Novel fluorinated hybrid polymer preparation from silsesquioxanes by radical polyaddition

Article abstract of DOI:10.1016/j.jfluchem.2004.03.005

Radical polyaddition of bis(α-trifluoromethyl-β, β-difluorovinyl) terephthalate [CF₂= C(CF₃)OCOC₆H₄COOC(CF₃) =CF₂] (BFP) with silsesquioxanes was investigated in order to produce a polymer

Full text of DOI:10.1016/j.jfluchem.2004.03.005

Journal of Fluorine Chemistry 125 (2004) 1279–1285
Novel fluorinated hybrid polymer preparation from
silsesquioxanes by radical polyaddition
Hirotada Fujiwaraa, Tadashi Naritaa,*, Hiroshi Hamanab
aDepartment of Materials Science and Engineering, Graduate School of Engineering, Saitama Institute of Technology,
1690 Fusaiji, Okabe, Saitama 369-0293, Japan
bDepartment of Applied Chemistry, Saitama Institute of Technology, 1690 Fusaiji, Okabe, Saitama 369-0293, Japan
Received 15 January 2004; received in revised form 8 March 2004; accepted 11 March 2004
Available online 28 July 2004
Abstract
Radical polyaddition of bis(a-trifluoromethyl-b,b-difluorovinyl) terephthalate [CF2¼C(CF3)OCOC6H4COOC(CF3)¼CF2] (BFP) with
silsesquioxanes was investigated in order to produce a polymer possessing silsesquioxane moiety in polymer main chain. 1,3,5,7,9,11,13,15-
octakis(dimethylsilyloxy)pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane (T8S) with BFP successfully afforded a polymer bearing a molecular
weight of about 2:5 Â 105. The polymer obtained were soluble in usual organic solvent such as methanol, tetrahydrofuran and chloroform. In
order to get some information on the polyaddition reaction mechanism, model reactions of 2-benzoxypentafluoropropene [CF2¼C(CF3)O-
)OCOC6H5] (BPFP) with dimethylphenylsilane, [(CH3)2SiHC6H5], BPFP with 1,1,3,3-tetramethyldisiloxane {[(CH3)2SiH]2O}, and BFP
with dimethylphenylsilane were carried out. The mechanism that the radical abstracts a hydrogen from silane compounds followed by the
addition of perfluoroisopropenyl groups was proposed.
# 2004 Elsevier B.V. All rights reserved.
Keywords: Bis(a-trifluoromethyl-b,b-difluorovinyl) terephthalate; Fluoropolymers; Hybrid polymers; Polyaddition; Radical polymerization; Silsesquioxane;
Silyl radical
1. Introduction
This report concerns the preparation of fluorinated hybrid
polymers bearing silyl groups by the radical polyaddition of
BFP with silsesquioxanes (T8) to obtain polymers possessing
silsesquioxane moiety in polymer main chain. The radical
addition reactions of BPFP with dimethylphenylsilane
and 1,1,3,3-tetramethyldisiloxane {[(CH3)2SiH]2O} were
also investigated as model reactions in order to get some
information on the structure of the polymer obtained and the
mechanism of polyaddition reaction.
During the study on the polymerization of 2-benzoxy-
pentafluoropropene [CF2¼C(CF3)OCOC6H5] (BPFP), the
radical addition reaction of BPFP with tetrahydrofuran
(THF) was discovered [1]. The reaction was developed to
preparation of polymers by the radical polyaddition of bis(a-
trifluoromethyl-b,b-difluorovinyl) terephthalate [CF2¼C-
(CF3)OCOC6H4COOC(CF3)¼CF2] (BFP) with the com-
pounds possessing carbon–hydrogen bonds such as 1,4-
dioxane [2], 1,2-dimethoxyethane [3], diformylalkane [4],
triethylamine [5] and dialkoxydialkylsilanes [6]. Diethox-
ydimethylsilane has exhibited the highest polyaddition
reactivity toward BFP among the dialkoxydialkylsilanes
examined to afford a polymer up to 106 as a number-average
molecular weight. The radical polyaddition has then been
proved to be a probable synthetic method for fluorinated
hybrid polymers bearing alkylsilyl groups in polymer main
chains.
