7896 Quirk et al.
Macromolecules, Vol. 38, No. 19, 2005
Scheme 2
Synthesis of 3-[N,N-bis(trimethylsilyl)amino]-1-pro-
pene.30 A solution of allyl bromide (8.9 g, 45 mmol) in 5 mL
of hexamethyldisilazane (HMDS) was slowly added via can-
nula to a suspension of potassium N,N-bis(trimethylsilyl)amide
(5.1 g, 42 mmol) in 50 mL of HMDS under a dry argon
atmosphere at 0 °C and stirred for 1 h, followed by stirring at
room temperature overnight. The resulting slurry was filtered
through Celite 545 in the drybox to remove the precipitated
salts. The silyl-protected allylamine was isolated by fractional
vacuum distillation, yielding 5.2 g (26 mmol, 62% yield) of a
colorless, clear liquid (bp 85 °C at 35 mbar; lit.7 bp 82 °C at 30
mbar). 1H NMR: δ 0.106 (s, 18H, Si(CH3)3), 3.461 (d, 2H,
CH2N), 5.061 ppm (dd, 2H, CH2d), 5.791 (m, 1H, dCH). 13C
NMR: δ 2.152 (Si(CH3)3), 47.504 (CH2N), 113.500 (CH2d),
141.459 ppm (dCH).
Synthesis of 1-(Chlorodimethylsilyl)-3-[N,N-bis(trim-
ethylsilyl)amino]propane.30 Two drops of Karstedt’s cata-
lyst, 1,3-divinyltetramethyldisiloxane-platinum complex, was
added to a mixture of 3-[N,N-bis(trimethylsilyl)amino]-1-
propene (4.3 g, 21 mmol) and chlorodimethylsilane (4.1 g, 43
mmol) under a dry argon atmosphere at room temperature.
Immediately after injection of a drop of Karstedt’s catalyst,
an exotherm was observed with a color change to light yellow.
While stirring the solution overnight, a continuous color
change was observed from light yellow through deep yellow
to light brown. 1-(Chlorodimethylsilyl)-3-[N,N-bis(trimethyl-
silyl)amino]propane was isolated in 81% yield (4.9 g, 17 mmol)
by fractional vacuum distillation as a colorless, clear liquid
(bp 115 °C at 1 mbar; lit.30 bp 104 °C at 1 mbar). 1H NMR: δ
0.106 (s, 18H, Si(CH3)3), 0.422 (s, 6H, ClSiCH3), 0.705 (m, 2H,
ClSiCH2), 1.437 (m, 2H, CH2), and 2.766 ppm (m, 2H, NCH2).
13C NMR: δ 1.826 (ClSi(CH3)3), 2.305 (NSi(CH3)3), 16.571
(CH2), and 28.779 ppm (ClSi(CH3)2), 48.827 (NCH2).
Polymerizations. All polymerizations were effected in
benzene at room temperature using sec-butyllithium as initia-
tor in all-glass sealed reactors with breakseals and standard
high-vacuum techniques.31 The concentration of styrene to
benzene (mL/mL) was 10 vol %. After 12 h and prior to
functionalization, an aliquot of poly(styryl)lithium was trans-
ferred to an empty ampule, flame-sealed, and quenched with
degassed methanol.
Functionalizations of Poly(styryl)lithium. Functional-
ization of poly(styryl)lithium (22.6 g, 9.8 mmol, Mn ) 2.2 ×
103 g/mol, Mw/Mn ) 1.04) was effected directly in the polym-
erization reactor by smashing the breakseal for the ampule
containing chlorodimethylsilane (2.5 mL, 22.5 mmol) in ben-
zene at room temperature; loss of the red color and salt
precipitation were observed almost immediately. After 11 h,
the resulting solution was precipitated into an 8-fold excess
of anhyd methanol and stirred for 1 h. After filtration and
washing, the white solid polystyrene derivative was dried in
a vacuum oven, followed by further intensive drying on the
high-vacuum line for 48 h. The final silane end-functionalized
polystyrene was isolated in 98% yield.
that many reactive groups, e.g., primary and secondary
amine, hydroxyl, carboxyl, and thio, must be converted
to stable derivatives using suitable protecting groups.4,9-11
The synthesis of these protected functional group de-
rivatives is often a multistep process, and the protecting
groups must be removed after the functionalization
reaction.
