End-quenching of TiCl4-catalyzed quasiliving polyisobutylene with alkoxybenzenes for direct chain end functionalization

Article abstract of DOI:10.1021/ma1015648

Alkoxybenzenes were used to end-quench TiCl₄-catalyzed quasiliving isobutylene polymerizations initiated from 2-chloro-2,2,4- trimethylpentane or 5-tert-butyl-1,3-di(1-chloro-1-methylethyl)benzene at -70 °C in 40/60 (v/v) hexane/methyl chloride. The alkoxybenzene/chain end molar ratios were in the range 2.5-4. Effective alkoxybenzene quenchers included those with simple alkyl groups, such as anisole and isopropoxybenzene, haloalkyl tethers, such as (3-bromopropoxy)benzene and (2-chloroethoxy)benzene, and even those with hydroxyl and amine functionality, such as 4-phenoxy-1-butanol and 6-phenoxyhexylamine. Alkylation was generally quantitative and occurred exclusively in the para position; multiple alkylations on the same alkoxybenzene were not observed. The alkylation reactions were tolerant of temperatures ranging from -70 to -30 °C and were unimpeded by the presence of endo- or exo-olefin termini. In situ cleavage of the ether linkage of anisole and isopropoxybenzene termini allowed single pot syntheses of phenol-terminated polyisobutylenes.

Full text of DOI:10.1021/ma1015648

8724 Macromolecules 2010, 43, 8724–8740
DOI: 10.1021/ma1015648
End-Quenching of TiCl4-Catalyzed Quasiliving Polyisobutylene with
Alkoxybenzenes for Direct Chain End Functionalization
David L. Morgan, Nemesio Martinez-Castro, and Robson F. Storey*
School of Polymers and High Performance Materials, The University of Southern Mississippi, Hattiesburg,
Mississippi 39406, United States
Received July 12, 2010; Revised Manuscript Received September 20, 2010
ABSTRACT: Alkoxybenzenes were used to end-quench TiCl4-catalyzed quasiliving isobutylene polymeri-
zations initiated from 2-chloro-2,2,4-trimethylpentane or 5-tert-butyl-1,3-di(1-chloro-1-methylethyl)benzene
at -70 °C in 40/60 (v/v) hexane/methyl chloride. The alkoxybenzene/chain end molar ratios were in the range
2.5-4. Effective alkoxybenzene quenchers included those with simple alkyl groups, such as anisole and
isopropoxybenzene, haloalkyl tethers, such as (3-bromopropoxy)benzene and (2-chloroethoxy)benzene, and
even those with hydroxyl and amine functionality, such as 4-phenoxy-1-butanol and 6-phenoxyhexylamine.
Alkylation was generally quantitative and occurred exclusively in the para position; multiple alkylations on
the same alkoxybenzene were not observed. The alkylation reactions were tolerant of temperatures ranging
from -70 to -30 °C and were unimpeded by the presence of endo- or exo-olefin termini. In situ cleavage of the
ether linkage of anisole and isopropoxybenzene termini allowed single pot syntheses of phenol-terminated
polyisobutylenes.
Introduction
initiator, and the other is addition of suitable nucleophiles to the
polymerization at full monomer conversion (end-quenching).
Polyisobutylene (PIB) is a versatile material with properties
desirable for applications ranging from lubricant additives1 to
biomaterials.2 However, the use of PIB in preparation of more
complex materials may require introduction of a reactive and/or
polar functionality at the chain end. For most commercially
produced PIBs the available starting functionality is olefin, which
arises naturally from β-proton expulsion in chain transfer domi-
nated polymerization processes. In BF3-catalyzed polymeriza-
tions the content of highly reactive methylvinylidene or exo-olefin
chain ends can be as high as 70-90%; however, protic initiation
causes these PIBs to contain only a single reactive terminus.3,4
With the development of methods enabling controlled polymeri-
zation of isobutylene from multifunctional initiators,5 synthesis
of telechelic PIBs became possible. These processes, mainly involv-
ing BCl3 or TiCl4 co-initiators, are generally conducted under
conditions whereby the growing chain ends are in equilibrium
between dormant and active states.6 Such conditions naturally
lead to tert-chloride functionality at the chain end,7 and post-
polymerization dehydrochlorination would still be required to
synthesize exo-olefin telechelic PIB.8-10
Olefin-terminated PIB has been subjected to numerous post-
polymerization transformations, including hydroboration-oxida-
tion,11 hydroformylation,12 epoxidation,13 ozonolysis,14,15 lithia-
tion,16 sulfonation,17 hydrosilylation,18 and hydrobromination.19
The terminal unsaturation has also been used as a Friedel-Crafts
alkylating agent20 and a substrate for the free radical addition of
thiols.21 These and subsequent postpolymerization transformations
provide useful chain end functionality, but often with difficultly
and/or significant expense. That has provided impetus for the
development of technology aimed at obtaining functionalities
other than tert-chloride and/or exo-olefin directly from isobutyl-
ene polymerizations. Two approaches to in situ functionalization
have been taken; one is to begin the polymerization with a functional
Functional initiators reported for isobutylene polymerization
have included structures with nonpolymerizable olefins,22-24
acetates,25 protected26 and unprotected27 phenols, and silyl
chlorides.28-31 Other reported initiatiors have involved cyclic
moieties such an epoxide32 or lactone33 that ring open in the
presence of TiCl4 to provide hydroxyl and ester functionality,
respectively. Unfortunately, functional initiators only provide the
desired functionality at the initiation site, and the PIB chain
terminus remains tert-chloride unless subsequently modified or a
coupling strategy is employed.
The approach of quenching an isobutylene polymerization
with a nucleophile that either adds to or modifies the chain end
has been somewhat more successful due to avoidance of compli-
cations that could arise during initiation and propagation from a
functional initiator. However, a judicious choice of nucleophile is
required because of rapid and often overwhelming interaction
with the Lewis acid catalyst, rendering one or both unreactive.
Soft π-nucleophiles, such as nonpolymerizable monomers34-38 and
heterocyclic aromatic substrates,39-41 have been used to success-
fully cap TiCl4-catalyzed quasiliving PIB. In addition, certain
hindered organic nitrogen bases,42,43 ethers/alkoxysilanes,44 and
(di)sulfides45 have proven useful for in situ transformation of the
PIB chain end to olefin. Despite many advances in quenching
technology, large scale practicability may be limited due to reagent
expense as well as requirements for low temperatures and/or
dilute reaction systems.
In cationic polymerization systems, alkylation of arenes
was recognized early but was generally regarded as a chain
transfer/termination reaction only useful for controlling molec-
ular weight. For example, Plesch et al. reported that polystyrene
polymerizations catalyzed by TiCl4 in toluene resulted in poly-
mers with tolyl end groups46 and that anisole may act as chain
terminating agent for TiCl4-catalyzed isobutylene polymeriza-
tion, as evidenced by p-methoxyphenyl end groups.47 Similarly,
Overberger et al.48-50 found that a wide variety of mono- and
*Corresponding author. E-mail: robson.storey@usm.edu.
pubs.acs.org/Macromolecules
Published on Web 10/11/2010
r 2010 American Chemical Society

