Introducing polar monomers into polyisobutylene by living cationic polymerization: structural and kinetic effects

Article abstract of DOI:10.1021/ma9025114

We report on the direct copolymerization of polar styrene monomers with isobutylene (IB) using living cationic polymerization with TiCl ₄/TMPCl as initiators, for the first time opening the possibility to introduce polar moieties in a direct co

Full text of DOI:10.1021/ma9025114

Macromolecules 2010, 43, 1761–1770 1761
DOI: 10.1021/ma9025114
Introducing Polar Monomers into Polyisobutylene by Living Cationic
Polymerization: Structural and Kinetic Effects
€
Katharina Hackethal, Diana Dohler, Susanne Tanner, and Wolfgang H. Binder*
Chair of Macromolecular Chemistry, Institute of Chemistry, Division of Technical and Macromolecular
€
Chemistry, Faculty of Natural Sciences II (Chemistry and Physics), Martin-Luther Universitat
Halle-Wittenberg, Halle 06099, Germany
Received November 13, 2009; Revised Manuscript Received January 11, 2010
ABSTRACT: We report on the direct copolymerization of polar styrene monomers with isobutylene (IB)
using living cationic polymerization with TiCl4/TMPCl as initiators, for the first time opening the possibility
to introduce polar moieties in a direct copolymerization approach into PIB polymers. The investigated polar
styrene monomers contain pyridine (1a), collidine (1b, 1c), thymine (2c), and/or triazole moieties (2a-2c).
Copolymerization with styrene monomers 1a, 1b, and 2c proceeded under incorporation of the comonomer
into the PIB polymer (as proven by MALDI and NMR spectroscopy), whereas monomer 1c was not
incorporated and resulted in broad polydispersities of the resulting PIB polymers. Inline-IR kinetic
measurements of the monomer consumption demonstrated strong effects of the monomer structure on
the polymerization kinetics, with rates of polymerization (kp) increasing up to a factor of 15. The addition
of nonpolymerizable additives containing triazole moieties revealed a strong dependency on the attached
residue R (R=hexyl (3a), phenyl (3b), p-methoxyphenyl (3c), p-methylphenyl (3d), p-chlorophenyl (3e)), with
a decreasing rate of polymerization (kp) in the order of 3e >3b >3c > 3e> 3a= kp(IB). Measurements of
kp/k-1 displayed significant changes with respect to homopolymerization of IB under the same conditions,
proving that ion equilibria are disturbed by addition of the polar species during the IB polymerization.
Introduction
molecular weight and polydispersity.19 As recently pointed out by
Storey et al.,20 the use of such additives serves primarily to control
Polyisobutylene (PIB) can be prepared solely by free or living
cationic polymerization of isobutene (IB), based on the well-
known chemistry to reduce the concentration of the cationic
intermediates by appropriate ion equilibria,1,2 thus avoiding
chain transfer reactions. As the monomer itself is limited in its
structural variability, the quest for modification and property
enhancement of PIB arises as an urgent need as PIB is used in
many technical applications3 as well as in special applications
such as in medicine4 and biology.5 Solutions to increase the
structural variability of PIB by introducing other monomer units
can either be approached by copolymerization or via appropriate
modifications at starting- or end-group moieties. Thus, the direct
copolymerization of IB with monomers subjectable to cationic
polymerization (such as styrene6-13 vinyl ethers5,14,15) yields
either statistical or block copolymers, thus expanding its struc-
tural and biological applications by the well-known modifica-
tions in thermal and chemical properties. Recently, a methylene-
homologous polymer of PIB via a ROMP polymerization has
been reported.16 However, the direct introduction of highly polar
monomers (i.e., those serving as hydrogen donor-acceptor
structures17) into PIB via cationic polymerization has not been
accomplished, as the complex equilibrium between “dormant =
tert-chlorine-telechelic” and “active=cationic” species are often
severely changed by the addition of even slightly polar additives,
leading to either a quench of the living PIB cation or to the
generation of exo-alkene end groups.18 The use of specific polar
additives to modify or improve control over the living cationic
polymerization of IB is well-known and has been investigated
extensively.15 Thus, sterically hindered amines (i.e., pyridine,
collidines, di-tert-pyridine), quaternary ammonium cations,
DMSO, or esters can be used to effect improved control over
the equilibrium between “dormant” and “active” species rather
than to remove protic impurities or reduce the “cationicity” of the
active (growing) species.
Another strategy to chemically modify PIB is directed toward
the use of functional initiator21,22 or quenching moieties.18 Well-
known examples include the use of nonpolymerizable quen-
chers with methanol (1,1-diphenylethylene/methanol),23 furane,24
4-alkoxybenzene,25 sulfonium,26 and N-methylpyrrole moieties.18
Other methods involve the “postmodification” of telechelic
PIB’s, introducing complex hydrogen bonds27-30 or amines,31
i.e., via azide/alkine “click” chemistry,28,30,32-34 nucleophilic
substitution reactions,27,29,31 or activated chloromethyl ethers.27
However, in these latter cases only the end group a PIB polymer
can be modified, whereas a direct introduction of hydrogen
bonding units by copolymerization has not been accomplished.
The present paper investigates the direct copolymerization of
polar monomers (bearing hydrogen donor/acceptor moieties)
with IB using the living cationic polymerization approach with
TiCl4/TMPCl as initiators. The polar moiety is introduced within
a styrene moiety, as structural variations on the IB molecule are
not possible due to the close proximity of the polar moiety to the
growing cation, which would immediately destroy the livingness
of the polymerization reaction (see Scheme 1). Polar moieties
such as pyridine, collidine, and thymine units are investigated.
As comparison, additional information on the copolymerization
is obtained by inline-IR monitoring of the polymerization kine-
tics, comparing the polar monomers with the structurally related
polar additives.
Experimental Part
Materials. Tetrahydrofuran (THF), toluene, and diethyl
ether were dried over KOH and freshly distilled over Na and
*Corresponding author. E-mail: wolfgang.binder@chemie.uni-halle.de.
r 2010 American Chemical Society
Published on Web 01/25/2010
pubs.acs.org/Macromolecules

1762 Macromolecules, Vol. 43, No. 4, 2010
Hackethal et al.
Scheme 1
(10 mL reaction mixture of 4; see Supporting Information) was
added dropwisely under soft stirring, during which the solution
was allowed to reach room temperature. After complete addi-
tion of 4 the mixture was heated to 40 °C and stirred for 3 days.
For quenching the reaction 2 mL of methanol was added, and
THF was removed under reduced pressure. The resulting oil was
dissolved in dichloromethane and washed with deionized water
and brine. The resulting solution was then dried over Na2SO4
and evaporated to dryness. The crude 1-(2-pyridylethyl)-4-vinyl-
benzene was purified by column chromatography (SiO2, di-
chloromethane/methanol=100/1; Rf =0.36-0.14) to yield 1a:
0.66 g (3.16 mmol, 63%). 1H NMR (CDCl3, 400 MHz): δ 8.46
(d, 2H, J=6.03, Ar-H), 7.28 (d, 2H, J=8.13, Ar-H), 7.08 (dd,
4H, J=6.09, Ar-H), 6.68 (dd, 1H, J=10.87, CHdC), 5.71 (d,
1H, J=16.74, CdCH2), 5.20 (d, 1H, J=10.88, CdCH2), 2,99
(s, 4H, CH2). 13C NMR (CDCl3, 100 MHz): δ 150.2 (CdN),
149.6 (tertC-hetero-Ar), 140.22 (tertC-CH2), 136.42 (CH=),
135.6 (tertC-CHdCH2), 128.5 (Ar), 126.2 (Ar), 123.8 (Ar),
113.2 (CH2=), 36.87 (CH2), 36.2 (CH2).
