Synthesis of novel-dl-α-tocopherol-based and sterically-hindered-phenol-based monomers and their utilization in copolymerizations over metallocene/MAO catalyst systems. A strategy to remove concerns about additive compatibility and migration

Article abstract of DOI:10.1021/ma0205008

In this paper we present an initial study on various synthetic routes to novel polymerizable dl-α-tocopherol derivatives and to a styrenic sterically hindered phenol which was stimulated by our desire to conduct copolymerization with these monomers with α-olefins over different metallocene/ methylalumoxane (MAO) catalyst systems. The syntheses of 6-hydroxyl-2,5,7,8-tetramethyl-2-(but-3-enyl)-chroman (1) and 5,7,8-trimethyl-3-(hex-5-enyl)benzofuran-6-ol (2-) were achieved by cyclocondensation of trimethylhydroquinone (TMHQ) with 3-methylhept-1,6-dien-3-ol and 2,7-octadienol, respectively. However, the latter tocopherol compound (2) could only be obtained in low yields, and all our attempts to isolate the product from its ring-opened isomers failed. This can be attributed to the fact that the reaction between TMHQ and 2,7-octadienol gave rise to a highly complex reaction mixture. Compound 3, 6-hydroxyl-2,2,8,9-tetramethyl-6-allylchroman, was prepared from the corresponding allylchromanoxy ether via Claisen rearrangement. In addition facile synthetic pathways to 4-methylene(3,5-di-tert-butyl-4-phenoxy)styrene (4) and its trimethylsilylated derivative 5, i.e., 4-methylene(3,5-di-tert-butyl-4-trimethylsiloxyphenyl)-styrene, were successfully developed. The chromanol 1 was copolymerized with ethylene over a rac-[dimethylsilylenebis(4,5,6,7-tetrahydro-1-indenyl)]zirconium dichloride/MAO catalyst system, and monomers 4 and 5 were copolymerized with styrene over an (η⁵-indenyl)trichlorotitanium (IndTiCl₃)/MAO catalyst system. The copolymers contained from 2.3 to 6.8 wt % functional units and exhibit enhanced thermooxidative stabilities in comparison to the corresponding homopolymers as determined by TGA and DSC analysis.

Full text of DOI:10.1021/ma0205008

8346
Macromolecules 2003, 36, 8346-8352
Synthesis of Novel-dl-R-Tocopherol-Based and
Sterically-Hindered-Phenol-Based Monomers and Their Utilization in
Copolymerizations over Metallocene/MAO Catalyst Systems. A Strategy
To Remove Concerns about Additive Compatibility and Migration
Ma r k k u Au er ,† Ron a n Nicola s,‡ Ar i Roslin g,‡ a n d Ca r l-Er ic Wile´n *,§
Laboratory of Polymer Technology, Åbo Akademi University, Biskopsgatan 8, Fin-20500 Åbo, Finland,
VTT Chemical Technology, Espoo, Finland, and Borealis Polymers Oy, P.O. Box 330,
Fin-06101 Porvoo, Finland
Received March 28, 2002; Revised Manuscript Received J uly 14, 2003
ABSTRACT: In this paper we present an initial study on various synthetic routes to novel polymerizable
dl-R-tocopherol derivatives and to a styrenic sterically hindered phenol which was stimulated by our
desire to conduct copolymerization with these monomers with R-olefins over different metallocene/
methylalumoxane (MAO) catalyst systems. The syntheses of 6-hydroxyl-2,5,7,8-tetramethyl-2-(but-3-enyl)-
chroman (1) and 5,7,8-trimethyl-3-(hex-5-enyl)benzofuran-6-ol (2) were achieved by cyclocondensation of
trimethylhydroquinone (TMHQ) with 3-methylhept-1,6-dien-3-ol and 2,7-octadienol, respectively. However,
the latter tocopherol compound (2) could only be obtained in low yields, and all our attempts to isolate
the product from its ring-opened isomers failed. This can be attributed to the fact that the reaction between
TMHQ and 2,7-octadienol gave rise to a highly complex reaction mixture. Compound 3, 6-hydroxyl-2,2,8,9-
tetramethyl-6-allylchroman, was prepared from the corresponding allylchromanoxy ether via Claisen
rearrangement. In addition facile synthetic pathways to 4-methylene(3,5-di-tert-butyl-4-phenoxy)styrene
(4) and its trimethylsilylated derivative 5, i.e., 4-methylene(3,5-di-tert-butyl-4-trimethylsiloxyphenyl)-
styrene, were successfully developed. The chromanol 1 was copolymerized with ethylene over a
rac-[dimethylsilylenebis(4,5,6,7-tetrahydro-1-indenyl)]zirconium dichloride/MAO catalyst system, and
monomers 4 and 5 were copolymerized with styrene over an (η5-indenyl)trichlorotitanium (IndTiCl3)/
MAO catalyst system. The copolymers contained from 2.3 to 6.8 wt % functional units and exhibit enhanced
thermooxidative stabilities in comparison to the corresponding homopolymers as determined by TGA
and DSC analysis.
In tr od u ction
phenol (BHT) and 2-tert-butyl-4-methoxyphenol (BHA)
as antioxidants for polyolefins in many applications.
