Preparation and characterization of nonpolar fluorinated carbosilane dendrimers by APcI mass spectrometry and small-angle X-ray scattering

Article abstract of DOI:10.1021/ja992794r

The following highly fluorinated nonpolar dendrimers were obtained in high yields from multiple hydrosilylation reactions between core hydride terminated carbosilane dendrimers and allyl-1,1-dihydrotrifluoroethyl ether or allyl-1,1-dihydroheptadecafluorononyl ether through divergent synthetic routes: Si[CH₂-CH₂SiMe₂(CH₂CH ₂CH₂OCH₂CF₃)]₄ (7), Si{CH₂CH₂SiMe[CH₂CH₂SiMe(CH ₂CH₂CH₂OCH₂CF₃) ₂]₂}₄ (8), Si[CH₂CH₂Si(CH₂CH₂CH ₂OCH₂C₈F₁₇)₃]₄ (9), Si[CH₂CH₂SiMe₂(CH₂CH ₂CH₂OCH₂C₈F₁₇)] ₄ (10), and Si{CH₂-CH₂Si[CH₂CH₂Si(CH ₂CH₂CH₂OCH₂C₈F ₁₇)₃]₃}₄ (11). These compounds were characterized by elemental and spectroscopic analyses. Valuable mass spectral data were obtained by using atmospheric pressure chemical ionization (APcI). The fluorinated dendrimer molecule and the nonfluorinated core scatter X-ray light differently and present unique slopes on the Guinier Plot of data from small-angle X-ray light scattering (SAXS) in hexafluorobenzene. Glass transition temperatures (Tg) and thermogravimetric analyses (TGA) of the dendrimers were determined.

Full text of DOI:10.1021/ja992794r

11130
J. Am. Chem. Soc. 1999, 121, 11130-11138
Preparation and Characterization of Nonpolar Fluorinated Carbosilane
Dendrimers by APcI Mass Spectrometry and Small-Angle X-ray
Scattering
Bamidele A. Omotowa,# Keith D. Keefer,† Robert L. Kirchmeier,# and
Jean’ne M. Shreeve*,#
Contribution from the Department of Chemistry, UniVersity of Idaho, Moscow, Idaho 83844-2343, and
William R. Wiley EnVironmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory,
P.O. Box 999, Richland, Washington 99352
ReceiVed August 5, 1999
Abstract: The following highly fluorinated nonpolar dendrimers were obtained in high yields from multiple
hydrosilylation reactions between core hydride terminated carbosilane dendrimers and allyl-1,1-dihydrotri-
fluoroethyl ether or allyl-1,1-dihydroheptadecafluorononyl ether through divergent synthetic routes: Si[CH2-
CH2SiMe2(CH2CH2CH2OCH2CF3)]4 (7), Si{CH2CH2SiMe[CH2CH2SiMe(CH2CH2CH2OCH2CF3)2]2}4 (8),
Si[CH2CH2Si(CH2CH2CH2OCH2C8F17)3]4 (9), Si[CH2CH2SiMe2(CH2CH2CH2OCH2C8F17)]4 (10), and Si{CH2-
CH2Si[CH2CH2Si(CH2CH2CH2OCH2C8F17)3]3}4 (11). These compounds were characterized by elemental and
spectroscopic analyses. Valuable mass spectral data were obtained by using atmospheric pressure chemical
ionization (APcI). The fluorinated dendrimer molecule and the nonfluorinated core scatter X-ray light differently
and present unique slopes on the Guinier Plot of data from small-angle X-ray light scattering (SAXS) in
hexafluorobenzene. Glass transition temperatures (Tg) and thermogravimetric analyses (TGA) of the dendrimers
were determined.
Introduction
Despite the presence of about a dozen papers on fluorinated
dendrimers in the literature, the reviews did not mention this
subclass.4-14 Fluorination imparts some typical properties to
dendrimers such as hydrophobicity and very good thermal
stabilities.4,6,9,13 Fluorinated dendrimers were obtained by
incorporation of fluorinated alkyl (or aryl) units into dendritic
branches in order to obtain chiral dendrimers.4,6,11 Based on
results from atomic force microscopy (AFM) micromachining
studies, a fluorinated dendrimer performed as a lubricating
material superior to the nonfluorinated analogue.5 A few
amphiphilic fluorinated dendrimers were synthesized, their
surfactant properties were evaluated,8,12,13 and at least one group
Synthesis and characterization of carbosilane dendrimers
terminating in polyfluoroalkyl ether units are significant since
they are likely to find applications outside the laboratory. Hence,
evaluation of alternative synthetic pathways to such compounds
and methods of characterizing them and of determining their
properties are of interest. Since the first report on cascade
molecules by Vo¨gtle et al. in 1978 and subsequent synthesis/
characterization by Newkome1 and Tomalia,1 more than 1200
papers have been published on this subject.1,2 There are many
review papers on this very interesting group of polymeric
compounds, but the most recent ones are perhaps most
comprehensive.1,3 Whereas Vo¨gtle and Fischer reviewed the
practical applications of these materials, Majoral and Caminade
reviewed dendrimers with a focus on heteroatoms in the
branching points of the core frame region.1,3 The review by
Bosman et al. covered the structure, physical properties and
applications of dendrimers and Newkome et al. summarized the
novel properties of metallodendrimers in their latest review.1
(4) Stark, B.; Steuhn, B.; Frey, H.; Lorenz, K.; Frick, B. Macromolecules
1998, 31, 5415-5423.
(5) Klug, C.; Kowalewski, T.; Schaefer, J.; Straw, T.; Tasaki, K.; Wooley,
K. Polym. Mater. Sci. Eng. 1998, 77, 99-100.
(6) Grieveldinger, G.; Seebach, D. Polym. Mater. Sci. Eng. 1997, 77,
134-135.
(7) Michalczyk, M. J.; Sharp, K. G. U.S. Patent 96-663834 19960614
(to E. I. Du Pont De Nemours and Co., U.S.A.), 1997.
(8) Chapman, T. M.; Mahan, E. J. Polym Mater. Sci. Eng. 1995, 73,
275-276.
* Corresponding author: Tel.: (208) 885 6651, Fax: (208) 885 6198,
e-mail: jshreeve@uidaho.edu.
(9) Miller, T. M.; Neenan, T. X.; Zayas, R.; Bair, H. E. J. Am. Chem.
Soc. 1992, 114, 1018-1025.
(10) Miller, T. M.; Neenan, T. X.; Zayas, R.; Bair, H. E. Polym. Prepr.
(Am. Chem. Soc. DiV. Polym. Chem.) 1991, 32, 599-600.
(11) Lorenz, K.; Frey, H.; Stuhn, B.; Mulhaupt, R. Macromolecules 1997,
30, 6860-6868.
(12) Cooper, A. I.; Londono, J. D.; Wignall, G.; McClain, J. B.; Samulski,
E. T.; Lin, J. S.; Dobrynin, A.; Rubinstein, M.; Burke, A. L. C.; Frechet, J.
M. J.; DeSimone, J. M. Nature 1997, 389, 368-370.
(13) Yu, D.; Frechet, J. M. J. Polymer Preprints 1998, 39, 633.