(4-(2,6-Dimethylpyridylethyl)-4-vinylbenzene (1b) and 1-(2-(4,6-
Dimethylpyridylethyl)-4-vinylbenzene (1c). The experimental pro-
cedure was adopted from ref 36. Butyllithium in hexane (2.5 M,
2 mL, 5 mmol) was dissolved in 1.2 mL of freshly distilled THF
(solution A). Diisopropylamine (DIPA) (0.7 mL, 5 mmol) was
dissolved in 15 mL of THF and added to solution A. After stirring
for15minasolutionofsym-collidine (0.67 mL, 5 mmol, dissolved in
2.5 mL of THF) was added dropwise to the reaction mixture. After
complete addition the reaction mixture was cooled (to -50 °C) and
stirred for 1 h at this temperature. Subsequently a solution of 4
(10 mL reaction mixture of 4; see Supporting Information) in THF
was added dropwise within 1 h while stirred at -50 °C. The reac-
tion mixture was then allowed to reach room temperature and
subsequently heated to 40 °C and stirred for 4 days, then cooled to
0 °C, and quenched by addition of 10 mL of cooled water. The
organic phase was washed with 10% NaOH solution and the
product was extracted with diethyl ether (3ꢀ30 mL) and dried over
Na2SO4. After evaporation of the solvent the product was dis-
solved in hexane. Purification was carried out by column chroma-
tography (SiO2 (80 g), hexane:dichloromethane = 1:3); Rf = 0.4
(dichloromethane:hexane:methanol=3:1:0.3). Because of still pre-
sent impurities a second column chromatography was required.
After drying the product excessively in high vacuum, the second
purification with column chromatography (SiO2 (160 g), hexane:
ethyl acetate = 1:3) yielded two products. The main product was
1b; the major second side product could be assigned to the regio-
isomer 1c (Rf = 0.37). Yield: 1b 230 mg (1 mmol, 20% o.th); 1c
60 mg (0.25 mmol, 5% o.th).
benzophenone. Hexane was distilled, heated under reflux with
sulfuric acid, washed with water and NaOH-solution, dried
over Na2SO4, and finally freshly distilled over CaH2. Dichloro-
methane (DCM) was dried over KOH and freshly distilled over
CaH2. Styrene was destabilized by washing with NaOH solution
and then with water and dried over Na2SO4 and freshly distilled
over CaH2. IB was piped through KOH for drying. 2-Chloro-
2,4,40-trimethylpentane (TMPCl) was synthesized as described
in the literature,35 and the pure product was stored in a freezer.
All other reagents, in particular the alkynes 7a (purity g95%),
7b (purity g97%), 8c, 8d (purity 97%), and 8e (purity 98%),
were purchased from Sigma-Aldrich and used without further
purification.
Instrumentation. 1H NMR (400 MHz) and 13C NMR (100 MHz)
spectra were recorded using CDCl3 as solvent on a Varian
Gemini 2000 FT-NMR spectrometer. For the interpretation
of the spectra MestReC 4.7.0.0 was used. The chemical shifts
were given in ppm, and the coupling constants were given in Hz.
Number-average molecular weights (Mn) and molecular weight
distribution were determined using gel permeation chromato-
graphy (GPC) with THF as eluent in a flow rate of 1 mL/min on
a Viscotek GPCmax VE 2001 using a refractive index detec-
tor (VE 3580 RI detector, Viscotek) and column set HHR
þ
GMHHR-N (Viscotek, mixed bed). Calibration was made by
polystyrene (1050-115 000 g/mol) and PIB standards (340-
87 300 g/mol).
Inline monitoring of the IB polymerization was done with a
Bruker Vertex 70 MIR spectrometer. The kinetic measurements
were made with an attenuated total reflection (ATR) FT-IR
fiber optics equipped with a diamante prism with a scan number
of 20 scans per spectra in a resolution of 4 cm-1 so that one
spectrum could be achieved within 9 s. Conventional IR mea-
surements were carried out with an ATR-Golden Gate unit
using a diamond crystal. The scan number was 32 scans per
spectra with a resolution of 2 cm-1
.
(4-(2,6-Dimethylpyridylethyl)-4-vinylbenzene (1b). 1H NMR
(CDCl3, 400 MHz): δ 7.3 (d, 2H, J = 6.1, Ar-H), 7.11 (d, 2H,
Ar-H), 6.76 (d, 2H, Ar-H), 6.68 (dd, 1H, J=10.88, CHdC),
5.71 (d, 1H, J=18.05, CdCH2), 5.18 (d, 1H, J=11.3, CdCH2),
2.85 (m, 2H, CH2), 2.81 (m, 2H, CH2), 2.46 (s, 6H, Ar-CH3).
13C NMR (CDCl3, 100 MHz): δ 157.6 (tertC-N), 150.9 (tertC-
hetero-Ar), 140.8 (tertC-CH2), 136.6 (CH=), 135.6 (tertC-
CHdCH2), 128.6 (Ar), 126.2 (Ar), 120.4 (Ar), 113.2 (CH2=),
36.9 (CH2), 36.4 (CH2), 24.4 (CH3).
Matrix-assisted laser desorption ionization (MALDI) time-
of-flight (TOF) mass spectroscopy (MS) measurements were
performed with a Bruker autoflex III smartbeam mass spectro-
meter equipped with a TOF analyzer and a nitrogen laser
delivering 3 ns laser pulses at 337 nm. The positive ions were
detected in the linear and reflectron mode. Polymer samples
(2 mg/mL) in THF were prepared with trans-2-[3-(4-tert-butyl-
phenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) mat-
rix (40 mg/mL in THF). To produce cations, silver trifluoro-
acetate (AgTFA) dissolved in THF at a concentration of 1 mg/mL
was added to the matrix/analyte solution. The solutions were
mixed in 10:5:1 volume ratio (matrix:analyte:salt). A volume of
0.5 μL of these solutions was deposited onto the target plate
(stainless steel) and allowed to air-dry. MALDI-TOF-MS spec-
tra were recorded with flexControl 3.0. Peaks were analyzed
using flexAnalysis 3.0 software. For simulation DataAnaly-
sis4.0 and IsotopePattern were used.