2. Results and discussion
2.1. Polyaddition reaction
The silsesquioxanes examined here are illustrated in
Scheme 1. The results of polyaddition reactions of BFP with
silsesquioxanes such as 1,3,5,7,9,11,13,15-octakis(dimethyl-
silyloxy)pentacyclo[9.5.1.13,915,15.17,13]octasiloxane (T8S),
1,3,5,7,9,11,13,15-octamethylpentacyclo[9.5.1.13,915,15
-
.17,13]octasiloxane (T8M), and 1,3,5,7,9,11,13,15-octaiso-
butylpentacyclo[9.5.1.13,915,15.17,13]octasiloxane (T8I) are
* Corresponding author. Tel.: þ81-48-585-6836; fax: þ81-48-585-6004.
E-mail address: narita@sit.ac.jp (T. Narita).
0022-1139/$ – see front matter # 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2004.03.005

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H. Fujiwara et al. / Journal of Fluorine Chemistry 125 (2004) 1279–1285
Scheme 1. Silsesquioxanes (T8): T8S, R ¼ (CH3)2SiHO; T8M, R ¼ CH3;
T8I, R ¼ (CH3)2CHCH2.
Fig. 1. SEC of polyaddition product of BFP with T8S.
summarized in Table 1. The polymers of BFP with T8S are
obtained in high conversions at 120 8C in the presence of di-
tert-butyl peroxide (DTBP) as an initiator probably because of
the highest hydrogen abstraction ability. The molecular weight
of polymers tends to increase with increasing the concentra-
tions of initiators charged in the polymerization systems. The
higher molecular weight polymers are obtained in the presence
of octafunctional T8S to bifunctional BFP to be from 1:1.3 to
1:2.0 in feed. The highest molecular weight of the polymer
obtained is about 7:9 Â 103 which is soluble in usual organic
solvent such as methanol, tetrahydrofuran and chloroform. The
polymers were then purified by size exclusion chromatography
(SEC) to remove BFP and T8S. Typical result of SEC is shown
in Fig. 1 which indicates a bimodal molecular weight distribu-
tion including high molecular weight polymers of 105. The
number average molecular weight of the higher molecular
weight region was calculated to be 2:5 Â 105 and the mole-
cular weight distribution was 2.1, and those of the lower
molecular weight region were 5:0 Â 103 and 2.0, respectively.
The radical polyadditions of BFP with T8S initiated by benzoyl
peroxide (BPO) and 2,20-azobisisobutyronitrile (AIBN) are
unsuccessful.
Any addition products and polymers were not detected by
the reactions of BFP with T8M with these initiators though
the conversions of BFP are between 16 and 25%. One to one
addition product of T8I with BFP was, on the other hand,
detected as a main product though many other products were
yielded, and the clear conclusions on the structures of these
products were then unable to be determined since the
isolation was difficult.
2.2. Model reaction
The results of BFP with T8 indicate that the polymers are
obtained by the polyaddition with T8S while methylsilyl
group of T8M and isobutylsilyl group of T8I showed scarce
Table 1
Radical polyaddition of BFP with silsesquioxanes
c
T8
T8:BFP (mol:mol)
Initiatora
DTBP
Eqivalent
Tol (eq.)
