Langmuir 1994,10, 994-995
994
Synthesis and Surfactant Properties of Novel Amphiphilic Fluorinated Silicon Oligomers Containing Carboxy Groups Hideo Sawada,**tNahoko Itoh,t Tokuzo Kawase,i Motohiro Mitani,B Hiromitsu Nakajima,g Masami Nishida,B and Yasuo Moriyall Department of Chemistry, Nara National College of Technology, Yata, Yamatokoriyama, Nara 639-11, Japan, Faculty of Science of Living, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558, Japan, Tsukuba Research Laboratory, NOF Corporation, Tokodai, Tsukuba, Ibaraki 300-26, Japan, and Chemicals Division, NOF Corporation, Yuraku-cyo, Chiyoda-ku, Tokyo 100, Japan Received November 8,1993. In Final Form: February 10,1994' New fluorinated silicon oligomers containing carboxy groups were prepared by the reactions of fluoroalkanoyl peroxides with acrylic acid and trimethylvinylsilane. These fluorinated silicon oligomers were found to indicate surface properties typical of the amphiphilic compounds and to be easily soluble in both water and aromatic solvents such as benzene, toluene, and m-xylene. Moreover, these oligomers were able to reduce the surface tension of these solvents effectively. Recently, there has been a great interest in the synthesis and applications of fluorinated surfactants, in particular, fluorinated amphiphiles such as double chain perfluoroalkylated surfactants because of their unique vesicle f0rmation.l Increasing interest has been also directed toward organosilicon compounds because of their unique properties as well as organofluorine compounds.2 Thus, the development for amphiphilic fluorinated silicon compounds as new functional materials possessing excellent properties imparted by both fluorine and silicon has been deeply desired. However, no preparation and applications of these compounds have hitherto reported. During our comprehensive study on the reactivities of fluoroalkanoyl peroxides, we found that fluoroalkanoyl peroxides are useful reagents for the introduction of fluoroalkyl groups into arenes and alkenese3Now, we found that amphiphilic fluorinated silicon compounds were obtained by the reactions of fluoroalkanoyl peroxides with acrylic acid and trimethylvinylsilane in excellent to moderate yields under very mild conditions, and the results will be described herein. A typical procedure for the synthesis of amphiphilic fluorinated silicon oligomers is as follows. A solution containing perfluorobutyryl peroxide (11.9 mmol), trimethylvinylsilane (24.0 mmol), and acrylic acid (47.2 mmol) in trifluorotrichloroethane (200g) was stirred a t 40 "C for 5 h under nitrogen, and the resulting white powder was reprecipitated from methanol-ethyl acetate to give a fluorinated silicon co-oligomer containing trimethylsilyl and carboxy groups (4.67g). This co-oligomer showed the following spectral data: IR (cm-l) 3130 (OH), 1712 (CO), 1350(CF3),1226 (CF2),840 (Si-Me); leFNMR (CD3-
* To whom all correspondence should be addressed.
t Nara National College of Technology.
t Osaka City University. i Teukuba Research Laboratory, NOF Corp. 1 Chemicals Division, NOF Corp. Abstract publiihed in Advance ACS Abstracts, March 15,1994. (1) (a) Kunitake, T. Angew. Chem., Znt. Ed. Engl. 1992,31,709. (b) Kuwahara, H.; Hamada, M.; Ishikawa, Y.; Kunitake, T. J. Am. Chem. SOC.1993,115,3002. (c) Menger, F. M.; Yamasaki, Y. J. Am. Chem. SOC. 1993,115,3840. (d) Trabelai, H.; Szonyi, S.; Gaysinski, M.; Cambon, A. Longmuir 1993,9, 1201. (2) (a)Patai, S., Rappoport, Z., Eds. The Chemistry of Organic Silicon Compounds;John Wdey and Sons: Chichester, 1989. (b) Miller, R. D.; Michl, J. Chem. Reu. 1989, 89, 1359. (c) Pawlenko, S. Organosilicon Chemistry; Walter de Gruyter: Berlin, 1986. (3) (a) Sawnda, H. J. Fluorine Chem. 1998,61, 253. (b) Sawada, H. Reurews on Heteroatom Chemistry;Oae, S., Ed.;Myu: Tokyo. 1993:Vol. 8, p 205. @
OD, ext. CF3C02H) 6 - 5.27 (6F),-36.60 (4F), -51.85 (4F); 'H NMR (CD30D) 6 -0.10 to 0.11 (-CHs), 1.28-2.08 (-CH2-), 2.18-2.63 ( 4 H - ) ; average molar mass = -1860, MJM, = 1.83 (determined by gel permeation chromatography (GPC) calibrated with standard polystyrenes). The co-oligomerizationsof fluoroalkanoylperoxideswith acrylic acid and trimethylvinylsilane were carried out at 40 "C for 5 h under nitrogen, and the results are listed in Table 1.
(K)
RF-(CH~CH)~-(CH~CH)~-RF
I
I
COzH
SiMe3
RF = C3F7, CF(CF3)[oCF2CF(CF3)]&C+F7:
m = 0, 1,2
As Table 1 shows, it was found that both perfluoropropylated and some perfluorooxaalkylated silicon oligomers were obtained in similar isolated yields. The products obtained are polydispersant mixtures of oligo-mers (MJM,> 1). We have reported that vinylsilanes ( C H d H S i R 3 ) react with fluoroalkanoyl peroxides to give fluorosilicon oligomers with two fluoroalkylated end groups [RF-(CH~CHS~M~~),,-RFIvia a radical process.* In our present oligomericcondition that the concentration of fluoroalkanoyl peroxide is higher than that of trimethylvinylsilane or acrylic acid compared with that of the usual radical polymerization, a oligomer with two fluoroalkyl fragments would be obtained via a primary radical termination of the growing radicals with the radical produced by the decomposition of peroxide, or via a chain transfer to the peroxide6 as well as the reactions of vinylsilanes with the peroxides. Interestingly, the fluorinated silicon co-oligomers thus obtained were found to be easily soluble in not only water but also common organic solvents such as methanol, ethanol, tetrahydrofuran, carbon tetrachloride, N,Ndimethylformamide, dimethyl sulfoxide,benzene, toluene, and xylene. In general, fluorinated Surfactants such as perfluoroalkanoic and perfluoroalkanesulfonic acids, and perfluoroalkyl acrylate polymers are well known to give a poor solubility in various solvents except for the ~~~~
(4) Snwndn, H.; Nakayama, M. J. Chem. SOC.,Chem. Commun. 1991, 677.
