Pi-conjugated chain extenders for the synthesis of optoelectronic segmented polyurethanes

Article abstract of DOI:10.1002/pola.24937

The optical properties of mechanochromic materials change under mechanical stress. Segmented polyurethanes are elastomers composed of amorphous, saturated chain soft segments, and rigid pi-conjugated hard domains. Within aggregates of hard domains pi-pi interactions may form and result in perturbation of the optoelectronic properties of the system. Disruption and restoration of these electronic interactions within the material may lead to observable mechanochromic response. A series of oligothiophene diols and diamines, as well as a naphthalene diimide diol, have been synthesized for incorporation into the hard domains of segmented polyurethanes and polyureas using long poly(tetramethylene oxide) chains as soft segments. The resulting polymers were evaluated to determine their extent of polymerization and their thermal stability. The optical properties of the materials were studied in solution and as thin films. Where possible the electrochemical properties of the polymers were also explored. The length of the soft segment chains in the segmented polyurethanes hindered electronic coupling of hard domains. Future work involving smaller, more solubilizing soft segments may allow for easier material characterization and mechanochromic response.

Full text of DOI:10.1002/pola.24937

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ARTICLE
Pi-Conjugated Chain Extenders for the Synthesis of Optoelectronic
Segmented Polyurethanes
1
1,2
Christopher P. Harvey, John D. Tovar
1
Department of Chemistry, Johns Hopkins University, 3400 N. Charles St. (NCB 316), Baltimore, Maryland 21218
Department of Materials Science and Engineering, Johns Hopkins University, 3400 N. Charles St. (NCB 316), Baltimore,
2
Maryland 21218
Correspondence to: J. D. Tovar (E-mail: tovar@jhu.edu)
Received 9 July 2011; accepted 10 August 2011; published online 7 September 2011
DOI: 10.1002/pola.24937
ABSTRACT: The optical properties of mechanochromic materials
change under mechanical stress. Segmented polyurethanes are
elastomers composed of amorphous, saturated chain soft seg-
ments, and rigid pi-conjugated hard domains. Within aggre-
gates of hard domains pi–pi interactions may form and result
in perturbation of the optoelectronic properties of the system.
Disruption and restoration of these electronic interactions
within the material may lead to observable mechanochromic
response. A series of oligothiophene diols and diamines, as
well as a naphthalene diimide diol, have been synthesized for
incorporation into the hard domains of segmented polyur-
ethanes and polyureas using long poly(tetramethylene oxide)
chains as soft segments. The resulting polymers were eval-
uated to determine their extent of polymerization and their
thermal stability. The optical properties of the materials were
studied in solution and as thin films. Where possible the elec-
trochemical properties of the polymers were also explored.
The length of the soft segment chains in the segmented poly-
urethanes hindered electronic coupling of hard domains.
Future work involving smaller, more solubilizing soft segments
may allow for easier material characterization and mechano-
chromic response. VC 2011 Wiley Periodicals, Inc. J Polym Sci
Part A: Polym Chem 49: 4861–4874, 2011
KEYWORDS: conjugated polymers; macromonomers; poly-
urethanes
INTRODUCTION Pi-conjugated electronic materials are now
recognized as viable and competitive active components for
lightweight and processable device applications requiring
talline chain segments rich in b-sheet peptide conformations.
The unique mechanical properties of these silks arise from
the strong restoring forces leading a mechanically deformed
material back to the initial state as driven by the re-estab-
lishment of the enthalpically favorable hydrogen-bonding
interactions among the b-sheets that make up the hard
domains. A variety of synthetic elastomers have been pre-
pared that mimic these mechanical properties such as the
1
–3
light emission, charge transport, or energy storage.
Although small molecule pi-conjugated organics can be
grown into high-quality single crystals suitable for inclusion
in sophisticated device architectures, these materials often
lack the solution processability of their polymeric counter-
parts. New synthesis technologies have led to the construc-
tion of highly regioregular conjugated polymers where the
solubilizing side-chain orientations provide critical control of
7
segmented polyurethanes (Spandex/Lycra). We report here
the syntheses of segmented polyurethanes and polyureas
where well-defined pi-conjugated oligomers (both potential
p-channel and n-channel materials) have been incorporated
into the hard domains of the polymer backbone as a means
to facilitate pi-electron delocalization within the hard
domains of the bulk polymeric material.
4
interpolymer packing of the pi-conjugated backbones. These
and other types of supramolecular organizations will play
key roles in the enhancement of pi-electron delocalization at
the molecular level that is ultimately parlayed functionally
5
into macroscopic substrates.
Our interest in segmented polyurethanes was inspired by
8
–10
With respect to supramolecular organization, natural silk
proteins exploit phase segregation en route to high-perform-
Rubner’s work with mechanochromic polydiacetylenes.
This polymer design involved the preparation of a soft
macromonomer through the endcapping of poly(tetramethy-
lene oxide) (PTMO) with a diisocyanate. This macromonomer
was subjected to chain extension polymerization with a buta-
diynyl diol thus yielding the segmented polymer. The
6
ance structural polymers. In these elastomeric materials,
there is a partitioning of a repetitive polymer into domains
of ‘‘soft’’ amorphous chain segments composed of disordered
peptide sequences accompanied by domains of ‘‘hard’’ crys-
Additional Supporting Information may be found in the online version of this article.
2011 Wiley Periodicals, Inc.
V
C
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diacetylenes were confined to the hard domain after phase
segregation and subsequently cross-linked through topo-
chemical polymerization. It was anticipated that mechanical
stresses would disrupt the chromophore arrangements
within the hard domains thus leading to altered optical
responses. Reversible chromic behavior was observed, but
these effects were attributed to changes in interactions
among the cross-linked hard domains rather than to specific
changes in interchromophore interactions.
tion behind this work was to explore the prospects for new
polymers that would undergo clear and reversible chromicity
changes due to the re-establishment of exciton coupling or
other types of pi–pi interactions within the hard domains, as
they reform in the absence of applied stresses.
In addition to preliminary synthetic work, we present the op-
tical and thermal characterization of the resulting polymeric
materials. Recent work has examined the incorporation of
functional electronic units such as 3,4-ethylenedioxythiophene
(EDOT) monomer, rylene diimides, and oligophenylene vinyl-
Chromic materials that are responsive to external mechanical
stimuli are important as sensors for applied stresses or loads
1
9,24–26
enes into polyurethane-type materials.
