Macromolecules, Vol. 37, No. 11, 2004
p-n-Alkyl-Substituted Polystyrenes 3977
Ta ble 1. Ch a r a cter iza tion of p-Alk yl-Su bstitu ted Styr en es
characterization
substituent
n-hexyl-
65% yield, colorless liquid; IR (neat): 3050 (C-H at sp2), 2925, 2852 (C-H), 1629 cm-1 (CdC); 1H NMR (CDCl3):
δ ) 0.89 (t, 3H), 1.30 (m, 6H), 1.61 (quintet, 2H), 2.60 (t, 2H), 5.20 (q, 1H), 5.70 (q, 1H), 6.71 (q, 1H) and 7.15 &
7.33 (q, 4H) ppm; 13C NMR (CDCl3): δ ) 14.60, 23.21, 29.55, 31.90, 32.27, 36.25, 113.01, 126.41, 128.80, 135.35,
137.10, and 143.01 ppm
n-octyl-
83% yield, colorless liquid; IR (neat): 3054 (C-H at sp2), 2928, 2859 (C-H), 1632 cm-1 (CdC); 1H NMR(CDCl3):
δ ) 0.89 (t, 3H), 1.29 (m, 10H), 1.59 (quintet, 2H), 2.59 (t, 2H), 5.20 (q, 1H), 5.72 (q, 1H), 6.70 (q, 1H) and 7.15 &
7.32 (q, 4H) ppm; 13C NMR (CDCl3): δ ) 14.60, 23.10, 29.72, 29.90, 31.90, 32.29, 36.15, 113.21, 126.31, 128.71,
135.21, 137.10, and 143.01 ppm
n-decyl-
n-dodecyl-
88% yield, colorless liquid; IR (neat): 3050 (C-H at sp2), 2923, 2855 (C-H), 1629 cm-1 (CdC); 1H NMR (CDCl3):
δ ) 0.88 (t, 3H), 1.28 (m, 14H), 1.57 (quintet, 2H), 2.55 (t, 2H), 5.15 (q, 1H), 5.68 (q, 1H), 6.67 (q, 1H) and 7.10 &
7.29 (q, 4H) ppm; 13C NMR (CDCl3): δ ) 14.64, 23.22, 29.90, 31.96, 32.42, 36.19, 112.99, 126.39, 128.82, 135.29,
137.02, and 142.94 ppm
92% yield, colorless liquid; IR (neat): 3050 (C-H at sp2), 2926, 2855 (C-H), 1629 cm-1 (CdC); 1H NMR (CDCl3):
δ ) 0.89 (t, 3H), 1.30 (m, 18H), 1.61 (quintet, 2H), 2.60 (t, 2H), 5.18 (q, 1H), 5.69 (q, 1H), 6.71 (q, 1H) and 7.15 &
7.33 (q, 4H) ppm; 13C NMR (CDCl3): δ ) 14.42, 23.00, 29.62, 29.90, 31.76, 32.24, 36.00, 112.99, 126.38, 128.83,
135.30, 137.03, and 143.00 ppm
spectra.17 The purity of the resulting styrene derivatives was
>99% as determined by HPLC and TLC analyses. The
characterization data for the synthesized p-alkyl-substituted
styrenes are listed in Table 1.
Exp er im en ta l Section
Ma ter ia ls. All materials were handled in a Schlenk line,
in a high-vacuum apparatus, or in a drybox.13,14 Styrene
(Aldrich, >99%) and p-methylstyrene (Aldrich, 96%) were dried
over calcium hydride for 2 days and distilled under high
vacuum before use. Toluene (Fisher, reagent grade) was dried
over calcium hydride for 2 days and sodium/benzophenone for
P olym er iza tion s. All polymerizations were performed
using a 300 mL Bu¨chi Mini-Clave glass reactor with
a
magnetic stirrer under a N2 atmosphere. In a drybox, the fully
dried glass reactor equipped with a thermocouple, and a
catalyst injector was filled with toluene, styrene monomer, and
powdered MAO as cocatalyst. The required amount of catalyst
[(Me)5CpTi(OMe)3] and 5 mL of toluene were added into the
catalyst injector. Then, the reactor was placed into a water
bath preheated to 50 °C. When temperature was equilibrated,
the catalyst solution was injected into the solution, stirred for
90 min, and then terminated by adding 5 mL of acidic
methanol (10 vol % HCl). The resulting polymers were
precipitated into 500 mL of acidic methanol, filtered, washed
with methanol, and dried under vacuum at 60 °C for 12 h.
2
days and then distilled under high vacuum before
use. Cyclopentadienyltitanium trichloride (CpTiCl3, 97%, Al-
drich) and pentamethylcyclopentadienyltitanium trimeth-
oxide [(Me)5CpTi(OMe)3, 95%, Aldrich] were used as received.