Article
Macromolecules, Vol. 43, No. 21, 2010 8725
dialkyl-substituted aromatics function as chain-terminating agents
in SnCl4-catalyzed polymerization of styrene at 0 °C. When
Russell et al.51-56 conducted SnCl4-catalyzed isobutylene poly-
merizations in ethyl chloride at -78.5 °C with phenol and sub-
stituted phenols as cocatalysts (initiators), they found evidence
of phenolic end groups; however, proton expulsion was also a
significant chain breaking event, leading to terminal unsaturation.57
The first attempts at controlled termination of carbocationic
polymerizations with an arene were reported by Kennedy et al.58-61
when they used a triphenylaluminum/tert-alkyl chlorideinitiating
system. The arylaluminum acted as both a catalyst and chain
terminating agent, yielding R,ω-diphenyl PIBs with 0.7-1.7
phenyl groups per chain. For polystyrene, Hunter et al.62 demon-
strated that 40-70% of the chain ends may be capped by
alkylphenols under AlCl3 catalysis. Zhang et al.63 reported direct
addition of triphenylamine to PIB synthesized from a H2O/
TiCl4 initiating system. The maximum capping efficiency was in
the 70-80% range, and the process was plagued by competitive
exo-olefin formation due to the presence of the basic amine.42
Fujisawa et al.64 disclosed quenching of SnCl4-catalyzed iso-
butylene polymerizations with vinylalkoxybenzenes. The alkyla-
tion reactions were performed in methylene chloride from -30 °C
to room temperature, and vinyl end group functionalities from 76
to 90% were obtained.
Because of limited success at in situ alkylation/incorporation of
arenes, namely phenol, at the PIB chain end, much attention has
been given to postpolymerization Friedel-Crafts alkylations.
Conventional PIBs made from AlCl3 catalysis have relatively
high amounts of tri- and tetra-substituted olefin end groups, and
the harsh acid catalysis required to induce alkylation via the
olefin end group may also induce fragmentation of the polymer
chain. Selection of appropriate alkylation catalysts65,66 and
conditions or modification of the polymer chain end67 can
minimize these problems. However, arene alkylation with the
olefin terminus became more practical with the commercial
availability of high methyl vinylidene (>70%) PIB. With the
highly reactive isomer, alkylation can be carried out in the
absence of molecular weight degradation.68 Typical alkylation
catalysts include Lewis acids (e.g., AlCl3, BF3, and BF3 complexes),
trifluoromethanesulfonic acid, and acidic molecular sieves (e.g.,
Amberlyst 36).
The discovery of conditions that allowed for controlled quasi-
living polymerization of isobutylene also led to polymers with
quantitative chain end functionality. Kennedy et al. made use of
these telechelic polyisobutylenes and reported postpolymeriza-
tion alkylation of phenol,69,70 anisole,71 benzene, toluene, and
xylene72 with both tert-chloride- and exo-olefin-terminated PIB.
The Friedel-Crafts alkylations were most often catalyzed by
BF3-etherate in hexanes or aromatic/dichloromethane solvent
mixtures at temperatures from 20 to 55 °C; unfortunately,
warmer temperatures, especially above 60 °C, apparently favored
cracking and depolymerization. Even with the more reactive
arenes, phenol and anisole, reaction times of 2 days were required
for complete conversion of the chain ends. Bergbreiter et al.73 also
reported the alkylation of highly activated benzene derivatives
with exo-olefin-terminated PIB in the presence of concentrated
sulfuric acid, but the reactions required 60 h for complete
conversion. Marechel et al.27,74 reported SnCl4-catalyzed alkyla-
tion of phenol with exo-olefin-terminated PIB at temperatures
from -50 to 0 °C in dichloromethane within 1-3 h; however,
polymer degradation was observed, becoming more severe at
higher temperatures. Kennedy et al.72,75 have reported alkylation
of less reactive arenes such as benzene, toluene, and 2-bromo-
ethylbenzene by tert-chloride-terminated PIB in fewer than 5 h
using aluminum trichloride catalysis at temperatures between
-50 and -80 °C. In these and all other alkylation reactions
involving arenes and PIB, selection of catalyst, solvent, and reaction
temperature is critical to prevent unwanted degradation and/or
cracking of PIB. Unfortunately, the conditions necessary for the
Friedel-Crafts alkylation reactions are usually not the same as
those required for quasiliving carbocationic polymerization of
isobutylene, and therefore, arene-functionalized PIBs have pre-
dominately been prepared in multistep processes.
Here, we report the successful alkylation of a range of
alkoxybenzene compounds with TiCl4-catalyzed quasiliving
PIB, leading to quantitative capping of the chain ends. Alkyla-
tion and subsequent in situ deprotection of simple alkyl
phenols allowed for direct synthesis of phenolic PIBs. In
addition, important functionalities such as primary halide,
hydroxyl, and amine were obtained at the PIB chain end in a
single step via end-quenching of the polymerization. The
alkylations were remarkably tolerant of changes in tempera-
ture, e.g., up to -30 °C, as well as the presence both endo- and
exo-olefin-terminated PIB.
Experimental Section
Materials. Hexane (anhydrous, 95%), titanium tetrachloride
(TiCl4) (99.9%), boron tribromide (BBr3) (99.9%), 2,6-lutidine
(redistilled, 99.5%), phenol (99%), anisole (anhydrous, 99.7%),
(2-chloroethoxy)benzene (98%), (2-bromoethoxy)benzene (98%),
(3-bromopropoxy)benzene (96%), allyl phenyl ether (99%), 2,6-
di-tert-butylphenol (99%), 2-bromopropane (99%), phenyl pro-
pargyl ether (90%), chlorotrimethylsilane (97%), tetrahydro-
furan (THF) (anhydrous, 99.9%), methyllithium (1.6 M in diethyl
ether), calcium hydride (CaH2) (95%), 4-phenoxybutyric acid
(98%), lithium aluminum hydride (LiAlH4) (powder, 95%), 1,6-
dibromohexane (96%), zinc (dust, 98%), butyl phenyl ether
(99%), potassium benzoate (99%), potassium tert-butoxide
(95%), tetrabutylammonium fluoride (1 M in THF) (TBAF),
and chloroform-d (CDCl3) were purchased from Sigma-Aldrich
and used as received. 3-Phenoxypropyldimethylchlorosilane
was purchased from Gelest and used as received. Dimethyl-
formamide (DMF) (99.8%), heptane, diethyl ether, ethyl acetate,
ammonium hydroxide (NH4OH), sodium hydroxide (NaOH),
concentrated sulfuric acid (H2SO4), anhydrous magnesium
sulfate (MgSO4), anhydrous sodium sulfate (Na2SO4), sodium
bicarbonate (NaHCO3), and ammonium chloride (NH4Cl) were
purchased and used as received from Fisher Scientific. Isobutyl-
ene (BOC Gases) and methyl chloride (Alexander Chemical
Corp.) were dried by passing the gases through columns of CaSO4/
molecular sieves/CaCl2 and condensed within a N2-atmosphere
glovebox immediately prior to use. Boron trichloride (BCl3) pur-
chased from Matheson was also condensed immediately prior to
use. The monofunctional initiator, 2-chloro-2,4,4-trimethyl-
pentane (TMPCl), was prepared by bubbling HCl gas through
neat 2,4,4-trimethyl-1-pentene (Sigma-Aldrich) at 0 °C. The
HCl-saturated TMPCl was stored at 0 °C, and immediately
prior to use itwasneutralizedwithNaHCO3, dried over anhydrous
MgSO4, and filtered. The difunctional initiator, 5-tert-butyl-1,3-
di(1-chloro-1-methylethyl)benzene (t-Bu-m-DCC), was synthe-
sized as previously reported76 and stored at 0 °C.
Isopropoxybenzene. Isopropoxybenzene was synthesized by
reaction of phenolate with 2-bromopropane. Typically, 30 g
(319 mmol) of phenol, 36 mL (383 mmol) of 2-bromopropane,
and 15.3 g (383 mmol) of NaOH were combined in 100 mL of
DMF and heated to reflux in a 70 °C oil bath. After 16 h, the
reaction was cooled, and the product was extracted into diethyl
ether, washed with deionized water, and dried over MgSO4.
Removal of solvent under reduced pressure and vacuum dis-
tillation from CaH2 provided 44 g (86%) of a colorless liquid. 1H
NMR (CDCl3) δ (ppm): 1.36 (d, methyl, J = 6.06 Hz, 6H), 4.57
(m, methine, J = 6.06 Hz, 1H), 6.92 (d, aromatic, 2H), 6.95 (d,
aromatic, 1H), 7.29 (t, aromatic, 2H). 13C NMR δ (ppm): 22.1
(methyl), 69.7 (methine), 115.9, 120.5, 129.5, 157.9 (aromatic).
Trimethyl(3-phenoxy-1-propynyl)silane. The alkyne moiety of
phenyl propargyl ether was protected with trimethylsilane.

