Synthesis and polymerization of novel bis(2-trifluoromethylacrylate)

Article abstract of DOI:10.1002/pola.24037

The radical reaction of ethylene bis(2-trifluoromethylacrylate) [CH ₂=C(CF₃)COOCH₂CH₂OCOC(CF ₃)=CH₂] (EBFA) was investigated to afford a polymer with the molecular weights of as high as 5.6 × 10⁴ in the presenceof large amount of DOX (1,4-dioxane). EBFA was synthesized by adding 0.18 mol of 2-trifluoromethylacryloyl chloride dropwise to dichloromethane solution of 0.081 mol of ethylene glycol and 0.18 mol of triethylamine at 0°C followed by stirring at room temperature for 3 hours. Radical polymerization of EBFA in DOX was carried out under the condition. Polymer was isolated by reprecipitation in hexane. ¹H NMR of the polymer obtained by the base-catalyzed hydrolysis of the polymer produced by the reaction of EBFA with DOX showed the decrease of the peaks assigned to -CH₂-CH-O and -CH ₂-CH(CF₃) and to -CH₂-CH₂- respectively.

Full text of DOI:10.1002/pola.24037

Synthesis and Polymerization of Novel Bis(2-trifluoromethylacrylate)
GENKI KURAKAMI,1 AKIHIRO HOSOYA,1 HIROSHI HAMANA,2 TADASHI NARITA1
1Department of Applied Chemistry, Graduate School of Engineering, Saitama Institute of Technology, 1690 Fusaiji,
Fukaya 369-0293, Japan
2Department of Life Science and Green Chemistry, Saitama Institute of Technology, 1690 Fusaiji, Fukaya 369-0293, Japan
Received 23 October 2009; accepted 14 March 2010
DOI: 10.1002/pola.24037
Published online in Wiley InterScience (www.interscience.wiley.com).
KEYWORDS: addition polymerization; fluoropolymers; radical polymerization; 2-trifluoromethylacrylate
INTRODUCTION As has been reported previously, the poor
polymerization reactivity of 2-trifluoromethylacrylate deriva-
tives is demonstrated under radical polymerization condi-
tions and high yields of 2-trifluoromethylacrylate polymers
are obtained only under anionic conditions.1 Facile radical
copolymerization was demonstrated by researchers at
IBM.2,3 High radical addition reactivity of perfluoroisopro-
penyl group has been reported in the reaction of 2-benzoxy-
pentafluoropropene [CF2¼¼C(CF3)OCOC6H5] with tetrahydro-
furan (THF) to produce a 1:1 addition compound.4 The
reaction has been further developed to produce fluorinated
polymers from bis(a-trifluoromethyl-b,b-difluorovinyl) ter-
ephthalate [CF2¼¼C(CF3)OCOC6H4COOC(CF3)¼¼CF2] and 1,4-
dioxane (DOX) yielding a polymer of a molecular weight of
9.9 ꢀ 103 by radical polyaddition (eq 1).4,5 High radical
addition reactivity of tert-butyl 2-trifluoromethylacrylate,
which possesses two less fluorine atoms compared with per-
fluoroisopropenyl group, with cyclic ethers such as THF,
DOX, 1,3-dioxolane, and tetrahydropyran has been reported
to afford corresponding 1:1 addition products in fairly high
yields through carbon–carbon bond formation.6 In this arti-
cle, the radical reaction of ethylene bis(2-trifluoromethylacry-
late) [CH2¼¼C(CF3)COOCH2CH2OCOC(CF3)¼¼CH2] (EBFA) was
investigated to afford a polymer with the molecular weights
of as high as 5.6 ꢀ 104 in the presence of large amount of
DOX.
Reagents
EBFA was synthesized by adding 0.18 mol of 2-trifluorome-
thylacryloyl chloride dropwise to dichloromethane solution
of 0.081 mol of ethylene glycol and 0.18 mol of triethylamine
at 0 ꢁC followed by stirring at room temperature for 3 h.
The reaction mixture was washed with 1 N hydrochloric
acid, saturated aqueous sodium hydrogencarbonate, and
then water.
EBFA was isolated by distillation; bp: 63–65 ꢁC/0.1 kPa;
1
yield: 40%; purity: 99% by GC. H NMR (in CDCl3): d ¼ 4.52
4
(s, 4H, ACH2CH2A), 6.47 (q, 1H, JHF ¼ 0.9 Hz, CH2 cis to
CF3), 6.74 (q, 1H, JHF ¼ 1.4 Hz, CH2 trans to CF3); 13C{(1H(5
4
1
ppm)} NMR: d ¼ 62.9 (ACH2CH2A), 121.2 (q, JCF ¼ 273 Hz,
2
3
ACF3), 131.0 (q, JCF ¼ 33 Hz, CH2¼¼CA), 133.6 (q, JCF
¼
4.8 Hz, CH2¼¼), 161.0 (C¼¼O); 19F{(1H(5 ppm)} NMR: d ¼
ꢂ65.7 (s, CF3); EIMS: m/z ¼ 69 (38), 95 (23), 123 (100),
166 (6), 167 (7); CIMS: m/z ¼ 167 (100), 307 (22, Mþ
þ
H); HRMS (CI) Calcd. for
307.0360.
C10H9O4F6 307.0405, found
2-Trifluoromethylacryloyl chloride was synthesized7,8 by the
reaction of 2-trifluoromethylacrylic acid (1.0 mol) with
ꢁ
phthaloyl dichloride (1.0 mol) at 120 C for 2 ꢁh. The product
was collected by fractional distillation; bp: 82 C; yield: 68%.
2-Trifluoromethylacrylic acid supplied by Tosoh F-Tech and
phthaloyl dichloride from Iharanikkei were used as received.
Benzoyl peroxide (BPO) and 2,20-azobisisobutyronitrile
(AIBN) were precipitated from chloroform and then recrys-
tallized in methanol at 0 ꢁC. Di-tert-butyl peroxide (DTBP)