The pi systems
1
1
being borne by a composite material. Segmented polyur-
ethanes containing pendent liquid crystal segments exhibit
changes in liquid-crystalline phase ordering in response to
embedded within the macromonomers here consist of a series
of telechelic oligothiophene diols and diamines as chain
extenders for complex polymer synthesis.
1
2–14
mechanical stress.
Another class of mechanochromic
EXPERIMENTAL
materials is the broad family of self-assembled colloidal par-
ticle arrays whose effects are rendered by altered lattice
spacings among silica or polymer particles dispersed within
a polymerized matrix upon application of a mechanical
All air or water sensitive syntheses were performed using
oven or flame dried glassware and air-free Schlenk line tech-
niques. Solvents were degassed by purging with N2 for at
least 30 min prior to use. All chemicals were used as
received from the supplier (Aldrich, Acros, Alfa Aesar), and
the palladium catalysts were obtained from Strem Chemicals.
1
5,16
stress.
Compression of the array alters the spacing and
the Bragg conditions thus impacting the optical properties
associated with reflected and refracted light. Related mecha-
nochromic effects can also be envisioned from deformations
of spherical block copolymer morphologies that exhibit spe-
2
7
0
2,5-Bis(tributylstannyl)thiophene
and 5,5 -bis(tributyl-
0
28
stannyl)-2,2 -bithiophene were prepared by lithiation of
thiophene or 2,2 -bithiophene with n-BuLi then quenching
1
7
0
cific photonic bandgaps. Mechanochromic responses can
also be triggered from molecular dyes dispersed within sup-
porting polymer matrices, whereby mechanical alterations of
interchromophore interactions will lead to altered absorption
with tributyl tin chloride followed by distillation. Molecular
weights and molecular weight distributions were determined
via gel permeation chromatography (GPC) using a Waters
chromatograph containing a two-column bed (styragel HR
7.8 ꢀ 300 mm columns with 5 lm beads size; 500–30,000
and 2,000–600,000 Da), a Waters 2414 refractive index
detector, and a Waters 2489 UV–visible detector (254 nm).
GPC samples were run in tetrahydrofuran (THF) at a flow
1
8–20
or photoluminescence profiles.
These effects arise from
altered influences of exciton coupling among dye aggregates
that allow for excimer/exciplex photoluminescence when the
dyes form nanoscopic aggregates in the relaxed polymer, and
regular fluorescence properties arising from a ‘‘molecularly
dispersed’’ dye when the polymers are stretched and the
aggregates are disrupted or broken up to a greater extent.
Mechanical deformation of the molecular dye–polymer com-
posite upon the application of mechanical stress led to irre-
versible spectral shifts due to the disruption of the aggre-
gated chromophore dopants. Mechanochromism was
reported where the application of mechanical stresses led to
specific and irreversible chemical alterations within embed-
ded photochromic dyes leading to direct color changes
rather than those through the light irradiation commonly
ꢁ
rate of 1 mL/min at 30 C and calibrated against polystyrene
standards. Analysis was done using Empower 2 software.
Differential scanning calorimetry (DSC) was performed using
TA Instruments DSC Q1000 V9.8 Build 296, and thermogra-
vimetric analysis (TGA) was performed using TA Instruments
TGA Q500 V6.7 Build 203. NMR data were obtained on
1
Bruker Avance instruments at either 400 or 300 MHz for H
1
3
spectra or 100 or 75 MHz for C spectra. A Varian Cary 50
Bio UV-Visible spectrophotometer was used to acquire UV–
vis data. Electrochemical measurements were conducted
using an Autolab PGSTAT 302 bipotentiostat. Solutions for
electrochemical experiments were prepared in THF contain-
ing 0.1M tetrabutylammonium hexafluorophosphate (TBAP)
2
1,22
used for photochromic switching.
The potential use of
mechanical stress to direct chemical reactions within poly-
2
3
meric materials is also being investigated.
2
as an electrolyte. Potentials were recorded at a 2 mm
platinum button electrode versus a quasi-internal Ag/Ag
In this report, we describe the synthesis of segmented poly-
urethanes and polyureas bearing well-defined pi-conjugated
units for potential use as mechanochromic materials with re-
versible optical responses due to the restoring forces present
in the covalent polymer backbone. The phase segregation is
expected to be disrupted under applied mechanical stress
due to the disruption of weak interactions such as hydrogen
bonding within the hard domains of the relaxed polymer.
More important from a chromic perspective is that this dis-
ruption may also change the optoelectronic properties of the
polymer due to alterations in exciton coupling. The motiva-
þ
reference.
tert-Butyldimethyl(thiophen-2-ylmethoxy)silane (2): 2-thio-
phenemethanol (1; 3.224 g, 28.20 mmol), imidazole (2.320 g,
34.08 mmol), and 12 mL of degassed dimethylformamide
(DMF) were added to a 50-mL flask. Then tert-butyldi-
methylsilyl chloride (5.142 g, 34.10 mmol) was added. After
24 h the cloudy, white reaction mixture was diluted with
ether (100 mL) and filtered. The filtered solution was placed
in a separation funnel and washed with water (2ꢀ 75 mL),
4
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then with saturated ammonium chloride solution (4ꢀ 50
mL), and then with water again (2ꢀ 75 mL). The organic
layer was collected, dried over magnesium sulfate, and con-
centrated under reduced pressure to provide the slightly yel-
ate addition was complete, the bubbling continued for ꢄ90
min. After 4 h, the reaction mixture was placed in a separa-
tion funnel and washed with water (3ꢀ 75 mL). The organic
layer was collected, dried over magnesium sulfate, and con-
centrated under reduced pressure to provide a yellow oil.
This oil was crystallized from boiling hexane. The crystallites
were collected by filtration and after rinsing with additional
1
low oil product (6.194 g, 27.11 mmol, 97%). H-NMR (400
MHz, CDCl , ppm) d: 7.23 (dd, J ¼ 4.9, 1.4 Hz, 1H), 6.98–6.95
3
1
3
(
m, 2H), 4.92 (s, 2H), 0.98 (s, 9H), 0.15 (s, 6H). C-NMR
(
2
2
100 MHz, CDCl , ppm) d: 145.3, 126.5, 124.6, 123.8, 60.8,
hexane yielded the product as a white solid (7.883 g, 36.99
3
1
6.0, 18.4, ꢂ5.2. HRMS (EI) m/z calculated for (C11
H
20OSSi)
mmol, 86%). H-NMR (400 MHz, CDCl
3
, ppm) d: 7.19 (dd,
þ
28.10042, found 228.09971 [M ꢃ].