All organic materials, including polyolefins, are sus-
ceptible to oxidation in a process called “autoxidation”.1
This degradation process is irreversible and leads
ultimately to polymer discoloration and loss of physical
properties. Primary antioxidants, known as radical
scavengers, are intended to interfere with the afore-
mentioned degradation process, and they prevent the
process from becoming autocatalytic.2 R-Tocopherol, or
vitamin E, is a fully substituted aromatic chromanol
with a phenolic group situated para to the oxygen of
the chroman ring. This antioxidant molecule, which has
been perfected by nature, is well-known as an effective
inhibitor of oxy radicals such as hydroxyl, alkoxyl,
hydroperoxyl, phenoxyl, and other reactive species
associated with oxidative damage in biological systems.
Thus, tocopherols are implemented to prevent oxidative
stress of lipid organelles, particularly the plasma mem-
brane.3 More recently, chemically synthesized versions
of vitamin E derivatives such as 2,5,7,8-tetramethyl-2-
(4′,8′,12′-trimethyltridecyl)-6-chromanol have shown po-
tential as stabilizers for polyolefins, especially in food
packaging and medical applications.4 The current trend
seems to be that vitamin E is displacing the conven-
tional mononuclear phenols such as 2,6-di-tert-butyl-
Health authorities in many countries within the
European Union (EU) and United States have stipu-
lated strict directives and legislation to control the use
of additives in plastics to minimize contamination risks
associated with migration of additives into the human
environment.5 Recently, concerns have been raised
especially about the role of hormone-like additives such
as hydroxylbiphenyls, alkylphenols, phthalates, etc.
which may exhibit adverse effects on male reproduction
in wildlife and laboratory animals due to their xe-
noestrogenic activity.6 As a rule, all low molecular
weight antioxidants in plastic materials are prone to
physical depletion and therefore constitute a potential
threat to the environment after leaching and/or migra-
tion from the host polyolefin. For instance, the migration
of R-tocopherol from LDPE into various food simulators
was shown to be highest in olive oil and in the fatty
food simulator heptane.7
As a consequence of this and to enhance the properties
of polyolefins in regard to adhesion, dyeability, and
compatibility, we have started to investigate polymer-
bound stabilizers.8 In this paper we report the synthesis
of 6-hydroxyl-2,5,7,8-tetramethyl-2-(but-3-enyl)chroman
(1), 5,7,8-trimethyl-3-(hex-5-enyl)benzofuran-6-ol (2),
and 6-hydroxyl-2,2,8,9-tetramethyl-6-allylchroman (3),
i.e., the synthetic route to three novel polymerizable
analogues of tocopherols and the copolymerization of 1
with ethylene over a rac-[dimethylsilylenebis(4,5,6,7-
tetrahydroindenyl)zirconium dichloride/methylalumox-
* To whom correspondence should be addressed. E-mail:
carl-eric.wilen@borealisgroup.com or cwilen@abo.fi.
† VTT Chemical Technology.
‡ Åbo Akademi University.
§ Borealis Polymers Oy.
10.1021/ma0205008 CCC: $25.00 © 2003 American Chemical Society
Published on Web 09/30/2003

Macromolecules, Vol. 36, No. 22, 2003
Synthesis of Tocopherol- and Phenol-Based Monomers 8347
from the glovebox, and the polymer was precipated from
methanol and washed with an excess of methanol. The product
was dried in an oven at 75-80 °C overnight. The polymer was
then extracted with 2-butanone for 48 h in a Soxhlet extractor
to remove any atactic polymer or residual comonomer.
ane (MAO) catalyst system. In addition, the synthetic
pathways to 4-methylene(3,5-di-tert-butyl-4-phenoxy)-
styrene (4) and its siloxy-functionalized analogue 4-
methylene(3,5-di-tert-butyl-4-trimethylsiloxyphenyl)sty-
rene (5) and their syndiospecific copolymerization with
styrene over an (η5-indenyl)trichlorotitanium (IndTiCl3)/
MAO catalyst system are also described.
P olym er Ch a r a cter iza tion . The melting temperatures
and enthalpies of the polymers were determined using a
Perkin-Elmer DSC 7 instrument. The samples were heated
twice (heating rate 10 or 20 °C/min in the case of homo- and
copolymers of syndiotactic polystyrene), and the second heating
curve was analyzed. The crystallinities were determined from
the DSC curves using the heat of fusion of folded-chain
polyolefin crystals (293 J /g for PE11 and 208 J /g for SPS12).
Molecular weights and molecular weight distributions were
determined by size exclusion chromatography on a Polymer
Laboratories instrument equipped with a Waters Styragel or
PLG gel MIXED-B column (exclusion limits for polystyrene
103, 104, 105, and 106 Å) in 1,2,4-trichlorobenzene at 135 °C
(flow rate 1 mL/min). The basic calibration was made by using
polystyrene standards with narrow molecular weight distribu-
tions and universal calibration using linear low-density poly-
ethylene and polystyrene, respectively. 13C and 1H NMR
spectra of polymers were recorded from solutions of 70-100
mg of polymer in 0.4 mL of C2D2Cl4 or 1,2,4-trichlorobenzene
at 120 °C. The spectrum was recorded using a 45° pulse by
applying single-pulse excitation with gated decoupling to
suppress NOE. The amount of bound chromanol was deter-
mined by UV analyses, and the numerical values were based
upon polypropylene/vitamin E standard films, which had a
thickness of ∼70 µm. UV-vis spectra were obtained with a
Schimadzu UV-240 spectrometer. Spectra were recorded be-
tween 220 and 350 nm. The chromanol exhibits a strong
absorbance in this region at 280 nm, and all measurements
were carried out at this wavelength. The oxidation induction
temperature was determined from data recorded during heat-
ing at a rate of 10 °C/min and keeping the sample under a
constant oxygen flow (30 mL/min). The DSC was calibrated
with an indium standard (Tfus ) 156.6 °C). A polymer sample
(∼6 mg) was placed in an aluminum pan and heated at 10
°C/min. The oxidation temperature was determined by ex-
trapolating the exotherm associated with the beginning of
oxidation to the baseline of the trace. A Mettler Toledo TA8000
system equipped with a TGA850 thermobalance was used for
thermal analyses (TG and SDTA). A heating rate of 10 °C/
min (starting from 25 °C and ending at 600 °C) was used under
an atmosphere of flowing nitrogen or air.