was used as received. THF, DOX, and triethylamine were
refluxed over calcium hydride and then distilled.
(1)
EXPERIMENTAL
Procedure
All experiments related to addition reactions and addition
polymerizations were carried out under a purified nitrogen
atmosphere to preclude oxygen and moisture.
Radical polymerization of EBFA in DOX was carried out
under the condition depicted in Table 1. Polymer was iso-
lated by reprecipitation in hexane. Methanol-insoluble part
Correspondence to: T. Narita (E-mail: narita@sit.ac.jp)
C
V
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, 2722–2724 (2010) 2010 Wiley Periodicals, Inc.
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NOTE
TABLE 1 Radical Reaction of EBFA in DOX
Initiatora
DOX
Yieldb
(%)
Mn (ꢀ104)c
Mw/Mn
c
Run
mmol (equiv)
mmol (equiv)
1
2
2.6 (40)
3.9 (60)
3.9 (60)
3.9 (60)
5.2 (80)
5.2 (80)
5.2 (80)
5.2 (80)
7.8 (120)
10.5 (160)
2.6 (40)
3.9 (60)
5.2 (80)
7.8 (120)
2.6 (40)
3.9 (60)
BPO
0.065 (1)
0.065 (1)
0.13 (2)
0.46 (7)
0.065 (1)
0.13 (2)
0.33 (5)
0.46 (7)
0.13 (2)
0.13 (2)
0.13 (2)
0.13 (2)
0.13 (2)
0.13 (2)
0.13 (2)
0.13 (2)
c
Gel
40
–
–
1.0
2.7
7.4
8.5d
2.0
4.9
1.7d
1.5d
2.0
1.4
–
3
62
50d
2.1
4
5.6d
0.73
0.82
2.4d
2.3d
0.27
0.32
–
5
45
6
70
7
25d
24d
43
8
9
10
11
12
13
14
15
16
49
DTBP
AIBN
Gel
3
0.25
0.48
0.49
–
1.6
1.8
1.3
–
45
52
Gel
79
0.36
3.3
EBFA: 0.33 mmol (5 equiv), reaction time: 3 days.
Estimated by SEC (polystyrene standards, eluent:
THF).
Methanol insoluble part.
a
Reaction temp. BPO and AIBN: 80 ꢁC, DTBP:
d
120 ꢁC.
b
Hexane insoluble part.
was obtained by reprecipitation of THF solution of hexane-
insoluble polymer in methanol.
of 19F NMR was determined on the basis of absolute mag-
netic field intensity. Size exclusion chromatography (SEC)
was measured with a Tosoh HLC-802A apparatus at 40 ꢁC
with a Shodex KF802.5þKF801 (2ꢀ) for low-molecular-
weight compounds and a Shodex KF805L (2ꢀ) for high-
molecular-weight compounds with THF as an eluent (flow
rate: 1.0 mL minꢂ1). The molecular weight of a polymer
measured by SEC was calculated from the calibration curve
for polystyrene standards. Thermogravimetric analysis (TGA)
was carried out with a Thermo Plus TG 8120 TG-DTA
(Rigaku) under Ar atmosphere with a heating rate of 5 ꢁC
Poly(EBFA with DOX): 1H NMR (in CDCl3, 500 MHz): d ¼
1.7–2.1 (br, ACH2ACH(CF3)A), 2.1–2.9 (br, ACH2AC(CF3)A),
3.2–3.6 (br, ACH2ACHAOA, ACH2ACH(CF3)A), 3.6–3.9
(br, ACH2ACH2AOACH2A), 3.9–4.9 (br, ACH2ACH2A).
13C{(1H(5 ppm)} NMR (in CDCl3, 125 MHz): d ¼ 28.5–32.2
(ACH2ACH(CF3)A), 47.4–48.0 (ACH(CF3)A), 56.7 and 58.8
(ACH2AC(CF3)A), 61.6 and 63.8 (ACH2ACH2A), 66.1 and
66.3 (ACHAOACH2ACH2A), 66.7 (>CHAOACH2ACH2A),
70.4 and 70.7 (>CHACH2AOACH2A), 71.5 and 73.1
(>CHAOACH2ACH2A), 125.0 (ACF3), 168.1–169.0 (>C¼¼O).
19F{(1H(5 ppm)} NMR (in CDCl3, 470 MHz): d ¼ ꢂ68.6 to
ꢂ66.2 (br, ACH2AC(CF3), ꢂ68.7 (s, ACH2ACH(CF3).
minꢂ1
.
RESULTS AND DISCUSSION
EBFA was synthesized by the reactions of 2-trifluoromethyla-
cryloyl chloride with ethylene glycol in the presence of trie-
thylamine as a hydrogen chloride acceptor in fairy high
yields. The structures were supported by MS and 1H, 13C,
and 19F NMR as shown in the Experimental section.
Measurements
Vapor phase chromatographic (GC) measurement was carried
out with a Hewlett-Packard 6890 equipped with flame ioni-
zation detector with a ZB-1, wide-bore capillary column
(15 m ꢀ 0.53 mm, film thickness: 1.5 lm). The column tem-
perature was programmed from 80 to 320 ꢁC at 20 ꢁC
minꢂ1. Mass spectra (MS) were measured by electron ioniza-
tion (EIMS) and chemical ionization methods (CIMS) on a
JEOL JMS-SX102. Isobutane was used as a reagent gas of
CIMS. 1H, 13C, and 19F NMR spectra were recorded on a
JEOL JNM-ECP500 Fourier transform NMR spectrometer at
500 MHz for 1H {nondecoupled and [19F (irradiation offset:
ꢂ100 ppm)]}, 125 MHz for 13C {[1H (5 ppm)], [1H (5 ppm),
and 19F (ꢂ100 ppm)]}, and 470 MHz for 19F [1H (5 ppm)]
NMR with deuterated chloroform as a solvent. Chemical shift
The results of radical reaction of EBFA in the presence of
large excess amount of DOX are summarized in Table 1. Gel
formation is observed by the addition of small amounts of
DOX to the reaction (Runs 1, 11, and 15). It seems that 60
equiv or more DOX with 5 equiv of EBFA are needed to
obtain soluble polymers. Polymers with molecular weight as
high as 5.6 ꢀ 104 are produced by the addition of larger
amount of initiators (Runs 4, 7, and 8). The structural analy-
ses with NMR measurements of the polymer obtained
showed no signals assigned to CH2¼¼ hydrogens and the
SYNTHESIS AND POLYMERIZATION OF NOVEL BIS(2-TRIFLUOROMETHYLACRYLATE), KURAKAMI ET AL.
2723

JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
It may be a new finding that the addition polymerization of
2-trifluoromethylacrylate group takes place under radical
reaction conditions to afford high-molecular-weight polymers
in high yields although low-molecular-weight oligomers have
been previously reported. This may be ascribable to large
substituents at chain ends to stabilize propagating radicals.
ꢁ
The 5% weight-loss temperature of the polymer was 309 C
as measured by TGA.
The authors are very much indebted to Tosoh F-Tech, Inc.
for providing 2-trifluoromethylacrylic acid and Iharanikkei
Co. for phthaloyl dichloride. They are grateful for the
financial support in part by the ‘‘Open Research Center’’
Project in Saitama Institute of Technology from the Minis-
try of Education, Culture, Sports, Science, and Technology
of Japan, 2007–2009.
FIGURE 1 1H NMR of reaction product of EBFA in DOX.
polymer incorporates DOX moieties, as shown in Figure 1
and the Experimental section, which demonstrates that the
addition polymerization of a 2-trifluoromethylacrylate takes
place with radical addition of DOX at the pendant 2-trifluoro-
methylacrylate group quantitatively as shown by eq 2. The
conclusion was supported by the results of the model reac-
tions of ethyl 2-trifluoromethylacrylate with THF and DOX.
1H NMR of the polymer obtained by the base-catalyzed hy-
drolysis of the polymer produced by the reaction of EBFA
with DOX showed the decrease of the peaks assigned to
ACH2ACHAOA and ACH2ACH(CF3)A and to ACH2ACH2A,
respectively, because of decrease of ester groups although a
homopolymer of CH2¼¼C(CF3)COOH could not be isolated
probably because of the incomplete hydrolysis in polymer
reaction.
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