.
To the best our knowledge, ladder polysilsesquioxanes contain-
ing SiAN containing side groups have not currently been reported.
Based on silazane chemistry, the SiAN bond also has varied reac-
tivity, such as hydrolysis, varied substitution reactions, oxidation,
etc.; moreover, it is easier to control the reactivity of the SiAN
bond than the SiAH bond. Furthermore, the organic group bonded
to the N-atom can not only supply supramolecular interactions to
result in an easier synthesis but also provide better product solu-
bility than the ladder polysilsesquioxanes containing SiAH bonds.
⇑
Corresponding author. Tel./fax: +86 10 62565612.
E-mail address: zhangrb@iccas.ac.cn (R. Zhang).
1381-5148/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.reactfunctpolym.2012.05.003

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Z. Chen et al. / Reactive & Functional Polymers 72 (2012) 503–508
Therefore, ladder polysilsesquioxanes containing SiAN bonds may
be a better precursor for providing a versatile method for produc-
ing ladder polysiloxanes containing various functional groups. In
this paper, we report the synthesis of ladder-like poly(p-decyl ani-
lino)silsesquioxane (PASQ) using the SCP method (Scheme 1A). The
regularity and reactivity of PASQ were also confirmed.
25 °C. Solution 1H NMR and 13C NMR measurements were per-
formed on a Bruker AV-400 FT-NMR spectrometer at room temper-
ature. Solution and solid-state 29Si NMR measurements were
performed on Bruker AV-300 and Bruker AV III-400 NMR instru-
ments, respectively. XPS data were collected using an ESCA-
Lab220i-XL electron spectrometer from VG Scientific with 300 W
Al
Ka
radiation. The base pressure was approximately
3 Â 10À9 mbar. The binding energies were referenced to the C1s
line at 284.8 eV from adventitious carbon. Elemental analysis
was performed on a Heraeus CHN-RAPID/DATEL System (Ger-
many). X-ray diffraction (XRD) measurements were performed
2. Experimental
2.1. Materials
on a Rigaku D/max 2400 diffractometer with Cu Ka radiation at a
Hexachlorodisiloxane was purchased from Gelest (Morrisville,
United States). Trimethylchlorosilane and trimethylsilanol were
purchased from Aldrich. 4-decyl aniline was purchased from Alfa
Aesar. Toluene, 1,4-dioxane and triethylamine (TEA) were distilled
over a sodium benzophenone complex. Acetone was distilled over
potassium carbonate.
scanning rate of 5° minÀ1. VPO analyses were conducted in dry tol-
uene at 40 °C on a Knauner VPO instrument (Germany) at 20% rel-
ative humidity. UV–vis spectra were obtained on a Shimadzu UV–
vis spectrometer model UV-1601PC. Gel permeation chromatogra-
phy (GPC) measurements were performed using a Waters chro-
matograph connected to a Water 410 differential refractometer
with THF as an eluent. Thermogravimetric analyses (TGA) were
performed on a SDT Q600; the sample was heated from 30 °C to
1000 °C at a rate of 10 °C minÀ1 in a dynamic nitrogen atmosphere
2.2. Characterization
Infrared Spectrometry (IR) spectra were recorded using a Bruker
Tensor 27 spectrophotometer between 400 and 4000 cmÀ1 (KBr) at
with a flow rate of 100 mL minÀ1
.
Scheme 1. Synthetic route for PASQ and LMQ.