P r ep a r a tion of 6-Hyd r oxy-2,5,7,8-tetr a m eth yl-2-(bu t-
3-en yl)ch r om a n (1). To vinylmagnesium chloride (0.4 mol)
in THF (160 mL) was added dropwise a solution of 5-hexen-
2-one (24.8 g, 0.25 mol) in anhydrous THF (150 mL). After
being stirred at room temperature for 20 h, the reaction
mixture was cautiously poured into 450 mL of cold saturated
aqueous NH4Cl solution. The organic phase was concentrated
and extracted with dichloromethane, dried over Na2SO4, and
concentrated. The residue was distilled, giving 19.0 g (61.6%)
of 3-methylhept-1,6-dien-3-ol, bp 45 °C, 10 mmHg. Then 3.73
g (29.6 mmol) of 3-methylhept-1,6-dien-3-ol together with
trimethylhydroquinone (4.5 g, 29.6 mmol) was dissolved in 10
mL of formic acid (98%) in a 50 mL flask. The solution was
heated to reflux and stirred at this temperature for 3 h. The
reaction mixture was poured onto crushed ice and extracted
with diethyl ether (3 × 50 mL). The organic phase was
separated and filtered. After removal of solvent, the residue
was dissolved in methanol, 1 mL of concentrated HCl was
added, and the solution was refluxed for 30 min to hydrolyze
the formate ester of 1. The solvent was evaporated and the
residue dissolved in diethyl ether. The organic phase was
washed with water and aqueous saturated sodium carbonate
solution and again with water. The organic phase was dried
over anhydrous sodium sulfate, filtered, and concentrated
under reduced pressure to afford 4.33 g (54%) of 6-hydroxy-
2,5,7,8-tetramethyl-2-(but-3-enyl)chroman after distillation,
bp 151 °C, 1 mmHg. MS: m/e (rel intens) M+ 260 (69), 205
(9), 165 (100), 121 (10), 91 (7), 55 (7). 1H NMR (CDCl3, δ): 1.22
(s, 3H, CH3C(2)); 1.65 (m, 2H, ArCH2CH2-); 1.8 (m, 4H,
Exp er im en ta l Section
Ma ter ia ls. All materials used for the preparation of 1-5
were of reagent grade and purchased from Aldrich or Tokyo
Chemical Industry (TCI). The rac-[dimethylsilanylenebis-
(4,5,6,7-tetrahydro-1-indenyl)]zirconium dichloride was pre-
1
pared according to the literature.9 The H NMR spectra of the
monomers and intermediates were recorded in CDCl3 relative
to that of TMS on a J EOL J NM-A-500 or J EOL J NM-L-400
spectrometer. The carbon nuclear magnetic resonance spectra
were determined on a J EOL 500 operating at 125.78 MHz;
chemical shifts in the proton-decoupled spectra are reported
in parts per million downfield from the peak of TMS. GC-MS
analyses were performed with an HP 5890 gas chromatograph
and an HP 5970 mass-selective detector. The ionizing potential
was 70 eV. Mass spectral peaks are given in units of mass per
charge followed by the relative peak intensity in parentheses.
High-purity ethylene and propylene were further purified over
a series of columns containing molecular sieves, CuO, and
Al2O3. High-purity toluene was refluxed over sodium and
subsequently distilled under an argon atmosphere. MAO (10%
w/w toluene) was purchased from Witco and used as received.
P olym er iza tion P r oced u r e. The sampling of catalyst,
activator, and functional monomers was carried out under
nitrogen in an MBRAUN glovebox containing <2 ppm oxygen
and <5 ppm water. The reaction temperature was controlled
within (0.3 °C by a Lauda Ultra circulating water bath.
However, during the first 5 min an increase of temperature
by 3-5 °C could be observed. The slurry ethylene polymeriza-
tions were carried out in a 0.5 L jacketed glass autoclave
(Bu¨chi, Switzerland) equipped with a blade turbine stirrer. The
dry glass autoclave was evacuated and back-flushed with
nitrogen. This procedure was repeated several times. Then 250
mL of freshly distilled toluene was pumped into the autoclave.