J ¼ 4.4, 2.0 Hz, 1H) 6.93 (m, 2H), 4.98 (br, 1H), 4.46 (d, J ¼
13
5
.4 Hz, 2H), 1.46 (s, 9H). C-NMR (100 MHz, CDCl , ppm) d:
3
((5-Bromothiophen-2-yl)methoxy)(tert-butyl)dimethylsilane (3):
1
55.8, 142.2, 127.0, 125.2, 80.0, 39.8, 28.7. HRMS (EI) m/z cal-
2
(10.251 g, 44.876 mmol) and 100 mL degassed DMF were
þ
culated for (C H NO S) 213.08235, found 213.08247 [M ꢃ].
10
15
2
added to a dried 250-mL Schlenk flask. The reaction vessel
was wrapped in foil to exclude light then N-bromosuccinamide
3
1
Compound previously reported by Klare et al.
tert-Butyl (5-bromothiophen-2-yl)methylcarbamate (7):
1.003 g, 4.707 mmol) was added to a 50-mL flask and dis-
(NBS; 8.801 g, 49.45 mmol) was added portion-wise. After 18
6
h, the dark red reaction mixture was diluted with ether to 700
mL total volume. The resulting mixture was washed with satu-
rated ammonium chloride solution (4ꢀ 150 mL) and then with
water (2ꢀ 200 mL). The organic layer was collected, dried
over magnesium sulfate, and concentrated under reduced pres-
sure to a dark red oil. This oil was loaded onto a silica gel plug
packed in hexane and eluted with 1 L of 20% dichloromethane
in hexane. The solvent was concentrated under reduced pres-
(
solved in 10 mL of degassed DMF. The reaction vessel was
then wrapped in foil to exclude light, and NBS (0.907 g, 5.10
mmol) was then added portion-wise. After 18 h, the light
yellow reaction mixture was diluted with ether to 200 mL
total volume. This mixture was washed with saturated am-
monium chloride solution (4ꢀ 100 mL) and then with water
(
2ꢀ 100 mL). The organic layer was collected, dried over
sure to provide the oil product (11.93 g, 38.82 mmol, 86%).
1
magnesium sulfate, and concentrated under reduced pres-
sure to provide the light yellow oil product that was used
H-NMR (400 MHz, CDCl , ppm) d: 6.90 (d, J ¼ 3.68 Hz, 1H),
3
6
9
1
.68 (d, J ¼ 3.64 Hz, 1H), 4.82 (d, J ¼ 1.04 Hz, 2H), 0.98 (s,
13
without further purification (1.37 g, 4.69 mmol, quantita-
H), 0.15 (s, 6H). C-NMR (100 MHz, CDCl , ppm) d: 147.21,
3
1
tive). H-NMR (400 MHz, CDCl , ppm) d: 6.82 (d, J ¼ 3.6 Hz,
3
29.25, 123.62, 111.10, 60.90, 25.90, 18.35, ꢂ5.21. HRMS (EI)
1
H), 6.64 (d, J ¼ 3.5 Hz, 1H), 5.21 (br, 1H), 4.32 (d, J ¼ 5.7
m/z calculated for (C11
3
H
19BrOSSi) 306.01093, found
13
þ
Hz, 2H), 1.42 (s, 9H). C-NMR (100 MHz, CDCl
, ppm) d:
3
06.01133 [M ꢃ].
155.8, 144.3, 129.6, 125.83, 111.5, 80.0, 39.9, 28.6. HRMS
2
9
Compound previously reported by Cama et al. and Rivero
et al.
(
2
EI) m/z calculated for (C H BrNO S) 290.99286, found
1
0
14
2
3
0
þ
90.99243 [M ꢃ].
tert-Butyldimethyl((5-(tributylstannyl)thiophen-2-yl)methoxy)
silane (4): 2 (1.094 g, 4.789 mmol) and 10 mL dry THF
were added to a dried 50-mL flask. The reaction vessel was
cooled in an ice bath, and then, 1.47M n-butyl lithium in hex-
ane (3.4 mL, 5.0 mmol) was added drop-wise. During this
addition, the reaction mixture became tan/yellow. After 1 h,
tributyltin chloride (1.665 g, 5.115 mmol) was added in one
portion, which caused the solution to turn a light golden
color. The ice bath was removed, and after 3 h the reaction
mixture was loaded onto a silica gel plug packed and eluted
with hexane (300 mL). The collected solvent was concen-
trated under reduced pressure to provide the yellow oil
product (2.167 g, 4.188 mmol, 87%) with slight tributyltin
31
Compound previously reported by Klare et al.
tert-Butyl (5-(tributylstannyl)thiophen-2-yl)methylcarbamate
8): 6 (1.606 g, 7.537 mmol) was added to a 100-mL
(
Schlenk flask and dissolved in 30 mL of dry THF. The reac-
tion mixture was cooled in an ice bath. n-Butyl lithium
(1.59M) in hexane (10.4 mL, 16.5 mmol) was added to the
reaction drop-wise forming a dark purple/brown mixture.
ꢁ
The reaction was maintained at 0 C for 45 min, and then
Bu SnCl (5.426 g, 16.67 mmol) was added drop-wise result-
3
ing in a dark purple solution. The ice bath was removed, and
after 6 h the reaction mixture was diluted with THF (350
mL) and washed with brine (4ꢀ 100 mL). The organic layer
was collected, dried over magnesium sulfate, and concen-
trated under reduced pressure to provide a dark brown oil.
This oil was dissolved in 10% EtOAc/hexane and loaded
onto a silica gel plug packed and eluted with 10% EtOAc/
hexane (1 L). Collected eluent was concentrated under
reduced pressure to provide the dark red oil product (3.770
g, 7.505 mmol, 99%) with slight tributyltin impurity which
1
impurity which was used without further purification. H-
NMR (300 MHz, CDCl , ppm) d: 7.00 (m, 2H), 4.96 (s, 2H),
1
3
.62 (m, 6H), 1.39 (m, 6H), 1.14 (m, 6H), 0.98 (s, 9H), 0.92
(
m, 9H), 0.15 (s, 6H).
tert-Butyl thiophen-2-ylmethylcarbamate (6): 2-thiophene-
methylamine (5; 4.858 g, 42.92 mmol) and 100 mL dry
dichloromethane were added to a dried 250-mL Schlenk
flask. Then, triethylamine (6.721 g, 66.42 mmol) was added
to the solution. Di-tert-butyl dicarbonate (11.282 g, 51.693
mmol) was then added portion-wise which caused bubbles
to evolve from the solution. Once the di-tert-butyl dicarbon-
1
was used without further purification. H-NMR (400 MHz,
CDCl , ppm) d: 7.05 (bs, 1H), 7.00 (d, J ¼ 4.3 Hz, 1H), 4.81
3
(bs, 1H), 4.51 (d, J ¼ 7.7 Hz, 2H), 1.56–1.53 (m, 6H), 1.46 (s,
9H), 1.37–1.29 (m, 6H), 1.11–1.05 (m, 6H), 0.92–0.87 (m,
9H).