8726 Macromolecules, Vol. 43, No. 21, 2010
Morgan et al.
Typically, 12.3 mL (95.5 mmol) of phenyl propargyl ether was
dissolved in 50 mL of THF and chilled to -30 °C. To this
solution was added dropwise 66 mL (106 mmol) of methyl-
lithium as a 1.6 M solution in diethyl ether. After 15 min, 24 mL
(189 mmol) of chlorotrimethylsilane was slowly charged to the
reactor. After the initial exotherm, the reaction was allowed to
warm and sit overnight at room temperature. The reaction
mixture was filtered and concentrated on a rotary evaporator.
Vacuum distillation from CaH2 afforded 15.6 g (80%) of color-
δ (ppm): 1.45 (m, methylene, 6H), 1.77 (m, C6H5O-CH2CH2-,
2H), 2.67 (t, -CH2NH2, J = 6.84 Hz, 2H), 3.93 (t, C6H5O-
CH2-, J = 6.49 Hz, 2H), 6.88 (d, aromatic, 2H), 6.95 (d, aromatic,
1H), 7.27 (t, aromatic, 2H). 13C NMR δ (ppm): 26.0 (C6H5O-
CH2CH2CH2-), 26.7 (-CH2CH2CH2NH2), 29.3 (C6H5O-
CH2CH2-), 33.7 (-CH2CH2NH2), 42.1 (-CH2NH2), 67.7
(C6H5O-CH2-), 114.5, 120.5, 129.4, 159.0 (aromatic).
6-Phenoxy-1-hexanol and 8-Phenoxy-1-octanol. The longer
chain phenoxyalkanols were synthesized by reaction of pheno-
late with haloalkanols. For synthesis of 6-phenoxy-1-hexanol,
18.9 g (0.201 mol) of phenol and 18.3 g (0.457 mol) of NaOH
were combined in 100 mL of DMF and heated to 80 °C. To the
heated solution was charged 25 g (0.183 mol) of 6-chloro-1-
hexanol. After 3 h, the reaction mixture was neutralized with HCl,
and the product was extracted into diethyl ether and washed
with deionized water. Vacuum distillation provided 34.8 g (78%)
of a crystalline solid. 1H NMR (CDCl3) δ (ppm): 1.47 (m,
methylene, 4H), 1.61 (m, -CH2CH2OH, 2H), 1.80 (m, C6H5O-
CH2CH2-, 2H), 3.65 (m, -CH2OH, 2H), 3.96 (t, -CH2-OC6H5,
J = 6.48 Hz, 2H), 6.88 (d, aromatic, 2H), 6.95 (d, aromatic, 1H),
7.27(t, aromatic, 2H). 13C NMR δ (ppm): 25.6 (-CH2CH2CH2-
OH), 25.9 (C6H5O-CH2CH2CH2-), 29.3 (-CH2CH2-OH),
32.7 (C6H5O-CH2CH2-), 62.9 (-CH2OH), 67.7 (C6H5O-
CH2-), 114.5, 120.5, 129.4, 159.0 (aromatic). A similar reaction
with 8-chloro-1-octanol yielded 8-phenoxy-1-octanol.
1
less oil. H NMR (CDCl3) δ (ppm): 0.20 (s, methyl, 9H), 4.69
(s, methylene, 2H), 6.99 (d, aromatic, 2H), 7.02 (d, aromatic,
1H), 7.31 (t, aromatic, 2H). 13C NMR δ (ppm): -0.3 (methyl),
56.7 (methylene), 92.6 (C-Si), 100.1 (CH2C) , 114.9, 121.4, 129.4,
158.7 (aromatic).
4-Phenoxy-1-butanol. 4-Phenoxy-1-butanol was synthesized
by LiAlH4 reduction of 4-phenoxybutyric acid. Typically, 50 g
(277 mmol) of 4-phenoxybutyric acid in 100 mL of THF was
added dropwise to 10.5 g (277 mmol) of LiAlH4 in 150 mL of
THF at room temperature under N2. After the initial exotherm,
controlled by refluxing THF, the reaction sat overnight at room
temperature. An aqueous solution of hydrochloric acid (0.1 M)
was added to release the product, which was then extracted into
diethyl ether and washed with deionized water until neutral. The
organic layer was dried with Na2SO4, and the solvent was removed
under vacuum. Vacuum distillation from calcium hydride af-
forded 33 g (72%) of colorless oil. 1H NMR (CDCl3) δ (ppm):
1.73 (m, -CH2CH2OH, 2H), 1.86 (m, C6H5O-CH2CH2-, 2H),
3.68 (t, -CH2OH, J = 6.17 Hz, 2H), 3.98 (t, C6H5O-CH2-,
J= 6.17 Hz, 2H), 6.88 (d, aromatic, 2H), 6.95 (d, aromatic, 1H), 7.27
(t, aromatic, 2H). 13C NMR δ (ppm): 25.8 (C6H5O-CH2CH2-),
29.5 (-CH2CH2OH), 62.4 (-CH2OH), 67.7 (C6H5O-CH2-),
114.5, 120.5, 129.4, 159.0 (aromatic).
Instrumentation. Nuclear magnetic resonance (NMR) spectra
were obtained using a 300 MHz Varian Mercuryplus NMR
(VNMR 6.1C) spectrometer. Standard 1H and13C pulse sequences
were used. Composite pulse decoupling was used to remove
proton coupling in 13C spectra. All 1H chemical shifts were
referenced to TMS (0 ppm), and all 13C shifts were referenced to
the CDCl3 solvent resonance (77.0 ppm). Samples were prepared
by dissolution in CDCl3 (20-50 mg/mL) and charging this solu-
tion to a 5 mm NMR tube.
6-Phenoxyhexylamine. 6-Phenoxyhexylamine was synthe-
sized by reaction of phenolate with excess 1,6-dibromohexane,
followed by displacement of bromide with azide and reduction
of azide. Typically, 19.3 g (205 mmol) of phenol and 8.6 g
(215 mmol) of NaOH were combined in 200 mL of DMF, and
the reaction flask was heated to 80 °C.After10min,100g(410mmol)
of 1,6-dibromohexane was charged to the reaction. After 1 h, the
reaction mixture was cooled, and the product was extracted into
diethyl ether and washed with deionized water. Fractional vacuum
distillation from CaH2 provided 25.1 g (48%) of (6-bromo-
hexoxy)benzene as a colorless oil. 1H NMR (CDCl3) δ (ppm): 1.5
(m, methylene, 4H), 1.8 (m, methylene, 2H), 1.9 (m, methylene,
2H), 3.41 (t, -CH2Br, 2H), 3.95 (t, C6H5O-CH2-, 2H), 6.88 (d,
Number-average molecular weights (Mn) and polydisper-
sities (PDI = Mw/Mn) were determined with a gel-permeation
chromatography (GPC) system consisting of a Waters Alliance
2695 separations module, an online multiangle laser light scat-
tering (MALLS) detector fitted with a gallium arsenide laser
(power: 20 mW) operating at 658 nm (miniDAWN TREOS,
Wyatt Technology Inc.), an interferometric refractometer
(Optilab rEX, Wyatt Technology Inc.) operating at 35 °C and
685 nm, and two PLgel (Polymer Laboratories Inc.) mixed E
3
˚
columns (pore size range 50-10 A, 3 μm bead size). Freshly
distilled THF served as the mobile phase and was delivered at a
flow rate of 1.0 mL/min. Sample concentrations were ca. 15-20
mg of polymer/mL of THF, and the injection volume was 100
μL. The detector signals were simultaneously recorded using
ASTRA software (Wyatt Technology Inc.), and absolute molec-
ular weights were determined by MALLS using a dn/dc calcu-
lated from the refractive index detector response and assuming
100% mass recovery from the columns.
aromatic, 2H), 6.95 (d, aromatic, 1H), 7.27 (t, aromatic, 2H). 13
C
NMR δ (ppm): 25.3, 28.0, 29.1, 32.7 (methylene), 33.9 (-CH2Br),
67.6 (C6H5O-CH2-), 114.5, 120.5, 129.4, 159.0 (aromatic).
In conversion of bromide to azide, 25.1 g (97.6 mmol) of (6-
bromohexoxy)benzene and 19 g (293 mmol) of sodium azide
were placed in 100 mL of DMF, and the mixture was heated at
90 °C for 3 h. The product was extracted into diethyl ether,
washed with H2O, and dried over Na2SO4, and the residual
solvents were removed under vacuum to yield 17.7 g (83%) of
(6-azidohexoxy)benzene. 1H NMR (CDCl3) δ (ppm): 1.5 (m,
methylene, 4H), 1.64 (m, methylene, 2H), 1.8 (m, methylene, 2H),
3.28 (t, -CH2N3, 2H), 3.96 (t, C6H5O-CH2-, 2H), 6.88 (d,
aromatic, 2H), 6.95 (d, aromatic, 1H), 7.27 (t, aromatic, 2H).
13C NMR δ (ppm): 25.7, 26.5, 28.8, 29.2 (methylene), 51.4
(-CH2N3), 67.6 (C6H5O-CH2-), 114.5, 120.5, 129.4, 159.0
(aromatic).
Real-time ATR-FTIR monitoring of isobutylene polymeri-
zations was performed using a ReactIR 4000 (Mettler-Toledo)
integrated with a N2-atmosphere glovebox (MBraun Labmaster
130).78 Isobutylene conversion during polymerization was de-
termined by monitoring the area, above a two-point baseline, of
the absorbance centered at 887 cm-1, associated with the =CH2
wag of isobutylene.
Polymerization, Quenching, and Postpolymerization Reac-
tions. Table 1 lists conditions for polymerization and quenching
reactions used to produce the various PIBs reported herein and
molecular weight data for the resulting prequench tert-chloride
PIBs, quenched PIBs, and further derivatives. Polymerization
and quenching reactions were performed within a N2-atmo-
sphere glovebox equipped with cryostated heptane bath. Total
reaction volumes of 100-200 mL, typically comprising a 40/60
(v/v) hexane/methyl chloride mixture, were contained in 250 mL
round-bottom flasks equipped with an overhead stirrer, ther-
mocouple, and ReactIR probe. TiCl4-catalyzed polymerizations
In reduction of the azide,77 17.7 g (80.7 mmol) of (6-azido-
hexoxy)benzene and 8.6 g (161 mmol) of ammonium chloride
were placed into 100 mL of ethyl acetate at room temperature.
While vigorously stirring, 7.9 g (121 mmol) of zinc dust was
slowly added, and the exotherm was controlled by refluxing
ethyl acetate. After 15 min, the reaction mixture was washed
with NH4OH and then deionized water. Removal of the solvent
under vacuum, followed by vacuum distillation from calcium
hydride provided 14.3 g (92%) of colorless oil. 1H NMR (CDCl3)