Half of the methylalumoxane/toluene solution to be used was
added to the reactor together with tocopherol monomer and
stirred for 30 min. After 25 min the metallocene catalyst was
dissolved in the remaining amount of the MAO/toluene solu-
tion and preactivated for 5 min by allowing the resulting
mixture to stand at room temperature. Then the catalyst/
activator mixture was charged into the reactor by using an
ethylene overpressure. The pressure of ethylene was kept
constant by controlling the gas feed automatically over the
entire reaction period with a Bu¨chi Pressflow gas controller,
model bpc 1202. The copolymerization was quenched after 20
min by rapidly venting ethylene and adding 100 mL of ethanol.
The catalyst residues of the produced copolymer were removed
by treatment with 1 L of ethanol containing 40 mL of 10%
HCl solution overnight. After filtration, the copolymer was
washed again twice with ethanol, dried in a vacuum, and
weighted to determine the polymerization yield. The copoly-
mers were extracted with refluxing 2-propanol/cyclohexane10
(volume ratio 1:1) for 24 h in a Soxhlet apparatus prior to the
determination of the amount of bound chromanol and ther-
mooxidative studies.
The syndiospecific styrene homo- and copolymerizations
were carried out in a dried glass reactor (50 mL) equipped with
a magnetic stirrer inside the glovebox. The dried amounts of
toluene, styrene, and comonomer were added via separate
syringes into the reactor. Then, the reactor was placed into a
bath with the designated temperature and stirred for 10 min,
after which half of the MAO amount (∼1.45 g) was added. The
solution was stirred for another 10 min before the rest of the
MAO and metallocene catalyst were loaded into the reactor.
The polymerization was quenched after 20 min by adding a
10% solution of HCl in methanol. The reactor was removed

8348 Auer et al.
Macromolecules, Vol. 36, No. 22, 2003
Resu lts a n d Discu ssion
-CH2CH2--); 2.1, 2.12, 2.15 (3S, 9H, ArCH3); 2.62 (t, 2H, CH2-
Ar); 4.23 (s, 1H,OH); 4.8-5.0 (m 2H, dCH2); 5.7-5.9 (m,1H,
dCH). 13C NMR (CDCl3, δ): 11.3, 11.8, 12.2, 20.7, 23.6, 28.0,
31.7, 38.7, 74.1, 76.7, 77.0, 77.3, 114.2, 117.1, 118.5, 139.1,
144.7, 145.4.
Syn th etic Rou tes to Vita m in E Mon om er s. The
structure of natural vitamin E is essentially based on a
chroman skeleton having a phytyl chain attached to it
containing three chiral carbons atoms on the 2, 4′, and
8′ positions. The high antioxidant activity of R-toco-
pherol has been attributed to stereoelectronic effects
exerted by the chroman structure. Hence, its two-ring
structure gives additional stability to the tocopheroxyl
radical through interaction of the orbital overlap be-
tween the p-type lone pair orbital of the oxygen para to
the -OH group and the semioccupied molecular orbital
of the tocopheroxyl radical. Thus, the chroman structure
is responsible for the intrinsic antioxidant activity of
vitamin E, while the long side chain only acts to enhance
the solubility of the polymer.14 Therefore, in the present
work, our primary synthetic strategy to produce poly-
merizable vitamin E derivatives was to preserve the
chromanol moiety and replace the long phytyl side chain
moiety with an R-alkenyl group at the 2 position. To
the best of our knowledge, the number of R-tocopherol
compounds having a polymerizable alkenyl group in the
2, 3, 4, 5, 7, or 8 position are unprecendented in the
literature. However, in previous studies a large number
of other model compounds of R-tocopherol have been
synthesized such as 6-hydroxyl-2,2,5,7,8-pentamethyl-
chroman, 6-hydroxyl-2,5-dimethyl-2-phytylbenzo[7,8]-
chroman,15 2,3-dihydroxy-2,2,4,6,7-pentamethylbenzo-
furan,16 and 6-hydroxylthiochroman17 derivatives. The
first model compounds of R-tocopherol were prepared
by Smith, Kareer, and Bergel already during late 1930
by condensation of trimethylhydroquinone (TMHQ) with
isophytol in the presence of various catalyst systems.18
During the following years, mainly modifications of
this process in terms of solvents and catalyst systems,
e.g., Lewis or Brønsted acids, were developed.19 Using
the same approach, we started to investigate synthetic
procedures to polymerizable hydroxylchromans. First,
we synthesized 3-methylhept-1,6-dien-3-ol due to the
fact that it contains an R-olefinic moiety and is other-
wise an analogous reagent to the first isoprenol unit of
isophytol. The condensation of TMHQ with 3-methyl-
hept-1,6-dien-3-ol in refluxing formic acid afforded 1 as
a slightly yellow liquid with a boiling point of 151 °C, 1
mmHg, in a moderate yield (54% yield). Thus, this
synthetic pathway depicted in Scheme 1a to polymer-
izable tocopherol derivatives could be of both industrial
and academic interest. As anticipated, the normal
condensation routes of TMQH with 3-methylhept-1,6-
dien-3-ol using either ZnCl2/HCl or AlCl3/CH3NO2 were
not convenient, due to the fact that the R-olefinic double
bond was chlorinated.20
P r ep a r a tion of 6-Allyl-7-h yd r oxy-2,2,8,9-tetr a m eth yl-
ch r om a n (3). 6-Hydroxy-2,2,7,8-tetramethylchroman (3.0 g,
11.5 mmol; synthesized according to the procedure described
in the literature13) was diluted in acetone, and then K2CO3
(1.60 g, 11.5 mmol) was added gradually. Then the reaction
mixture was allowed to react for 30 min followed by dropwise
addition of allyl bromide (1.40 g, 11.6 mmol). Finally, the
solvent was removed, the residue was taken up in diethyl ether
and washed with water, and the organic phase was dried over
sodium sulfate. After removal of solvent, allylchromanoxy
ether was obtained (2.55 g, 85 yield %). The produced allyl-
chromanoxy ether was dissolved in DMF and heated to 155
°C, whereby via Claisen rearrangement, crude 3 was obtained.