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0
0
13
5
,5 -Bis((tert-butyldimethylsilyloxy)methyl)-2,2 -bithiophene (9):
4.9 Hz, 4H), 1.47 (s, 18H). C-NMR (100 MHz, CDCl , ppm)
3
3
(1.464 g, 4.764 mmol), 4 (2.506 g, 4.843 mmol), and
d: 155.7, 141.3, 137.1, 126.2, 123.3, 80.0, 39.8, 28.5. HRMS
(FAB-MS) m/z calculated for (C H N O S ) 424.14905,
20 mL degassed DMF were added to a dried 100-mL Schlenk
2
0 28 2 4 2
þ
flask. Pd(PPh ) (0.097 g, 0.084 mmol) was added, and reac-
tion mixture was heated to 75 C in an oil bath. After
found 424.14880 [M ꢃ].
3
4
ꢁ
0
0
2
,2 -Bithiophene-5,5 -diyldimethanaminium chloride (12): 11
2
6
days, the dark brown reaction mixture was diluted with
00 mL of ether, and the resulting mixture was washed with
(
2.704 g, 6.369 mmol) was added to a 1-L round bottom
flask and dissolved in dioxane (450 mL) forming a red solu-
tion. Concentrated HCl (150 mL) was added to the vigo-
rously stirred solution, which clouded over time. After 18 h,
the reaction mixture was filtered and the gray solid product
saturated ammonium chloride solution (4ꢀ 150 mL) and
water (2ꢀ 200 mL). The organic layer was collected, dried
over magnesium sulfate, and the solvent was concentrated
under reduced pressure to provide a light brown oil. This oil
was loaded onto a silica gel column packed in hexane and
eluted with 30% dichloromethane in hexane. The fractions
containing product were concentrated under reduced pres-
sure to provide a green oil which solidified in the freezer.
was collected and dried under vacuum (1.633 g, 5.493
1
mmol, 86%). H-NMR (400 MHz, D O, ppm) d: 7.27 (d, J ¼
2
5
6
.0 Hz, 2H), 7.21 (d, J ¼ 5.0 Hz, 2H), 4.42 (s, 4H), 3.78 (s,
H)
3
3
Pale green crystals were collected by filtration (1.078 g,
Compound previously reported by Muguruma et al.
1
2.370 mmol, 50%). H-NMR (400 MHz, CDCl , ppm) d: 6.96
0
0
3
2
,2 -Bithiophene-5,5 -diyldimethanamine (13): 12 (1.621 g,
(
d, J ¼ 3.6 Hz, 2H), 6.79 (d, J ¼ 3.6 Hz, 2H), 4.83 (d, J ¼ 0.9
5.453 mmol) was added to a 1-L round bottom flask and dis-
13
Hz, 4H), 0.93 (s, 9H), 0.11 (s, 6H). C-NMR (100 MHz,
solved in water (400 mL.) Aqueous KOH (2M, 20 mL, 40
mmol) was added, which caused the solution to cloud. After
CDCl , ppm) d: 144.5, 137.2, 124.6, 123.1, 61.1, 26.2, 18.7,
3
ꢂ4.9. HRMS (FAB-MS) m/z calculated for (C22
38 2 2 2
H O S Si )
6
h, the reaction mixture was filtered, and the collected liq-
þ
454.18518, found 454.18414 [(MþH) ].
uid was extracted with dichloromethane (4ꢀ 200 mL). The
combined organic layers were dried over magnesium sulfate
and concentrated under reduced pressure to provide the
0
0
2,2 -Bithiophene-5,5 -diyldimethanol (10): 9 (1.078 g, 2.370
mmol) and 50 mL THF were placed in a 250-mL flask.
Twenty milliliters of 1M tetrabutylammonium fluoride
1
gray/tan solid product (1.180 g, 5.260 mmol, 96%). H-NMR
(
400 MHz, CDCl
3.5 Hz, 2H), 4.02 (s, 4H), 1.66 (bs, 4H). C-NMR (100
3
, ppm) d: 6.96 (d, J ¼ 3.6 Hz, 2H), 6.79 (d, J
(
TBAF; 20 mmol) in THF (with 5% water) solution was
13
¼
added which caused the initially light green reaction mixture
to become light yellow. After 2 days, the light brown reaction
mixture was loaded onto a silica gel plug packed and eluted
with ethyl acetate (800 mL). The collected solvent was con-
centrated under reduced pressure to provide a light yellow
oil, which was crystallized from boiling chloroform. The yel-
MHz, DMSO-d , ppm) d: 149.2, 136.2, 125.1, 123.8, 42.2.
6
HRMS (EI/CI) m/z calculated for (C H N S ) 224.04419,
1
0 12 2 2
þ
found 224.04428 [M ꢃ].
3
3
Synthesis previously reported by Muguruma et al.
00
0
0
00
5
,5 -Bis(((tert-butyldimethylsilyl)oxy)methyl)-2,2 :5 ,2 -terthio-
low solid product was collected by filtration (0.250 g, 1.105
mmol, 46%). H-NMR (300 MHz, CD OD, ppm) d: 7.02 (d, J
phene (15): 3 (6.628 g, 21.57 mmol) was added to a 250-
mL flask and dissolved in 100 mL degassed DMF. 2,5-Bis(tri-
butylstannyl)thiophene (14; 7.137 g, 10.78 mmol) and
Pd(PPh ) (0.745 g, 0.645 mmol) were added to the solution.
1
3
¼
3.6 Hz, 2H), 6.89 (dt, J ¼ 3.6, 0.8 Hz, 2H), 4.69 (d, J ¼ 0.5
13
Hz, 4H). C-NMR (75 MHz, CD
3
OD, ppm) d: 145.3, 138.5,
3
4
1
26.8, 124.0, 60.0. HRMS (EI/CI) m/z calculated for
The reaction vessel was placed in an oil bath and heated to
60–70 C. After 5 days, the cloudy, black reaction mixture
þ
(
C H O S ) 226.01222, found 226.01229 [M ꢃ].