Z. Chen et al. / Reactive & Functional Polymers 72 (2012) 503–508
505
2.3. Synthesis of ladder poly(p-decyl anilino)silsesquioxanes (PASQ)
A mixture of 4-decyl aniline (4.66 g, 20 mmol), triethylamine
(2.02 g, 20 mmol) and anhydrous toluene (100 mL) was added
dropwise into a three-necked flask containing anhydrous toluene
(50 mL) and hexachlorodisiloxane (2.84 g, 10 mmol) under an
argon atmosphere over 12 h at room temperature. After continu-
ous stirring for an additional 2 h, a mixture of toluene (50 mL),
1,4-dioxane (100 mL), water (0.36 g, 20 mmol) and triethylamine
(6.06 g, 60 mmol) was added drop-wise over 12 h at room temper-
ature. The mixture was then heated to 45 °C for 6 h. To end-cap the
terminal SiAOH group, Me3SiCl (0.5 mL) in toluene (20 mL) was
added slowly over the course of 2 h at 45 °C. First, 1,4-dioxane
and partial toluene were removed by distillation. Triethylamine
hydrochloride was then removed by filtration under argon. Finally,
anhydrous acetone was added to the remaining solution to precip-
itate a white solid (4.88 g). The yield was 86%. IR (KBr, thin film,
cmÀ1): 3372 (ANH), 2921, 2854 (ACH3CH2A), 1617 (APh), 1514
(SiAN), 1200–1000 (SiAOASi). 1H NMR (400 MHz, d4-o-dichloro-
benzene, d, ppm): 6.91 (4H, ArAH), 6.52 (4H, ArAH), 3.53 (2H,
ANH), 2.47 (4H, CH2), 1.53 (4H, CH2), 1.25–1.20 (28H, CH2), 0.86
(6H, CH3), 0.22 (3H, SiACH3). 13C NMR (100 MHz, d4-o-dichloro-
benzene, d, ppm): 143.9 (ArAC), 133.2 (ArAC), 129.4 (ArAC),
114.9 (ArAC), 35.1 (CH2), 31.9 (CH2), 29.7 (CH2), 23.1 (CH2), 14.0
(CH3), 1.2 (SiACH3). Solid 29Si NMR (100 HMz, d, ppm) 13.7
(AOASiMe3), À99.5 (ASi(NH)O3/2). Anal. found for C12H36Si4O2
(C32H52N2Si2O3)n: C 34.05, H 9.11, N 4.81.
Fig. 1. Solution 29Si NMR spectrum of BATD and solid-state 29Si NMR spectra of
PASQ and LMQ.
1A). The apparent degree of polymerization (DP) of LS formed in
0.1 mol/L toluene/dioxane (1/1 mL/mL) was determined by vapor
pressure osmometry (VPO) and was approximately 7. UV detection
was used to monitor the LS formation process (Fig. 2). In a toluene/
dioxane (1/1 mL/mL) mixture, as the monomer concentration in-
creases, the absorbance peak assigned to phenyl groups displays a
remarkable red shift from 284 nm to 298 nm, which can be attrib-
uted to the energy reduction induced by the intermolecular
NAHÁ Á ÁN hydrogen bonding. X-ray diffraction (XRD) is an effective
method to characterize the ordered structures, and it has been suc-
cessfully applied to characterize the ladder structure in the litera-
ture [13]. To maintain the well-organized molecular arrangement
in the solution, we used a freeze-drying method for preparing the
LS samples for XRD characterization. As shown in Fig. 3, the XRD
patterns of the LS sample from the toluene/dioxane solution
(0.1 mol/L) exhibit two characteristic peaks at approximately 3.2°
(2.76 nm) and 19.9° (0.44 nm) 2h. Based on the literature [13], these
peaks represent the ladder width and the ladder thickness. When
the temperature was increased to 80 °C, the intensity of the two
peaks decreased remarkably. The higher temperature apparently
destroyed the weak molecular interactions, resulting in the collapse
2.4. Synthesis of ladder-like trimethylsiloxysilicate (LMQ)
PASQ (2.84 g, 5 mmol of repeating unit), toluene (100 mL), and
trimethylsilanol (1.8 g, 20 mmol) were placed into a three-necked
flask equipped with a reflux condenser and a magnetic stir bar un-
der argon. The reaction was continued for 48 h at 50 °C. Finally,
methanol (100 mL) was added and the targeted product, LMQ
(1.30 g), was precipitated from the solution. The yield was 93%.
IR (KBr, thin film, cmÀ1): 2959 (ACH3), 1260, 849, 759 (SiACH3),
1190–1000 (SiAOASi). 1H NMR (400 MHz, d8-THF, d, ppm): 0.85
(SiACH3). 13C-NMR (100 MHz, CDCl3, d, ppm): 1.56 (SiACH3). Solid
29Si NMR (100 MHz, d, ppm): 13.3 (AOASiMe3), À106.6 (ASiO4/2).
Anal. found for C12H36Si4O2 (C6H18Si4O5)n: C 24.85, H 6.01.