(14) (a) Dagani, R. C&EN News 1999, February 8, 33-36, and references
therein. (b) Balogh, L.; Tomalia, D. A. J. Am. Chem. Soc. 1998, 120, 7355-
7356. (c) Zhao, M., Sun, L.; Crooks, R. M. J. Am. Chem. Soc. 1998, 120,
4877-4878. (d) Zhao, M.; Crooks, R. M. Angew. Chem., Int. Ed. Engl.
1999, 38, 364-365.
# University of Idaho.
† Pacific Northwest Laboratory.
(1) (a) Majoral, J. P.; Caminade, A. M. Chem. ReV. 1999, 99, 845-880.
(b) Bosman, A. W.; Janssen, H. M.; Meijer, E. W. Chem. ReV. 1999, 99,
1665-1688. (c) Newkome, G. R.; He, E..; Moorefield, C. N. Chem. ReV.
1999, 99, 1689-1746. (d) Newkome, G. R. Yao, Z. -Q.; Baker, G. R.;
Gupta, K. J. Org. Chem. 1985, 50, 2003-2004. (e) Tomalia, D. A., Baker,
H.; Dewald, J. R., Hall, M.; Kallos, G.; Martins, S., Roeck, J.; Ryder, J.;
Smith, P. Polym. J. (Tokyo) 1985, 17, 117-132 (f) Tomalia, D. A., Baker,
H.; Dewald, J. R., Hall, M.; Kallos, G.; Martins, S., Roeck, J.; Ryder, J.;
Smith, P. Macromolecules 1986, 19, 2466-2468.
(2) Chemical Abstract electronic search line.
(3) Fischer, M.; Vo¨gtle, F. Angew Chem., Int. Ed. Engl. 1999, 38, 884-
905.
10.1021/ja992794r CCC: $18.00 © 1999 American Chemical Society
Published on Web 11/18/1999

Nonpolar Fluorinated Carbosilane Dendrimers
J. Am. Chem. Soc., Vol. 121, No. 48, 1999 11131
has described their surfactant behavior in supercritical CO2.12
It thus appears that these fluorine-containing dendrimers have
considerable potential application. Dendrimers containing polar
groups in the core and terminating in perfluoroalkyl, perfluor-
aryl, or perfluoropolyether units are generally very nonpolar
and have been characterized solely by elemental analysis and
1H, 13C, or 19F NMR spectral techniques. Molecular masses of
fluorinated dendrimers containing heteroatoms in the polar
functionality were determined by MALDI time-of-flight spec-
trometry. However, no mass spectral characterization of the
nonpolar fluorinated dendrimers has been reported to date.
The only results obtained by X-ray and neutron scattering of
carbosilane dendrimers terminating in perfluoroalkyl groups
suggest that this technique has potential as an additional tool
for monitoring the changes in the molecule when they act as
surfactants.4 X-ray light scattering was used to study physical
properties of a number of dendrimers, and the different models
for analyzing them have produced a comprehensive background
for evaluating the results of scattering experiments.15 It appears
that the Sphere and Guinier models are more applicable than
the Zimm plot analysis, despite its strong advantages, because
the latter shows poor correlation with experimental deduction.6
Hence, evaluation of the response of other models for analysis
of fluorinated dendrimers was considered worthwhile.
We report here the syntheses of dendrimers that terminate in
polyfluoroalkyl ether groups from their hydride precursor via
hydrosilylation. The dendrimer hydrides served only once earlier
as substrate precursors for synthetic extensions16 and were useful
for the synthesis of the compounds described in this paper.
Interestingly, mass spectral characterizations were not reported
for the few fluorinated dendrimers in the literature.1,13 It is
difficult to generate ions for mass spectral studies by conven-
tional methods, e.g., electrospray and MALDI-TOF, from the
nonpolar polyfluoroalkyl ether dendrimers. Solvent ionization
from a Corona electric discharge induces the nonpolar fluori-
nated dendrimers to ionize for mass spectral characterization
by atmospheric pressure chemical ionization (APcI). This
technique and small-angle X-ray scattering (SAXS) also were
used to characterize the carbosilane dendrimers in this work.
convenient procedure for the synthesis of polyfluoroalkyl ethers
because alcohols do not add to olefins in the same manner under
mild conditions. Dendrimers terminating in silanes have been
useful substrates in a few successful reactions.16 They were very
appropriate for synthesis of compounds in this work.
Reactions of dendrimer silanes with Co2(CO)8 and (CH2d
CHC5H4)Fe(C5H5) have been utilized to produce the respective
dendritic derivative ending in -Me2SiCo(CO)4 and -Me2SiCH2-
CH2C5H4)Fe(C5H5), respectively.16 It was possible to monitor
the progress and/or completeness of transformation of Si-H
bonds to Si-C bonds via hydrosilylation by using a combination
of 1H and 29Si NMR spectra. The latter were particularly helpful.
The 29Si NMR signal typical of Si-H remains when conversion
to Si-C is incomplete. Thus, progress of the synthesis of the
desired dendrimers via reactions of fluoroalkyl ethers was readily
monitored.
The synthesis of Si-H terminated carbosilane dendrimers is
relatively straightforward.17,18 They are a relatively very stable
class of organosilicon compounds that are not noticeably
changed when handled in open air for short periods.17 Fully
-SiH3 and partially -Si(Me)H2 and -Si(Me)2H terminated
hydrides of the first to the fourth generation dendritic carbo-
silanes can be synthesized, but there is concern for possible
cleavage of the Si-H bonds when more drastic reaction
conditions are employed to force complete coupling in higher
(than second generation) dendrimers. Hence, only first- and
second-generation dendrimers were used in this study, and
evidence from NMR spectroscopy indicates that no cleavage
or any other silyl coupling occurred. Another consideration was
the anticipated poor solubility of the higher generation den-
drimers as was reported for dendrimers ending in polyfluoro-
alkylthioethers.11 Two first-generation carbosilane dendritic
compounds ending in four (1) and 12 (2) hydrides and two
second-generation analogues ending in 16 (4) and 36 (3)
terminal hydrides were synthesized in this work based on
literature procedures.17,18 The synthetic pathway for these
compounds is shown in Schemes 1-3. Of these, only 4 is a
new compound. All the dendrimer hydrides were characterized
on the basis of NMR and mass spectral data.