1-(2-(4,6-Dimethylpyridylethyl)-4-vinylbenzene (1c). 1H NMR
(CDCl3, 400 MHz): δ 7.3 (d, 2H, J = 6.1, Ar-H), 7.16 (d, 2H,
Ar-H), 6.79 (d, 2H, Ar-H), 6.67 (dd, 1H, J=10.88, CHdC), 5.7
(d, 1H, J=18.05, CdCH2), 5.18 (d, 1H, J=11.3, CdCH2), 2.99
(s, 4H, CH2), 2.49 (s, 3H, Ar-CH3), 2.23 (s, 3H, Ar-CH3). 13
C
NMR (CDCl3, 100 MHz): δ 160.3 (tertCdN), 157.6 (CH3-
tertCdN), 147.4 (CH3-tertC-hetero-Ar), 141.6 (tertC-CH2),
136.6 (CH=), 135.2 (tertC-CHdCH2), 128.6 (Ar), 126.1 (Ar),
121.6 (Ar), 120.7 (Ar), 112.9 (CH2=), 39.9 (CH2), 35.9 (CH2), 24.4
(CH3-CdN), 20.9 (CH3).
(4-Pyridylethyl)-4-vinylbenzene (1a). A solution of lithium
diisopropylamine (LDA) (0.58 g, 5.37 mmol) in 5 mL of dry
THF was added dropwise to a solution of picoline (0.50 g,
5.37 mmol) in 2 mL of dry THF at -80 °C under slow stirring.
The reaction mixture was stirred for 1 h while slowly raising the
temperature (after 1 h to -35 °C). Subsequently, a solution of 4
General Procedure for the Synthesis of the Triazoles 2a-2d
and 3a-3e. The basic reaction conditions and reaction proce-
dure were adopted from Yoo et al.37 To a stirred mixture contai-
ning the acetylene (7a-c;8a-e; 0.5 mmol), the azide (5,6;0.6mmol)

Article
Macromolecules, Vol. 43, No. 4, 2010 1763
and Cu(I)I (9.5 mg, 0.05 mmol) in THF (1.0 mL) and diisopropyl-
amine (DIPA) (0.085 mL, 0.597 mmol) at 25 °C were added slowly.
After the reaction mixture was stirred for 24 h at room temperature
(RT), it was diluted with DCM (2 mL) and then quenched with
saturated aqueous NH4Cl solution (3 mL). The mixture was stirred
for an additional 30 min at RT, and two layers were separated. The
aqueous layer was extracted with DCM (3 ꢀ 5-10 mL), and the
combined organic layers were washed additionally with saturated
aqueous NH4Cl solution until the aqueous layer stayed colorless.
The organic layer was dried over Na2SO4, filtered, and concentrated
in vacuum. The crude product was dissolved in DCM and purified
by column chromatography (SiO2, DCM or DCM/MeOH 100:1).
(4-Butyl-1-(4-vinylbenzyl)-1H-1,2,3-triazole) (2a). Yield: 128
mg (0.53 mmol, 94% o.th). 1H NMR (CDCl3, 400 MHz): δ 7.4
(d, 2H, J=8.2, Ar-H), 7.2 (m, 3H, Ar-H þ triazole;H), 6.7
(dd, 1H, CHdC), 5.75 (d, 1H, J = 17.6, CdCH2), 5.45 (s, 2H,
Ar-CH2), 5.28 (d, 1H, J=10.8, CdCH2), 2.67 (t, 2H, J=7.7,
alk;H), 1.6 (qi, 2H, J = 7.7, alk;H), 1.35 (qi, 2H, J = 7.5,
alk;H), 0.89 (t, 3H, J = 7.4, alk;H). 13C NMR (CDCl3, 100
MHz): δ 138.8 (CH=), 138.0 (tertC-CHdCH2), 135.9 (tertC-
CH2), 134.3 (tertC-triazole), 128.2 (Ar), 126.8 (Ar), 120.4 (CH-
triazole), 114.8 (CH2=), 53.8 (Ar-CH2-triazole), 31.5 (CH2), 25.4
(CH2), 22.4 (CH2), 13.8 (CH3). IR (cm-1): 3114.9, 3063.9, 2960.1,
2932.1, 2873.6, 2859.1, 1868.3, 1548.2, 1512.7, 1465.4, 1435.5,
1407.3, 1335.7, 1318.5, 1229.6, 1213.1, 1129.1, 1114.5, 1048.7,
994.1, 908.9, 859.2, 789.6, 762.1723.7, 702.6, 677.1.
(4-Phenyl-1-(4-vinylbenzyl)-1H-1,2,3-triazole) (2b). Yield:
141 mg (0.53 mmol, 96% o.th). 1H NMR (CDCl3, 400 MHz):
δ 7.8 (d, 2H, J = 7.1, Ar-H), 7.64 (s, 1H, triazole;H), 7.39-
7.27 (m, 7H, Ar-H), 6.7 (dd, 1H, CHdC), 5.77 (d, 1H, J =
17.0, CdCH2), 5.46 (s, 2H, Ar-CH2), 5.28 (d, 1H, J = 11.6,
CdCH2). 13C NMR (CDCl3, 100 MHz): δ 138.2 (CH=),
135.9 (tertC-CH2), 133.9 (tertC-CHdCH2), 130.8 (tertC-
triazole), 128.8 (Ar), 128.3 (Ar), 128.1 (Ar), 126.9 (Ar), 125.7
(Ar), 119.3 (CH-triazole), 114.9 (CH2=), 54.1 (Ar-CH2-
triazole). IR (cm-1): 3088, 3044.9, 2959.6, 1725.9, 1512.7,
1482.5, 1462.9, 1442.4, 1428.3, 1408.2, 1345.2, 1286.9, 1223.2,
1208.7, 1189.3, 1134.1, 1076.2, 1049.5, 1018.6, 991.0, 974.7,
918.1, 857.4, 830.7, 779.4, 764.2, 738.2, 716.6, 692.1.
(1-(1-(4-Vinylbenzyl)-1H-1,2,3-triazol-4-yl)-methylene-5-methyl-
pyrimidine-2,4(1H,3H)-dione) (2c). Acetonitrile was used as
solvent instead of THF. Yield of 2c: 0.661 mg (2.05 mmol,
89% (o.th.)). 1H NMR (CDCl3, 400 MHz): δ 8.16 (s, 1H, N-H),
7.56 (s, 1H, triazole-H), 7.39 (d, 2H, Ar-H), 7.31 (s, 1H,
Thy-H), 7.23 (d, 2H, Ar-H), 6.7 (dd, 1H, CHdC), 5.77 (d,
1H, J=17.0, CdCH2), 5.46 (s, 2H, Ar-CH2), 5.28 (d, 1H, J=
11.6, CdCH2), 4.9 (s, 2H, Thy-CH2), 1.88 (s, 3H, CH3). 13C
NMR (CDCl3, 100 MHz): δ 163.7 (CdO), 153.5 (CdO), 140.1
(=CH-N), 136.2 (CH=), 135.8 (tertC-CH2), 134.15 (tertC-
C=), 133.3 (tertC-triazole), 128.5 (Ar), 126.9 (Ar), 120.0 (CH-
triazole), 115.1 (CH2=), 111.2 (tertC-CH3), 56.0 (Ar-CH2-
triazole), 42.8 (triazole-CH2-pyrimidine), 12.3 (CH3). IR:
3131.2, 3033.2, 2832.9, 1682.5, 1647.0, 1513.5, 1464.8, 1380.2,
1351.1, 1338.3, 1308.9, 1342.8, 1215.4, 1133.8, 1063.7, 1029.1,
992.9, 903.5, 879.2, 781.3, 763.0, 721.3, 703.7, 559.9, 433.5, 473.8.
