Macromolecules, Vol. 35, No. 15, 2002
Functionalized Polycarbosilanes 5747
structure and reactive sites in each repeat unit.6 Un-
modified, the polymer is not very useful due to its
extreme hydrolytic sensitivity, but upon substitution,
a whole family of derivative polymers of increased
stability, but with differing properties, can be produced.
diethyl ether via a cannula. The 4-pentenylmagnesium bro-
mide formed was titrated by the method described in ref 9 (0.14
mol, 82.4%). Following titration, a 1000 mL three-neck, round-
bottom flask equipped with a condenser, an addition funnel,
and a stir bar was flame-dried under vacuum. After purging
the flask with Ar, 500 mL of dry heptane was added via a
cannula. SiCl4 (11.4 g, 0.063 mol) was diluted with 10 mL of
dry heptane in a separate 25 mL pear-shaped flask and added
to the round-bottom flask via a cannula. The Grignard solution
was transferred to an addition funnel via a cannula and added
dropwise over 2 h. The solution was refluxed overnight,
forming a white precipitate. The product was separated from
magnesium salts by filter cannulation into a 1000 mL Schlenk
flask; the residual salts were washed with 3 × 100 mL portions
of pentane, and all organic solutions were combined. All
solvent was removed in vacuo, giving a crude yellow liquid
product. The product, a clear, colorless liquid, was purified by
vacuum spinning band distillation. Boiling point: 90-92 °C
Exp er im en ta l Section
Ma ter ia ls. Standard glovebox and Schlenk techniques were
used in the preparation of air- and moisture-sensitive com-
pounds. 5-Bromo-1-pentene was purchased from Aldrich and
stored over activated 4 Å molecular sieves. 1,2-Dibromoethane
(Aldrich) was distilled from CaH2 and stored over activated 4
Å sieves. SiCl4 (Aldrich) was transferred to a dried Kontes flask
via cannula and stored in an Ar atmosphere glovebox. Mag-
nesium turnings (Aldrich) were cleaned and dried in a vacuum
oven at 100 °C before use. MeLi [1.4 M in Et2O] (Acros), PhLi
[1.8 M in cyclohexanes-ether] (Aldrich), and n-BuLi [2.5 M
in hexanes] (Aldrich) were used as received and titrated
according to the method of Suffert.7 N-Phenyl-1-naphthyl-
amine was dried at 56 °C under vacuum using an Abderhalden
apparatus. Diethyl ether and pentane (Fisher) were dried and
distilled over NaK-benzophenone ketyl. Benzene and THF
(Fisher) were dried and distilled over K-benzophenone ketyl.
Heptane, o-xylene (Aldrich), and toluene (Fisher) were dried
by distillation over Na-benzophenone ketyl. Chloroform and
CH2Cl2 (Fisher) were dried by distillation over P2O5. Methanol
(Fisher) was dried by distillation over Mg/I2 and stored over 3
Å sieves. Deuterated solvents (without TMS), C6D6 and CDCl3
(CIL), without TMS were dried by distillation over CaH2.
Schrock’s [Mo] catalyst 1, [ModCHCMe2Ph(dN-C6H3-i-Pr2-
2,6)(OCMe(CF3)2)2], was prepared using a literature proce-
dure.8
1
(4 mmHg), % yield (GC): 71%, isolated: 8.8 g, 38%. H NMR
(δ, CDCl3): 1.10 (Si-CH2) (m, 4H), 1.59 (CH2) (m, 4H), 2.10
(CH2CH) (m, 4H), 4.98 (CH2CH) (m, 2H), 5.74 (CHCH2) (m,
2H). 13C NMR (δ, CDCl3): 19.7 (Si-CH2), 21.7 (CH2), 36.2
(CH2CH), 115.5 (CHCH2), 137.7 (CHCH2). 29Si NMR (δ,
C6D6): 33.3 (R2SiCl2). Elemental Anal. for C10H18SiCl2: Calcd
(Found): C, 50.84 (50.79); H, 7.68 (7.78).
Syn th esis of P oly(1,1-d ich lor o-1-sila n on -5-en e) (3). A
25 mL round-bottom flask containing a Teflon stirbar and
equipped with an air-free Schlenk adapter was taken into an
inert atmosphere glovebox, and 0.72 g (0.0030 mol) of di(4-
pentenyl)dichlorosilane was added. Schrock’s catalyst 1 was
added (4.8 mg, 6.3 × 10-6 mol) in a monomer-to-catalyst ratio
of 500:1 (0.2%) to the liquid monomer; the evolution of ethylene
was immediate and vigorous. The flask was closed, taken out
of the glovebox, and connected to a high-vacuum line and
stirred with intermittent vacuum applied. Bubbling due to the
evolution of ethylene continued, and after 5 h, stirring was
hindered considerably due to increased solution viscosity. The
flask was then subjected to dynamic vacuum (1 × 10-4 mmHg),
the temperature was increased to 40 °C, and the contents of
the flask were stirred slowly for 48 h. After this time period,
stirring ceased, and the polymerization procedure was stopped
by exposure of the flask contents to air that was carefully dried
by passing through a drierite/molecular sieve column. The
flask was taken into the glovebox due to the high hydrolytic
sensitivity of the polymer. The resulting dichlorocarbosilane
polymer was soluble in hydrocarbon solvents such as toluene
and benzene but insoluble in more polar media such as CHCl3
and THF. The polymer was used for further functionalization
without any additional purification. Using spectroscopy, only
linear polymer and no cyclic byproducts were observed. 1H
NMR (δ, C6D6): 0.90 (SiCH2) (br, 4H), 1.45 (CH2) (br, 4H), 1.90
(CH2CH) (br, 4H), 5.40 (CH) (br, 2H). 13C NMR (δ, C6D6): 20.0
(SiCH2), 22.6 (CH2), 35.3 (CH2CH), 130.6 (CH). 29Si NMR (δ,
C6D6): 33.5 (R2SiCl2). Elemental Anal. for C10H18SiCl2: Calcd
(Found): C, 46.15 (45.64); H, 6.78 (6.65); Cl, (33.62) 27.28.