After distillation 2.3 g of 3 (bp 120 °C/0.1 mmHg) was obtained
as a slightly yellow liquid. MS: m/e (rel intens) M+ 246 (47),
190 (34), 175 (23), 149 (10), 127 (6), 113 (10), 97 (15), 85 (47),
71 (69), 57 (100). 1H NMR (CDCl3, δ): 1.25, 1.28 (2s, 6H,
-CH3); 1.77 (2s, 4H, CH2); 2.11, 2.15 (2s, 6H, ArCH3); 2.66
(m, 2H, -CH2); 3.36-3.38 (m, 3H, CH2CHd); 4.40 (s, 1H, OH);
5.01-5.08 (m, 2H, dCH2), 5.9-6.0 (m, 1H, dCH,). 13C NMR
(CDCl3, δ): 11.9, 12.1, 14.1, 20.5, 22.7, 26.7, 29.7, 30.5, 31.9,
33.1, 72.5, 115.4, 116.8, 120.0, 122.1, 123.8, 135.9, 145.1, 145.9.
P r ep a r a tion of 4-Meth ylen e-(3,5-d i-ter t-bu tyl-4-p h en -
oxy)styr en e (4). To a solution of 2,6-di-tert-butylphenol (103
g, 0.5 mol) in 300 mL of methanol was added dropwise a
solution of KOH (32.74 g, 0.57 mol) in 200 mL of methanol.
The mixture was stirred overnight, giving a potassium salt of
the phenolic derivative. The methanol was evaporated, leaving
a green powdery residue. The residue was dissolved in 500
mL of dimethylformamide (DMF), then vinylbenzyl chloride
(91.5 g, 0.6mol) was added dropwise under agitation followed
by addition of tetrabutylammonium bromide (1.6 g, 5.0 mmol),
and the temperature was raised to 100 °C. After 12 h the
solvent was evaporated, and the remaining residue was
suspended in Et2O and filtered through brine. Then, the
solvent was evaporated, and the unreacted vinylbenzyl chlo-
ride and 2,6-di-tert-butylphenol were removed by distillation
under reduced pressure. The residue was recrystallized four
times from acetone to afford 9.82 g (6% yield) of 4 with a
melting point of 129-131 °C. MS: m/e (rel intens) M+ 322 (44),
307 (100), 265 (8), 139 (4), 117 (43), 91 (4), 57 (5). 1H NMR
(CDCl3, δ): 1.40 (s, 18H, C(CH3)3), 3.88 (s, 2H, CH2), 5.05 (s,
1H, OH), 5.19 (dd, 1H, J ) 10.9, 1.0 Hz, dCH2), 5.70 (dd, 1H,
J ) 17.6, 1.0 Hz, dCH2), 6.69 (dd, 1H, J ) 17.6, 10.9 Hz, CHd
CH2), 6.98 (s, 2H, Ar), 7.16 (d, 2H, J ) 8.1 Hz, Ar), 7.33 (dt,
2H, J ) 8.1, 1.7 Hz, Ar). 13C NMR (CDCl3, δ): 30.29, 34.27,
41.54, 112.94, 125.39, 126.21, 128.95, 131.40, 135.20, 135.82,
136.69, 141.56, 152.05.
P r ep a r a t ion of 4-Met h ylen e-(3,5-d i-ter t-b u t yl-4-t r i-
m eth ylsiloxyp h en yl)styr en e (5). To a solution of 4 (0.50 g,
1,55 mmol) in 3 mL of THF was added dropwise a solution of
BuLi (2.5 M in hexanes, 0.62 mL) at -80 °C, and the reaction
mixture was stirred for 10 min. Chlorotrimethylsilane (0.40
mL, 3.10 mmol) was then slowly added to the reaction mixture,
and stirring was continued for 30 min at -80 °C and 1 h at 0
°C. The solution was neutralized with water (5 mL), hexane
(50 mL) was added, and the organic phase was washed with
water (50 mL), dried over sodium sulfate, filtered, and
concentrated under reduced pressure. Chromatography of the
residue with hexane afforded 5 (570 mg, 93%) as a white solid,
mp 48 °C. MS: m/e (rel intens): M+ 394 (39), 379 (43), 323
(5), 305 (4), 117 (61), 73 (100), 57 (16). 1H NMR (CDCl3, δ):
0.38 (s, 9H, Si(CH3)3), 1.35 (s, 18H, C(CH3)3), 3.86 (s, 2H, CH2),
5.18 (dd, 1H, J ) 10.9, 1.0 Hz, dCH2), 5.69 (dd, 1H, J ) 17.6,
1.0 Hz, dCH2), 6.68 (dd, 1H, J ) 17.6, 10.9 Hz, CHdCH2),
7.03 (s, 2H, Ar), 7.14 (d, 2H, J ) 8.0 Hz, Ar), 7.32 (d, 2H, J )
8.0 Hz, Ar). 13C NMR (CDCl3, δ): 3.93, 31.24, 35.05, 41.34,
112.90, 126.18, 126.20, 129.01, 132.07, 135.17, 136.72, 140.50,
141.52, 151.38.