(1-Benzyl-4-butyl-1H-1,2,3-triazole) (3a). Yield: 100 mg (0.46
mmol, 83% o.th). 1H NMR (CDCl3, 400 MHz): δ 7.4-7.17 (m,
5H, Ar-H þ triazole-H), 5.47 (s, 2H, Ar-CH2), 2.67 (t, 2H,
J=7.7, alk;H), 1.6 (qi, 2H, J=7.7, alk-H), 1.35 (qi, 2H, J=
7.5, alk-H), 0.89 (t, 3H, J = 7.4, alk-H). 13C NMR (CDCl3,
100 MHz): δ 129.0 (Ar), 128.6 (tertC-triazole), 127.9 (Ar), 120.6
(CH-triazole), 54.3 (Ar-CH2-triazole), 31.6 (CH2), 25.4
(CH2), 22.5 (CH2), 13.9 (CH2). IR: 3114.4, 3063.4, 2959.3,
2925.1, 2857.9, 1726.3, 1557.0, 1495.5, 1448.4, 1310.3, 1287.6,
1228.2, 1215.4, 1176.2, 1131.3, 1051.9, 1033.0, 856.8, 824.8,
747.8, 703.5, 673.3, 641.7.
MHz): δ 134.6 (tertC-triazole), 130.4 (tertC-CH2), 129.1 (CH-
triazole), 128.8 (Ar), 128.2 (Ar), 128.0 (Ar), 125.7 (Ar), 54.4
(Ar-CH2-triazole). IR: 3121.7, 3096.0, 3064.6, 2972.5, 2936.6,
1607.6, 1496.9, 1483.4, 1466.7, 1455.4, 1441.9, 1426.8, 1356.8,
1320.2, 1224.6, 1205.8, 1155.6, 1074.9, 1049.2, 1028.5, 1003.2,
975.5, 913.3, 898.3, 827.3, 780.3, 765.0, 726.5, 708.0, 691.7.
(1-Benzyl-4-(4-methoxyphenyl)-1H-1,2,3-triazole) (3c). Yield:
175 mg (0.45 mmol, 91% o.th). 1H NMR (CDCl3, 400 MHz): δ
7.7 (d, 2H, J =8.8, Ar-H), 7.55 (s, 1H, triazole-H), 7.4-7.28
(m, 5H, Ar-H), 6.91 (d, 2H, J=8.8, Ar-H), 5.55 (s, 2H, CH2),
3.8 (s, 3H, CH3). 13C NMR (CDCl3, 100 MHz): δ 159.6
(tertC-O), 148.0 (tertC-triazole), 134.7 (tertC-CH2), 129.1
(CH-triazole), 128.7 (Ar), 128.0 (Ar), 126.9 (Ar), 123.2 (Ar),
118.7 (Ar-tertC-triazole), 114.2 (CH-O), 55.3 (CH3-O), 54.3
(Ar-CH2-triazole). IR: 3137.5, 3048.6, 2927.8, 2837.1, 2349.2,
2049.9, 1897.1, 1614.9, 1578.1, 1557.5, 1495.5, 1454.1, 1439.1,
1349.1, 1301.6, 1249.4, 1217.6, 1170.9, 1070.0, 1048.8, 1027.7,
972.8, 833.8, 794.8, 718.1, 658.2, 579.4, 532.4, 477.2.
(1-Benzyl-4-p-tolyl-1H-1,2,3-triazole) (3d). Yield: 94 mg (0.38
mmol, 75% o.th). 1H NMR (CDCl3, 400 MHz): δ 7.7 (d, 2H, J=
8.2, Ar-H), 7.6 (s, 1H, triazole-H), 7.4-7.25 (m, 5H, Ar-H),
7.18 (d, 2H, J=7.8, Ar-H), 5.55 (s, 2H, CH2), 2.3 (s, 3H, CH3).
13C NMR (CDCl3, 100 MHz): δ 137.9 (tertC-triazole), 134.7
(tertC-CH2), 129.4 (Ar), 129.1 (CH-triazole), 128.7 (tertC-
CH3), 128.0 (Ar), 127.8 (Ar), 125.6 (Ar), 54.4 (Ar-CH2-
triazole), 21.4 (CH3). IR: 3145.3, 3019.0, 2955.7, 2916.4,
2858.3, 1683.2, 1602.9, 1586.1, 1495.6, 1452.9, 1348.7, 1222.9,
1182.4, 1136.8, 1067.3, 1047.4, 970.6, 827.1, 792.4, 718.5, 663.4,
604.9, 580.5, 512.7, 480.5.
(1-Benzyl-4-(4-chlorophenyl)-1H-1,2,3-triazole) (3e). Yield:
97 mg (0.43 mmol, 85% o.th). 1H NMR (CDCl3, 400 MHz): δ
7.7 (d, 2H, J = 8.5, Ar-H), 7.62 (s, 1H, triazole-H), 7.4-7.34
(m, 5H, Ar-H), 7.3 (m, 2H, Ar-H), 5.56 (s, 2H, CH2). 13C
NMR (CDCl3, 100 MHz): δ 147.14 (tertC-triazole), 134.49
(tertC-CH2), 133.89 (tertC-Cl), 129.18 (Ar), 129.07 (Ar),
128.98 (Ar), 128.85 (Ar), 128.08 (Ar), 126.93 (Ar), 119.47 (Ar),
54.43 (Ar-CH2-triazole). IR: 3117.4, 3069.2, 3040.8, 2950.3,
1682.9, 1606.3, 1551.2, 1478.3, 1452.2, 1432.7, 1403.3, 1344.8,
1225.8, 1207.9, 1186.4, 1136.1, 1090.8, 1068.7, 1051.9, 1012.9,
977.3, 809.9, 723.9, 707.4, 659.9, 583.6, 513.6, 474.9, 458.9.
General Procedure for PIB Polymerization. Polymerization
and copolymerization were carried out in a two-necked Schlenk
tube under an atmosphere of argon. A solution of hexane, DCM
(60: 40, v:v) (20 mL) with N,N-dimethylacetamide (DMA) (c=
4.4ꢀ10-3 mol/L), and the Lewis base (2,6-di-tert-butylpyridine)
(c =2.5 ꢀ 10-3 mol/L) was cooled to -10 °C, and TMPCl was
added. The comonomer (1a-2c) or the additives (3a-3e) or the
amino bases in amounts of 1-7 mol % were added as solution in
DCM to the reaction mixture. After initiator addition the poly-
merization mixture was cooled to final temperature of -80 °C,
and IB (c=1.2 mol/L) was added (prepared by condensation at
-80) via a syringe. Finally, the co-initiator (TiCl4 (final con-
centration the polymerization mixture is 0.124 mol/L)) was
added to start the polymerization.6 The overall volume of the
polymerization was about 20 mL. The polymerization was
conducted after complete conversion by kinetic measurements
was determined and subsequently quenched with distilled
MeOH (3 mL). The reaction mixture was then allowed to warm
up to RT and precipitated in acetone (2a-2c) or acetone/
methanol v:v 50:50 mixture (for 1a-1c). The absence of residual
monomer was checked by TLC (DCM/MeOH = 100/1). The
precipitated polymer was dissolved in DCM, washed with
NaHCO3 solution and water, dried over Na2SO4, and filtered.