Article
Macromolecules, Vol. 43, No. 21, 2010 8727
Table 1. Conditions for Quasiliving Isobutylene Polymerizations and Alkylation (Quenching) Reactions
component concentration (mol/L)a
reaction time (h)
TiCl4
pzn
TiCl4
quencher quench
entry
quencher
initiator IB
pzn
quench
Mn ꢀ 10-3 (PDI)f
1
2
3
4
5
6
7
8
9
anisole
isopropoxybenzene
2,6-di-tert-butylphenol
allyl phenyl ether
(2-chloroethoxy)benzene
(3-bromopropoxy)benzene
0.025b 1.14 0.016
0.025b 1.12 0.015
0.025c 0.75 0.017
0.050c 1.75 0.015
0.040c 1.59 0.012
0.050b 2.08 0.012e
0.125
0.125
0.100
0.150
0.100
0.250
0.060
0.100
0.144
0.125
0.066
0.115
0.167
0.100
0.092
0.112
0.100
0.167
0.494
0.190
0.36
0.36
0.71
0.56
1.42
1.58
0.33
0.68
0.40
0.48
3.63
2.05
1.06
2.16
3.42
3.42
1.50
5.35
7.70
9.00
2.9 (1.14), 3.1 (1.10), 3.2 (1.08)g
3.4 (1.05), 3.4 (1.04), 3.5 (1.03)g
2.0 (1.14), 2.2 (1.09)
2.7 (1.34), 2.9 (1.31)
3.0 (1.21), 2.9 (1.23), 3.0 (1.22)h
3.1 (1.13), 3.5 (1.04), 3.5 (1.12)i
4.9 (1.01), 5.6 (1.05)
3-phenoxypropyldimethylchlorosilaned 0.010b 0.76 0.100
trimethyl(3-phenoxy-1-propynyl)silane 0.025c 0.75 0.017
2.2 (1.19), 2.5 (1.18), 2.5 (1.16)j
2.9 (1.07), 3.2 (1.05)
4-phenoxy-1-butanol
6-phenoxyhexylamine
0.024b 1.05 0.014
0.025b 1.09 0.015
10
3.1 (1.07)
a Polymerization and alkylation reactions at -70 °C in 40/60 (v/v) hexane/methyl chloride in the presence of 0.005 M 2,6-lutidine. b Initiated from
bDCC. c TMPCl. d 60/40 (v/v) hexane/methyl chloride. e Added in two equal portions to control exotherm. f Molecular weight prior to alkylation, after
alkylation, and after further modification (see Experimental Section) to phenolic (g), vinyl ether (h), hydroxyl (i), and alkynyl functional PIB (j).
Figure 1. 1H NMR (300 MHz, CDCl3, 22 °C) spectra of (A) R,ω-bis(4-methoxyphenyl)polyisobutylene and (B) R,ω-bis(4-isopropoxyphenyl)polyiso-
butylene obtained by direct addition of anisole and isopropoxybenzene, respectively, to TiCl4-catalyzed quasiliving isobutylene polymerizations and
(C) R,ω-bis(4-hydroxyphenyl)polyisobutylene obtained by in situ demethylation or deisopropylation (Table 1, entries 1 and 2).
of isobutylene at -70 °C in the presence of 2,6-lutidine (0.005 M)
were initiated from either TMPCl or t-Bu-m-DCC at concentra-
tions of 0.01-0.05 M. Isobutylene charges were chosen to target
molecular weights of 2000-5000 g/mol. The TiCl4 polymerization
catalyst, typically around 0.015 M, resulted in polymerization
times from 20 to 90 min, depending on the initiator and its

8728 Macromolecules, Vol. 43, No. 21, 2010
Morgan et al.
Figure 2. 13C NMR (75 MHz, CDCl3, 22 °C) spectra of (A) R,ω-bis(4-methoxyphenyl)polyisobutylene and (B) R,ω-bis(4-isopropoxyphenyl)polyiso-
butylene obtained by direct addition of anisole and isopropoxybenzene, respectively, to TiCl4-catalyzed quasiliving isobutylene polymerizations and
(C) R,ω-bis(4-hydroxyphenyl)polyisobutylene obtained by in situ demethylation or deisopropylation (Table 1, entries 1 and 2).
concentration. At full monomer conversion, the alkoxybenzene
quenchers were charged to the reaction, typically at 2.5-4 equiv
per chain end. Additional TiCl4 (1-6 equiv per chain end) was
added to catalyze the alkylations reactions, resulting in overall
TiCl4 concentrations near 0.1 M. For alkoxybenzenes such as
4-phenoxy-1-butanol and 6-phenoxyhexylamine the TiCl4 con-
centrations were augmented to account for complexation of the
hydroxyl and amine moieties, respectively. Alkylations were
allowed to proceed from 1 to 4 h in most cases; however, the
highly complexing alkoxybenzenes required 7-9 h for complete
capping of the chain ends. Finally, the catalysts were destroyed
by addition of excess methanol, and the PIBs were isolated by
precipitation from hexane into methanol.
With anisole and isopropoxybenzene an additional deblock-
ing step was required before destruction of the catalyst to obtain
phenolic PIB. For anisole, cleavage of the terminal methyl ether
involved charging the reactor with an excess (6 equiv per chain
end) of BBr3 and allowing the reaction to warm at room
temperature for 22 h. For isopropoxybenzene, additional TiCl4
(2 eq per chain end) and H2SO4 (0.3 mL) were charged to the
reactor, and it was allowed to warm at room temperature for 5.5 h.
The primary chloride functional PIB obtained via quenching
with (2-chloroethoxy)benzene was converted to a vinyl ether by
dehydrochlorination with potassium tert-butoxide. Typically,
15 mL of heptane was used to dissolve 1.6 g of monofunctional
primary chloride PIB (2.9 ꢀ 103 g/mol), and to this mixture was
added an equal volume of DMF and 0.62 g (10 equiv per chain
end) of potassium tert-butoxide. The two-phase reaction mix-
ture was heated, upon which it became monophasic, and the
reaction was conducted at reflux for 1 h. The reaction mixture
was cooled, whereupon a biphasic mixture re-formed, and the
heptane and DMF layers were separated. The heptane layer was
washed with deionized water, dried over MgSO4, and filtered,
and finally the solvent was removed under vacuum.
The primary bromide functional PIB obtained via quenching
with (3-bromopropoxy)benzene was converted to primary hydroxyl
by displacement with benzoate, followed by hydrolysis. Typically,
2.5 g of difunctional primary bromide PIB (3.5 ꢀ 103 g/mol) was
dissolved in 25 mL of heptane. This solution was added to 1.83 g
(8 equiv per chain end) of potassium benzoate in 25 mL of DMF.
The two-phase system was heated, upon which it became mono-
phasic, and the reaction was conducted at reflux for 4 h. After
cooling, the heptane layer was separated from the DMF layer
and subsequently contacted with 2.2 g of NaOH in 25 mL of DMF.
The reaction was again heated to reflux for 12 h. After cooling and
phase separation, the heptane layer was washed with deionized
water and dried over Na2SO4, and the solvent was removed under
vacuum.