In recent years there has been a continuous search
for vitamin E analogues with enhanced antioxidant
activity. The most notable improvements in antioxidant
activity have been measured for the class of five-
membered heterocyclic ring analogues such as 2,3-
dihydroxybenzofuran and for the R-naphthofuran class
of derivatives such as 6-hydroxy-2,5-dimethyl-2-phytyl-
7,8-benzochroman, which exhibit higher kinh values 1.8-
10 times that of R-tocopherol.21 This encouraged us to
try to develop a one-step synthetic route to 2 from cheap
starting materials, i.e., TMHQ and a mixture of cis/
trans-2,7-octadien-1-ol, as illustrated in Scheme 1b.
However, despite numerous modifications of the reac-
tion conditions, the result was always a complex reac-
tion mixture.22 This is in accordance with the results

Macromolecules, Vol. 36, No. 22, 2003
Synthesis of Tocopherol- and Phenol-Based Monomers 8349
Sch em e 1. Syn th etic Rou tes to (a ) 1, 2, a n d 3
Ta ble 1. Cop op lym er iza tion of Eth ylen e a n d 1 over a r a c-[Dim eth ylsilylen ebis(4,5,6,7-tetr a h yd r o-1-in d en yl)]zir con iu m
Dich lor id e/Meth yla lu m oxa n e Ca ta lyst System a
concn of
R-tocopherol,
mmol /L
activity,
concn of 1,
mmol /L
kg of polym/
concn of bound
entry
cryst,b %
73
Tm,°C
Mn
Mw
Mn/Mw
(mol of Zr h) antioxidant, wt %c OIT,e °C
1
2
3
4
128.4
10300
31300
3.0
5600
3200
2400
2500
210
210
210
244
130f
370f
tocopherol
290
56
127.2
20500
41000
2.0
2.3
a
Copolymerization conditions: [Zr] ) 44 µmol/L, Al/Zr ) 3000, Pethylene ) 2 bar, polymerization time 30 min, T ) 80 °C, and Vtoluene
)
b
250 mL. Here, “cryst” denotes the polymer crystallinity, which was determined from DSC curves, and the heat of fusion of a folded-
chain polyethylene crystal has been taken as 293 J /g. c Determined by UV analysis. e The oxidation induction time (OIT) was determined
after extraction of polymer samples. The OIT was determined from DSC curves by extrapolating the exotherm associated with the beginning
of oxidation to the baseline of the trace. f Tocopherol was added instead of the functional monomer 1.
reported by Robillard et al.23 on their work with related
hydroxythiochromans.
2,2,7,8-tetramethylchroman via Friedel-Crafts alkyla-
tion were more or less unsuccessful in terms of yields
and problems with isolation of the desired product. On
the other hand, we were able to synthesize the latter
chromanol 3 by first treating 6-hydroxyl-2,2,7,8-tetram-
ethylchroman with potassium carbonate and allyl bro-
mide to give the corresponding allylchromanoxy ether.
In the second step the produced allylchromanoxy ether
was successfully converted by Claisen rearrangement
to 3, as shown in Scheme 1c.
In our opinion tocopherol 1 seemed to be the most
promising candidate of the aforementioned tocopherol
monomers 1, 2, and 3 in terms of synthetic yield,
polymerizability, and tolerance by methylalumoxane-
activated metallocene catalysts in terms of retained
polymerization activity. In light of this, we copolymer-
ized 1 with ethylene over a rac-[dimethylsilylenebis-
(4,5,6,7-tetrahydro-1-indenyl)]zirconium dichloride/MAO
catalyst system, and the results are presented in Table
1. In addition, two standard ethylene polymerizations
were conducted in the presence of various amounts of
R-tocopherol to determine the degree of deactivation of
active sites. The activity for ethylene and 1 copolymer-
izations was more or less half of that recorded for
ethylene homopolymerization, whereas the molecular
weights of the produced copolymers were similar to that
In our previous studies, we have noticed that certain
sterically hindered phenolic derivatives such as 2,6-di-
tert-butylphenol and 6-tert-butyl-2-(1,1-dimethylhept-6-
enyl)-4-methylphenol significantly enhance the polym-
erization rate of propylene and ethylene over different
metallocene catalyst systems.24 Other research groups
have also verified this observation,25 whereas other
reports describing the copolymerization of R-olefins with
various nonbulky polar monomers, such as 9-decen-1-
ol and 5-hexen-1-ol, show that the molecular weight
decreases with higher incorporation of polar monomer
to the polymer backbone and also activity.26 Further-
more, Ferreira and co-workers have studied the effect
of copolymerizable and noncopolymerizable Lewis bases
on propylene polymerization with an Et(Ind2)ZrCl2/MAO
catalyst system, and they have also observed that
deactivation occurs upon addition of Lewis bases.27
As a consequence of this and other considerations, we
sought synthetic routes to more crowded hydroxylchro-
manol monomers than 6-hydroxy-2,5,7,8-tetramethyl-
2-(but-3-enyl)chroman such as 6-hydroxyl-5-(1,1-dime-
thylhept-6-enyl)-2,2,7,8-tetramethylchroman and 3. All
of our attempts to prepare the former chromanol
monomer from 7-methyl-1,6-octadiene and 6-hydroxyl-