Methylaluminoxane (MAO, 30 wt % in toluene, Albemarle) was
evacuated under high vacuum for 3 days to remove toluene
and free methylaluminum and then stored in a drybox under
an argon atmosphere and used as a white granular solid.15
An empirical formula of C5.5H17.5Al4O4 for the solid sample
which approximately corresponds to the tetramer structure
of MAO15 was obtained from elemental analysis done by
Galbraith Laboratories Inc.16
1
Ch a r a cter iza tion . H NMR spectra of the p-alkyl-substi-
tuted styrenes were recorded on
a Varian Mercury 300
Syn th esis of p-Alk yl-Su bstitu ted Styr en e Der iva tives.
The synthetic route was based on Wang’s work.12 Acetic
anhydride (89.8 g, 0.88 mol in 100 mL of CH2Cl2) was added
to a stirred mixture of AlCl3 (227 g, 1.76 mol) in CH2Cl2 (800
mL) at 0 °C over 30 min. After stirring for 15 min at 0 °C, a
solution of alkylbenzene (0.4 mol) in CH2Cl2 (100 mL) was
slowly added over 30 min and stirred for 5 h at room
temperature. Then, the reaction mixture was poured onto
crushed ice (1500 mL). The separated organic layer was
washed sequentially with 10% aqueous HCl solution (2 × 500
mL), saturated aqueous Na2CO3 (2 × 500 mL), and brine (2 ×
500 mL), dried over anhydrous MgSO4, and concentrated. The
resulting p-alkylacetophenone was purified by crystallization
from methanol.
To a stirred mixture of 0.3 mol of p-alkylacetophenone in
1000 mL of MeOH, 0.09 mol (3.4 g) of sodium borohydride was
slowly (10 aliquots, 5 min) added at 0 °C. The mixture warmed
to room temperature and was stirred for 2 h. After methanol
was removed using a rotary evaporator, 1000 mL of n-hexane
was added. The hexane solution was washed sequentially with
10% aqueous HCl solution (2 × 500 mL) and brine (2 × 500
mL), dried over anhydrous MgSO4, filtered, concentrated, and
crystallized at low temperature (∼-20 °C) to obtain p-
(alkylphenyl)methylcarbinol.
To a solution of 0.052 mol of (p-alkylphenyl)methylcarbinol
in 500 mL of toluene in a flask equipped with a Dean-Stark
trap was added 0.26 g (2 mol %) of p-toluenesulfonic acid
monohydrate. The solution was heated to reflux, stirred for 2
h, allowed to cool to room temperature, washed with H2O (500
mL), dried over anhydrous MgSO4, and concentrated to a
colorless liquid identified as p-alkylstyrene. The resulting
product was purified by column chromatography using acti-
vated basic alumina as support and n-hexane as eluent. The
substitution reactions were observed to occur exclusively at
the para position on the phenyl ring as determined by the AB
splitting patterns for the aromatic protons in 1H NMR
spectrometer operating at 300 MHz with CDCl3 solvent and
TMS as reference at 30 °C. 13C NMR analyses of the alkyl-
substituted styrenes and the resulting polymers were per-
formed using a Varian Mercury 300 spectrometer operating
at 75 MHz in CDCl3 solvent at 30 °C and a Bruker DRX 500
spectrometer operating at 125 MHz in a solvent mixture of
1,2,4-trichlorobenzene (TCB) and C6D6 (7/3 w/w) at 120 °C.
1
An inverse gated H-decoupling mode and 10 s of pulse delay
time were applied for the polymers in both 13C NMR experi-
ments. FTIR spectra of neat synthesized monomer samples
on a KBR window were obtained on a Mattson Genesis Series
FTIR. HPLC chromatograms of the monomers were obtained
using a Waters 501 HPLC with a Zorbax column and diode
array detector at 30 °C in cyclohexane solvent. Thin-layer
chromatography analyses were carried out on silica gel plates
(Eastman Kodak silica gel chromatogram sheet 131811) with
n-hexane as eluent. The molecular weights and molecular
weight distributions of the polymers were measured with a
Waters 150C GPC equipped with three Waters HR columns
(Styragel HR1 100 Å, Styragel HR 4E 50-104 Å, and Styragel
HR SE 100-106 Å) in THF at 30 °C and with a PL 210 GPC
equipped with two PLgel 10 µm mixed-B columns in TCB
solvent at 135 °C using calibration with polystyrene standards.
Thermal properties (Tg and Tm) were measured using a Dupont
DSC 2910 at 10 °C/min heating rate under a N2 atmosphere.
DSC thermograms were obtained during second heating. Wide-
angle X-ray diffraction measurements for the as-polymerized
samples were carried out using a Rigaku X-ray diffractometer
with Cu KR radiation at the ambient temperature.
Resu lts a n d Discu ssion
As shown in Table 1, p-alkyl-substituted styrenes
with different alkyl group lengths were synthesized in
high purity and in relatively high yields. These mono-