3. Results and discussion
3.1. Formation and characterization of the ladder suprastructures (LSs)
As shown in Scheme 1A, 1,3-bis-(p-decyl anilino)-1,1,3,3-tetra-
chloro-disiloxane (BATD) was synthesized through the dehydro-
chlorination of hexachlorodisiloxane and 4-decyl aniline with
triethylamine (TEA) as a catalyst and acid-absorbent. Two equiva-
lents of 4-decyl aniline were added dropwise into hexa-
cholorodisiloxane at room temperature. The structure of BATD
was confirmed using 29Si NMR, which gives a resonance at d
À52.6 ppm that indicates that there was only one type of Si-atom,
namely (ANH)Si(O)Cl2 (Fig. 1), without Si(O)Cl3, (ANH)2Si(O)Cl and
(ANH)3Si(O). Because the SiACl and SiANH bonds are both mois-
ture sensitive, both TEA and toluene were dried over a sodium
benzophenone complex before use. The system must remain anhy-
drous and anaerobic throughout the reaction process. The resulting
BATD was not separated, but was preserved in the solution to con-
tinue the following reaction.
In solution, BATD was observed to be able to spontaneously
assemble into the ladder superstructure (LS) primarily through
the synergistic interactions of NAHÁ Á ÁN hydrogen bonding and
the van der Waals interaction among the octyl groups (Scheme
Fig. 2. UV spectra of LSs.

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Z. Chen et al. / Reactive & Functional Polymers 72 (2012) 503–508
Fig. 3. XRD patterns of LMQ, PASQ, LS, and LS at 80 °C; schematic diagrams of LMQ and PASQ with three repeating units.
of the LS. This phenomenon confirmed that the LS should indeed be
a supramolecular aggregate. Combining these results, it can be de-
duced that BATD actually self-assembled into regular LSs rather
than the randomly interlaced or branched structures.
lower DP may first transform into oligomers with SiAOH and SiACl
end groups, which further grow into the higher molecular weight
PASQs by dehydrochlorination. Obviously, the DP data should be
affected by the monomer concentration, the reaction time and
other reaction conditions. In addition, the number-average molec-
ular weight (Mn) of PASQ is determined to be 13.2 kDa with
PDI = 1.46 by GPC in THF with polystyrene as standards, implying
that the DP is ꢀ23 (Fig. 4). The nitrogen content determined from
elemental analysis is 4.81 wt.%, from which the DP could be calcu-
lated to be ꢀ20. The DP values calculated from the three measure-
ments for PASQ and in good agreement with each other.
The structure of PASQ was characterized using IR and NMR. The
IR characterization supported the assumption that the SiAN bonds
are intact because of the immediate absorption of released HCl by
TEA. As shown in Fig. 5, there are absorption bonds for ANH
(ꢀ3372), CH3ACH2A (2921, 2854), ASiAN (ꢀ1514), APh (ꢀ1617)
and SiAOASi (1200–1000 cmÀ1); however, there are no absorption
bonds for SiAOH and ANH2, which indicates that the breaking of
SiAN bond is prevented. In Fig. 6A, the 1H NMR spectrum of PASQ
shows the resonances of hydrogen corresponding to SiACH3 (d
0.22), AC10H21 (d 0.86, 1.20, 1.25, 1.53, 2.46), ANHA (d 3.53) and
3.2. Synthesis and characterization of ladder poly(p-decyl
anilino)silsesquioxanes (PASQ)
The obtained highly regular LSs are critical for producing the
well-defined ladder PASQ. The LSs performed as a reaction tem-
plate for directing the hydrolysis and condensation polymerization
of BATD into PASQ. Here, although BATD has four functional
groups, it actually behaves like a di-functional monomer due to
the confinement of the supramolecular ladder structure. As de-
scribed above, LSs are based on dynamic, non-covalent interac-
tions. Therefore, to ensure that the LSs remained undestroyed
and directed the entire PASQ polymerization process, it is neces-
sary to control the rigorous reaction conditions. For example, the
reaction temperature was maintained below 50 °C, the optimal sol-
vent system was a toluene/dioxane mixture with low polarity and
low electron-donating ability [28], a low monomer concentration
(ꢀ0.1 mol/L) was used, etc. In addition, the half-quantity hydroly-
sis of the SiACl bonds in BATD and the following dehydrochlorina-
tion condensation was used rather than the total-amount
hydrolysis and dehydration condensation to reduce the use of
the polar mixture solvent [15]. Because the SiACl bond is quite
reactive and the dehydration condensation occurs as soon as
SiAOH bonds form, controlled amounts of water were added drop-
wise to avoid some side reactions, such as gelation. TEA was used
as a catalyst and HCl-adsorbent to avoid the undesired cleavage of
the SiAN bonds. At the end of the polymerization, trimethylchloro-
silane was used to end-cap the SiAOH bonds to avoid defects of the
end chain.