8350 Auer et al.
Macromolecules, Vol. 36, No. 22, 2003
Ta ble 2. Syn d iosp ecific Cop olym er iza tion of Styr en e w ith 4 a n d 5 over a n In d TiCl3/MAO Ca ta lyst System a
amt of
comonomer,
mmol
concn of bound
entry
comonomer
syndiotactic,b %
Tm, °C
Mn
Mw
Mn/Mw
yield, g
antioxidant, wt %c
3
4
5
92.5
93.1
94.0
269.5
245.4
263.6
52000
80000
60000
81000
120000
100000
1.6
1.5
1.7
0.92
0.15
0.50
4
5
0.78
0.32
6.8
2.4
a
b
Polymerization conditions: at 60 °C for 20 min, Vstyrene ) 10 mL, Vtoluene ) 20 mL, [Ti] ) 130 µM, and Al/Ti ) 2000. Portion of the
syndiotactic polymer insoluble in boiling 2-butanone. c Determined by 1H NMR analysis.
Ta ble 3. Resu lts of Th er m ogr a vim etr ic An a lysis of P olystyr en e, P oly(styr en e-co-4), a n d P oly(styr en e-co-5)a
temp interval
of thermal
decomp, °C
temp interval of
thermal decomp, °C
entry
atmosphere
entry
atmosphere
polystyrene
nitrogen
air
nitrogen
air
374-470
268-430
405-470
300-430
poly(styrene-co-5)
nitrogen
air
390-470
285-430
poly(styrene-co-4)
a
A Mettler Toledo TA8000 system equipped with a TGA850 thermobalance was used for thermal analysis (TG and SDTA). A heating
rate of 10 °C/min (starting from 25 °C and ending at 600 °C) under an atmosphere of flowing nitrogen or air.
Sch em e 2. Syn th etic P a th w a y to 4 a n d 5
of polyethylene prepared under similar reaction condi-
tions. Thus, the novel tocopherol monomer 1 has a
tendency of rendering the metallocene/MAO catalyst
activity to a certain degree as also could be predicted
from the results obtained from standard ethylene
polymerizations in the presence of R-tocopherol.
The produced poly(ethylene-co-1) exhibited enhanced
thermooxidative stability even after extraction with
2-propanol/cyclohexane for 24 h in a Soxhlet apparatus
in comparison to polyethylene; i.e., the oxidation induc-
tion temperature in an oxygen atmosphere for the
copolymer was around 244 °C, whereas the extracted
polyethylene samples (entries 2 and 3) and the pure
polyethylene sample (entry 1) showed an oxidation
induction temperature of only ∼210 °C. Thus, on the
basis of the thermooxidative stability tests, one can
conclude that the comonomer 1 has indeed been copo-
lymerized with ethylene.
Syn th etic Rou tes to a Styr en ic P h en ol Der iva -
tive a n d Its Tr im eth ylsilyla ted An a logu e. In 1986,
Ishihara and co-workers synthesized the first pure
syndiotactic polystyrene over a titanium/MAO catalyst
system.28 After this announcement intensive work has
been aimed at the synthesis of various homogeneous
organometallic catalyst systems that would exhibit high
productivity and stereospecificity in syndiotactic styrene
polymerizations. More recently, approaches to function-
alized syndiotactic polystyrenes with improved adhesion
and compatibility with other polymers have been re-
ported. Thus, Chung et al.29 have successfully prepared
a new family of syndiotactic styrenic polymers contain-
ing primary amino groups. Furthermore, 4-tert-bu-
tyldimethylsiloxystyrene has been successfully both
homo- and copolymerized with styrene using a metal-
locene catalyst system.30 However, to the best of our
knowledge, there have been no reports where a styrenic
type of antioxidant monomer would have been syn-
diospecifically copolymerized with styrene to give self-
stabilized syndiotactic polystyrene grades. Prompted by
this, we wanted to develop a synthetic route to styryl-
substituted antioxidant monomers such as 4 and its
trimethylsilylated analogue 5 (see Scheme 2) and copo-
lymerize these novel monomers with styrene over a half-
sandwich metallocene/MAO catalyst system to give
syndiotactic polystyrenes with enhanced thermooxida-
tive properties. The results of styrene copolymerizations
with 4 and 5 over an IndTiCl3/MAO catalyst system are
presented in Table 2. The results show clearly that the
unprotected hydroxyl functionality of monomer 4 inter-
acts with the active sites, since the recorded catalyst
activity is significantly lower than in homopolymeriza-
tion of styrene under similar conditions, whereas in the
case of the trimethylsilyl masked monomer the catalyst
activity was close to 60% of styrene homopolymerization.