Article
Macromolecules, Vol. 43, No. 21, 2010 8729
Figure 4. 1H NMR (300 MHz, CDCl3, 22 °C) spectrum of 2,6-di-tert-
butyl-4-polyisobutylphenol and 2-tert-butyl-4-polyisobutylphenol ob-
tained by direct addition of 2,6-di-tert-butylphenol to a TiCl4-catalyzed
quasiliving isobutylene polymerization (Table 1, entry 3).
representing the ultimate quaternary and gem-dimethyl carbons
of tert-chloride PIB, respectively, were not present after the
alkylation reaction and were replaced by a new set of
resonances in the aromatic region and a resonance at 55.15
ppm due to the anisole methyl carbon.
The anisole end group by itself is not particularly useful,
but demethylation via cleavage of the terminal ether would
provide phenolic PIB, a product of significant importance.
Ether cleavage is often performed under strongly acidic
conditions; however, methyl ethers are relatively difficult
to cleave.80 Under the conditions used for quasiliving iso-
butylene polymerization and quenching, i.e., with TiCl4 present
at -70 °C, no cleavage of the terminal ether was observed. To
achieve quantitative ether cleavage to phenolic end groups
required addition of excess BBr3 and 22 h at room tempera-
Figure 3. GPC differential refractive index traces of PIB obtained from
TiCl4-catalyzed quasiliving isobutylene polymerizations quenched with
(A) anisole, (B) isopropoxybenzene, (C) 2,6-di-tert-butylphenol, and
(D) allyl phenyl ether: prequench (dotted); postquench (solid); and after
deblocking (dashed) to provide phenolic PIB (A and B only) (Table 1,
entries 1-4).
1
ture. Figure 1C shows the H NMR spectrum of phenolic
PIB obtained from the BBr3-assisted demethylation of
anisole-capped PIB. The resonance at 3.79 ppm due to the
terminal methyl group was replaced by a new resonance at
4.57 ppm with 1/3 the intensity due to the phenolic proton.
Demethylation was also evidenced in the 13C NMR spectrum
of Figure 2C by a disappearance of the methyl resonance at
55.15 ppm and an upfield shift of the resonance due to the
aromatic carbon adjacent to oxygen from 157.1 to 152.9
ppm. The GPC traces of Figure 3A indicated no coupling
during the alkylation/quenching reaction and no significant
polymer degradation or depolymerization during BBr3-
assisted deblocking.
The trimethylsilyl protecting group on PIB capped with tri-
methyl(3-phenoxy-1-propynyl)silane was removed with TBAF.
Typically, 0.4 g of trimethyl(3-phenoxy-1-propynyl)silane-capped
PIB (2.5 ꢀ 103 g/mol) was contacted with 10 mL of 1 M TBAF
solution for 3 h at room temperature. The polymer solution was
washed with deionized water, dried with MgSO4, and filtered,
and the solvent was removed under vacuum.
Results and Discussion
Anisole. Direct addition of anisole to a TiCl4-catalyzed
isobutylene polymerization at -70 °C in a 40/60 (v/v)
hexane/methyl chloride solvent system resulted in alkylation
of anisole and quantitative end-capping of the polyisobutyl-
ene chains. Exclusively monoalkylation, para to the alkoxy
moiety, was observed. This is consistent with previous
reports of TiCl4-catalyzed Friedel-Crafts alkylation of arenes
with tert-butyl and tert-amyl chlorides, which suggested
that para substitution products dominate.79 As shown by the
1H NMR spectrum in Figure 1A, resonances that would
otherwise appear at 1.69 and 1.96 ppm due to the ultimate
gem-dimethyl and methylene unit of tert-chloride PIB were
absent, and a new resonance appeared at 1.79 ppm due to the
ultimate PIB methylene unit adjacent to anisole, as well as
resonances at 6.82, 7.27, and 3.79 ppm, due to the alkylated
anisole. Integration of the anisole moiety resonances in
comparison with the aromatic initiator resonance at 7.17 ppm
indicated quantitative capping of the chain ends. Further
evidence of anisole alkylation is shown by the 13C NMR
spectrum in Figure 2A. Resonances at 71.9 and 35.2 ppm,
Isopropoxybenzene. The in situ demethylation of anisole-
capped PIB to provide phenolic end groups required harsh
conditions, i.e., addition of BBr3, due to the strength of the
methyl ether bond. More facile ether cleavage would be
possible with bulkier alkyl groups; therefore, isopropoxy-
benzene was alkylated by quasiliving PIB under conditions
similar to those used with anisole. Other alkyl groups could
be used to protect phenol, but they must be stable under the
alkylation reaction conditions.
1
A H NMR spectrum of the isopropoxybenzene-capped
PIB is shown in Figure 1B. Resonances due to the alkylated
isopropoxybenzene ring appear at 6.79 and 7.23 ppm, and a
resonance for the methine proton of the isopropyl moiety
appears at 4.51 ppm. Evidence of isopropoxybenzene alkyla-
tion is also given by the 13C NMR spectrum of Figure 2B by
resonances in both the aromatic region and at 22.2 and 69.7
ppm due to the terminal isopropyl moiety.
Attempted cleavage of the terminal isopropyl ether with
excess TiCl4 (5 equiv per chain end) at room temperature for
30-48 h resulted in near quantitative (91%) phenol functionality.

8730 Macromolecules, Vol. 43, No. 21, 2010
Morgan et al.
However, subsequent experiments with the addition of ex-
cess BBr3 (5 equiv) or BCl3 (15 equiv) quantitatively cleaved
the ether in less than 3 h while warming from -70 °C. The
simplest approach found for rapid cleavage of the isopropyl
ether was the addition of protic acid, namely H2SO4. With
TiCl4 and H2SO4 present in the reactor, less than 5 h was
required to obtain quantitative phenol functional PIB. NMR
spectra of the polymer obtained by H2SO4-assisted deblock-
ing of isopropoxybenzene-capped PIB were identical to those
in Figures 1C and 2C. Again, GPC traces of Figure 3B indi-
cated no chain coupling and no polymer degradation during
quenching and deblocking.
2,6-Di-tert-butylphenol. Addition of phenol and various
ring-alkylated phenols, such as 2-tert-butyl phenol, to TiCl4-
catalyzed isobutylene polymerizations did not yield alkyl-
ated chain ends. Failure of alkylation was probably due to
insolubility of the phenolic-TiCl4 complexes in the polym-
erization cosolvents in combination with deactivation of the
Lewis acid catalyst, as evidenced by the near quantitative
return of tert-chloride PIB. Only with the highly hindered
phenol, 2,6-di-tert-butylphenol, did alkylation proceed at
-70 °C in the 60/40 (v/v) methyl chloride/hexane solvent
system. Monoalkylation occurred in the para-position; how-
ever, de-tert-butylation from the ortho position was also
observed. De-tert-butylation on arenes is known to occur
in the presence of Lewis acids,81 and under appropriate
conditions, selective ortho-de-tert-butylation of substituted
phenols has been demonstrated.82 As shown by the 1H NMR
spectrum in Figure 4, 37% of the chain ends were de-tert-
butylated in about 1 h, and this amount increased over time:
44% at 5 h and 57% at 7 h. GPC traces shown in Figure 3C
indicate the absence of chain coupling.
Allyl Phenyl Ether. Quenching with an alkoxybenzene
whose alkoxy group contains a terminal olefin would repre-
sent a potential means of obtaining PIBs with an R-olefin
terminus. Unfortunately, alkylation of the simplest alkoxy-
benzene with R-olefin functionality, allyl phenyl ether, was
accompanied by simultaneous Claisen rearrangement and
ether cleavage. Narasaka et al.83 reported on the usefulness
of TiCl4 in catalyzing the [3,3]-sigmatropic concerted peri-
cylic rearrangement of allyl aryl ethers and found that hydro-
chloric acid generated during the reaction often resulted in
Figure 5. PIB chain-end composition after direct addition of allyl phenyl
ether to a TiCl4-catalyzed isobutylene polymerization. Alkylation of
allyl phenyl ether (O) is accompanied by Claisen rearrangement to form
2-allylphenol end groups (0) and ether cleavage to form phenol end
groups (Δ). The allyl functionality is also hydrochlorinated to provide
2-(2-chloropropyl)phenol end groups (ꢀ) (Table 1, entry 4).
Figure 6. 1H NMR (300 MHz, CDCl3, 22 °C) spectra of (A) 1-(2-chloroethoxy)-4-polyisobutylbenzene and (B) 1-vinyloxy-4-polyisobutylbenzene
obtained by direct addition of (2-chloroethoxy)benzene to TiCl4-catalyzed quasiliving isobutylene polymerization and subsequent postpolymerization
dehydrochlorination of the primary halide terminus (Table 1, entry 5).

Article
Macromolecules, Vol. 43, No. 21, 2010 8731
Figure 7. 13C NMR (75 MHz, CDCl3, 22 °C) spectra of (A) 1-(2-chloroethoxy)-4-polyisobutylbenzene and (B) 1-vinyloxy-4-polyisobutylbenzene
obtained by direct addition of (2-chloroethoxy)benzene to TiCl4-catalyzed quasiliving isobutylene polymerization and subsequent postpolymerization
dehydrochlorination of the primary halide terminus (Table 1, entry 5).
concomitant hydrochlorination of the newly formed o-allyl-
phenol. As shown in Figure 5, simultaneous Claisen rear-
rangement and hydrochlorination were observed in addition
to ether cleavage to provide chain ends capped with 2-(2-
chloropropyl)phenol and phenol functionality. The GPC
traces shown in Figure 3D indicate that the R-olefin was
unreactive toward polymerization and chain coupling. Higher
R-olefin homologues were not investigated because olefin
functionality can more easily be obtained via dehydrohalo-
genation of a primary halide functional PIB obtained via
in situ alkylation of ω-halo-alkoxybenzene.
(2-Chloroethoxy)benzene. Primary halide functional PIB
was readily obtained by quenching quasiliving PIB with (ω-
haloalkoxy)benzenes. For example, direct addition of 3
equiv per chain end of (2-chloroethoxy)benzene to a TiCl4-
catalyzed isobutylene polymerization at -70 °C in a 40/60
(v/v) hexane/methyl chloride solvent system resulted in
alkylation of (2-chloroethoxy)benzene, as shown by the 1H
NMR spectrum in Figure 6A. A resonance for the ultimate
PIB methylene unit adjacent to (2-chloroethoxy)benzene
appeared at 1.79 ppm, and resonances at 3.79 (triplet), 4.21
(triplet), 6.83 (doublet), and 7.27 ppm (doublet) were due to
the alkylated (2-chloroethoxy)benzene. Evidence of (2-
chloroethoxy)benzene alkylation is also given by the 13C
NMR spectrum of Figure 7A. Resonances at 71.9 and 35.2 ppm,
representing the ultimate quaternary and gem-dimethyl carbons
of tert-chloride PIB, respectively, were not present after the
alkylation reaction. A new set of resonances appeared in
Figure 8. GPC differential refractive index traces of PIB obtained from
both the aromatic region and at 41.8 and 68.0 ppm due
methylene carbons of the (2-chloroethoxy)benzene moieties.
Primary halide offers a wealth of opportunity for facile
nucleophilic substitution reactions useful in conversion to
other functionalities.84 With a two-carbon tether between
the halide and oxygen an easy transformation to a reactive
macromer can be achieved by dehydrohalogenation. The
primary chloride functional PIB was converted to a vinyl
TiCl4-catalyzed quasiliving isobutylene polymerizations quenched with
(A) (2-chloroethoxy)benzene and (B) (3-bromopropoxy)benzene: pre-
quench (dotted); postquench (solid); and after conversion of the
primary halide to vinyl ether (A only) and hydroxyl via benzoate
hydrolysis (B only) (dashed) (Table 1, entries 5 and 6). (C) Olefin-
terminated PIB (mixed olefin isomers: exo/endo = 5.4 mol/mol) was
also used to alkylate (3-bromopropoxy)benzene under conditions for
TiCl4-catalyzed quasiliving isobutylene polymerization: prequench (dotted);
postquench (solid).