ꢁ
1
0
10
2
2
3
2
was diluted with ether to 700 mL total volume. The resulting
mixture was filtered through a cotton plug into a separation
funnel and washed with saturated ammonium chloride solu-
tion (4ꢀ 150 mL) and then with water (2ꢀ 200 mL). The
organic layer was collected, dried over magnesium sulfate,
and concentrated under reduced pressure to provide an
amber/yellow solid. This solid was recrystallized from meth-
Compound previously reported by Joo et al.
0
0
tert-Butyl
2,2 -bithiophene-5,5 -diylbis(methylene)dicarba-
mate (11): DMF (250 mL) was placed into a 500-mL Schlenk
flask and degassed with nitrogen purge for 1 h. 8 (6.034 g,
12.01 mmol) was added to the solvent forming a red solu-
tion. 7 (3.527 g, 12.07 mmol) and Pd(PPh ) (0.395 g, 0.342
mmol) were added. The reaction flask was placed in an oil
bath and heated to 65 C. After 3 days the reaction mixture
3
4
anol to yield clean product as a red/brown solid (4.033 g,
ꢁ
1
7
.511 mmol, 70%). H-NMR (400 MHz, CDCl , ppm) d: 7.02
3
was cooled to room temperature, diluted with ether (500
mL), and washed with saturated ammonium chloride solu-
tion (4ꢀ 150 mL) and water (2ꢀ 150 mL). The organic layer
was collected, dried over magnesium sulfate, and concen-
trated under reduced pressure to provide a red/brown solid.
Hexane (500 mL) was added to the collected solid, and the
mixture was sonicated for several minutes. The brown solid
(
(
s, 2H), 6.99(d, J ¼ 3.6 Hz, 2H), 6.81 (d, J ¼ 3.6 Hz, 2H), 4.84
13
s, 4H), 0.94 (s, 18H), 0.12 (s, 12H). C-NMR (100 MHz,
CDCl , ppm) d: 145.0, 136.7, 136.6, 124.8, 124.3, 123.4, 61.2,
2
3
6.2, 18.7, ꢂ4.9. HRMS (FAB-MS) m/z calculated for
þ
(
C H O S Si ) 536.17290, found 536.17186 [(MþH) ].
2
6
40
2
3
2
0
0
00
00
[2,2 :5 ,2 -Terthiophene]-5,5 -diyldimethanol (16): 15 (1.495
g, 2.784 mmol) was placed in a 250-mL flask and dissolved
in 80 mL THF forming a red/amber solution. TBAF (1M) in
THF (12 mL, 12 mmol; with 5% water) solution was added to
product was collected by filtration (2.746 g, 6.468 mmol,
1
5
4%). H-NMR (400 MHz, CDCl , ppm) d: 6.94 (d, J ¼ 3.6
3
Hz, 2H), 6.82 (d, J ¼ 3.1 Hz, 2H), 4.91 (bs, 2H), 4.43 (d, J ¼
4
864
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ARTICLE
flask. After 20 h, the reaction mixture was loaded onto a silica gel
plug packed in ethyl acetate. This plug was eluted with 1 L of
were added to the solution. The reaction vessel was placed
in an oil bath and heated to 70 C. After 5 days, the reaction
ꢁ
1
0% methanol in ethyl acetate solution. Collected solvent was
mixture was diluted with 500 mL ether and filtered remov-
ing a red/brown solid. The collected liquid was added to a
separation funnel and washed with saturated ammonium
chloride solution (4ꢀ 100 mL) and then with water (2ꢀ 100
mL). The organic layer was collected, dried over magnesium
sulfate, and concentrated under reduced pressure to provide
a red/orange solid. This solid was washed with boiling etha-
concentrated under reduced pressure to provide a red/orange
solid. This solid was recrystallized from boiling chloroform. The
yellow/orange solid product was collected by filtration (0.466 g,
1
1.51 mmol, 54%). H-NMR (400 MHz, CDCl , ppm) d: 7.09 (s, 2H),
3
7
.07 (d, J ¼ 3.6 Hz, 2H), 6.92 (d, J ¼ 3.6 Hz), 4.71 (s, 4H).
32
34
Compound previously reported by Joo et al. and Kim et al.
nol and filtered to collect the dark red solid product (0.266
0
0
00
00
1
Di-tert-butyl ([2,2 :5 ,2 -terthiophene]-5,5 -diylbis(methyle-
ne))dicarbamate (17): 7 (0.413 g, 1.41 mmol) was added to
a 100-mL Schlenk flask, and 25 mL DMF was added. The
resulting solution was degassed with a nitrogen purge for 60
min. 2,5-Bis(tributylstannyl)thiophene (14; 0.485 g, 0.732
mmol) was added to the flask forming a greenish solution.
Pd(PPh ) (0.030 g, 0.026 mmol) was added to the solution,
g, 0.430 mmol, 34%). H-NMR (400 MHz, CDCl , ppm) d:
3
7.34 (d, J ¼ 3.8 Hz, 2H), 7.29 (d, J ¼ 3.8 Hz, 2H), 7.23 (d,
J ¼ 3.6 Hz, 2H), 6.00 (d, J ¼ 3.6 Hz, 2H), 4.89 (s, 4H), 0.94
(
(
s, 18H), 0.14 (s, 12H). HRMS (FAB-MS) m/z calculated for
þ
C
30
H
42
O
2
S
4
Si
2
) 618.16062, found 618.16059 [M ].
0
0
00 00 000
000
[
2,2 :5 ,2 :5 ,2 -Quaterthiophene]-5,5 -diyldimethanol (22):
3
4
2
1 (0.101 g, 0.163 mmol) was added to a 25-mL round
which turned yellow. The reaction vessel was placed in an oil
bath and heated to 65 C. After 3 days, the dark brown/black
bottom flask and dissolved in 10 mL THF forming a dark
amber solution. 1M TBAF in THF solution (0.5 mL,
ꢁ
reaction mixture was diluted with 350 mL of ether and washed
with saturated ammonium chloride solution (4ꢀ 50 mL) and
then with water (2ꢀ 50 mL). The organic layer was collected,
dried over magnesium sulfate, and concentrated under reduced
pressure to provide an orange solid. This solid was recrystallized
from boiling ethanol and filtered providing the desired product
0.5 mmol) was added to the solution, which caused it to
cloud. After 20 h, the reaction mixture was diluted with 500
mL of ether. Resulting mixture was filtered through a cotton
plug into a separation funnel and washed with brine (4ꢀ
75 mL). The organic layer was collected, dried over magne-
1
sium sulfate, and concentrated under reduced pressure to
provide a red/orange solid. This solid was washed in boiling
chloroform, and the red/orange solid product was collected
as a red solid (0.124 g, 0.245 mmol, 35%). H-NMR (400 MHz,
CDCl , ppm) d: 7.00 (s, 2H), 6.97 (d, J ¼ 3.6 Hz, 2H), 6.84 (d, J ¼
3
3
.5 Hz, 2H), 4.93 (br, 2H), 4.44 (d, J ¼ 5.3 Hz, 4H), 1.47 (s, 18H).
