Macromolecules
Article
35.1, 33.7, 22.5, 14.0. HR-ESI ([C28H33N]H+) m/z: calcd: 384.2686;
found: 384.2671. Error: 3.8 ppm.
Bis(4-trifluoromethylphenyl)-(4-vinylphenyl)amine (5). Method
A. Compound 5 was prepared as 3 using 1-bromo-4-trifluorome-
thylbenzene (0.357 g, 1.59 mmol) and 6 (0.418 g, 1.59 mmol) in
toluene (15 mL) (colorless oil, 0.040 g, 6%).
Method B. Compound 5 was prepared as 3 using 1-iodo-4-
trifluoromethylbenzene (0.645 g, 2.37 mmol) and 6 (0.568 g, 2.16
mmol) in toluene (20 mL). The reaction mixture turned purple during
the addition of the solvent. The desired product was isolated in traces
(0.023 g, 3%).
voltammogram deviates from the ideal reversible behavior
(symmetric peak shape, small peak split). However, the
mathematical transformation (vs t1/2) of the current−voltage
data into its semi-differential/semi-integral form simplifies the
quantitative analysis of the redox processes:26 The semi-integral
form m(t) of the faradaic current i(t) is then independent of the
scan rate and reaches a maximum plateau when the surface
concentration of the analyte is zero; moreover, the obtained
signal is then independent from diffusional processes.27
Consequently, the semi-differential shows a sharp symmetrical
peak for the forward and the backward scan,28,29 which further
serves to discern subtle differences that are usually hidden in
the “shape” of the CV wave.30,31 Although this described
transformation is generally not performed routinely, it is
implemented in most electrochemical software packages or
available by simple postprocessing of the ordinary CV data.
More importantly, it not only provides the potential of a redox
process (abscicca) but also contains valuable information on
the current data (ordinate) to quantify the same process. In
addition, the spectroelectrochemical analysis of the homopoly-
mers yielded the characteristic absorption spectra of the
oxidized pTARA units, which constitute the basis for the
subsequent electron transfer studies of the block copolymers.
First, the stepwise electrochemical oxidation of block
copolymers was investigated to exclude any undesired
interference of the blocks. In this regard, the semi-integral
analysis is a convenient tool to determine the ratio of
transferred electron per block and compare this value to the
stoichiometric ratio of both redox units within the macro-
molecule. Finally, directional charge transfer between the
blocks was investigated by UV−vis redox titration. This process
was followed by the characteristic spectral changes that occur
upon addition of a solution of a chemically oxidized
homopolymer to a second solution containing a homopolymer
with lower oxidation potential. The experiment mimics the
directional electron transfer that also occurs after light-induced
charge separation32 and, thus, addresses the general utility of
pTARA-based block copolymers for light-driven energy
conversion schemes.
1H NMR (300 MHz, CDCl3) δ: 7.41 (d, J = 8.6 Hz, 4H, ArH), 7.30
(d, J = 8.6 Hz, 2H, ArH), 7.06 (d, J = 8.6 Hz, 4H, ArH), 7.00 (d, J =
8.6 Hz, 2H, ArH), 6.62 (dd, J = 17.6, 10.9 Hz, 1H, CHCH2), 5.63
(d, J = 17.6 Hz, 1H, CHCH2−trans), 5.17 (d, J = 10.9 Hz, 1H,
CHCH2-cis). 13C NMR (100 MHz, CDCl3) δ: 149.9, 145.6, 135.8,
134.5, 128.3, 127.7, 126.7 (2×), 126.6 (2×), 125.9, 125.6, 125.3, 125.0,
124.6, 124.3, 123.1, 122.9, 120.2, 113.8. HR-ESI ([C22H15F6N]+) m/z:
calcd: 407.1103; found: 407.1111. Error: 1.9 ppm. MS (MALDI-TOF,
DCTB) m/z: 407.182 ([M]•+).
(4-Trifluoromethylphenyl)-(4-vinylphenyl)amine (6). Method A.
Compound 6 was prepared as 3 using 1-bromo-4-trifluoromethylben-
zene (2.000 g, 8.90 mmol) in toluene (40 mL) (colorless oil, 0.418 g,
36%).
Method B. Compound 6 was prepared as 3 using 1-iodo-4-
trifluoromethylbenzene (2.000 g, 7.40 mmol) in toluene (40 mL)
(0.150 g, 16%).
1H NMR (300 MHz, CDCl3) δ: 7.44−7.25 (m, 4H, ArH), 7.07−
6.93 (m, 4H, ArH), 6.61 (dd, J = 17.6, 10.9 Hz, 1H, CHCH2), 5.86
(s, 1H, NH), 5.59 (dd, J = 17.6, 0.8 Hz, 1H, CHCH2-trans), 5.11
(dd, J = 10.9, 0.8 Hz, 1H, CHCH2-cis).