It is interesting to note that the copolymers had molec-
ular weights and molecular weight distributions very
similar to those of polystyrene, whereas in the afore-
mentioned work28 describing the copolymerization of
styrene with 4-tert-butyldimethylsiloxystyrene using an
IndTiCl3/MAO catalyst system the obtained copolymer
had a relatively low molecular weight (Mn ) 9200 and
Pd ) 2.2). These experimental results clearly show the
advantage of having bulky tert-butyl substitutions in the
ortho positions of the phenol moiety in terms of retain-
ing catalyst activity and producing copolymers of high
molecular weight. In general, the effect is similar to that
of generating steric hindrance in the catalyst substitu-
tion of Cp by bulky substitutions such as n-propyl and
n-butyl.31
In addition, it can be seen from Table 2 that all
polymer samples showed similar syndiotacticities and
that the melting points were markedly lower for the
copolymers. The 1H spectra of the three prepared
syndiotactic polymers, i.e., syndiotactic polystyrene,
poly(styrene-co-4), and poly(styrene-co-5), are shown in
Figure 1. There are four common strong signals in all
three spectra. Thus, the first two peaks at 1.45 and 1.95
ppm (a triplet typical for syndiotacticity) corresponds
to the CH2 and CH protons in the polymer backbone,
and the two later peaks at δ ) 6.7 and 7.2 ppm are due

Macromolecules, Vol. 36, No. 22, 2003
Synthesis of Tocopherol- and Phenol-Based Monomers 8351
protons of the methyl groups adjacent to the silicon
atom. The good agreement between expected and mea-
sured peak intensity ratios for the protons in each group
indicates, within experimental error, that both copoly-
mers are clean. On the basis of 1H NMR spectral
analysis the incorporation degree of functional styrene
into the copolymer chain was determined to be 6.8 wt
% in the case of poly(styrene-co-4) and 2.4 wt % for poly-
(styrene-co-5). The 13C NMR spectrum of poly(styrene-
co-4) reveals that the quaternary C1 carbon atom of the
unsubstituted styrene gives a very sharp resonance at
δ ) 145.7 ppm. This sharpness together with the
characteristic shifts indicates a highly syndiotactic
microstructure for the copolymer.
TGA of Syn d iota ctic P olystyr en e, P oly(styr en e-
co-4), a n d P oly(styr en e-co-5). The thermal degrada-
tion of syndiotactic polystyrene, poly(styrene-co-4), and
poly(styrene-co-5) was investigated by TGA in both
nitrogen and air atmospheres using a heating rate of
10 °C/min up to 600 °C. The TGA results are presented
in Table 3. In nitrogen, the TGA curve showed that
syndiotactic polystyrene degrades in a single step begin-
ning at 374 °C and ending at 470 °C. In addition, the
curve showed that the maximum rate of weight loss
occurred at 416.5 °C. In the case of poly(styrene-co-4)
and poly(styrene-co-5) the degradation takes place
between 405 and 470 °C with maximum weight losses
at 426.5 and 390-470 °C and at 420.5 °C, respectively.
In the presence of air, the pure polystyrene sample
degrades primarily in a single step starting at 268 °C
and reaches zero mass at 430 °C. Thus, the degradation
of syndiotactic polystyrene begins immediately after the
melting point of the polymer has been reached. For poly-
(styrene-co-4) and poly(styrene-co-5) the weight loss due
to thermooxidation starts to occur when the melting
points of the copolymers have been exceeded by 20-50
°C, i.e., at 300 and 285 °C, respectively.
Con clu sion s
In this work we demonstrate that novel R-tocopherol
comonomers such as 1 can be manufactured by acid-
catalyzed condensation of TMHQ with 3-methylhept-
1,6-dien-3-ol, whereas the tocopherol compound 2 could
only be obtained in very low yields and isolation of the
product turns out to be very difficult. Furthermore, a
synthetic pathway to ortho-allylated tocopherol mono-
mer was constructed and successfully completed. Thus,
ortho-allylated chromanol denoted as 3 was obtained by
Claisen-rearrangement of the corresponding allylchro-
manoxy ether. The tocopherol monomer denoted 1 was
successfully copolymerized with ethylene over a metal-
locene/MAO catalyst system. The prepared self-stabi-
lized copolymers exhibited improved thermooxidative
stabilities in comparison to polyethylene. In addition,
a novel styrene derivative, 4, and its methylsilylated
analogue 5 were successfully synthesized and copoly-
merized with styrene over an IndTiCl3/MAO catalysts
system. The copolymers produced exhibited relatively
high syndiotacticities and molecular weights and high
thermal stabilities.
F igu r e 1. 1H NMR spectrum of (a) syndiotactic polystyrene,
(b) poly(styrene-co-4), and (c) poly(styrene-co-5).
to aromatic proton resonances. The spectrum of poly-
(styrene-co-4) shows the following additional peaks: the
peak at δ ) 1.48 ppm can be assigned to the tert-butyl
group protons, and the peaks at δ ) 3.9 and 4.9 ppm
can be assigned to the methylene protons between the
aromatic rings and the hydroxyl proton, respectively (18:
2:1 ratio of integrated intensity). In addition, aromatic
proton resonances from the functional monomer can be
seen in the region of 6.5 and 6.9 ppm. The 1H NMR
spectrum of poly(styrene-co-5) is very similar to that of
poly(styrene-co-4) except for the fact that the hydroxyl
proton at δ ) 4.9 ppm is missing and a new peak at δ
) 0.5 ppm has appeared that can be assigned to the
Ack n ow led gm en t. We gratefully acknowledge Carl-
J ohan Wikman, Ulrika Lindqvist, and Arja Vesterinen
for experimental assistance, and we are indebted to VTT
Chemical Technology, Finland, for financial support.
The reviewers are also thanked for valuable comments.

8352 Auer et al.
Macromolecules, Vol. 36, No. 22, 2003
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