The two polyfluoroalkyl ether olefins used in this work were
obtained in high yields by metathetical reactions of the alkali
metal derivative of the respective fluoroalkyl alcohol with allyl
bromide (see Experimental Section). Allyl-1,1-dihydrotri-
fluoroethyl ether (5), bp ) 49 °C and MS (EI) M+ ) 140, is a
low molecular weight species, and addition to terminal silyl
hydride in substrate dendrimers 1 and 4 occurs to form 7 and
8, respectively (Scheme 1). These two new dendrimers that
terminate in four and 16 trifluoroalkyl ether units contain
relatively small amounts of fluorine and thus were soluble in
organic solvents, such as THF, diethyl ether, and dichloro-
methane. They were isolated as air stable, colorless liquids. Not
surprisingly compound 8 is much more viscous than 7. Any
excess of low boiling 5 was removed under vacuum at room
temperature. Elemental analysis and nuclear magnetic resonance
and mass spectral data were used to satisfactorily characterize
the fluorinated dendrimers. After removing any volatile materi-
als, elemental analyses confirmed that the products are analyti-
cally pure. Olefin polymerization does not occur with 5. The
hydride substrates 1 and 4 were stable to decomposition in a
sealed degassed tube at 75 °C for 24 h. NMR evidence for
completed reaction is the disappearance of the allylic signals,
Results and Discussion
The carbosilane dendrimers terminating in polyfluoroalkyl
ethers (7-11) were synthesized by adding two different
polyfluorinated ether olefins to dendrimers with multiple
terminal hydride functionalities. Although nonfluorinated spacers
are usually necessary to prevent expected interactions between
silicon and vicinal fluorine atoms, our aim was to introduce as
few methylene groups as possible. Researchers in this field have
shown preference for dendrimers terminating in olefins (vinyl
and allyl) as substrates for developing synthetic extensions
through hydrometalation.11 For example, it was convenient to
couple a fluorinated alkanethiol to an allyl-terminal in the
substrate dendrimer by hydrosulfurylation.11 This is not a
(15) (a) Kleppinger, R.; Reynaers, H.; Desmedt, K.; Forier, B.; Dehaen,
W.; Koch, M.; Verhaert, P. Macromol. Rapid Commun. 1998, 19, 111-
114 (b) Prosa, T. J.; Bauer, B. J.; Amis, E. J.; Tomalia, D. A.; Scherrenberg,
R. J. Polym. Sci., Part B: Polym. Phys. 1997, 35, 2913-2924 (c) Bauer,
B. J.; Hammouda, B.; Barnes, J. D.; Briber, R. M.; Tomalia, D. A. Polym.
Mater. Sci. Eng. 1994, 71, 704-5 (d) Bauer, B. J.; Topp, A.; Prosa, T. J.;
Amis, E. J.; Yin, R.; Qin, D.; Tomalia, D. A. Polym. Mater. Sci. Eng. 1997,
77, 87-88 (e) Topp, A.; Bauer, B. J.; Amis, E. J.; Scherrenberg, R. Polym.
Mater. Sci. Eng. 1997, 77, 82-83.
(16) (a) Cuadrado, I.; Moran, M.; Moya, C.; Casado, C. M.; Barranco,
M.; Alonso, B. Inorg. Chim. Acta 1996, 251, 5. (b) Losada, J.; Cuadrado,
I.; Moran, M.; Casado, C. M.; Alonso, B.; Barranco, M. Anal. Chim. Acta
1997, 338, 91. (c) Cuadrado, I.; Casado, C. M.; Alonso, B.; Moran, M.;
Losada, J.; Belsky, V., J. Am Chem. Soc. 1997, 119, 7613.
(17) Chai, M.; Pi, Z.; Tessier, C.; Rinaldi, P. L. J. Am. Chem. Soc. 1999,
121, 273-279.
(18) Seyferth, D.; Son, D. Y. Organometallics 1994, 13, 2682-2690.

11132 J. Am. Chem. Soc., Vol. 121, No. 48, 1999
Omotowa et al.
Scheme 1
Scheme 2
1
i.e., H: 5.08-5.28 (td), 5.65-5.90 (m) and 13C: 133.1 and
1
119.4 ppm; however, the ether (CH2OCH2) linkage, i.e., H:
3.58-3.94 (t), 4.02 (q) and 13C: 73, 67, 69 ppm, is retained.
1
The peaks for (Si-H) in the H NMR spectra at ca. 3.5 ppm
1
(JSi-H ) 192 Hz) also disappear completely. New H NMR
signals that result from the newly formed -CH2CH2- linkage
as a product of hydrosilylation reactions at the terminal four
silicon atoms are observed between 1.20 and 1.80 ppm. Data
supporting this linkage are also observed in the 13C NMR signals
at ca. 7.0 and 10.0 ppm. The equivalence of the four terminal
silicon atoms in the new compounds was monitored by the
changed pattern of the 29Si NMR spectra, and these data are
reported in the Experimental Section.
Scheme 3
The allyl-1,1-heptadecafluorononyl ether (6) is a higher
molecular weight, air stable analogue of 5, bp ) 58 °C/0.3 mm,
and MS (EI) M+ ) 490. This compound was synthesized by
utilizing the procedure for the lower homologue, allyl-1,1-
pentadecafluoroaoctyl ether.19 It was characterized in a manner
similar to that for 5. When the dendrimer hydride 2 or 3 was
added from a syringe into a mixture of an excess of 6 and
catalytic amounts of chloroplatinic acid in 2-propanol and
maintained at about 90 °C under anaerobic conditions, viscous,
light brown colored oils 9 or 11, respectively, were obtained.
Compound 10 was synthesized from the analogous reaction
between 1 and 6. These highly fluorinated materials were soluble
only in fluorinated solvents, such as 1,1,2-trifluorotrichloro-
ethane (Freon 113) and hexafluorobenzene. Based on NMR
spectral evidence, the three were unreactive toward organic
acids, bases, and oxidizing and reducing agents. Since the
polyfluoroalkyl ether chains in 9-11 are much longer than in
7 and 8, incomplete coupling of the terminal silane with 6 might
be expected but does not occur. Again, the progress of the
reaction was monitored by using a combination of 1H and 29Si
NMR spectra.
The respective 29Si NMR signals were observed at ca. -53.5
(-SiH3:
2 and 3), -29.7 (-SiMeH2: 4), or -10.5
equivalence of all the terminal silicon atoms (i.e. four atoms in
9 and 10, 12 in 11) that would be present when all Si-H bonds
were displaced. The new signals for the silicon atoms were
observed in the 29Si NMR spectra at ca. -22 [-Si(CH2CH2-
CH2OCH2Rf)3; 9 and 11], -10 [-SiMe(CH2CH2CH2OCH2Rf)2;
8]. or -3.0 [-SiMe2(CH2CH2CH2OCH2Rf); 7 and 10]. How-
ever, the intensities of the signals for the terminal silicon atoms
are usually very strong. When samples are taken from the
reaction system for 29Si NMR measurement, signals of silicon
atoms bearing Si-CH2- and Si-H were seen along with those
of the others in the core of the dendrimer to indicate the degree
(-SiMe2H: 1) for the terminal silicon atoms (Schemes 1-3).
The reactions are allowed to continue until the Si-H signals
had disappeared completely in both the 1H and 29Si NMR spectra
and new ones formed at the expected positions. The 29Si NMR
spectra of 3 and 11 are in Figure 1.
New Si-CH2 NMR signals that appear between 1.20 and
1.80 ppm in the H NMR spectra confirm successful hydro-
silylation. However, it was important to confirm the chemical
1
(19) Holbrook, G. W.; Steward, O. W. U.S. Patent 3, 012, 006 (to Dow
Corning Co., MI), 1961.

Nonpolar Fluorinated Carbosilane Dendrimers
J. Am. Chem. Soc., Vol. 121, No. 48, 1999 11133
Figure 2. APcI mass spectrum for Si[CH2CH2SiMe2(CH2CH2CH2-
OCH2C8F17)]4 (10).
spectrum as did DHB. It was not possible to confirm whether
the source of the m/z ) 30 in the [M+ + 30] signal was the
dendrimer or the matrix. Two methyl moieties were assumed
to be cleaved and subsequently recombined with another
molecular unit, perhaps at the oxygen atom in the ether linkages.
Efforts were made to determine if the process that generated
the signal at 2366 took place either during the experiment or
under mass spectral conditions by using a different mass spectral
experimental technique for the same compound. Atmospheric
pressure chemical ionization (APcI) technique was found to be
useful. When APcI was used, the signal at 2366 was absent,
and signals at 2332-2335 were observed (Figure 2).