The solvent was evaporated to dryness, and the resulting poly-
mer was dried under high vacuum.27
Kinetic IR Monitoring. The progress of polymerization
was monitored with attenuated total reflectance (ATR) probes.
The probe was immersed in the polymerization medium and
interfaced to a Bruker Vertex 70 FTIR unit by fiber-optic cables.
A background spectrum (32 scans, resolution 4 cm-1) was taken
(1-Benzyl-4-phenyl-1H-1,2,3-triazole) (3b). Yield: 115 mg
1
(0.49 mmol, 88% o.th). H NMR (CDCl3, 400 MHz): δ 7.8
(d, 2H, J=7.1, Ar-H), 7.64 (s, 1H, triazole-H), 7.4-7.28 (m,
8H, Ar-H), 5.56 (s, 2H, Ar-CH2). 13C NMR (CDCl3, 100

1764 Macromolecules, Vol. 43, No. 4, 2010
Hackethal et al.
Scheme 2
after the initiator, additives, and solvents were added. After ini-
tiation with TiCl4, a spectrum (each spectrum consists of 20 scans
and a resolution of 4 cm-1) was collected every 9 s. Reaction
conversion was determined by monitoring the =CH2 wag at
887 cm-1 according to Storey et al.38 (The overlap of the stretching
vibration at 1655 cm-1 with a vibration of the active species at
1640 cm-1 (see Supporting Information Figure S 23) rendered the
integration of the peak area impossible and was therefore not
used.) Integration of the peak area leads to the values for the first-
order kinetic plots. kapp values were determined from the ln-
[M0]/[Mt] vs time (t) plots by selecting the linear range from
ln[M0]/[Mt]=0 to ∼ln[M0]/[Mt] =2.0 (see eqs 1-3).
ln ½Mꢁ0=½Mꢁt ¼ kapp
t
ð1Þ
2
kapp ¼ kpKeq½Iꢁ0½LAꢁ0
ð2Þ
-
-
RN ¼ ðkp½PnþTi2Cl9 ꢁ½MꢁÞ=ðk-i½PnþTi2Cl9 ꢁÞ
¼ kp½Mꢁ=k-i
ð3Þ
Scheme 3. Synthesis of Monomers 1a-1c, 2a-2c and Additives 3a-3ea
a LDA = lithium diisopropylamine, DIPA = diisopropylamine, and THF = tetrahydrofuran.
Table 1. Copolymerization of IB with 1a in Comparison to Pure Picoline as Additivea
entry monomer/additive mol % Mnb [g/mol] Mw/Mn incorp (%)c conversion (%)i kapp (10-3 s-1
)
yield (%) kpd (108 s-1 M-1
)
RN
1
2
3
4
5
6
-
1a
0
1
2
5
7
1
2395e
2800e
2800e
6300f
4000f
9900g
1.1
1.4
1.3
1.4
>2.3
1.3
-
20.1
18.9
15.4
80.8
6.9
90
80
78
76
70
82
1.54
2.57
1.96
23.1
-
7.69
2.47
4.11
3.12
36.96
-
∼1
2.5
2.1
0.75
0.3
94
93
98
83
96
17.1
12.29
h
7
8
9
picoline
1
2
5
4600f
5600e
4000f
1.2
1.2
1.1
-
94
97
97
8.6
19.3
23.8
90
85
90
8.59
4.9
4.32
4.98
7.84
6.9
h
-
h
-
a [IB] = 1.2 M; [TiCl4] = 0.128 M; [DtBP] = 2.2 mM; [DMA] = 5.4 mM; n-hexane-DCM v:v 60:40, -80 °C. b Mn determined by GPC measurement
in THF as solvent, calibration with PIB standards (g/mol). c Determined by integration of 8.5-8.6 ppm (1a) vs 1.0-1.1 ppm (IB) 1H NMR.
d Determination by eq 3 (k-i = 7.5 ꢀ 107 1/s, ki = 15 1/(s M2))38 with kp determined by combination of eqs 1 and 2 (Keq = ki/k-i) with respect to the
dimeric form of the LA ([LA]02).46 e Calcd Mn = 3000 g/mol; [IB] 1.2 M; [TMPCl] = 0.0224 M. f Calcd Mn = 6000 g/mol; [IB] 1.2 M; [TMPCl] = 0.0112
M. g Calcd Mn = 10 000 g/mol; [IB] 1.2 M; [TMPCl] = 0.0067 M. h Additive, no incorporation possible. i Determined by inline FTIR-spectroscopy
ln[M]0/[M]t plot; limited by detection of concentrations below ∼0.07 mol/L (IB).

Article
Macromolecules, Vol. 43, No. 4, 2010 1765
Figure 1. 1H NMR of (a) pure comonomer 1a and (b) PIB-1a copolymer with 1 mol % of 1a, with respect to the integration of the pyridyl-C-H at
8.5 ppm 1a vs the -CH2 PIB at 1.4 ppm.
Calculation of kp was then accomplished according to eq 2 using
k-i =7.5ꢀ107 1/s and ki =15 1/(s M2) from Storey et al.38
reactions with nonpolymerizable additives resembling the
monomers 1a-1c and 2a-2c were studied with respect to their
influence on the living cationic polymerization. Thus, pyridine,
collidine, and picoline were used as polar additives resembling
the chemical structures of monomers 1a-1c; the additives
3a-3e were used to study the influence of the triazole moiety
and the attached alkyl/phenyl moieties on the polymerization
process.
Determination of kp/k-i According to Muller et al.39 The rate
constant of deactivation (k-i) can be determined from the
€
molecular weight distribution vs initiator concentration plot
by linear curve fitting with a conversion of 100% according to
39
€
eq 2 as derived by Muller et al.
PDI ≈ 1 þ 1=βð2=x - 1Þ
ð4Þ
Monomer and Additive Synthesis. The synthesis of mono-
mers 1a-1c (see Scheme 3) was accomplished via a nucleo-
philic reaction between the lithiated collidines and 4-bromo-
methylstyrene (4) (see Supporting Information).36,40,41 In-situ
prepared 4-vinylbenzyl bromide (4) was directly used by coup-
ling with picoline or sym-collidine deprotonated with a Li-
organyl. The isomers 1a-1c could be isolated up to 63%
yield. Reaction of 4 with sym-collidine generated the isomeric
products 1b and 1c, which could be separated by column
chromatography and assigned unambiguously by 2D H-C
long-range COSY-NMR analysis (see Supporting Infor-
mation).