Conversionb (%)
Mn (Â103)
Mw/Mn
T8S
1:0.6
1:1
0.4
0.4
0.4
0.6
0.6
0.8
0.4
0.4
9.5
9.5
14.3
8.0
6.0
9.5
9.5
9.5
22
95
<1.8
2.9
1.2
1:1
31
<1.8
7.9
1:1.3
1:1.6
1:2
100
100
100
62
2.1d
4.4
4.0
6.8
6.6
1:1
BPO
<1.8
1:1
AIBN
4e
T8M
T8I
1:1
1:2
2:1
DTBP
0.4
0.4
0.4
13.7
13.7
27.5
19e
16e
25e
1:1
1:2
2:1
DTBP
0.4
0.4
0.4
25.9
25.9
40.0
49f
8f
36f
a Reaction temperature: BPO, 80 8C; DTBP, 120 8C; AIBN, 60 8C.
b Conversion of BFP measured by GC.
c Estimated by GPC (PSt standards, eluent; THF).
d Purified by SEC.
e No addition product was detected.
f 1:1 addition product was obtained.

H. Fujiwara et al. / Journal of Fluorine Chemistry 125 (2004) 1279–1285
1281
Table 2
Model reaction of perfluoroisopropenyl compounds with silanes
Eqivalent
Silane
Eqivalent
Initiator
DTBP
Eqivalent
Conversiona (%)
BPFP
BPFP
BFP
1.0
8.0
8.0
8.0
DMSH
8.0
8.0
8.0
8.0
0.2
0.2
0.4
0.2
100
58
66
BPO
>2
1.0
1.0
8.0
1.0
TMSOH
DMSH
8.0
8.0
8.0
8.0
DTBP
0.2
0.4
0.2
0.2
43
52
43
13
BPO
1.0
1.0
8.0
6.0
DTBP
BPO
0.2
0.2
100
36
a Conversion of BPFP or BFP measured by GC.
Fig. 2. NMR of 1:1 addition product of BPFP with DMSH: (a) 1H (19F decoupled), (b) 1H, (c) 13C (1H decoupled), (d) 13C (1H and 19F decoupled), and (e)
19F (1H decoupled).

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H. Fujiwara et al. / Journal of Fluorine Chemistry 125 (2004) 1279–1285
reactivity. Model reactions of monofunctional BPFP
with dimethylphenylsilane, [(CH3)2SiHC6H5] (DMSH),
BPFP with 1,1,3,3-tetramethyldisiloxane {[(CH3)2SiH]2O}
(TMSOH), and bifunctional BFP with DMSH were carried
out in order to get some information on the analyses of the
polymer structures and on the polyaddition reaction mechan-
ism. The results of the model reactions are summarized in
Table 2. The tendency of increasing the conversions of BPFP
and BFP by the initiation with DTBP compared to that of
BPO is demonstrated. The higher conversions are obtained by
the addition of increased amount of initiator in feed. These are
the similar results to those of polyaddition reaction mentioned
above. Eight-fold excess amount of DMSH in feed is needed
to obtain enough conversions of BPFP.
area ratio is in accord with six hydrogens. The reaction is,
therefore, supposed to take place by Eq. (1). The reactions of
BPFP with TMSOH and BFP with DMSH take place in the
similar fashion as illustrated in Eqs. (2) and (3) resulted from
the measurements of MS and NMR as shown in experi-
mental part. The ratios of 1:1 and 1:2 addition products of
the reactions of monofunctional BPFP with difunctional
TMSOH and difunctional BFP with monofunctional DMSH
are 38:62 and 52:48, respectively.
(1)
(2)
(3)
The addition product of BPFP with DMSH was isolated
by SEC in 38% yield and analyzed by gas chromatography
(GC), mass-spectrum (MS) and 1H, 13C and 19F NMR. The
MS measured by electron ionization (EI) method showed the
molecular ion peak at m=z ¼ 388 which was in accord with
the 1:1 addition compound of BPFP with DMSH as shown in
experimental part, and fragment pattern of spectrum sup-
ported the conclusion. The results of MS measured by
chemical ionization (CI) method might also support since
the peaks at m=z ¼ 387 and 389 were observed.