The advantage of using APcI, an LC-MS technique, is in its
ability to produce singly charged protonated or deprotonated
molecular ions for a broad range of nonvolatile and thermally
labile analytes such as the nonpolar polyfluorinated dendrimers
in this work that are only soluble in fluorinated solvents. When
the solvent emerges from the LC column into the MS probe it
is rapidly expanded into the vapor/gas phase and rapidly reacts
with ions from the corona discharge to produce stable reagent
ions.20 It is the reaction between this reagent ion and the
dendrimers at atmospheric pressure that typically generate the
protonated (in the positive mode) or deprotonated species (in
the negative mode) that goes into the mass spectrometer.20 Thus
the choice of solvent is an important factor that is compound
specific in APcI studies.
Two other dendrimers, 7 and 8, containing polyfluoroether
chains as terminal groups were examined by using APcI. Quasi-
molecular masses were obtained in the negative ion mode, and
the useful signals were considered as originating from the
molecular ion. The [M- - CF3] signal was observed as a strong
base peak signal at 867 for compound 7. The relationship of
the higher signal at m/z ) 941 to M- expected at m/z ) 935
for 7 is unclear. In the APcI- spectrum for 8, a significant
negative ion signal was observed at ca. 3280. This signal
represents an [M- + 140] mass. Since THF is the solvent mobile
phase for 8 in the APcI studies, it is assumed that two
tetrahydrofuran units more than the expected dendrimer mass
are responsible.
Peaks having reasonable signal/noise-level ratio and appearing
at m/z values lower than the molecular ion may be arise from
either fragmentation of the molecule, the incompletely formed
dendrimers or from nonrelated impurities. The mass spectra of
dendrimers ending in the trifluoroethyl ether (monomer arm)
units, i.e., -CH2CH2CH2OCH2CF3 in 7 and 8 showed few lower
mass peaks. These peaks do not arise from loss of monomer
Figure 1. 29Si NMR spectra (ppm) of a second-generation dendrimer
hydride substrate (3) and the fluorinated derivative (11).
of completeness of the reaction. The dendrimers, especially 9
and 11 as the longer polyfluoroalkyl ether chain, were charac-
terized from the combination of 1H/29Si NMR and their
elemental analyses.
The 19F NMR spectra confirmed the presence of the terminal
fluoroalkyl chains in these dendrimers, but not surprisingly the
positions of the signals and the multiplicities were not noticeably
changed moving from the alcohol to the polyfluoroether olefins
(5 and 6) to the fluorinated dendrimers (7-11). Therefore, the
fluorine NMR spectra are not particularly useful in determining
the extent of reaction.
Earlier, either size exclusion chromatography (SEC) or small-
angle X-ray light scattering (SAXS) was used to determine the
molecular masses of fluorinated dendrimers that terminated in
perfluoropolyether or polyfluorothioether chains.4,14 These
compounds were generally nonpolar and soluble only in
perfluorinated solvents. Hence, they responded poorly to
experimental conditions for providing ions in electrospray and
MALDI time-of-flight mass spectral studies aimed at determin-
ing accurate molecular masses.
In this work, the dendrimers 9-11 that terminate in the long
polyfluoroalkyl chains were also insoluble in nonfluorinated
solvents, but 7 and 8 that contained a relatively small amount
of fluorine were soluble in organic solvents. The latter two
compounds were intentionally designed in order to assist in the
different maneuvers of mass spectrometry to obtain characteristic
data for at least some of the dendrimers by using standard mass
spectrometric techniques.
Molecular ions for the dendrimers ending in silanes [1 (M+,
376), 2 (M+, 264), 3 (M+, 962), and 4 (M+, 896)] were obtained
by electron ionization (EI) or by MALDI time-of-flight mass
spectral analysis. Our experiments that sought to generate both
positive and negative ions with three matrixes: R-cyano-4-
hydroxycinnamic acid, indoleacrylic acid, and 5-chlorosalicylic
acid, at two levels of dilution only gave some fairly complex
and unexplainable signals in MALDI studies. The dendrimers
did not incorporate into the crystallized matrix. The strong
positive ion signal obtained for 10 at m/z 2366.4, i.e., M+
+
30, by using 2,4-dihydroxybenzoic acid (DHB) matrix (mass
verified with an internal standard) results from our single
successful incorporation of the dendrimer into the matrix crystal.
Addition of silver trifluoroacetate produced no silver adduct.
No other matrix gave the signal at 2366 or as strong and clean
(20) Micromass’ users Guide book on Quatro II mass spectrometer.

11134 J. Am. Chem. Soc., Vol. 121, No. 48, 1999
Omotowa et al.
Table 1. Characterization by Mass Spectrometry
compound
MW (calcd)
Silane Dendrimers
MS (obsd)
MS method
Si[CH2CH2SiMe2H]4 (1)
Si[CH2CH2SiH3]4 (2)
Si[CH2CH2SiMe(CH2CH2SiMeH2)2]4 (4)
Si[CH2CH2Si(CH2CH2SiH3)3]4 (3)
376
264
896
962
375
263
895
961
EI
EI
MALDI
MALDI
Polyfluoroalkylether Dendrimers
Si{CH2CH2Si[CH2CH2Si(CH2CH2CH2OCH2C8F17)3]3}4 (11)
Si[CH2CH2SiMe2(CH2CH2CH2OCH2CF3)]4 (7)
18 600
936
2336
6144
3136
a
a
941 and 867
2366/2335
a
APcI
MALDI/APcI
a
Si[CH2CH2SiMe2(CH2CH2CH2OCH2C8F17)]4 (10)
Si[CH2CH2Si(CH2CH2CH2OCH2C8F17)3]4 (9)
Si{CH2CH2SiMe2[CH2CH2SiMe(CH2CH2CH2OCH2CF3)2]2}4 (8)
3280
APcI
Polyfluoroether Olefins
CH2)CHCH2OCH2CF3 (5)
CH2)CHCH2OCH2C8F17 (6)
140
491
140
491
EI
EI
a Mass spectral data were not obtained. See discussions of small angle X-ray scattering.
constituents but agree with calculations of cleavage of each of
the fluoroethyl ether chains at the oxygen atom. This occurred
irrespective of the dendrimer generation. However, 10, which
terminates in -CH2CH2CH2OCH2C8F17 units, showed fewer
mass peaks and signals supporting loss of the CH2CH2SiMe2-
CH2CH2CH2OCH2C8F17 units (m/z ) 1761 and 1285 in Figure
2). Since the Si-H signals had completely disappeared in the
1H and 29Si NMR spectra of 8, the logical explanation is that
these result from loss of arms, rather than being due to
incomplete reaction. The spectrum reveals loss of methyl and
methylene groups from several ion masses and a loss of one
methyl unit from each of the three -SiMe2 moieties of the
species with m/z ) 1761, accompanied by protonation of the
three Si atoms would give the base peak signal at m/z ) 1719,
HSi[CH2CH2Si(H)MeCH2CH2CH2OCH2C8F17]3.
There is a concentration of peaks with relatively very high
intensities at regions below m/z 800 for 8 (M+, 3136) and m/z
1000 for 10 (M+, 2336). These signals represent the several
fragments from the dendrimer arms or possible nonvolatile
impurities, and they could not be completely assigned. A
summary of the significant signals from the mass spectrometric
studies is shown in Table 1.