Syn th esis of P oly(1,1-d im eth yl-1-sila n on -5-en e) (4). Di-
(4-pentenyl)dichlorosilane (0.56 g, 0.0024 mol) was polymerized
in a 25 mL flask using 350:1 monomer:catalyst ratio of [Mo]
catalyst 1 under typical ADMET conditions. After backfilling
the flask with Ar, the polymer was dissolved in 15 mL of dry
benzene and chilled to 0 °C using an ice bath. A 2-fold excess
of 1.4 M MeLi per Si-Cl bond was added (5.8 mL, 0.0093 mol)
via a syringe dropwise over 15 min. White LiCl salts precipi-
tated out of solution as the alkyllithium reagent was added.
The contents of the flask were stirred overnight under Ar and
slowly allowed to warm to room temperature (RT). The
reaction mixture was then transferred via a cannula needle
into a Schlenk flask containing 200 mL of cold, dry MeOH.
The alkyllithium solution color disappeared, all LiCl salts
dissolved, and a tacky white polymer precipitated from solu-
tion. All solvents were then removed via a cannula, and the
resulting off-white polymer was dried for 24 h in vacuo at RT.
Yield after precipitation: 0.31 g, 78%. 1H NMR (δ, CDCl3):
-0.08 (SiCH3) (s, 6H), 0.46 (CH2) (br, 4H), 1.31 (CH2) (br, 4H),
1.97 (CH2CH) (br, 4H), 5.36 (CH) (br, 2H). 13C NMR (δ, CDCl3):
In str u m en ta tion . All NMR spectra, 1H (300 MHz), 13C (75
MHz), and 29Si (60 MHz), were conducted on either a Varian
VXR, Gemini, or Mercury series superconducting spectrometer
system and referenced to residual C6H6 or CHCl3 solvent
signals. For the 29Si NMR spectra, a heteronuclear gated
decoupling pulse sequence with a pulse delay of 30 s was used,
with a 1% internal TMS reference added. Gas chromatography
was performed on a Shimadzu GC-17A gas chromatograph
equipped with a 15 m Restek RTX-5 cross-bonded 5% di-
phenyl-95% dimethylsiloxane column using He as the carrier
gas and a FID detector. Gel permeation chromatography was
performed using two 300 mm Polymer Laboratories gel 5 µm
mixed-C columns. The GPC instrument consisted of a Rainin
SD-300 pump, a Hewlett-Packard 1047-A RI detector, a Kratos
Spectroflow 757 UV detector (254 nm), a TC-45 Eppendorf
column heater set to 30 °C, and a Waters U6K injector. The
solvent used was CHCl3 at a flow rate of 1.0 mL/min, and the
peaks were referenced to narrow polydispersity polystyrene
standards from Polymer Laboratories (Amherst, MA). Dif-
ferential scanning calorimetry measurements were taken
using a Perkin-Elmer DSC 7 instrument equipped with TAC
7/DX controller and a CCA7 cooling accessory. The samples
were scanned from -95 to 75 °C at a heating rate of 10 °C/
min after annealing the samples to destroy any thermal
history. Liquid N2 was used as the coolant. Spinning band
distillation was performed using a B&R Instruments model
8T regulated with a dibutylphthlate-filled manostat. Elemental
analyses were performed by Atlantic Microlab (Norcross, GA).
Syn th esis of Di(4-p en ten yl)d ich lor osila n e (2). A 500
mL three-necked flask equipped with an addition funnel, a
condenser, and a Teflon stirbar was flame-dried under vacuum.
The apparatus was then flushed with Ar, and 4.9 g of Mg
turnings (0.20 mol) was weighed and added to the flask.
Freshly distilled dry diethyl ether (175 mL) was added to the
flask via a cannula, followed by the addition of 0.2 mL of 1,2-
dibromoethane. Bubbling ensued, and the gray mixture was
stirred at room temperature for 1 h. 5-Bromo-1-pentene (25.3
g, 0.17 mol) was added dropwise via an addition funnel over 2
h. The reagent was refluxed overnight, followed by removal
of insoluble material by filter cannulation into a 250 mL
volumetric flask fitted with an air-free adapter. This gray
solution was filled to the volume mark with additional dry