It may be concluded that the hydrogens of methyl groups
bonded to silicone atom are scarcely reactive and the hydride
bound to silicone atom shows higher reactivity in the reac-
tion system.
2.3. Structure of the polymer
The structure of the polymer yielded from the radical
polyaddition of BFP with T8S was investigated by referring
to the results obtained from the model reactions. The poly-
mer was purified by SEC and then measured by NMR. The
results are shown in Fig. 3. The assignments are depicted in
the figures. The hydride hydrogen bonded to silicone atom is
found to transfer to the a-carbon of BFP moiety in the
polymer main chain. The structure of the T8S moiety in the
polymer is hardly determined since T8S possesses eight
hydride hydrogens which are probable to be attacked by
radical. The polyaddition might take place via Eq. (4).
The NMR spectra of the product are depicted in Fig. 2. In
1H NMR the peak at 5.7 ppm is assigned to the a-hydrogen
of BPFP moiety in the product, which suggests the transfer
of the hydride hydrogen bound to silane atom takes place.
This is supported by the 13C NMR which demonstrates the
peak at 69 ppm as a singlet in Fig. 2d measured under proton
and fluorine decoupled condition. The doublet peak at about
0.5 ppm in Fig. 2a is assignable to methyl hydrogens whose
(4)

H. Fujiwara et al. / Journal of Fluorine Chemistry 125 (2004) 1279–1285
1283
Fig. 3. NMR of polyaddition product of BFP with T8S: (a) 1H, (b) 13C (1H and 19F decoupled), and (c) 19F (1H decoupled).
The polyaddition of BFP with T8S might take place by the
similar mechanism to the polyaddition of BFP with diethox-
ydimethylsilane [6]. The reaction might be initiated with the
hydrogen abstraction of hydride bonded to silicone atom of
T8S to form silyl radical which adds onto perfluoroisopro-
penyl group. This may be supported by the fact that the
polyaddition takes place more easily by the initiation with
DTBP which is well-known compound of high hydrogen
abstraction ability. The fluorinated carbon radical produced
at the a-carbon of BFP moiety might be destabilized by
fluorine substituents and produce silyl radical again by
intramolecular hydrogen abstraction of hydride hydrogen
since the fluorinated carbon radical is scarcely reactive onto
fluorinated vinyl group. The equimolarity of feed ratio of
BFP to T8S may then be neglected. The polymer would be
yielded by the cycle. The polyaddition might be terminated
by the intermolecular hydrogen abstraction.
The branched structure would be suggested since the area
ratios of fluorine resonance of perfluoroisopropenyl group in
Fig. 3b seem to be larger compared to those calculated from
molecular weight of the polymer, probably because T8S
performs as slightly more than bifunctional compound.
3. Conclusion
To develop the radical polyaddition of perfluoroisopro-
penyl compounds with organic compounds bearing carbon–

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H. Fujiwara et al. / Journal of Fluorine Chemistry 125 (2004) 1279–1285
hydrogen bonds, a fluorinated hybrid polymer bearing alkyl-
silyl groups in polymer main chain was prepared by BFP
with T8S. A polymer of 2:5 Â 105 as a molecular weight was
obtained though a molecular weight distribution was bimo-
dal. The polyaddition mechanism that the hydrogen abstrac-
tion of hydride hydrogen bonded to silicone atom of T8S by
radical evolved from peroxide initiators takes place followed
by the addition onto perfluoroisopropenyl group and then
intramolecular hydrogen abstraction was proposed.
concentrated by removing low-boiling materials under reduced
pressure, and the addition products were isolated by SEC.