Dendrimers that terminate in CH2CH2CH2OCH2C8F17 (9-
11) in the present work were soluble in Freon 113 and in
hexafluorobenzene, and those ending in CH2CH2CH2OCH2CF3
(7 and 8) dissolved in fluorinated and nonfluorinated solvents
as well, e.g., THF, dichloromethane, and diethyl ether. There-
fore, Freon 113 (10) and tetrahydrofuran (7 and 8) were the
solvents used in our work. The Micromass user’s instruction
Guide book on Quatro II mass spectrometer emphasizes that
the value of the sample cone determines whether the resulting
spectra will be a protonated molecular ion peak or consisting
of diagnostic fragment ions.20 Regulating this parameter to 20
V should normally yield soft ionization leading to molecular
ion peak, and a setting to 50 V results in a spectrum that
contained ion peaks from significant fragmentation of an
analyte.20 The cone had to be set at 59 V in order to generate
ionization for positively charged signals in the APcI+ mode for
10 and partly explains the large number of fragment signals in
the resulting spectrum (Figure 2). A setting at 25 V was adequate
to generate negative ions in the APcI- mode for 7 and 8, and
the spectra contain relatively fewer significant fragment ions.
An evaluation of the spectra for 7 and 8 from the APcI+ mode
gave no useful information, but the spectra from the APcI- mode
were very helpful.
The signals did not give isotopic patterns that are important for
a possible successful deconvolution to reveal the higher than
m/z ) 4000. Therefore, it was not possible to measure the
response of the polyfluorinated dendrimers 9 (expected MW )
6144) and 11 (expected MW ) 18 600). Thus a combination
of elemental analysis and 1H/29Si NMR were used to characterize
the two compounds.
When a 1:9 Freon 113/hexane solution of 10 was allowed to
remain in a refrigerator at -15 °C, transparent single crystals
grew, but the quality was not adequate for single-crystal X-ray
diffraction. The crystal melted in solution at -10 °C. This
suggested that there was some order in the structure of these
dendrimers. Therefore, an attempt was made to obtain experi-
mental evidence to support this by exposing dilute solutions of
9 and 11 in hexafluorobenzene to small-angle X-ray scattering
measurements. Experimental results indicate that the higher
generations of polyamidoamine dendrimers have spheroidal
shapes and that the smaller relatives are assumed to be similar.15
The radius of gyration is known to be generation dependent
because of different electron density around the nucleus.
Molecular masses (hyperbranched polymers) were deduced
from Zimm plot analysis, but the technique was shown to be
inaccurate when applied to dendrimers.15b However, the Guinier
plot provide accurate and reliable results for evaluating shapes
and sizes of dendrimers.15b Over comparable q ranges the
reciprocal of the dimension causing the scattering according to
Guinier’s Approximate Law may be used to analyze the
scattering curves.21 The law, exact in the limit q f 0 and stated
2
as21 ln I(q) ) ln(Ie(q)N[∆FV)2] - q2Rg /3, was used to analyze
our scattering curves15 (where N is the number of independent
scattering particles, ∆F is the electron density contrast between
the particle and the matrix in which it is embedded, V is the
volume of the particle, and Rg is the electronic radius of gyration
of the particle, i.e., the electronically weighted root-mean square
radius of the particle about its electronic center of mass).
The plot ln(q) vs q2, according to the Guinier equation,
generates some linearity over q ranges where the law is followed
2
and have a slope equal to -Rg /3. The Guinier plots of the data
for 9 and 11 are shown in Figure 3. The plot for 11 has two
distinct linear regions, and the lower angle region is regarded
to be due to the total size of the dendrimer contrasted with the
solvent and gives an Rg of 2.7 ( 0.1 nm. The higher angle part
is due to the contrast between the nonfluorinated core of the
dendrimer and the surrounding fluorocarbon chains and gives
a Rg of 1.1 ( 0.05 nm. A poor signal-to-noise ratio precluded
The mass range of its detection window at 4000 molecular
mass units is, unfortunately, the limitation of this MS technique.
(21) Guinier, A.; Fournet G. Small-Angle Scattering of X-rays; John
Wiley & Sons: 1955.

Nonpolar Fluorinated Carbosilane Dendrimers
J. Am. Chem. Soc., Vol. 121, No. 48, 1999 11135
Figure 3. The Guiner plot of the small angle X-ray scattering (SAXS)
data for 9 and 11 in hexafluorobenzene.
reliable analysis of the low angle region of the curve for 9, but
the higher angle region corresponds to a core with a Rg of 0.9
( 0.05 nm.
The dendrimers were assumed to be simple spherical shells
for the interpretation of their electron density pair correlation
function. The radius of gyration of a sphere, Ds, is related to
the algebraic slope value Rg by the equation, Ds ) 2x(5/3)Rg.
The corresponding diameter of the dendrimer 11 is then 7.0
nm and its core 2.8 nm. The core of 9 is 2.6 nm. Both of these
values are in excellent agreement with those that would be
predicted from their molecular structure (Figure 4), 11 having
the larger core due to its longer nonfluorinated chains. The
observed diameter of 11 is close to the maximum it would have
if the chains were fully extended which is exactly what would
be expected for bulky fluorocarbon chains tethered to a central
core. Inward folding and interpenetration of endgroup chains
may be expected from third (and higher) generation den-
drimers.1b,14 The use of very dilute solutions in SAXS experi-
ments minimize the contributions from this phenomenon to the
results described in this work. Even though, almost all theoretical
models predict backfold branches, the fairly strong correlation
of predicted and SAXS experimental deductions on electron
density and sizes of the dendritic cores and overall molecules
further supports our deductions.1b The combination of evidence
from NMR, i.e., that all Si-H had been converted, and SAXS
support the proposed composition for these compounds.
Thermal properties of the dendrimers in this work are
summarized in Table 2. Glass transition temperatures, Tg, of
the dendrimer hydrides were observed at -125 (2), -104 (4),
and -98 °C (3), correlating an increase in Tg values with
increasing molecular weight. The trend is comparable to that
reported for other carbosilane dendrimers.11,22 Glass transition
temperatures were also observed for the fluorinated dendrimers,
9-11. Phase and glass transitions in the DSC thermogram 9
were at Tg at -10 and -33 °C, respectively, as shown in Figure
5. The thermogram for 10 and 11 showed a Tg at -26 and -52
°C, respectively. The dendrimer 7 exhibited no mesophase.
The results of thermogravimetric analysis (TGA) data for
8-11 and the results are summarized in Figure 6. The plot
relates molecular weight of the compounds and composition to
thermal stability. The temperatures for 50% weight loss of 8-11
occur over a range between 196 and 480 °C and are reported
in Table 2. The relative position of this value for each compound
indicates that their thermal stability correlates directly with
increase in molecular weight.
Figure 4. Relative sizes of 9 and 11 as deduced from SAXS.