(5) Higashimura, T. Yuki Gosei Kagaku Kyokaishi 1984,42, 330.
0743-7463/94/2410-0994$04.50/00 1994 American Chemical Society
Letters
Langmuir, Vol. 10, No. 4, 1994 995 Table 1. Synthesis of Fluorinated Silicon Co-oligomersContaining Carboxy Groups R~-(CHZCHI,-(CHZCH),F
I
SiMea peroxide (mmol)
I
COlH
CHdHSiMes (mmol)
CHdHC02H (mmol)
yield
(FJK)
(%)a
@:q)b
24.0
47.2
48
1860 (1.83) (1387)
23.2
51.3
37
3770 (1.55) (11:89)
51.3
34
5030 (1.39) (1585)
14.1
33
RF CF(CFs)OCsF7 11.6
RF CF(CFdOCF2CF(CFs)OCF2CF(CFa)OCaF7 3.2 6.4
5670 (1.25) (9:91) 4 The yields are baaed on the starting materials (trimethylvinylsilane, acrylic acid, and the decarboxylated peroxide unit (RF- RF)). Cooligomerization ratio was determined by lH NMR.
fluorinated ones. However, our oligomers were found to give an excellent solubility even in aromatic solvents. To the contrary, we previously reported that acrylic acid oligomers having two fluoroalkyl end groups [RdCHzCHCOZH),-RF] are highly soluble in polar solvents such as water, methanol, and tetrahydrofuran but insoluble in perhalogenated solvents and aromatic hydrocarbons.6 Furthermore, we prepared a series of fluorinated cooligomers replaced trimethylsilyl group with various hydrocarbon side chains by using alkyl methacrylates (CHyCMeC02R) instead of trimethylvinylsilane under similar conditions as follows: C~F~OCF(CF~)-(CHZCM~COZR),-(CH~CHC~~H),-CF(CF~)OC~F~ (Ia-c): R = CHzCHs (Ia),M, = 5570 @:q = 23:77); R = CHzCHzCH2CHs (Ib),M,= 7120 @:q 19:81);R = CHzCH(CH2CHs)(CH2)&H3 (IC), = 8970 @:q = 14:86). However, the introduction of these hydrocarbon side chains into co-oligomers were not able to lead to good solubility in water and aromatic solvents such as benzene and toluene. In fact, Ia was clarified to be insoluble in both water and aromatic solvents such as benzene and toluene. Ib and IC became turbid in aromatic solvents (benzene and toluene) but were insoluble in water. It is considered that the interesting property for solubility of our fluorinated silicon co-oligomers would be due to the presence of trimethylsilyl group. Thus, these fluorinated silicon cooligomers are clarified to indicate the properties typical of the amphiphilic compounds. With respectto the surfaceactivitiesof these fluorinated silicon co-oligomers, we have measured the reduction of (6) Sawada,H.; Gong,Y.-F.; Minoshima,Y.; Mataunoto,T.; Nakayama, M.; Koeugi, M.; Migita, T. J. Chem. SOC.,Chem.'Commun. 1992, 537.
surface tension by each oligomer in Table 1 with the Wilhelmy plate method at 25 OC. These amphiphilic were oligomers [RE-(CHZCHS~M~~),-(CH~CHCOZH),-RFI found to decrease the surface tension of both water and m-xylene from 72.3 and 28.8 mN m-l, respectively, to as follows at the concentration of 10 g dm-? RF = (38.1 =CF(CFa)OCaF? = CF(CFs)OCF2CF(CFs)OC@7 = CF(CFs)OCFzCF(CFs)OCFr CF(CFdOCaF7 0 5 g dma.
water 20.8 (21.4)' 20.6 (20.9) 23.9 (25.1) 25.7 (26.4)
m-xylene 24.9 (27.6)' 23.1 (25.1) 14.7 (17.6) 14.8 (20.4)
The degree of reduction in surface tension of m-xylene depends on the length of fluoroalkyl group in oligomers as well as the usual fluorinated ~urfactants.~ Thus, longer fluoroalkyl chains, especially perfluorooxaalkyl chains, reduce the surface tension of m-xylene more effectively. On the other hand, in the case of aqueous solution of fluorinated silicon oligomers, shorter perfluorooxaalkyl chains were effective in reducing the surface tension of water to 20.6 (20.9)mN m-l. Furthermore, the aqueous solution of fluorinated silicon oligomers could afford quite stable emulsions with aliphatic and aromatic hydrocarbons. These unique modes of reduction of surface tension by the present amphiphilic fluorinated silicon oligomers cannot be explained in detail at the present time. However, to our knowledge, this is the first example of fluorinated silicon compounds that are soluble in both water and aromatic hydrocarbons and reduce effectively the surface tension of these solvents. Further studies are actively in Dromess. (7)Abe, M.; Morikawa, K.; Ogino, K.;Sawada, H.; Mataunoto, T.; Nakayama, M. Langmuir 1992,8, 763.