1
Mono-addition product of BPFP with DMSH: H NMR
¯
(in CDCl3): d ¼ 0:51, 0.53 (6H, s, SiÀCH3), 5.76 (1H, m,
¯
¯
CF2ÀCHðCF3ÞO), 7.21 (2H, t, J ¼ 5 Hz, SiÀC6H5(m)),
¯
7.26 (1H, d, J ¼ 5 Hz, SiÀC6H5(p)), 7.34 (2H, t,
¯
J ¼ 5 Hz, OCOÀC6H5(m)), 7.48 (2H, d, J ¼ 5 Hz,
¯
¯
OCOÀC6H5(o)), 7.53 (1H, t, J ¼ 5 Hz, OCOÀC6H5(p)),
¯
7.77
(2H,
d,
J ¼ 5 Hz,
SiÀC6H5(o)).
13C
1
¯
NMR{ H(5 ppm)}: d ¼ À6:2, À5.9 (s, SiÀCH3), 69.6
¯
¯
(m, CF2ÀCHðCF3ÞO), 122.5 (q, J ¼ 281 Hz, CF3), 125.0
¯
4. Experimental
(t, J ¼ 270 Hz, CF2), 128.3, 128.6, 130.4, 130.7, 134.2,
134.5 (s, C6H5). 19F NMR {1H (5 ppm): d ¼ À70:6 (3F, s,
¯
¯
¯
All experiments related to reaction and polymerization
were carried out under a purified nitrogen atmosphere in
order to preclude oxygen and moisture.
CF3), À117.2, À122.2 (2F, d, J ¼ 348 Hz, CF2).
MW ¼ 388:04: MS (EI, m/z): 375 [M–(CH3)]þ, 311 [M–
C6H5]þ, 135 [C6H5Si(CH3)2]þ, 105 [C6H5CO]þ, 77
[C6H5]þ. (CI, m/z): 389 [M þ 1]þ, 387 [M À 1]þ.
4.1. Reagent
Mono-addition product of BPFP with TMSOH: MW ¼
386:46: MS (EI, m/z): 386 [M]þ, 371 [M–(CH3)]þ, 253-
[M–(Si(CH3)2–O–Si(CH3)2H)]þ,
133
[Si(CH3)2–O–
BPFP was synthesized by the reaction of benzoyl chloride
with lithium enolate derived from 1,1,1,3,3,3-hexafluoro-
propan-2-ol (HFIP) with 2 eq. of butyllithium in THF [7].
Commercial butyllithium in hexane solution was used after
determination of the concentration by alkalimetry. HFIP
(Central Glass Co.) was dried by refluxing over calcium
hydride and distilled. BFP was synthesized by the similar
method to that of BPFP from terephthaloyl chloride. Com-
mercial T8M, T8S and T8I were used as received. DMSH
and TMSOH were distilled under reduced pressure. THF
toluene were purified by distillation under purified nitrogen
atmosphere after being dried by refluxing with potassium
benzophenone ketyl before use. Benzoyl peroxide was pre-
cipitated from chloroform and then recrystallized in metha-
nol at 0 8C. DTBP was used as received.
Si(CH3)2H]þ, 105 [C6H5CO]þ, 77 [C6H5]þ. (CI, m/z):
387 [M þ 1]þ, 386 [M]þ, 385 [M À 1]þ, 311 [M–(O–
Si(CH3)2H]þ.
Di-addition product of BPFP with TMSOH:
MW ¼ 638:60: MS (EI, m/z): 623 [M–(CH3)]þ, 533 [M–
(C6H5–CO)]þ,
327
[M–(C6H5–COO–CH(CF3)CF2–
Si(CH3)2)]þ, 311 [C6H5–COO–CHðCF3ÞCF2–Si(CH3)2]þ,
105 [C6H5CO]þ, 77 [C6H5]þ. (CI, m/z): 637 [M À 1]þ.
Mono-addition product of BFP with DMSH:
MW ¼ 562:43: MS (EI, m/z): 562 [M]þ, 547 [M–
(CH3)]þ, 543 [M–(F)]þ, 485 [M–(C6H5)]þ, 415 [M–
(CF2¼C(CF3)–O)]þ, 283 [C6H5–Si(CH3)2–CF2–CH(CF3)–
O]þ, 279 [M–(C6H5–Si(CH3)2–CF2–CH(CF3)–O)]þ. (CI, m/
z): 637 [M À 1]þ, 562 [M]þ, 547 [M–(CH3)]þ, 543 [M–
(F)]þ, 485 [M–(C6H5)]þ, 415 [M–(CF2¼C(CF3)–O)]þ.