Conclusions
Hydrosilylation reactions between a dendrimer hydride core
and polyfluorinated allyl ethers were carried out with complete-
ness of the reaction being monitored by a combination of H
1
and 29Si NMR spectra. Mass spectral characterizations of the
nonpolar compounds were obtained by using APcI. Results of
small-angle X-ray light scattering of two fluorinated dendrimers
in hexafluorobenzene show good correlation of expected values
and the experimentally deduced sizes of the nonfluorinated core
and the full dendrimer molecule. This level of accuracy makes
(22) Lorenz, K.; Muellhaupt, R.; Frey, H.; Rapp, U.; Mayer-Posner, F.
J. Macromolecules 1995, 28, 6657-6661.

11136 J. Am. Chem. Soc., Vol. 121, No. 48, 1999
Table 2. Thermal Properties of the Carbosilane Dendrimers
Omotowa et al.
glass transition
temp of 50% wt
loss in TGA (°C)
compound
temp, Tgb (°C)
Si[CH2CH2SiMe2H]4 (1)
Si[CH2CH2SiH3]4 (2)
-125
-104
-98
a
-10
-26
-52
Si[CH2CH2SiMe(CH2CH2SiMeH2)2]4 (4)
Si[CH2CH2Si(CH2CH2SiH3)3]4 (3)
Si[CH2CH2SiMe2(CH2CH2CH2OCH2C8F17)]4 (8)
Si{CH2CH2SiMe2[CH2CH2SiMe(CH2CH2CH2OCH2CF3)2]2}4 (9)
Si[CH2CH2Si(CH2CH2CH2OCH2C8F17)3]4 (10)
Si{CH2CH2Si[CH2CH2Si(CH2CH2CH2OCH2C8F17)3]3}4 (11)
196
378
425
480
a No mesophase and crystalline; Tg was not observed. b Tg values were obtained from Differential Scanning Calorimetry (DSC).
General. A standard Schlenk line system was used for handling the
reactions under anaerobic (dry nitrogen) conditions. Elemental analysis
of percentage carbon and hydrogen were performed by Desert Analytics
Laboratory, Tucson, AZ. All reactions and manipulations were carried
out in an atmosphere of dry nitrogen or argon. The TGA data were
collected on a Perkin-Elmer 7 series thermal analyzer under an argon
atmosphere with a heating rate of 20 °C/min. Infrared spectra are
recorded as neat liquids between KBr plates on a Bio-Rad FTS 3000
1
Excalibur series infrared spectrometer. H, 13C or [13C{F}], 19F, and
29Si NMR spectra were obtained on a Brucker AMX (200, 300, or 500
MHz) at 200, 50, 188, and 59 MHz, respectively, using CDCl3 as
locking solvent except where otherwise indicated. Chemical shifts were
reported with respect to Me4Si (1H, 13C and 29Si) or CFCl3 (19F). Mass
spectra (EI and CI) were obtained from a Finnigan GCQ or a JEOL
JMS-AX505HA mass spectrometer connected with a Hewlett-Packard
HP 6890 series GC system.
Figure 5. DSC thermogram of 9.
Atmospheric Pressure Chemical Ionization (APcI) Mass Spec-
trometry. Mass spectral determinations of molecular masses for the
fluorinated dendrimers with expected molecular masses under 4000
were done on a Quattro II triple quadruple mass spectrometer
(Micromass Inc., U.K.). The APcI interface consists of a heated
nebulizer probe, and the standard atmospheric pressure source config-
ured with a corona discharge pin. Other parameters were corona 1.80
kV (APcI-) or 3.50 kV (APcI+), cone 59V (APcI-) or 25V (APcI+),
Skimmer Lens offset 5V, source temperature 80 °C (APcI- and APcI+),
APcI probe temperature 20 °C (APcI-) or 35 °C (APcI+), and a
resolution of 15/15 (MS1/MS2). The samples were dissolved in either
THF or 1,1,2-trichlorotrifluoroethane (Freon-113) at a concentration
of 0.1 mg/10 mL of solvent. The solutions were normally filtered and
stored in clean glass vials with silicon-protected caps to prevent
contamination.
Figure 6. Thermogravimetric data for 8-11.
MALDI Time-of-Flight Mass Spectrometry. The MALDI-TOF
mass spectra were obtained on PerSeptive Biosystems Inc., Voyeger-
this technique relevant for determination of any change in the
electron density of either the core or in the region of fluorinated
terminal chains. The results demonstrate that X-ray scattering
is a useful technique with potential application for studying
rather complex compounds.
DE RP mass spectrometer (Cambridge, MA), with a nitrogen laser
emitting at 337 nm for desorbing the sample ions. The instrument
operated in the linear delayed-extraction mode at an accelerating voltage
of 25 kV and was internally calibrated. Detection was by means of a
microchannel plate detector and a digitizing oscilloscope operating at
250 MHz. Approximately 1 mmol sample solutions were made for the
dendrimer hydrides and the polyfluoroether dendrimers in chloroform
and Freon-113, respectively. We tried both positive and negative ions
out of four matrixes at two levels of dilution: R-cyano-4-hydroxy-
cinnamic acid, indoleacrylic acid, 5-chlorosalicylic acid, and 3,5-
dihydrobenzoic acid (DHB) in THF (2.0 M). One microliter of a
solution prepared by combining 1.0 µL of matrix solution and 0.1 µL
of sample solution was placed on the stainless steel MALDI target and
analyzed following evaporation of the solvents. Addition of silver
trifluoroacetate produced no silver adduct.
Experimental Section
Materials. The solvents, tetrahydrofuran (THF), diethyl ether, and
dichloromethane, were dried with sodium and distilled over purple
solution of benzophenone and dimethylsulfoxide (DMSO) over calcium
hydride. Allyl-1,1-dihydroheptadecafluorononyl ether was synthesized
by a modification of the method for allyl-1,1-dihydropentadecafluoro-
octyl ether.19 Three of the four dendrimer precursors ending in silanes,
i.e., first-generation ending in four and 12 Si-H groups, Si(CH2CH2-
SiMe2H)4 (1) and Si(CH2CH2SiH3)4 (2), respectively, as well as second-
generation ending in 36-H groups, Si[CH2CH2Si(CH2CH2SiH3)3]4 (3),
were synthesized according to literature procedures.6,8 The second-
generation dendrimer, Si[CH2CH2SiMe(CH2CH2SiMeH2)2]4 (4), that
terminates in 16 silane units was synthesized by the same procedures,
and data on this compound are provided below. Karstedt’s catalyst
(obtained as a 2-3% solution in xylenes) was purchased from PCR-
Lancaster and stored under nitrogen. Chloroplatinic acid and all other
chemicals were used as received from either of Aldrich.
Small-Angle X-ray Scattering. The small-angle X-ray scattering
(SAXS) measurements were made on the 7-m, pinhole collimated
instrument. This instrument has a Bruker (formerly Siemens) rotating
Cu anode X-ray generator with a high brilliance 0.3 × 0.3 mm focal
spot and a set of cross-coupled graded multilayer “mirrors”. The output
beam divergence is 0.04° fwhm, and its size at the sample position is
0.7 × 0.7 mm. The sample was contained in a 0.7 mm thick cell with
Kapton windows. The data were recorded with a Bruker “Hi-Star” two-
dimensional position sensitive proportional counter at point-to-point

Nonpolar Fluorinated Carbosilane Dendrimers
J. Am. Chem. Soc., Vol. 121, No. 48, 1999 11137
resolution of 0.2 mm over an area of 512 × 512 pixels. The sample-
to-detector distance was 2.75 m, and the beam path was fully evacuated.