1
1
3
by filtration (0.039 g, 0.100 mmol, 61%). H-NMR (400 MHz,
C-NMR (100 MHz, CDCl , ppm) d: 137.0, 136.5, 126.6, 124.5,
3
DMSO-d
6
, ppm) d: 7.29 (d, J ¼ 3.7 Hz, 2H), 7.23 (d, J ¼ 3.9
123.6, 40.0, 28.7. HRMS (FAB-MS) m/z calculated for
þ
Hz, 2H), 7.19 (d, J ¼ 2.7 Hz, 2H), 6.93 (d, J ¼ 3.7 Hz, 2H),
(C
24
H
30
N
2
O
4
S
3
) 506.13677, found 506.13486 [M ].
5.56 (t, J ¼ 5.3 Hz, 2H), 4.63 (d, J ¼ 5.0 Hz, 4H).
0
0
00
00
[
2,2 :5 ,2 -Terthiophene]-5,5 -diyldimethanammonium chlo-
3
2
Compound previously reported by Joo et al.
ride (18): 17 (0.196 g, 0.387 mmol) and dioxane (18 mL)
were added to a 50-mL flask. Concentrated HCl (6 mL) was
added drop-wise. After 24 h, the cloudy, yellow reaction mix-
ture was filtered and the collected pale yellow solid product
0
0
00 00 000
000
Di-tert-butyl ([2,2 :5 ,2 :5 ,2 -quaterthiophene]-5,5 -diylbis
(methylene))dicarbamate (23): 7 (0.734 g, 2.51 mmol) was
added to a 100-mL Schlenk flask, and 30 mL DMF was
added. The resulting solution was degassed with a nitrogen
1
was rinsed with ethanol (0.134 g, 0.353 mmol, 91%). H-
0
0
NMR (400 MHz, D O, ppm) d: 7.26 (s, 2H), 7.25 (d, J ¼ 3.8
2
purge for 1 h. 5,5 -Bis(tributylstannyl)-2,2 -bithiophene (20;
.850 g, 1.15 mmol) and Pd(PPh3)4 (0.093 g, 0.080 mmol)
Hz, 2H), 7.18 (d, J ¼ 3.8 Hz, 2H), 4.39 (s, 4H)
0
3
3
were added to the solution. The reaction vessel was placed
Compound previously reported by Muguruma et al.
ꢁ
in an oil bath and heated to 70 C turning the initially yellow
0
0
00
00
[
(
2,2 :5 ,2 -Terthiophene]-5,5 -diyldimethanamine (19): 18
0.040 g, 0.105 mmol) was placed in a 250-mL flask and dis-
solution red/orange. After 4 days, the dark brown/black
reaction mixture was diluted with 500 mL ether, and the
resulting mixture was filtered. The collected liquid was
washed with saturated ammonium chloride solution (3ꢀ
solved in 100 mL water. KOH solution (2M, 4.5 mL, 9.0 mmol)
was added drop-wise causing the initially yellow reaction mix-
ture to cloud. After 2 h, the reaction mixture was filtered, and
the collected solid was rinsed with additional water. The col-
lected orange/brown solid product was dried under high vac-
uum (0.015 g, 0.049 mmol, 47%). H-NMR (400 MHz, CDCl ,
1
00 mL) and then with water (2ꢀ 100 mL). The combined
aqueous layers were extracted with ether (2ꢀ 100 mL). The
combined organics were dried over magnesium sulfate and
concentrated under reduced pressure to provide a red/or-
ange solid. This red/orange solid was washed in boiling
ethanol, cooled, and filtered providing the red/orange
1
3
ppm) d: 7.01 (br, 4H), 6.8 (s, 2H), 4.04 (s, 4H).
3
3
Synthesis previously reported by Muguruma et al.
1
000 0 0 00 00
,5 -Bis(((tert-butyldimethylsilyl)oxy)methyl)-2,2 :5 ,2 :5 ,
solid product (0.105 g, 0.270 mmol, 23%). H-NMR (400
5
2
0
00
-quaterthiophene (21): 3 (0.791 g, 2.57 mmol) was added
MHz, CDCl
3
, ppm) d: 7.04 (quartet, J ¼ 3.8 Hz, 4H), 6.99 (d, J
to a dried 100-mL Schlenk flask and dissolved in 30 mL
DMF. The resulting solution was degassed with a nitrogen
purge for 1 h. 5,5 -Bis(tributylstannyl)-2,2 -bithiophene (20;
¼ 3.6 Hz, 2H), 6.85 (d, J ¼ 3.4 Hz, 2H), 4.89 (br, 2H),
4.44 (d, J ¼ 5.8 Hz, 4H), 1.48 (s, 18H). HRMS (FAB-MS) m/z
0
0
calculated for (C28
H
N
32
O
S
4
) 588.12449, found 588.12506
2
4
þ
0.946 g, 1.27 mmol) and Pd(PPh3)4 (0.093 g, 0.080 mmol)
[M ].
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0
0
00 00 000
000
[
2,2 :5 ,2 :5 ,2 -quaterthiophene]-5,5 -diyldimethanammonium
Bithiophene Diamine Polyurea (30)
4,4 -Methylenebis(phenyl isocyanate) (0.245 g, 0.979 mmol)
0
chloride (24): 23 (2.123 g, 0.3606 mmol) and dioxane (450
mL) were added to a 1-L flask. The resulting suspension was
heated with a heat gun, until the solid was in solution and
subsequently cooled to room temperature. Concentrated HCl
and dry toluene (10 mL) were added to a 100-mL Schlenk
flask. The reaction vessel was placed in an oil bath and
ꢁ
heated to 70 C. Then PTMO (2,900 g/mol average molecular
(
150 mL) was added, which caused a precipitate to form.
weight; 1.421 g, 0.4900 mmol), which had been dried under
high vacuum at 65 C for several days, was dissolved in 12
mL of dry toluene. This PTMO solution was added to the
ꢁ
After 18 h, the reaction mixture was filtered and the tan/
orange solid product is collected (1.428 g, 3.094 mmol,
86%).
reaction vessel over 1 h via syringe pump. 13 (0.110 g,
0
.4903 mmol) and 20 mL of dry toluene were mixed in a
Compound is too insoluble for NMR characterization.