After polymerization, the obtained PASQ was purified by precip-
itation in anhydrous acetone, and then dried in a vacuum oven at
room temperature. PASQ was readily soluble in common organic
solvents such as toluene, chloroform, and THF. Furthermore, thin
films of PASQ were found to be easily fabricated by casting and
spin-coating from solution. The VPO measurement provides a
DP ꢀ 21 for PASQ, which is larger than DP ꢀ 7 of the dynamic
supramolecular polymer LSs. From Scheme 1A, the LSs with the
Fig. 4. GPC curves of PASQ and LMQ.

Z. Chen et al. / Reactive & Functional Polymers 72 (2012) 503–508
507
ArAH (d 6.53, 6.92 ppm). In addition, from the integral ratio of
ACH3 and SiACH3, DP could also be calculated to be 28. In
Fig. 6B, the 13C NMR spectrum of PASQ exhibits the resonances
of carbon corresponding to SiACH3 (d 3.9), AC10H21 (d 14.0–35.8)
and ArAC (d 115, 129.1, 129.4, 143 ppm). For 29Si NMR, because
the resonances of (ANH)SiO3/2 may overlap with the glass peak, so-
lid 29Si NMR was used to characterize PASQ. As shown in Fig. 1,
there are two peaks with d 13.7 and À99.5 ppm, which could be
attributed to end groups of AOASiMe3 and the repeating units of
ASi(NH)O3/2, respectively.
After the polymerization has completed, the ladder structure is
chemically fixed. The ladder structure of PASQ was also character-
ized using XRD (Fig. 3). PASQ displays two distinct peaks at approx-
imately 2.76° (3.17 nm) and 19.9° (0.44 nm) 2h. According to a
previous report [13], the former peak represents the intramolecu-
lar chain-to-chain distance (i.e., the width of the ladder) in the
polymer, and the latter is the thickness of the macromolecular
chain. These data are very close to the predicted values (3.00 nm
and 0.43 nm) based on molecular simulation calculations (using
Materials Studio). In addition, note that there was also a small dif-
ference between the ladder width of the LS (2.76 nm) with the pre-
dicted values of the PASQs. Considering the flexibility of AC10H21
and the sensitivity of LS to the environment, this small difference
was easily understood. Therefore, the consistent ladder width of
the LS and the LPASQ implied that the former was the precursor
of the latter, which also confirmed the supramolecular template
polymerization mechanism.
3.3. Synthesis and characterization of ladder-like
trimethylsiloxysilicate (LMQ)
MQ silicone resin consists of mono-functional units (R3SiO1/2
)
Fig. 6. (A) 1H NMR and (B) 13C NMR spectra of PASQ and LMQ.
and tetra-functional units (SiO4/2). Because of its excellent proper-
ties, such as high hardness, antifriction and radiation resistance, it
has been widely used in adhesives, paints, personal care products
and other fields [29–32]. However, the synthesis mechanism for
MQ is still not clear, and neither its synthesis process nor structure
is controllable [33,34]. It is well known that SiAN and SiAOH
bonds could react to form SiAOASi bonds. To further confirm the
ladder structure of PASQ and to determine the reactivity of its SiAN
groups, Me3SiOH was used and reacted with PASQ to form ladder-
like trimethylsiloxysilicate (LMQ), as shown in Scheme 1B.