Data were recorded for 3600-5000 s over a scattered wavevector, q,
range of 0.12-0.86 nm, where q ) 4π sinΘ/λ, 2Θ is the scattering
angle, and λ is the wavelength of the scattered radiation 0.1541 nm for
CuKR. A background of neat hexafluorobenzene, recorded for 60 000 s
was subtracted after correction for detector sensitivity, positional
nonlinearity, and transmission. The data were azmuthially averaged
into 200 bands having a constant width of q2. Data compromised by
scatter from the beam stop were removed.
the volatile contents, i.e., THF, 2-propanol, and excess olefin, as the
mixture warmed to room temperature. After 6 h under vacuum, the
glass reactor was filled with nitrogen and disconnected. Further handling
was done in open air. The polyfluoroether dendrimer 7 was obtained
as a viscous colorless liquid in 95% yield. IR, 1295, 1170 cm-1 ν(CH2-
OCH2). NMR (CDCl3 + Freon 113): 1H, δ 0.28 (s, 24H, Si(1)Me2),
0.66 (br, 16H, SiCH2CH2Si), 1.67 (br, 16H, SiCH2CH2CH2O), 3.59
(br, 8H, SiCH2CH2CH2O), 3.91 ppm (t, 8H, OCH2CF3); 13C{1H}, δ
0.4, 2.5, 7.1, 10.3, 24.0, 68.6, 121.3 ppm; 19F, δ -82.4, -120.7, -123.0,
-123.8, -124.4, -127.4 ppm. 29Si, δ 9.8 [Si(0)] and -3.2 ppm [Si(1)
]
in 7. MS (APcI) (m/z, species): 867, (M- - CF3). Elemental analysis
for C64H72O4F68Si5: Calcd.: C, 32.88; H, 3.06%. Found C, 32.36; H,
2.89%.
Syntheses. Synthesis of Si(0)[CH2CH2Si(1)Me(CH2CH2Si(2)MeH2)2]4
(4). The procedure used for synthesis of 4 is a modification of the ones
described in earlier literature.17,18 The following characteristic spec-
troscopic data were obtained for 4. IR, 2118 cm-1, ν(Si-H). NMR
(CDCl3): 1H, δ 0.13 (m, 36H, MeSi), 0.66 (s, 16H, Si(0)CH2CH2Si(1)),
0.92 (m, 32H, Si(1)CH2CH2Si(2)), and 3.6 ppm (J(Si-H) ) 192 Hz) (s,
Si(0){CH2CH2Si(1)Me2[CH2CH2Si(2)Me2(CH2CH2CH2OCH2-
CF3)2]2}4 (8). This procedure for the synthesis of dendrimer 8 is similar
to one described for 7. Yield, 93%. IR, 1290, 1175 cm-1 ν(CH2OCH2).
NMR (CDCl3 + Freon 113): 1H, δ 0.29 (s, 24,Si(1)Me2), 0.31 (s, 48H
Si(2)Me2), 0.66 (br, 16H, Si(0)CH2CH2Si(1)), 0.92 (br, 32 H, Si(1)Me2-
CH2CH2Si(2)) 1.67 (br, 64H, Si(2)Me2CH2CH2CH2O), 3.59 (br, 32H,
Si(2)Me2CH2CH2CH2O), 3.91 (t, 32H, Si(2)Me2CH2CH2CH2OCH2CF3);
13C{1H}, δ -0.6, -0.2, 1.3, 6.8, 9.6, 18.8, 22.5, 24.3, 60.5, 67.6, 123.9;
19F, δ -74.4, ppm. 29Si, δ 9.7 [Si(0)], 8.9 [Si(1)], -8.2 ppm [Si(2)] in 8.
MS (APcI) (m/z, species): 3280, M+ + 140. Elemental analysis for
16H, Si-H); 13C, δ -3.2, -0.6, 3.8, 5.6, 6.6, 7.8 (Si(0)CH2CH2Si(1)
-
MeCH2CH2Si(2)Me) ppm. 29Si, δ 10.3 [Si(0)], 8.9 [Si(1)] and -29.8 ppm
[Si(2)
]
Si(0){CH2CH2Si(1)Me2[CH2CH2Si(2)MeH2]2}4; MS(MALDI-
TOF): 895 [M+-1].
Synthesis of Allyl-1,1-Dihydrotrifluoroethyl Ether (5),
CH2dCHCH2OCH2CF3. Solid sodium trifluoroethoxide (25.0 g, 204.9
mmol) was dissolved in 30 mL of DMSO in a flame-dried 250 mL
two-necked flask connected with a three-way stopcock for nitrogen
gas inlet. This solution was maintained at 10 °C, and allyl bromide
(24.7 g, 204.1 mmol) was added dropwise such as to maintain the same
temperature throughout the reaction. Sodium bromide precipitated with
each drop of the allyl bromide into the stirring reaction mixture. The
reaction was allowed to slowly assume room temperature while stirring
for another 12 h. The colorless allyl-1,1-dihydrotrifluoroethyl ether was
distilled from the reaction mixture; bp ) 49 °C in 75% yield. IR, 1642,
992 ν(CHdCH2), 1297, 1181 ν(CH2OCH2), 1142 cm-1 ν(CF3). NMR
(CDCl3): 1H, δ 3.58-3.94 (t, 2H, CH2C8F17), 4.02 (d, 2H, CH2-
OCH2C8F17), 5.08-5.29 (td, 2H, CHdCH2), 5.65-5.90 ppm (m, 1H,
CH)H2); 13C{1H}, δ 133.1 [C(1)], 119.4 [C(2)], 73.0 [C(3)], 66.8, 68.7
[q, C(4)], 121.3 [q, C(5)] in C(1)H2dC(2)HC(3)H2OC(4)H2C(5)F3; 19F, δ
-74.6 ppm. MS (EI, 70 eV) (m/z, % intensity); M+, 140, 45.5; M -
CF3, 71, 100.
Synthesis of Allyl-1,1-dihydroheptadecafluorononyl Ether (6),
CH2dCHCH2OCH2C8F17. This procedure is a modification of the one
used in the synthesis of allyl-1,1-dihypentadecafluorooctyl ether.19 In
a flame-dried 100 mL two-necked flask, fitted with a magnetic stir-
bar and condenser and maintained under nitrogen flow was placed a
mixture of 12.50 g (27.78 mmol) of 1,1-dihydroperfluorononanol, 5.6
g (46.28 mmol) of allyl bromide, and 12 g (86.96 mmol) of oven dried
anhydrous potassium carbonate. To this was added 15 mL of acetone,
and the resulting mixture was refluxed under nitrogen flow for 84 h.
Afterward, the salts formed were removed by filtration in a Schlenk
system. Benzene (50 mL) was added to the filtrate followed by 10 mL
of water. Water was removed azeotropically from the clear solution
resulting by using the Dean and Stark system.19 The product was then
fractionated to obtain clear colorless allyl-1,1-dihydroheptadeca-
fluorononyl ether, CH2dCHCH2OCH2C8F17 (bp 57 °C/ 5 mmHg) in
70% yield. IR 1637, 991 ν(CHdCH2), 1297, 1178 ν(CH2OCH2). NMR
(CDCl3): 1H, δ 3.60-3.99 (t, 2H, CH2C8F17), 4.07 (d, 2H, CH2-
OCH2C8F17), 5.14-5.32 (td, 2H, CHdCH2), 5.74-5.94 ppm (m, 1H,
CH)H2); 13C, δ 132.9 [C(1)], 118.2 [C(2)], 73.2 [C(3)], 65.9, 66.4
[C(4)] 106-122 [m, C(5-13)] in C(1)H2dC(2)HC(3)H2OC(4)H2C(5-13)8F17;
19F, δ -82.4, -120.7, -123.0, -123.8, -124.4, -127.4 ppm. MS (EI,
70 eV) (m/z, % intensity); M+, 490, 20; M - C8F17, 71, 100.