ꢁ
separate flask and heated to 90 C. The resulting mixture
was cannulated into the reaction flask, and after 2.5 h, the
PTMO addition was complete. The resulting cloudy white
3
3
Compound previously reported by Muguruma et al.
0
0
00 00 000
000
[
2
1
2,2 :5 ,2 :5 ,2 -Quaterthiophene]-5,5 -diyldimethanamine (25):
4 (0.104 g, 0.225 mmol) was placed in 200-mL flask, and
50 mL water was added. The resulting suspension was
heated but the solid never fully dissolved. KOH solution (2M,
.0 mL, 6.0 mmol) was added drop-wise, which caused a
ꢁ
reaction mixture was maintained at 80 C. After 5 days, the
reaction mixture was allowed to cool to room temperature
and was poured into a flask containing 600 mL of methanol.
The resulting mixture was filtered and yellow solid product
was isolated (1.080 g, mass yield: 61%). GPC: Mw 77,400 Da,
3
precipitate to form immediately. After 3 h, the reaction mix-
ture was filtered, and the collected solid was rinsed with
additional water. The collected red solid product was dried
M 43,600 Da.
n
1
Terthiophene Diol Polyurethane (31)
under high vacuum (0.060 g, 0.154 mmol, 67%). H-NMR
0
4,4 -Methylenebis(phenyl isocyanate) (0.180 g, 0.719 mmol)
(
300 MHz, DMSO-d , ppm) d: 7.26 (d, J ¼ 3.8 Hz, 2H), 7.19
6
and dry toluene (60 mL) were added to a 250-mL two-neck
round bottom flask. The reaction vessel was placed in an oil
bath and heated to 60 C. Then, PTMO (2900 g/mol average
molecular weight; 1.044 g, 0.360 mmol), which had been
dried under high vacuum at 60 C for several days, was dis-
solved in 15 mL of dry toluene. This PTMO solution was
added to the reaction vessel over 1 h via syringe pump. The
oil bath temperature was raised to 80 C. 16 (0.111 g, 0.360
(d, J ¼ 3.8 Hz, 2H), 7.15 (d, J ¼ 3.5 Hz, 2H), 6.89 (m, 2H),
3
.89 (s, 4H).
ꢁ
3
3
Synthesis previously reported by Muguruma et al.
ꢁ
0
Bis-N,N -(2-hydroxyethyl)-1,4,5,8-naphthalenetetracarboxylic
diimide (27): ethanolamine (125 mL, 2.0 mol) was added
to a 250-mL flask. Naphthalene tetracarboxylic dianhydride
ꢁ
(
26; 6.659 g, 24.83 mmol) was added to the flask which
mmol) was added to the reaction, and after 3 h, the PTMO
addition was complete. The cloudy yellow reaction mixture
was heated to reflux. After 5 days, the reaction mixture was
allowed to cool to room temperature and was poured into a
flask containing 400 mL of methanol. The resulting mixture
was filtered, and tan/yellow solid product was isolated.
More material precipitated from the filtered liquid, and this
was also collected by filtration. The collected product was a
yellow/tan solid (0.356 g, mass yield: 27%). Polymer is too
insoluble for GPC analysis.
caused a gas to evolve. The reaction mixture became a dark
slurry. After 24 h, the dark purple reaction mixture was
diluted with 600 mL of methanol and filtered. Light purple
solid product was collected by filtration and dried under
1
high vacuum (7.017 g, 19.80 mmol, 80%). H-NMR (400
MHz, CDCl
3
, ppm) d: 8.79 (s, 4H), 4.49 (t, J ¼ 5.5 Hz, 4H),
4
.02 (t, J ¼ 5.5 Hz, 4H).
3
5
Compound previously reported by Fierz-David and Rossi.
Bithiophene Diol Polyurethane (29)
0
4
,4 -Methylenebis(phenyl isocyanate) (0.520 g, 2.078 mmol)
Terthiophene Diamine Polyurea (32)
and dry toluene (15 mL) were added to a 100-mL Schlenk
flask. The reaction vessel was placed in an oil bath and heated
0
4
,4 -Methylenebis(phenyl isocyanate) (0.252 g, 1.007 mmol)
and dry toluene (10 mL) were added to a 100-mL Schlenk
flask. The reaction vessel was placed in an oil bath and
ꢁ
to 65 C. Then, PTMO (2,900 g/mol average molecular weight;
3
.018 g, 1.039 mmol), which had been dried under high vac-
ꢁ
heated to 65 C. Then, PTMO (2900 g/mol average molecular
ꢁ
uum at 60 C for several days, was dissolved in 15 mL of dry
toluene. This PTMO solution was added to the reaction vessel
over 1 h via syringe pump. 10 (0.236 g, 1.039 mmol) was
added to the reaction 3 h after the PTMO addition was com-
plete. The cloudy, pale yellow/tan reaction mixture was main-
weight; 1.465 g, 0.5052 mmol), which had been dried under
ꢁ
high vacuum at 65 C for several days, was dissolved in 10
mL of dry toluene. This PTMO solution was added to the
reaction vessel over 1.25 h via syringe pump. 19 (0.154 g,
0
.503 mmol) and 25 mL of dry toluene were mixed in a sep-
ꢁ
tained at 80 C. After 46 h, the reaction mixture was allowed
ꢁ
arate flask and heated to 90 C. The resulting mixture was
cannulated into the reaction flask, and after 4 h, the PTMO
addition was complete. The resulting cloudy orange reaction
to cool to room temperature and was poured into a flask con-
taining 300 mL of methanol. The resulting mixture was fil-
tered, and pale yellow solid product was isolated (3.113 g,
ꢁ
mixture was maintained at 75 C. After 3 days, the reaction
mass yield: 82%). GPC: Mw 58,000 Da, M 23,700 Da.
n
mixture was allowed to cool to room temperature and was
poured into a flask containing 500 mL of methanol. The
resulting mixture was filtered and brown solid product was
All polymerizations are based on synthesis reported by
8
Rubner.
4
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ARTICLE
SCHEME 1 2-Thiophenemethanol-based precursor syntheses.
ꢁ
isolated (1.071g, mass yield: 57%). GPC: Mw 41,500 Da, Mn
2,600 Da.
under high vacuum at 60 C for several days, was dissolved
in 8 mL of o-dichlorobenzene. This PTMO solution was
added to the reaction vessel over 75 min via syringe pump.