8732 Macromolecules, Vol. 43, No. 21, 2010
Morgan et al.
Figure 9. 1H NMR (300 MHz, CDCl3, 22 °C) spectra of (A) R,ω-bis[4-(3-bromopropoxy)phenyl]polyisobutylene obtained by direct quenching of a
TiCl4-catalyzed quasiliving isobutylene polymerization with (3-bromopropoxy)benzene, (B) R,ω-bis[4-(3-benzoyloxypropoxy)phenyl]polyisobutylene
obtained by displacement of the primary bromide with benzoate, and (C) R,ω-bis[4-(3-hydroxypropoxy)phenyl]polyisobutylene obtained by
subsequent hydrolysis (Table 1, entry 6).
ether macromer by reaction with excess potassium tert-
butoxide in a refluxing mixture of 50/50 (v/v) heptane/DMF.
Under the conditions used, dehydrochlorination was com-
plete in less than 1 h. As shown in the 1H NMR spectrum in
Figure 6B, the resonances at 3.79 and 4.21 ppm due to the (2-
chloroethoxy)benzene methylene units are replaced by three
doublet-of-doublets centered at 4.37, 4.72, and 6.63 ppm due
to the terminal vinyl ether. The 13C NMR spectrum of Figure 5B
indicates formation of the vinyl ether by appearance of reso-
nances at 94.3 and 148.6 ppm. The GPC traces in Figure 8A
show that no chain coupling occurred during the alkylation
reaction, and no changes in molecular weight distribution
were observed after dehydrochlorination to the PIB-vinyl
ether macromer.
1H and 13C NMR spectra, respectively, of primary bromide
telechelic PIB obtained by directly charging an excess (2.5
equiv per chain end) of (3-bromopropoxy)benzene to TiCl4-
catalyzed quasiliving polyisobutylene in 40/60 (v/v) hexane/
methyl chloride at -70 °C. Evidence of (3-bromopropoxy)-
benzene alkylation is given in the 1H NMR spectrum by the
resonance for the ultimate PIB methylene unit adjacent to (3-
bromopropoxy)benzene at 1.79 ppm, and by resonances at
3.60 (triplet), 2.30 (quintet), 4.07 (triplet), 6.83 (doublet), and
7.27 ppm (doublet), due to the (3-bromopropoxy)benzene
moiety. After alkylation, the 13C NMR spectrum exhibited
new resonances in the aromatic region and at 30.1, 32.5, and
65.2 ppm due to methylene carbons of the (3-bromopropoxy)-
benzene moiety.
(3-Bromopropoxy)benzene. A primary bromide end group
offers even easier transformation to other functionalities via
nucleophilic substitution. Our previous publication demon-
strated quenching of a TiCl4-catalyzed quasiliving isobutyl-
ene polymerization with (3-bromopropoxy)benzene and
subsequent transformation of the primary bromide terminus
to azide and primary amine.85 An additional transformation
of interest is to primary hydroxyl. Figures 9A and 10A show
Conversion to primary hydroxyl was achieved by displace-
ment of bromide with excess sodium benzoate and sub-
sequent hydrolysis of the newly formed ester linkage.86 The
conversion was done in two steps in a solvent mixture of 50/
50 (v/v) heptane/DMF, which in such proportions are immis-
cible at room temperature but become monophasic upon
heating above 70 °C. The thermomorphic behavior of this
solvent system allows for polar reactants to be mixed and

Article
Macromolecules, Vol. 43, No. 21, 2010 8733
Figure 10. 13C NMR (75 MHz, CDCl3, 22 °C) spectra of (A) R,ω-bis[4-(3-bromopropoxy)phenyl]polyisobutylene obtained by direct quenching of a
TiCl4-catalyzed quasilivingisobutylene polymerization with(3-bromopropoxy)benzeneand(B)R,ω-bis[4-(3-hydroxypropoxy)phenyl]polyisobutylene
obtained by displacement of the primary bromide by benzoate and subsequent hydrolysis (Table 1, entry 6).
reacted with polyisobutylene at high temperatures, while
allowing facile purification of the polymer upon cooling
due to its high phase selectivity for heptane.87 Sodium
benzoate and the primary bromide-terminated PIB were
refluxed in 50/50 (v/v) DMF/heptane for 4 h. After cooling
and phase separation, the benzyl ester-terminated polymer
was isolated in the heptane layer. The 1H NMR spectrum in
Figure 9B shows the presence of the phenyl ester by multi-
plets at 7.43, 7.55, and 8.04 ppm, and the resonance for the
terminal tether methylene unit has shifted downfield from
3.60 to 4.52 ppm due the electron-withdrawing ester linkage.
The PIB in heptane was then mixed with an equal volume of
DMF containing sodium hydroxide and heated to reflux for
12 h. After cooling and phase separation, the primary hydroxyl-
terminated polymer was isolated in the heptane layer.
TiCl4-catalyzed quasiliving PIB in 60/40 (v/v) hexane/methyl
chloride at -70 °C. As evidenced by the methyl resonance at
3.44 ppm, the highly reactive silyl chloride end groups were
converted to silyl methoxy end groups after destroying the
catalyst with excess methanol. The GPC traces shown in
Figure 12 indicated that a small amount of chain coupling
occurred. However, coupling was due to mutual reaction of
the silyl end groups during work-up, rather than dialkylation
of the 3-phenoxypropyldimethylchlorosilane.
Trimethyl(3-phenoxy-1-propynyl)silane. There has been
recent interest in alkyne-terminated PIB for use in Huisgen
1,3-dipolar cycloaddition (“click”) reactions, which provide
a facile route for the synthesis of block copolymers,90,91
cyclic PIBs,92 and supramolecular gels.93 Alkyne functional-
ity on an alkoxybenzene presents difficulty due the activity
of the triple bond in polymerization. When phenyl propargyl
ether was added directly to a TiCl4-catalyzed quasiliving iso-
butylene polymerization, a significant amount of chain coupling
occurred. To prevent coupling, a trimethylsilyl blocking
group was added, which was sufficient to prevent carboca-
tion addition across the triple bond. As indicated by the
resonance at 0.17 ppm in the 1H NMR spectrum of Figure 13A,
∼90% of the trimethylsilyl groups remained intact after
termination of the polymerization. Upon treatment with
TBAF, the alkyne proton triplet at 2.49 ppm became evident
as shown in the 1H NMR spectrum of Figure 13B. The GPC
traces in Figure 12B indicate no chain coupling during
polymerization, quenching, and deblocking.
1
Figure 9C shows a H NMR spectrum of the purified PIB
in which the resonance for the methylene unit adjacent to the
terminal hydroxyl appears at 3.87 ppm. Primary hydroxyl
functionality is also evidenced in the 13C NMR spectrum of
Figure 10B by the resonance at 60.9 ppm due the carbon
adjacent to the hydroxyl. The GPC traces of Figure 8B
indicated no changes in molecular weight during nucleo-
philic displacement of the bromide and hydrolysis of the ester.
3-Phenoxypropyldimethylchlorosilane. Functionalization
of PIB with Si-Cl and Si-H termini was first achieved by
Kennedy et al.88 via hydrosilylation of exo-olefin-terminated
PIB. Later, silicon functional initiators were developed,89
and subsequent work has shown that silyl chlorides can
survive conditions of TiCl4-catalyzed quasiliving isobutylene
polymerization.29-31 These approaches to silicon functional
PIBs require either multiple steps or initiators that are not
commercially available. With the alkoxybenzene quencher,
3-phenoxypropyldimethylchlorosilane, we were able to ob-
tain silicon functional PIB in a single step. Figure 11 shows a
1H NMR spectrum of silicon functional PIB obtained by
direct addition of 3-phenoxypropyldimethylchlorosilane to
Phenoxyalkanol and Phenoxyalkylamine. Direct addition
of molecules with unprotected hydroxyl groups to reaction
media containing strong Lewis acids such as TiCl4 generally
leads to decomposition of the Lewis acid (formation of
titanates) and cessation of catalyst activity. Thus, most
literature reports indicate that when a TiCl4-catalyzed quasi-
living isobutylene polymerization is charged with a hard
nucleophile such as hydroxyl, tert-chloride chain ends are