Di-addition product of BFP with DMSH: MW ¼ 698:70:
MS (EI, m/z): 698 [M]þ, 683 [M–(CH3)]þ, 621 [M–
(C6H5)]þ, 431 [M–(C6H5–Si(CH3)2CF2CHCF3)]þ, 415
4.2. Addition reaction
The polyaddition reaction of BFP with T8 was carried out
by adding BFP (0.79 mmol, 0.22 ml), T8, initiator and
toluene in sealed glass ampoule which was carefully flame
dried. After a definite time, the reaction was ceased by
bubbling oxygen and the concentration of BFP was mea-
sured by GC by means of tridecane as an external standard.
The polymer was isolated by SEC since the polymer was
soluble in usual organic solvents. The molecular weight of
the polymer was determined by SEC. The structure of the
[M–(C6H5–Si(CH3)2CF2CHCF3–O)]þ,
283
[C6H5–
Si(CH3)2CF2CHCF3–O]þ, 185 [C6H5–Si(CH3)2CF2]þ, 135
[C6H5–Si(CH3)2]þ. (CI, m/z): 621 [M–C6H5]þ.
4.3. Measurements
1H, 13C and 19F NMR spectra were recorded on a JEOL
JNM-ECP500 Fourier transform NMR spectrometer at
500 MHz for 1H {non-decoupled and [19F (irradiation offset:
À85 ppm)]}, 125 MHz for 13C {[1H (5 ppm)], [1H (5 ppm)
and 19F (À85 ppm)]}, and 470 MHz for 19F [1H (5 ppm)]
NMR with deuterated chloroform as a solvent. Chemical shift
of 19F NMR was determined on the basis of absolute magnetic
field intensity. GC measurement was carried out with a
Hewlett-Packard 6890 equipped with flame ionization detec-
tion with a DB-1, wide-bore fused silica capillary column
(15 m  0:53 mm, film thickness: 1.5 mm, J&W). The col-
umn temperature was programmed from 100 to 300 8C at
1
resulting reaction product was determined by H, 13C and
19F NMR.
The model reaction of BPFP or BFP with DMSH or
TMSOH was carried out by adding silyl compound
(13.05 mmol), perfluoroisopropenyl compound, peroxide
initiator, and toluene in sealed glass ampoule which was
carefully flame dried. After a definite time, the reaction was
ceased by bubbling oxygen and the concentrations of BPFP
and addition products were measured by GC by means of
tridecane as an external standard. The reaction system was

H. Fujiwara et al. / Journal of Fluorine Chemistry 125 (2004) 1279–1285
1285
20 8C minÀ1. The mass spectra were measured on a JEOL
JMS-SX102. Isobutane was used as a reagent gas of chemical
ionization method. SEC was measured with a Tosoh HLC-
802A apparatus at 40 8C with a Shodex KF802.5-KF801 (2Â)
for low-molecular-weight compounds and a Shodex KF 805L
(2Â) for high-molecular-weight compounds with THF as an
eluent (flow rate: 1.0 ml minÀ1). The molecular weight mea-
sured by SEC was calculated from the calibration curve for
standardized polystyrene. Preparatory SEC was carried out
with an LC-908JAI (Japan Analytical Ind.) with Gel H1 and
H2 column series with chloroform as an eluent at room
temperature (flow rate: 3.8 mL minÀ1).
of Education, Culture, Sports, Science and Technology of
Japan, which the authors are grateful.
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This work was financially supported in part by the High-
Tech Research Center Program of Saitama Institute of
Technology founded in 1999 by the support of the Ministry
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