In this equation β = k([I]0kp)1/2, where [I]0 is the initiator
concentration, kp the rate constant of propagation, and PDI
the polydispersity index with PDI=Mw/Mn. Equation 1 is valid
when the fraction of the chain end [PþLAnCl-]/[I]0 is e10-2 and
β g 10. If exchange is not extremely slow, i.e., β . R (fraction of
the active chains in equilibrium), this leads to an equation for
Pw ≈ 1 þ γ(1 þ 1/β) (with γ=β/R), and consequently, the poly-
dispersity index (PDI) at x= 1 is
PDI ≈ 1 þ 1=β ¼ 1 þ kp=k- i½Iꢁ0
ð5Þ
Monomers 2a, 2b and the additives 3a-3e were prepared
starting from 4-vinylbenzyl azide (5) and 4-azidomethylben-
zene (6) synthesized according to the literature42,43 via an azide/
alkine “click” reaction32,33 using THF as solvent, Cu(I)I, and
diisopropylamine (DIPA) in the ratios of (0.08:1:1 = Cu(I):
DIPA:azide) according to Yoo et al.37 Monomer 2c was pre-
pared from 1-(prop-2-ynyl)-5-methylpyrimidine-2,4-(1H,3H)-
dione (7c)44 using reaction conditions from Tilliet et al.45
Copolymerization with Polar Monomers 1a-1c. As a first
step, the copolymerization reactions of IB with monomer 1a
(containing a pyridyl unit attached to the styrene moiety)
were investigated, adding 1-7 mol % of 1a as comonomer
directly to the polymerization mixture before starting the
polymerization by addition of TiCl4 as co-initiator at -80 °C
(see Table 1). Solubility tests prior to the polymerization
reaction ensured the solubility of the monomers in the final
reaction mixture at -80 °C. The projected molecular weight
was either 3000 or 6000 g mol-1. Results of the polymeriza-
tion reaction are shown in Table 1; incorporation of the
comononer 1a was determined by integration of the pyridyl
for Pn . 1. For determining kp/k-i different polymerizations
with a variable initiator concentration ([I]0=0.0026-0.022 mol/L)
were prepared, and the polydispersity index (PDI = 1.48-1.15)
was determined by GPC-measurements (see Figure 7).
Results and Discussion
Concept. The structures of the used monomers investiga-
ted in the copolymerization reactions are given in Scheme 2.
Thus, monomers 1a-1c derived from styrene with atta-
ched pyridine and collidine moieties were investigated. An
1,2-ethylene chain was placed between the functional group
and the styrene moiety in order to reduce eventual unfavo-
rable electronic effects on the styrene moiety. In order to
expand the structural variability, the triazole-containing
monomers 2a-2c were included, as their preparation can
be easily accomplished by azide/alkine “click” reactions via
p-azidomethylstyrene. In this case, the influence of the tri-
azole moiety on the living cationic polymerization was studied
as a concept for further modification of the PIB backbone.
For comparison of all polar monomers the polymerization

1766 Macromolecules, Vol. 43, No. 4, 2010
Hackethal et al.
Figure 2. MALDI TOF MS of PIB-1a (as prepared from Tablþe 1, entry 1) with one unit of incorporated 1a in the second series (a, b). (c) Simulation for
[PIB50E1Hþ] the first series. (d) Simulation for [PIB591a1E1H ] as the second series (E1 = tert-chloride).
Figure 3. MALDI TOF MS PIB-1a (a) with expansion (b); (c-f) simulation of the isotopic pattern the four series (c) [PIB351a3E2]þ, (d) [PIB411a2E2]þ,
(e) [PIB421a1E2]þ, and (f) [PIB351a3E1Li]þ (E1 =tert-chloride; E2 =vinyl).
resonances at 8.46 ppm vs the main resonances of the PIB
chain in the final polymer (precipitation of the polymer in
acetone/methanol ensured the complete removal of even-
tually unreacted comonomer 1a as judged by NMR spec-
troscopy and TLC).
Thus, the polymerization yields polymers with polydisper-
sities below 1.4 upon addition of monomer 1a up to 5 mol %
(entries 2-4). At higher amounts (7 mol %, entry 5), the
polymerization is no longer controlled, with polydispersities
Mw/Mn > 2.3 and an expected molecular weight far below

Article
Macromolecules, Vol. 43, No. 4, 2010 1767
the expectations. In a further series of experiments the
addition of picoline as additive without the use of comono-
mer 1a was probed in order to check for the influence of the
pyridyl moiety on the polymerization (see entries 6-8),
revealing low polydispersities but small to significant devia-
tions from the expected molecular weights.
allows for the incorporation of ∼1 unit of 1a, a higher
molecular weight (Mn = 10 000 g mol-1) under the same
reaction conditions (1 mol % of 1a, see Table 1, entry 6) was
probed. MALDI results of this polymer are shown in
Figure 3, clearly demonstrating the incorporation of one,
two, and three monomeric units of 1a, as visible in the
four series via the respective ions (c) [PIB351a3E2]þ, (d)
[PIB411a2E2]þ, (e) [PIB421a1E2]þ, and (f) [PIB351a3E1Li]þ
(with E1 = tert-chloride; E2 = vinyl).
1
Incorporation of monomer 1a was checked by H NMR
spectroscopy (see Table 1 and Figure 1) and MALDI-TOF
methods (see Figures 2 and 3). As judged by NMR spectro-
scopy, the incorporation of monomer 1a is possible up to
∼2.5 mol % (entries 2-5). However, at 7 mol % amount of
comonomer 1a less than 1 mol % is incorporated into the
PIB polymer. Figure 2 shows the MALDI results of a
polymer obtained in a copolymerization with 1 mol % of
1a (see Table 1, entry 2) with a projected molecular weight
Mn = 3000 g mol-1. MALDI-mass spectrometry clearly
shows two series of PIB polymer (all with the expected
∼56 g mol-1): the first, low molecular weight series can be
assigned to PIBnE1Hþ ions (n = 50) devoid of comonomer
1a, where E1 can be assigned as tert-chloride end group.
Simulation of the respective ions proves the assigments
via excellent overlap of the simulated isotope pattern and
the respective peak series (see Figure 2c,d). The higher mole-
cular weight part clearly shows the expected incorporation of
one unit of 1a, visible as [PIBn1a1E1Hþ] ion (n = 59; E1 =
tert-chloride).
This clearly demonstrates the successful incorporation of
the polar comonomer 1a into the growing PIB chains;a
result unexpected with this level of (a) control over the
polymerization reaction and (b) with respect to the amount
of incorporated monomer. Therefore, a more detailed look
on the reaction kinetics of the IB polymerization in the
presence of either monomer 1a or the analogous base pico-
line (structurally reminiscent of the picoline unit in 1a) was
conducted (see Figure 4). Basically, both types of polymer-
ization reactions show linear ln[M0]/[M] vs time (t) plots up
to conversions of 92% or more, with an increase of the
apparent rate of polymerization (kp) by a factor of 2-4 (see
also data for kp and kapp in Table 1) as compared to the IB or
styrene polymerization under exactly the same reaction
conditions. Thus, the polymerization is enhanced by addi-
tion of up to 5 mol % of either monomer 1a or pure picoline.
As both;the comonomer 1a and the pure additive pico-
line;yielded similar results, a purely stereoelectronic effect
exerted from the closely present nitrogen in 1a can be
excluded, thus hinting toward a change in the equilibrium
between the “dormant = tert-chlorine-telechelic” and the
“active=cationic” species20 rather than a removal of protic
impurities or reduction in the “cationicity” of the actively
(growing) species.