8734 Macromolecules, Vol. 43, No. 21, 2010
Morgan et al.
Figure 11. 1H NMR (300 MHz, CDCl3, 22 °C) spectrum of R,ω-bis[4-(3-methoxydimethylsilylpropoxy)phenyl]polyisobutylene obtained by direct
quenching of a TiCl4-catalyzed quasiliving isobutylene polymerization with 3-phenoxypropyldimethylchlorosilane and subsequent reaction with
methanol (Table 1, entry 7).
returned.94 However, the successful use of low concentra-
tions of unprotected hydroxyl groups on initiators27 and
capping agents95 has been reported, but with complica-
tions. To alleviate such problems, the hydroxyl group
may be protected and unmasked only after the TiCl4 catalyst
has performed its service.96 Rather than seek a suitable
blocking group for a phenoxyalkanol, our approach in-
volved direct addition of an unmodified phenoxyalkanol to
the quasiliving PIB. The rationale for such an approach was
that the site of alkylation, i.e., the phenyl ring, could be
spatially separated from the functionality of interest, i.e., the
hydroxyl. If sufficient TiCl4 remained in the reaction after
titanate formation, then the alkylation could be successfully
carried out, albeit with a higher demand for TiCl4.
Our initial attempts with the simplest phenoxyalkanol
having a two-carbon tether, 2-phenoxyethanol, proved un-
successful. Subsequent systematic experimentation showed
that with tether lengths of two and three carbons interaction
with TiCl4 was detrimental to the desired alkylation; how-
ever, phenoxyalkanols with carbon tethers of four or greater
were alkylated by TiCl4-catalyzed quasiliving PIB. Figure 14
illustrates the effect of the TiCl4 concentration during alkyl-
ation of 4-phenoxy-1-butanol. The alkylation reaction pro-
ceeds rapidly at first and then slows, and higher levels of
TiCl4 provide higher capping efficiencies for a given reaction
time. However, analysis of the data in Figure 14A,B shows
that the disappearance of tert-chloride functionality is more
rapid than the appearance of hydroxyl functionality, parti-
cularly at high [TiCl4]. This indicates accumulation of a
slowly reacting intermediate, which we propose to be isomerized
chain ends resulting from carbenium ion rearrangement.97
Figure 12. GPC differential refractive index traces of PIB obtained from
When the ratio of TiCl4 to 4-phenoxy-1-butanol was 2.5 or
higher, over 60% of the chain ends were capped within
30 min; however, 30-40% of the chain ends had also become
rearranged. Despite the loss of tert-chloride functionality,
alkylation slowly continued, and the hydroxyl functionality
increased over time as shown in Figure 14B. In this latter
stage of reaction, we propose that alkylation occurs through
isomerized tertiary and possibly secondary chloride struc-
tures that arise from TiCl4-catalyzed rearrangement. Longer
tether lengths were investigated to determine the effect of
increased separation between the titanate and the site of
alkylation. As shown in Figure 15, increasing the tether
a TiCl4-catalyzed quasiliving isobutylene polymerization quenched
with (A) 3-phenoxypropyldimethylchlorosilane, (B) trimethyl(3-phen-
oxy-1-propynyl)silane, and (C) 4-phenoxy-1-butanol: prequench (dotted);
postquench (solid), and after deprotection of the alkyne moiety (dashed,
B only) (Table 1, entries 7-9).
length to six and eight carbons did provide increased hydro-
xyl functionality for a given reaction time. However, the
phenoxyalkanols with longer tethers were marginally better
since the same result could be achieved with 4-phenoxy-
butanol using longer reaction time or more TiCl4.
To achieve near-quantitative hydroxyl functionality via
direct quenching, the alkylation of 4-phenoxy-1-butanol was

Article
Macromolecules, Vol. 43, No. 21, 2010 8735
Figure 13. 1H NMR (300 MHz, CDCl3, 22 °C) spectra of (A) 1-(3-trimethylsilyl-2-propynyloxy)-4-polyisobutylbenzene and (B) 1-(propargyloxy)-4-
polyisobutylbenzene obtained by direct addition of trimethyl(3-phenoxy-1-propynyl)silane to TiCl4-catalyzed quasiliving isobutylene polymerization
and subsequent postpolymerization removal of the trimethylsilyl blocking group (Table 1, entry 8).
Figure 15. Number-average hydroxyl functionality of quasiliving PIB
quenched with4-phenoxy-1-butanol(Δ), 6-phenoxy-1-hexanol(O), and
8-phenoxy-1-octanol (0). Polymerization/quench at -70 °C in 40/60
(v/v) hexane/methyl chloride, [2,6-lutidine] = 0.005 M, [t-Bu-m-DCC ] =
0.025 M, [isobutylene] = 1.1 M, [TiCl4] = 0.015 M (polymerization),
[quencher] = 0.125 M, and [TiCl4] = 0.19 M during quench.
allowed to proceed for 8 h in the presence of a large excess of
TiCl4 as described in Figures 16A. The terminal methylene
unit adjacent to the hydroxyl end group was observed at 3.72
ppm (triplet) in the 1H NMR spectrum of Figure 16A and at
62.6 ppm in the 13C NMR spectrum of Figure 17A. The GPC
traces in Figure 12C indicate that no coupling or degradation
Figure 14. Fraction of chain ends bearing (A) tert-chloride and (B)
hydroxyl functionality as a function of time for various concentrations
of TiCl4 after direct addition of 4-phenoxy-1-butanol to TiCl4-catalyzed
quasiliving isobutylene polymerizations. Polymerization/quench at -70 °C
in 40/60 (v/v) hexane/methyl chloride, [2,6-lutidine] = 0.005 M, [t-Bu-
m-DCC ] = 0.025 M, [isobutylene] = 1.1 M, [TiCl4] = 0.015 M (poly-
merization), [4-phenoxy-1-butanol] = 0.125M, and[TiCl4] = 0.165 (0),
0.19 (O), 0.215 (Δ), and 0.315 M (ꢀ) during quench.
occurred during the 8 h alkylation reaction.
Arguably the more difficult direct functionalization via
alkoxybenzene quenching would be with amine because of
anticipated reactivity toward both TiCl4 and PIB carbenium
ions. To prevent proton abstraction from the carbenium ion
chain end, the amine either must be sufficiently hindered to
prevent approach to the chain end or sufficiently unhindered

8736 Macromolecules, Vol. 43, No. 21, 2010
Morgan et al.
Figure 16. 1H NMR (300 MHz, CDCl3, 22 °C) spectra of (A) R,ω-bis[4-(4-hydroxybutoxy)phenyl]polyisobutylene obtained by direct quenching of
a TiCl4-catalyzed quasiliving isobutylene polymerization with 4-phenoxy-1-butanol and (B) R,ω-bis[4-(6-aminohexoxy)phenyl]polyisobutylene
obtained by quenching with 6-phenoxyhexylamine (Table 1, entries 9 and 10).
Figure 17. 13C NMR (75 MHz, CDCl3, 22 °C) spectra of (A) R,ω-bis[4-(4-hydroxybutoxy)phenyl]polyisobutylene obtained by direct quenching of
a TiCl4-catalyzed quasiliving isobutylene polymerization with 4-phenoxy-1-butanol and (B) R,ω-bis[4-(6-aminohexoxy)phenyl]polyisobutylene
obtained by quenching with 6-phenoxyhexylamine (Table 1, entries 9 and 10).