The IR spectrum of LMQ exhibits absorption bands for SiACH3
(ꢀ2959, 1260, 849, 759) and SiAOASi (1190–1000 cmÀ1) groups
(Fig. 5). Compared to the IR spectrum of PASQ, the absorption
bands for NH (ꢀ3372), ASiAN (ꢀ1514) and APh (ꢀ1617 cmÀ1
)
are absent, indicating the complete cleavage of the SiANHA side
groups. The 1H NMR spectrum of LMQ only presents a peak at d
0.1 ppm assigned to SiACH3, whereas the 13C NMR spectrum of
LMQ also only presents a peak at d 1.56 ppm assigned to SiACH3,
further indicating the disappearance of the SiANHA side groups
(Fig. 6). The solid-state 29Si NMR spectrum of LMQ, shown in
Fig. 1, exhibits two resonances at approximately d 13.3 and
À106.6 ppm, which are ascribed to AOASiMe3 and ASiO4/2, respec-
tively. The disappearance of the peak at d À99.5 ppm was ascribed
to ASi(NH)O3/2, and the remarkable increase of the resonance inte-
gral ratio of the end groups to the repeating units distinctly indi-
cates the conversion from the SiAN-based side groups to the
SiAOASi-based side groups. In the XPS spectrum of LMQ, the dis-
appearance of the peak assigned to the N1s electrons also implies
the complete removal of the p-decyl anilino groups (Fig. 7).
The DP of LMQ determined by VPO is approximately 22, which
is very close to the DP ꢀ 20 of PASQ. The GPC curve of LMQ exhibits
a peak with Mn ꢀ 6680, and thus, DP ꢀ 23 (Fig. 4). Meanwhile, the
elemental analysis presents a carbon content of 24.85 wt.%, from
which DP can be calculated to be ꢀ23. Obviously, the DPs obtained
using three methods are highly consistent and close to the DP of
PASQ. The little variation of the DPs from PASQ to LMQ suggests
that the reaction is just a conversion of the side groups without a
change of the double-chain backbone.
LMQ is easily prepared from PASQ and trimethylsilanol under
50 °C for 48 h. The conversion of PASQ into LMQ was well moni-
tored using IR, NMR and X-ray photoelectron spectroscopy (XPS).
The ladder structure of the final LMQ was also verified using
XRD characterization (Fig. 3). The XRD pattern of LMQ shows two
distinct peaks at approximately 7.9° and 19.5° 2h. The correspond-
Fig. 5. IR spectra of PASQ and LMQ.

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Z. Chen et al. / Reactive & Functional Polymers 72 (2012) 503–508
intermolecular weak interactions, regular ladder superstructures
were formed first, and then directed the synthesis of the well-de-
fined PASQ. The ladder structures of the LSs and PASQ were thor-
oughly characterized. PASQ was converted to LMQ in high yield,
which further demonstrated its ladder structure and reactivity. Be-
cause the SiAN bond can react with all types of functional groups,
it is noteworthy that PASQ can be used as an effective macromono-
mer for preparing materials that have well-defined inorganic-or-
ganic hybrid structures.
Acknowledgements
The financial support of NSFC [Nos. 50821062, 21104002] is
gratefully acknowledged. The authors also thank Prof. Zhibo Li
from the Institute of Chemistry of CAS and Prof. Shouke Yan of
the Chemical Resource Engineering Beijing University of Chemical
Technology for their beneficial suggestions.
Fig. 7. XPS spectra of PASQ and LMQ.
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ing spacing, 1.11 nm and 0.44 nm, represents the ladder width and
ladder thickness. This result is consistent with the simulated
dimensions (1.05 nm and 0.45 nm) using Materials Studio. We also
investigated the thermal stability of LMQ using thermo-gravimet-
ric analysis (TGA). As shown in Fig. 8, the decomposition tempera-
ture is approximately 510 °C and the ultimate weight loss is 33.8%,
which is in agreement with the content of the organic groups in
LMQ. The high thermal stability of LMQ also suggests its ordered
ladder structure.
By combining all of the above characterization results, it can be
concluded that the regular ladder-like LMQ was successfully pre-
pared by the functionalization of PASQ. Because the conversion
does not involve any breaking of the main chain of PASQ, the
well-defined ladder structure of LMQ could reflect the ordered lad-
der structure of PASQ. The successful preparation of LMQ derived
from PASQ may not only open a new way to synthesize MQ silicone
resins but also suggests that PASQ is a promising precursor for pre-
paring other hybrid materials with ladder polysiloxane structures.
4. Conclusions
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A soluble, reactive PASQ was successfully prepared using a
simple one-step polymerization. By fully taking advantage of the