As the initially projected molecular weight of Mn=3000 g
mol-1 with 1 mol % 1a as comonomer statistically only
In order to check for the influence of small structural
variations in monomer 1a, the isomeric monomers 1b and 1c
reminiscent of a collidine base were checked in a similar
copolymerization. The data are shown in Table 2, and the
respective kinetic investigations in are shown in Figure 5.
Thus, already 1 mol % of 1b leads to strongly increased
polydispersities (Mw/Mn = 1.8) and a molecular weight
above the expectations. Higher amounts of 1b still lead to a
definite loss of control over the polymerization reaction with
mostly bimodal molecular weight distributions (see entries
1-3). Monomer 1c behaves a little differently at 1 mol % but
similarly at higher amounts (2 mol %). As comparison, sym-
collidine as additive yielded comparably poor results, under-
lining the fact that these bases do not lead to controlled
cationic homo- or copolymerization reactions. In both cases,
however (see Figure 4), the kinetics show a linear monomer
Figure 4. First-order plot of the copolymerization of IB with mono-
mer 1a. Conditions: n-hexane-DCM (v/v) 60:40; -80 °C; [M]0=1.2 M,
[TMPCl]0 = 0.01 M; [TiCl4] = 0.128 M; [DtBP] = 2.2 mM; [DMA] =
5.4 mM.
Table 2. Copolymerization of IB with 1b and 1c in Comparison to sec-Collidine as Additivea
entry monomer/additive mol % Mnb [g/mol] Mw/Mn incor (%)c conversion (%)g kapp (10-3 s-1 yield (%) o.th kpd (108s-1 M-1
)
)
RN
1
2
3
1b
1
2
5
9100
8700
6700
255
4200
800
2000
1.9
1.8
1.2
1.8
1.1
1.1
1.5
1
0.4
2
96
98
97
45.7
61.8
9.73
75
80
<10
18.8
24.4
2.96
30.16
38.99
4.73
e
4
5
1c
1
2
-
92
19.1
75
-
3.64
5.82
e
-
-
-
-
-
6
7
8
sym-collidine
1
2
5
2800
6600
-
1.2
1.3
-
-4e
95
97
-
62.9
23.5
-
89
4.84
7.07
-
7.74
11.24
-
e
-
f
f
f
-
f
f
f
-
f
f
a [IB]=1.2 M, [TMPCl]=0.01 M; [TiCl4]=0.128 M; [DtBP]=2.2 mM; [DMA]=5.4 mM; n-hexane-DCM v:v 60:40, -80 °C; calcd Mn=6700 g/mol.
b Mn determined by GPC measurement in THF as solvent, calibration with PIB standards (g/mol). c Determined by integration of 6.8-7.1 ppm 1b, 1c vs
=
1.0-1.1 ppm (IB) 1H NMR. d Determination by eq 3 (k-i=7.5 ꢀ 107 1/s, ki=15 1/(s M2))38 with kp determined by combination of eqs 1 and 2 (Keq
ki/k-i) with respect to the dimeric form of the LA ([LA]02).46 e No incorporation detected. f No polymerization observed. g Determined by inline FTIR
spectroscopy ln[M]0/[M]t plot; limited by detection of concentrations below ∼0.07 mol/L (IB).

1768 Macromolecules, Vol. 43, No. 4, 2010
Hackethal et al.
consumption and a significant acceleration of the polymeri-
zation in comparison to picoline as additive or monomer 1a.
Incorporation of monomer 1b in amounts up to ∼2 mol %
Copolymerization with Triazole-Containing Additives
3a-3d. In order to check for the influence of the triazole
moiety on the IB polymerization, the use of the triazole-
containing additives 3a-3d was probed, as shown in Table 3
(entries 6-12) and Figure 7. Thus, the kinetics upon addition
of 1 mol % 3a-3d as additives were followed by inline
monitoring of the IB polymerization. Except for additives
3a and 3d (containing a butyl moiety and a 4-methylphenyl
moiety, respectively, at the triazole moiety), the polymeriza-
tion reaction displayed low polydispersities of the obtained
polyisobutylenes. A slight electronic influence of the sub-
stituent of the triazole moiety is seen, with electron-donating
moieties (such as PhMe (3d), Ph-OCH3 (3c), and butyl
(3a) leading to strongly enhanced rates of polymerization,
whereas Ph-Cl (3e) and Ph (3b) display significantly reduced
polymerization rates. As these substances do not act as
comonomers but just as additives during the polymerization,
this kinetic effect can only be explained by changes of the
equilibrium between active/dormant species during the liv-
ing cationic polymerization. A comparison of comonomer
2b and the additive 3b at higher amounts of 1, 2, and 7 mol %
(for data see Supporting Information Figure S 24) leads to a
still living polymerization with a reduction of the rate con-
stants by a factor of ∼10 (7 mol % of 2b) and ∼3 (7 mol % of
3b) with increasing amount of 2b or 3b, respectively.
1
were detected by H NMR spectroscopy and MALDI (see
Supporting Information for detailed spectra).
Copolymerization with Triazole-Containing Monomers
2a-2c. As the structural variability and also synthetic acces-
sability of the monomers 1a-1c were quite limited, a simpler
structural approach to styrene-type monomers was investiga-
ted. Coming up with the azide/alkine “click” reaction,32,33,47-49
the monomers 2a-2c with a 4-(methylene-triazole) moiety
were prepared and investigated toward their influence and
incorporation during a living cationic polymerization of IB.
All monomers 2a-2c (see Table 3) did not show a living
copolymerization of IB, as clearly visible by high polydisper-
sities and strong deviations from the expected molecular
weights.
However, despite the fact that the incorporation could not
be detected with H NMR spectroscopy (sensitivity limit
1
∼1%), it was possible to detect the species with one incor-
porated monomer unit 2c within the MALDI spectrum (see
Figure 6). As the absolute amount of incorporation must be
low, a preferential desorption of the strongly ionic species
[PIB2c1Li]þ, [PIB2c2]þ, and [PIB2c2Ag]þ with respect to the
pure [PIBLi]þ can be assumed and also expected. Thus, the
obviously extremely low incorporation of 2c is visible quite
strongly in the respective MALDI spectra.
From these data, it seemed conclusive that the triazoles,
whether or not as additive of comonomer, lead to a change in
the equilibrium between the active/dormant species during
the IB polymerization. Measurements of the equilibrium
constant K of this ion equilibrium can be achieved either
by inline UV spectroscopy or via indirect methods, such as
determination of Mw/Mn at low conversions as used by
Storey et al.20 As low-temperature UV spectroscopy or
probe sampling at (-80 °C) could not be achieved, the
39
indirect method as discussed by Muller et al. was used,
€
relying on measurements of Mw/Mn at 100% conversion by
variations of the initiator concentration [I0] (see Experimen-
tal Part) and determining kp/k-i by plotting Mw/Mn vs [I0]
(see Experimental Part, eqs 4 and 5). Thus (see Figure 8), a
value for kp/k-i=15.52 can be determined for 1 and 2 mol %
of additive 3b. Using the so-determined kp/k-i value, the rate
constant of initiation (ki) can be calculated via eq 6, with ki
the rate constant of initiation, k-i the rate constant of
deactivation, kp the rate constant of propagation, the appar-
ent rate constant (kapp), [I]0 as the starting concentration of
Figure 5. First-order plot of the copolymerization of IB with mono-
mers 1a, 1b, and 1c. Conditions: n-hexane-DCM (v/v) 60:40; -80 °C;
[M]0 = 1.2 M, [TMPCl]0 = 0.01 M; [TiCl4] = 0.128 M; [DtBP] =
2.2 mM; [DMA] = 5.4 mM.