Synthesis of the Carbosilane Dendrimers Terminating in Poly-
fluoroether Units. Si(0)(CH2CH2Si(1)Me2CH2CH2CH2OCH2CF3)4 (7).
An excess of allyl-1,1-dihydrotrifluoroethyl ether (1.56 g, 11.1 mmol),
two drops of 0.1 M chloroplatinic acid solution in 2-propanol, 3 mL
of THF, and 0.5 g (0.56 mmol) of the dendrimer hydride 1 were added
in that order into a flame-dried glass vessel (50 mL) under nitrogen
flow. The mixture was cooled to liquid nitrogen temperature, degassed,
sealed under vacuum, and left to gradually warm to room temperature.
The mixture was placed in an oven set to 70 °C for 24 h and gradually
cooled again to room temperature. The glass reactor was cooled in liquid
nitrogen, carefully opened, and connected to a vacuum line to remove
C
116H212O16F48Si13: Calcd.; C, 44.32; H, 6.70%. Found; C, 44.39; H,
6.76%.
Si(0)[CH2CH2Si(1)(CH2CH2CH2OCH2C8F17)3]4 (9). An excess of
allyl-1,1-dihydroheptadecafluorononyl ether (13.92 g, 28.4 mmol) and
a magnetic stir-bar are placed carefully under inert atmosphere transfer
conditions into a flame dried 50 mL three-necked flask fitted with a
condenser and connected with a nitrogen flow inlet through a three-
way stopcock. Two drops of 0.1 M chloroplatinic acid solution in
2-propanol was added, and the flask temperature was raised to 90 °C.
THF (5 mL) and 2 (0.50 g, 1.89 mmol] were added slowly from a
syringe needle. The reaction mixture was stored at this temperature
for 24 h. The product, Si[CH2CH2Si(CH2CH2CH2OCH2C8F17)3]4 (9),
was obtained by evaporating excess allyl-1,1-dihydroheptadeca-
fluorononyl ether and other volatile solvents under vacuum (∼0.05
mmHg) at 40 °C for 3 h. Residues of the catalyst were washed off
with chloroform. The fluorinated organosilicon product is insoluble in
chloroform, but its solution in 1,1,2-trichlorotrifluoroethane (Freon-
113) was filtered through a fine frit Schlenk-type filter. When the Freon-
113 was evaporated, the resulting product is a viscous, colorless liquid
(yield 10.70 g, 92%). IR 1292, 1169 cm-1 ν(CH2OCH2). NMR (CDCl3
+ Freon 113): 1H, δ 0.64 (br, 16H, Si(0)CH2CH2Si(1)), 1.73 (br, 48H,
Si(1)CH2CH2CH2O), 3.57 (br, 24H, Si(1)CH2CH2CH2O), 3.91 (t, 24H,
Si(1)CH2CH2CH2OCH2C8F17); 13C{1H}, δ 6.8, 9.6, 18.7, 22.5, 60.5, 67.6,
104-110 (m), 123.9 (t); 19F, δ -82.4, -120.7, -123.0, -123.8,
-124.4, -127.4 ppm. 29Si, δ 10.5 [Si(0)], -21.9 [Si(1)] in 9. Elemental
analysis for C152H112O12F204Si5: Calcd.; C, 29.69; 1.82%. Found; C;
28.87; H, 1.65%.
The other fluoroorganosilicon products {i.e., Si(0)[CH2CH2-
Si(1)Me2(CH2CH2CH2OCH2 C8F17)3]4 (10) and Si(0){CH2CH2Si(1)
-
[CH2CH2Si(2) (CH2CH2CH2OCH2C8F17)3]3}4 (11)} were obtained from
very similar procedure involving the respective carbosilane dendrimer
hydride substrate and allyl-1,1-dihydroheptadecafluorononyl ether. Their
characteristic data are stated below.
Si(0)[CH2CH2Si(1)Me2(CH2CH2CH2OCH2C8F17)]4 (10). Yield, 96%.
IR, 1290, 1174 cm-1 ν(CH2OCH2). NMR (CDCl3 + Freon 113): 1H,
δ 0.29 (s, 24H, Si(1)Me2), 0.64 (br, 16H, Si(0)CH2CH2Si(1)), 1.60 (br,
16H, Si(1)CH2CH2CH2O), 3.62 (br, 8H, Si(1)CH2CH2CH2O), 3.88 (t, 8H,
SiCH2CH2CH2OCH2C8F17); 13C{1H}, δ 0.5, 6.4, 9.2, 19.2 22.2, 61.3,
66.9, 122.6 (t); 19F, δ -82.5, -120.3, -123.2, -123.8, -124.1, -126.9
ppm; 29Si, δ 9.8 [Si(0)], -3.3 ppm [Si(1)] in 10. MS (APcI) (m/z, species);
2335, [M+ - 1]. Elemental analysis for C64H72O4F68Si5: Calcd.; C,
32.88; H, 3.06%. Found; C, 32.36; H, 2.89%.
Si(0){CH2CH2Si(1)[CH2CH2Si(2)(CH2CH2CH2OCH2C8F17)3]3}4 (11).
Yield, 95%. IR, 1298, 1170 cm-1 ν(CH2OCH2). NMR (CDCl3 + Freon
113): 1H, δ 0.68 (br, 16H, Si(0)CH2CH2Si(1)), 0.96 (br, 48 H,
Si(1)CH2CH2Si(2)) 1.65 (br, 48H, Si(1)CH2CH2CH2O), 3.64 (br, 72H, Si(1)-
CH2CH2CH2O), 3.95 (t, 72H, SiCH2CH2CH2OCH2C8F17); 13C{1H}, δ
6.3, 9.7 (SiCH2CH2Si), 21.9, 60.3, 67.3, 124.2 (t); 19F, δ -82.6, -120.5,

11138 J. Am. Chem. Soc., Vol. 121, No. 48, 1999
Omotowa et al.
-122.7, -123.4, -123.9, -128.1 ppm; 29Si, δ 10.1 [Si(0)], 8.9 [Si(1)],
-21.9 ppm [Si(2)] in 11. Elemental analysis for C464H352O36F612Si17:
Calcd.; C, 29.94; H, 1.89%. Found; C, 28.77; H, 1.80%.
Dr. Gary Knerr for some high resolution NMR and mass spectral
data. The small-angle X-ray scattering experiments described
in this manuscript were performed at the W. R. Wiley
Environmental Molecular Sciences Laboratory, Pacific North-
west National Laboratories, Richland, WA 99352.
Acknowledgment. Gratitude for financial support of this
work is expressed to the National Science Foundation (CHE-
9720635) and the ACS-Petroleum Research Fund. We thank
Dr. Andrzej Paszczynski of EBI for the APcI experiments and
JA992794R