Herein a general functionalization methodology is
described that involves first the quantitative termina-
tion of living polymeric organolithium compounds with
dimethylchlorosilane to form the corresponding ω-silyl
hydride functionalized polymer. The resulting silyl
hydride functionalized polymer can then react with a
variety of readily available substituted alkenes to form
the corresponding chain-end-substituted polymers via
efficient, regioselective transition metal catalyzed hy-
drosilation reactions (Scheme 2).12-15 Riffle and co-
workers16 first described this methodology to prepare
an epoxide-functionalized polymer by reacting poly-
(butadienyl)lithium (prepared in THF/cyclohexane) with
chlorodimethylsilane, hydrogenating the double bonds,
and then effecting hydrosilation with allyl glycidyl ether.
Recently, Loos and Mu¨ller17 prepared maltoheptaose-
block-polystyrene by the hydrosilation reaction of a silyl
hydride functionalized polystyrene (prepared in THF at
-78 °C) with trieicosaacetyl-N-allylmaltoheptaonamide.
One of the unrealized advantages of this methodology
is that the hydrosilation reaction is relatively insensitive
to anionically reactive functional groups such as car-
boxyl, phenol, and nitro, as well as primary and second-
ary amine groups, i.e., no protecting groups are re-
quired.14 The utility of this methodology is illustrated
herein by its application to the facile synthesis of
ω-primary amine functionalized polystyrene for which
few other simple, efficient anionic functionalization
procedures are available.7,8,18-27
Functionalizations of poly(styryl)lithium with benzene solu-
tions of 1-(chlorodimethylsilyl)-3-[N,N-bis(trimethylsilyl)-ami-
no]propane (3 mol equiv) were effected by breaking the
respective ampule connected directly to the reactor containing
poly(styryl)lithium. After 12-24 h, the functionalized polymers
were isolated by precipitation into excess anhyd methanol,
filtered, and dried.
Functionalization by Hydrosilation. Silane-functional-
ized polystyrene (3.0 g, 1.3 mmol, Mn ) 2200 g/mol), allylamine
(0.3 mL, 0.23 g, 4.0 mmol), and dry benzene (12 mL) were
added into a two-necked round-bottomed flask (25 mL) equipped
with a stopcock and septum in the drybox. The flask was then
removed from the drybox and was connected to a Schlenk line.
To the mixture was added 2 drops of Karstedt’s catalyst with
vigorous stirring under an argon atmosphere at room temper-
ature. The resulting solution was stirred for 72 h and subse-
quently precipitated into a 7-fold excess of anhyd methanol
followed by filtration and freeze-drying in benzene. Pure
functional polymer was obtained in 98% yield (3.0 g, 1.3 mmol).
Protected amine functionalized polystyrene was also syn-
thesized in good yield (3.1 g, 95%) by the same procedure
Experimental Section
Chemicals and Solvents. Styrene (99% Aldrich) and
benzene (EM Science, ACS grade) were purified as described
previously.28 sec-Butyllithium (FMC, Lithium Division; 12 wt
% in cyclohexane) was used as received after double titration
with allyl bromide.29 Chlorodimethylsilane (98% Aldrich) was
stirred over CaH2, vacuum transferred onto and stored over
activated 3 Å molecular sieves, followed by distillation into
calibrated, flame-sealed ampules. Potassium N,N-bis(trimeth-
ylsilyl)amide (95%, Aldrich) was used after evacuation and
drying under high vacuum. Allyl bromide (97%, Aldrich) was
purified by drying over CaCl2 followed by distillation. Karstedt’s
catalyst, 1,3-divinyltetramethyldisiloxane-platinum, (Gelest,
2.1-2.4% Pt conc in xylene) and hexamethyldisilazane (99%,
Aldrich, HMDS) were used as received. Allylamine (99%,
Aldrich) was dried over activated 3 Å molecular sieves. Argon
and nitrogen gases were passed through columns filled with
mixtures of alumina and deoxygenation catalyst (De-Ox, Alfa
Aesar) activated by heating at 250 °C under vacuum.