Table 3. Kinetic Values of the Copolymerization of IB with 1 mol % of the Polar Monomers 2a-2c in Comparison to the Polymerization of IB
in the Presence of the Polar Additives 3a-3da
d
monomer/
additive
mol %
corr to IB
Mw/
Mn
conversion
(%)g
incor
(%)c
kapp
(10-2 s-1
kp
(108 s-1 M-1
entry
Mnb [g/mol]
)
yield (%)
)
RN
e
1
2
3
4
5
2a
2b
2b
2b
2c
1
1
2
7
1
12000
3600
3100
5400
3100
5.9
1.6
1.5
1.3
1.5
-
n.d.
8.72
3.94
0.63
2.98
<5
86
85
85
85
-
-
22.8
8.58
2.46
6.7
97
97
90
97
<1
<1
<1
<1
14.2
5.5
1.5
4.19
f
6
7
8
3a
3b
3b
3b
3c
3d
3e
1
1
2
7
1
1
1
5800
2000
5200
2000
7500
7300
5200
2.3
1.3
1.3
1.3
1.2
1.8
1.2
95
94
91
97
97
99
98
-
0.57
8.16
1.60
3.00
3.58
19.20
1.65
80
90
85
80
87
90
85
1.5
7.4
3.8
2.7
12.2
63.5
3.8
2.4
11.84
6.06
f
-
f
-
f
9
-
4.35
f
10
11
12
-
19.45
101.6
6.03
f
-
f
-
a [IB] = 1.2 M; [TMPCl] = 0.01 M; [DtBP] = 2.5 ꢀ 10-3 mol/L, [TiCl4] = 0.124 mol/L, [DMA] = 4.41 ꢀ 10-3 mol/L, n-hexane-DCM (v/v) 60:40;
-80 °C; calcd Mn = 6000 g/mol. b Mn determined by GPC measurement in THF as solvent, calibration with PIB standards (g/mol). c Determined by
integration of 5.4-5.5 pmm (2a-2c) vs 1.0-1.1 ppm (IB) 1H NMR spectroscopy. d Determination by eq 3 (k-i = 7.5 ꢀ 107 1/s, ki = 15 1/(s M2))38 with
kp determined by combination of eqs 1 and 2 (Keq = ki/k-i) with respect to the dimeric form of the LA ([LA]02).46 e No signals from the comonomer
visible in 1H NMR. f Additive, no incorporation possible. g Determined by inline FTIR spectroscopy ln[M]0/[M]t plot; limited by detection of
concentrations below ∼0.07 mol/L (IB).

Article
Macromolecules, Vol. 43, No. 4, 2010 1769
Figure 6. (a, b) MALDI-TOF MS of PIB-2c with (c-f) simulation of the isotopic pattern four series: (c) [PIB242c2E2Ag]þ, (d) [PIB272c2E1]þ,
(e) [PIB38E1Li]þ, and (f) [PIB352c1E1Li] þ (E1 =tert-chloride; E2 =vinyl).
€
Figure 8. Determination of kp/k-i by Muller with 100% conversion f
kp/k-i =15.52.
Figure 7. First-order kinetic plots of IB polymerization in presence of
1 mol % additive 3a to 3e. n-Hexane-DCM (v/v) 60:40; -80 °C; [M]0=
1.2 M, [TMPCl]0 = 0.01 M; [TiCl4] = 0.128 M; [DtBP] = 2.2 mM;
[DMA]=5.4 mM.
Conclusion
We have studied the direct copolymerization of polar styrene
monomers containing pyridine (1a), collidine (1b, 1c), thymine
(2c), and/or triazole moieties (2a-2c) with IB using living
cationic polymerization. Whereas the copolymerization with
the styrene monomers 1a, 1b, and 2c proceeded under incorpora-
tion of up to 2 mol % of the comonomer into the PIB polymer as
proven by MALDI methods and NMR spectroscopy, the como-
nomer 1c was not incorporated and resulted in broad polydis-
persities of the resulting PIB polymers. For structural
comparison, the triazole-containing additives 3a-3d (1 mol %)
were probed in the IB polymerization under the same conditions,
revealing a strong structural effect, especially for the additives 3a
and 3d (containing a butyl moiety and a 4-methylphenyl moiety,
the initiator, and [TiCl4] the starting concentration of the
Lewis base.
2
ki ¼ kapp=ð½Iꢁ0½TiCl4ꢁ ðk-i=kpÞ
ð6Þ
Using this equation with the determined value (Table 3, entry
7) ki = 34.19 1/(s M2) can be calculated. This value is about
double of the value reported in literature by Storey et al.38
(ki = 15.5 1/(s M2)). We thus conclude that the ion equili-
brium of this polymerization is disturbed by addition of the
triazole-containing additive 3b.

1770 Macromolecules, Vol. 43, No. 4, 2010
Hackethal et al.
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respectively, bound to the triazole moiety), which lead to high
polydispersities and an uncontrolled polymerization reaction.
Inline IR kinetic measurements of the monomer consumption
demonstrated strong effects of the comonomer structure 1a-1d
on the polymerization kinetics, with rates of polymerization (kp)
increasing up to a factor of 15 with respect to the native (living) IB
polymerization. Moreover, the addition of nonpolymerizable
additives containing triazole moieties revealed a strong depen-
dency on the attached residue R (R = hexyl (3a), phenyl (3b),
p-methoxyphenyl (3c), p-methylphenyl (3d), p-chlorophenyl
(3e)), with a decreasing kp in the order of 3e>3b>3c>3e>3a=
kp/k-1. Measurements of kp/k-1 of the triazole-containing
additive 3b demonstrated a change by a factor of ∼4.5 to the
homopolymerization of IB under the same conditions, proving
that ion equilibria are disturbed by addition of polar species
during the IB polymerization. The presented method for the first
time opens the possibility to introduce polar moieties in a direct
copolymerization approach into PIB polymers via living cationic
polymerization. Investigations of the copolymerization with
other polar comonomers are in progress in our laboratories.
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Acknowledgment. Grants from the DFG INST 271/249-1,
INST 271/247-1, and INST 271/248-1 are gratefully acknow-
ledged.
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1
Supporting Information Available: H/13C NMR spectra for
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monomers 1a-2c and additives 3a-3e, C-H long-range COSY
NMR spectra of 1b and 1c; preparative procedures for 4, 5, 6,
and 7c; MALDI TOF MS spectra for poly(IB-rnd-2c) polymer;
IR online measurement spectra showing the overlapping IB
stretching band and an active species; conversion vs time plots
obtained from inline IR for poly(IB-rnd-2b) in comparison to
PIB in the presence of additive 3b. This material is available free
of charge via the Internet at http://pubs.acs.org.
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