General Polymerization Procedure. A glass tube equipped with
a septum and an external overhead flushing with nitrogen was used for
the polymerizations. The reaction vessel was charged with monomer,
initiator, and solvent, purged with nitrogen for 20 min, and placed in a
preheated oil bath (120 °C). Samples were taken for NMR and SEC
characterization. The purification is described for each polymer.
Reaction time, used initiator, monomer concentration, and M/I ratio
are given in Table 1 and the Supporting Information.
Table 1. Selected Characterization Data of Homopolymers
and Copolymers Prepared by NMP
a
b
entry
polymer
p111
Mn [g/mol]
Đ
initiator
1
3300
3500
1.20
1.13
1.17
1.09
1.12
1.09
1.07
1.21
1.20
1.42
1.32
CMSt-TIPNO
CMSt-TIPNO
CMSt-TIPNO
CMSt-TIPNO
CMSt-TIPNO
CMSt-TIPNO
CMSt-TIPNO
CMSt-TIPNO
p49
EXPERIMENTAL SECTION
■
2
p212
p250
p312
p411
p49
Materials. 4-Methyl-N-p-tolyl-N-(4-vinylphenyl)aniline (2), 4-
methoxy-N-(4-methoxyphenyl)-N-(4-vinylphenyl)aniline (1), and 4-
fluoro-N-(4-fluorophenyl)-N-(4-vinylphenyl)aniline (4) were prepared
as described in the literature.9,10 All monomers are sensitive to UV
light, leading to irreversible reactions; thus all compounds were
protected from light and stored in the fridge.
3
10600
4200
4
5
3200
6
2600
c
7
p56
3000
8
p44-stat-p280
p49-b-p2170
p49-b-p1120
p212-b-p1144
25000
38000
26000
39000
Bis(4-(n-butyl)phenyl)-(4-vinylphenyl)amine (3). A flask was
charged with 4-aminostyrene (4.000 g, 33.56 mmol), 1-bromo-4-n-
butylbenzene (14.310 g, 66.72 mmol), sodium tert-butoxide (11.285 g,
1 3 3 . 7 1 m m o l ) , 8 , 9 - t r i i s o b u t y l - 2 , 5 , 8 , 9 - t e t r a a z a - 1 -
phosphabicyclo[3.3.3]undecane (0.095 g, 0.27 mmol), and bis-
(dibenzylideneacetone)palladium(0) (0.154 g, 0.27 mmol). After
flushing with nitrogen, dry degassed toluene (500 mL) was added,
and the reaction mixture was heated to 85 °C overnight. The reaction
mixture was cooled to room temperature and filtered through Celite.
Afterward, the filtrate was concentrated in vacuo and was purified by
flash column chromatography (silica, hexane/dichloromethane 90/10)
(colorless oil, 3.500 g, 27%). 1H NMR (400 MHz, CDCl3) δ: 7.25 (d,
J = 7.5 Hz, 2H, ArH), 7.14−6.95 (m, 10H, ArH), 6.65 (dd, J = 17.6,
10.9 Hz, 1H, CHCH2), 5.61 (d, J = 17.6 Hz, 1H, CHCH2−
trans), 5.12 (d, J = 10.9 Hz, 1H, CHCH2-cis), 2.56 (t, J = 7.7 Hz,
4H, 2 × CH2), 1.81−1.46 (m, 4H, 2 × CH2), 1.46−1.30 (m, 4H, 2 ×
CH2), 1.03−0.84 (m, 6H, 2 × CH3). 13C NMR (100 MHz, CDCl3) δ:
148.0, 145.3, 137.7, 136.4, 131.0, 129.2, 126.9, 124.5, 122.5, 111.6,
9
10
11
p49
p212
a
Number of repeating units according to 1H NMR analysis.
b
According to SEC analysis (chloroform/isopropylamine/triethyl-
c
amine 94/2/4, polystyrene calibration). Main fraction after
preparative SEC (see text).
p111 was prepared according to the general procedure using 1
(0.500 g, 1.51 mmol), CMSt-TIPNO (0.028 g, 0.08 mmol), and
anisole (0.6 mL). After the given time the reaction mixture was diluted
with dichloromethane and precipitated in cold methanol. Unreacted
monomer was removed by preparative SEC (Bio-Beads S-X1,
dichloromethane). The polymer was obtained as a white powder
after precipitation in methanol. Yield: 0.215 g.
B
Macromolecules XXXX, XXX, XXX−XXX