Article
Macromolecules, Vol. 43, No. 21, 2010 8737
Figure 18. Second-order kinetic plot for TiCl4-catalyzed alkylation of
butyl phenyl ether (O), (3-bromopropoxy)benzene (ꢀ), anisole (0), allyl
phenyl ether (þ), (2-bromoethoxy)benzene (Δ), and (2-chloroethoxy)-
benzene (]) by quasiliving PIB. Polymerization/quench was con-
ducted at -70 °C in 40/60 (v/v) hexane/methyl chloride, with [2,6-
lutidine] = 0.005 M, [TMPCl] = 0.05 M, [IB] = 1.58 M, [TiCl4] =
0.015 M (polymerization), [quencher] = 0.1 M, and [TiCl4] = 0.09 M
(quench).
so that its nucleophilicity is mitigated through quantitative
complexation with TiCl4. When the completely unhindered
amine, 6-phenoxyhexylamine, was charged to a quasiliving
isobutylene polymerization, with excess TiCl4 to account for
complexation, alkylation proceeded as with 4-phenoxybuta-
nol, and over 65% of the chains were capped within the first
20 min. The rate of alkylation then slowed significantly,
likely due to depletion of TiCl4 via formation of Ti2Cl9- ions,
which are formed when the amino tethers are protonated by
the HCl generated from the alkylation reaction. After 9 h,
near-quantitative primary amine functionality was obtained.
The 1H NMR spectrum of the product in Figure 16B shows a
triplet at 2.70 ppm characteristic of the terminal methylene
unit adjacent to the amine, and the 13C NMR spectrum in
Figure 17B shows a resonance at 42.1 ppm, also character-
istic of the terminal methylene unit adjacent to the amine. In
Figure 19. Plots of the apparent second-order rate constant (kcKeq-
[TiCl4]effective2[PIBCl]0) for TiCl4-catalyzed alkylation of anisole by
quasiliving PIB as a function of (A) the anisole concentration as M =
[anisole]0/[TMPCl] and (B) the effective TiCl4 concentration, defined as
[TiCl4]effective = [TiCl4] - 2[2,6-lutidine]. Polymerization/quench at -70 °C
in 40/60 (v/v) hexane/methyl chloride, [2,6-lutidine]=0.005 M, [TMPCl]=
0.05 M, [isobutylene]=1.58 M, [TiCl4]=0.015 M (polymerization),
[anisole] = 0.125 M (B only), and [TiCl4]=0.09 M (quench, A only).
under the conditions described in Figure 18, near-quantita-
tive capping of the chain ends could be achieved in ∼10 min.
For anisole, (3-bromopropoxy)benzene, and allyl phenyl
ether, the rate of alkylation was more than 2.5 times slower
than for butyl phenyl ether. When electron-withdrawing
halides become closer to the phenyl ring as with (2-bromo-
ethoxy)benzene and (2-choroethoxy)benzene, the reactiv-
ity was further decreased by a factor of 5. Though longer
alkyl tethers help to minimize electronic and steric inter-
ference with the alkylation reactions, as well as promote
solubility, they come at the expense of increased mass at the
PIB chain end.
1
both the 13C and H NMR spectra there is no evidence of
olefin formation.
Alkylation Kinetics. The rate of alkoxybenzene alkylation
by TiCl4-catalyzed quasiliving PIB (quenching) may be
described by the following second-order rate equation
dp
2
¼ kcKeq½TiCl4ꢁ ½PIBClꢁ0ð1 - pÞðM - pÞ
ð1Þ
dt
where p is conversion of tert-chloride chain ends, kc is the rate
constant for alkylation, [PIBCl]0 is initial chain end concen-
tration, [TiCl4] is the effective concentration of TiCl4 avail-
able for participation in the ionization equilibrium, M =
[alkoxybenzene]0/[PIBCl]0 is the ratio of the initial alkoxy-
benzene concentration to the initial tert-chloride chain end
concentration, and Keq is the ionization equilibrium con-
stant. If [TiCl4] is in large excess relative to basic additives
such as 2,6-lutidine, then the formation of onium salts
through HCl scavenging does not significantly diminish
[TiCl4], and eq 1 may be integrated to yield
Second-order kinetics for anisole alkylation were further
studied as a function of both M and the effective TiCl4
concentration, defined as [TiCl4]effective = [TiCl4] - 2[2,6-
lutidine]. This definition of [TiCl4]effective accounts for the
fact that all of the 2,6-lutidine in the system is converted to
onium salts (C8H10NþTi2Cl9-) early in the reaction. Figure
19A is a plot of the slope obtained from eq 2 as a function of
M; Figure 19B is a ln-ln plot of the slope obtained from eq 2
as a function of [TiCl4]effective. The kinetic model represented
by eq 2 does not account for diminution in TiCl4 activity as a
result of interaction between the alkoxybenzene and TiCl4.
However, the effect of interaction is clearly manifested in
Figure 19A by the initially declining slope as M rises from
1 to about 1.6. This represents the range of M for which
[anisole] < [TiCl4]effective, and therefore, increasing [anisole]
reduces TiCl4 activity. For values of M greater than 1.6,
[anisole] > [TiCl4]effective. Within this regime of anisole con-
centrations, the anisole-TiCl4 interaction is saturated, and
additional anisole causes no further decline in the slope or
decrease in TiCl4 activity. Figure 19B shows that the alkylation
of anisole has a second-order dependence on the effective
ꢀ
ꢁ
M - p
Mð1 - pÞ
2
ln
¼ kcKeq½TiCl4ꢁ ½PIBClꢁ0ðM - 1Þt
ð2Þ
Figure 18 shows data for the alkylation of several alkoxy-
benzenes by TiCl4-catalyzed quasiliving PIB at -70 °C in
40/60 (v/v) hexane/methyl chloride, plotted according to
eq 2. From the plots it is clear that the rate of alkylation is
heavily dependent on the identity of the alkyloxy tether. The
fastest rate of alkylation was for butyl phenyl ether, and

8738 Macromolecules, Vol. 43, No. 21, 2010
Morgan et al.
TiCl4 concentration, reflecting the well-known second-order
dependency of ionization on [TiCl4]effective
Alkylation with Olefinic PIB. For all of the TiCl4-catalyzed
isobutylene polymerizations and in situ alkylation reactions
discussed to this point, yield of the desired alkylated PIB was
never diminished because of the presence of terminal un-
saturations, even under conditions where olefin-terminated
PIB would likely be formed via β-proton expulsion or
abstraction, i.e., above -40 °C.99 Even when small fractions
of olefin termini were observed in a prequench aliquot, they
disappeared over the course of the alkylation (quenching)
reaction. Though it is not surprising that a PIB olefin
terminus serves as an alkylating agent, this observation is
technologically important because it signifies that quantita-
tive functionalization with an alkoxybenzene is still attain-
able even under conditions where the prior polymerization is
less than perfectly living and termination has occurred. To
definitively illustrate alkylation via olefinic PIB, a sample of
monofunctional, olefin-terminated PIB (mixed olefin iso-
mers: exo/endo = 5.4 mol/mol) was reacted with (3-bromo-
propoxy)benzene under conditions similar to those used in
the quasiliving polymerization of isobutylene, i.e., TiCl4
catalysis at -70 °C in 40/60 (v/v) hexane/methyl chloride.
As shown by the 1H NMR spectra of Figure 21, both the exo-
and endo-olefin were rapidly hydrochlorinated in the pre-
sence of TiCl4. Within the first 5 min of the reaction, no exo-
olefin remained and ∼10% of chains exhibited endo-olefin
termini. Within 3.5 h all of the exo- and endo-olefin chain
ends were capped with (3-bromopropoxy)benzene as indi-
cated by the disappearance of resonances at 1.69 and 1.96
ppm due to the ultimate gem-dimethyl and methylene units
of tert-chloride PIB as well as the disappearance of the
resonances at 1.78, 2.0, 4.64, and 4.84 ppm due to the
exo-olefin and 1.62, 1.66, and 5.15 ppm due to endo-olefin.
98
.
Figure 20 demonstrates that the rate of alkylation in-
creases with decreasing temperature. This phenomenon is
due to the apparent negative activation energy associated
with the TiCl4-catalyzed ionization of the tert-chloride chain
ends. Activation energies for the apparent rate constant
kcKeq calculated from the slopes of the data in Figure 20
were -7.0 and -6.6 kcal/mol for the hexane/methyl chloride
and toluene/dichloromethane solvent systems, respectively.
Figure 20. van’t Hoff plots for TiCl4-catalyzed alkylation of anisole by
quasiliving PIB using 40/60 (v/v) hexane/methyl chloride (O) and 50/50
(v/v) toluene/methylene chloride (0) solvent systems. Polymerization/
quench at -70 to -40 °C, [2,6-lutidine] = 0.005 M, [TMPCl] = 0.05 M,
[isobutylene] = 1.58 M, [TiCl4] = 0.015 M (polymerization), [anisole] =
0.1 M, and [TiCl4] = 0.09 M (quench).
Figure 21. 1H NMR (300 MHz, CDCl3, 22 °C) spectra of olefin-terminated PIB (mixed olefin isomers: exo/endo = 5.4 mol/mol) as a function of time
during the TiCl4-catalyzed alkylation of (3-bromopropoxy)benzene. Alkylation was conducted at -70 °C in 40/60 (v/v) hexane/methyl chloride;
[PIB] = 0.01 M, [(3-bromopropoxy)benzene] = 0.03 M, and [TiCl4] = 0.06 M.

Article
Macromolecules, Vol. 43, No. 21, 2010 8739
ꢀ
€
(10) Feldhusen, J.; Ivan, B.; Muller, A. H. E. Macromol. Rapid Com-
The remaining resonances after 3.5 h at 1.79, 2.30, 3.60, 4.07,
6.83, and 7.27 ppm were due to the (3-bromopropoxy)-
benzene-capped chain ends. The GPC traces (Figure 8C) of
the olefin-terminated PIB precursor and final product
showed no significant differences; the molecular weight
(polydispersity) before and after the alkylation reaction were
3.1 ꢀ 103 (1.35) and 3.3 ꢀ 103 g/mol (1.30), respectively. The
reaction as described in Figure 21 was performed in the
absence of a basic additive; however, in the presence of an
additive typically used to enhance “livingness” of the iso-
butylene polymerization, e.g., 2,6-lutidine, both hydrochlori-
nation and subsequent alkylation by olefin-terminated PIB
were greatly inhibited. This was expected; the base serves as a
proton trap, and the olefin cannot be protonated to form a
carbenium ion. When quenching an isobutylene polymeri-
zation at higher temperatures (>-40 °C), where the end
groups are mixed tert-chloride and olefin, alkylation by the
former produces HCl concentrations in far excess of the
basic additive for moderately high chain end concentrations,
i.e., >0.01 M, and alkylation via olefin end groups is
uninhibited.
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Supporting Information Available: 13C NMR spectrum of
1-(3-bromopropoxy)-4-polyisobutylbenzene obtained by alkyl-
ation of 3-bromopropoxybenzene by olefin-terminated PIB
(mixed olefin isomers: exo/endo = 5.4 mol/mol), catalyzed by
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0.01 M, [(3-bromopropoxy)benzene] = 0.03 M, [TiCl4] = 0.06
M (Figure A). This material is available free of charge via the
Internet at http://pubs.acs.org.
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