2
Quaterthiophene Diol Polyurethane (33)
2
7 (0.174 g, 0.491 mmol) and 20 mL o-dichlorobenzene
0
4
,4 -Methylenebis(phenyl isocyanate) (0.101 g, 0.404 mmol)
were mixed in a separate flask and heated with a heat gun.
The resulting suspension was cannulated into the reaction
flask, and after 3 h, the PTMO addition was complete. Once
this cannulation was complete, the reaction mixture was
and dry toluene (10 mL) were added to a 100-mL three-
neck flask. The reaction vessel was placed in an oil bath and
ꢁ
heated to 60 C. Then, PTMO (2,900 g/mol average molecu-
lar weight; 0.583 g, 0.201 mmol), which had been dried
ꢁ
heated to 110 C. After 2 days, the reaction mixture was
ꢁ
under high vacuum at 60 C for several days, was dissolved
allowed to cool to room temperature and was poured into a
flask containing 300 mL of methanol. The resulting mixture
was filtered, and the dark red solid product was isolated
in 9 mL of dry toluene. This PTMO solution was added to
the reaction vessel over 1 h via syringe pump. 22 (0.079 g,
0.202 mmol) was added to the reaction, and after 3 h, the
(
1.429 g, mass yield: 77%). GPC: M
w n
70,700 Da, M
PTMO addition was complete. A condenser was attached to
the reaction vessel, and the reaction mixture was heated to
reflux. After 24 h, an additional 10 mL of dry toluene was
used to rinse down the sides of the reaction vessel. After 6
days, the reaction mixture was allowed to cool to room tem-
perature and was poured into a flask containing 300 mL of
methanol. The resulting mixture was filtered and dark red
solid product was isolated (0.149 g, mass yield: 20%). Poly-
mer was too insoluble for GPC analysis.
3
4,100 Da.
RESULTS AND DISCUSSION
The segmented polyureas and polyurethanes that are the
focus of this work have three components: a PTMO soft seg-
ment chain, an oligothiophene diol (to form polyurethanes)
or diamine (to form polyureas), and a diisocyanate, 4,4 -
methylenebis(phenyl isocyanate) (MDI). The PTMO chain uti-
lized in this work has a number average molecular weight
0
Quaterthiophene Diamine Polyurea (34)
(M ) of 2900 g/mol. The diamine or diol segments used con-
0
n
4
,4 -Methylenebis(phenyl isocyanate) (0.255 g, 1.019 mmol)
tain two, three, or four thiophene rings and were prepared
by Stille cross-coupling reactions. Naphthalene diimide has
also been utilized as a hard segment. We present the synthe-
ses of the requisite chain extenders and polymer syntheses
with thermal, optical, electrochemical, and characterization
data.
and o-dichlorobenzene (10 mL) were added to a 250-mL
Schlenk flask. The reaction vessel was placed in an oil bath
ꢁ
and heated to 70 C. Then, PTMO (2,900 g/mol average mo-
lecular weight; 1.478 g, 0.5097 mmol), which had been dried
ꢁ
under high vacuum at 65 C for several days, was dissolved
in 10 mL of o-dichlorobenzene. This PTMO solution was
added to the reaction vessel over 1 h via syringe pump. 25
Precursor Syntheses
(0.199 g, 0.5121 mmol) and 150 mL of o-dichlorobenzene
The synthesis of Stille cross-coupling precursors to oligothio-
phene diols is shown in Scheme 1. 2-Thiophenemethanol 1
was protected with tert-butyldimethylsilyl (TBDMS) chloride
using imidazole as a base. The protected alcohol 2 was
brominated using NBS in DMF, while excluding light to
form the thienyl bromide cross-coupling partner 3.
tributylstannane 4 was generated from 2 by deprotonation
of the a-position of the thiophene ring with n-BuLi
then quenching with tributyl tin chloride. This reaction pro-
ceeded well, although the crude product was difficult
to purify due to problems with decomposition on silica
gel or during distillation. Because of these difficulties the
crude stannylated product 4 was carried forward without
purification.
were mixed in a separate flask and heated to reflux. The
resulting mixture was cannulated into the reaction flask, and
after 5.5 h, the PTMO addition was complete. The resulting
ꢁ
dark red reaction mixture was maintained at 100 C. After 4
days, the reaction mixture was allowed to cool to room tem-
perature and was poured into a flask containing 600 mL of
methanol. The resulting mixture was filtered, and brown
solid product was isolated (>1.932 g, mass yield: quant.).
29,30
The
GPC: Mw 37,600 Da, M 14,300 Da.
n
Naphthalene Diimide Diol Polyurethane (35)
0
4
,4 -Methylenebis(phenyl isocyanate) (0.247 g, 0.987 mmol)
and o-dichlorobenzene (10 mL) were added to a 100-mL
Schlenk flask. The reaction vessel was placed in an oil bath
ꢁ
and heated to 60 C. Then PTMO (2900 g/mol average mo-
Likewise, the syntheses of building blocks for the oligo-
thiophene diamines are shown in Scheme 2. The amine of 2-
lecular weight; 1.436 g, 0.4952 mmol), which had been dried
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SCHEME 2 2-Thiophenemethylamine-based precursor syntheses.
thiophenemethylamine 5 was protected with the tert-buty-
The syntheses of bifunctionalized terthiophenes, 16 and 19,
2
7
loxycarbonyl (Boc) group using triethylamine as a base to
utilized 2,5-bis(tributylstannyl)thiophene 14 as a coupling
partner in twofold Stille couplings with the thienyl bromides
described earlier (3 and 7, respectively), as shown in
Scheme 4. Once the terthiophenes were formed the protect-
ing groups were removed as before. The TBDMS groups of
15 were removed by TBAF treatment to give the free diol
3
1
form 6. Boc-protected amine 6 was then brominated using
NBS in DMF while shielding the reaction from light to give
3
1
bromide 7. Similar to the protected alcohol 2, the Boc-pro-
tected amine 6 was lithiated at the thiophene a-position
using n-BuLi and then quenched with tributyl tin chloride to
form the tributylstannane 8. This stannane also could
decompose on silica or during distillation, so the crude prod-
uct 8 was also used without purification.
3
2,34
16.
with HCl forming the hydrochloride salt 18, then treatment
The Boc-protected amines of 17 were first treated
3
3
with KOH gave the free-base diamine 19. The protected
terthiophenes have been synthesized on 100s of milligrams
to gram scales.
Chain Extender Syntheses
Scheme 3 shows the syntheses of the bithiophene chain
extenders. The previously synthesized bromide 3 and stan-
nane 4 were joined through a Stille cross-coupling reaction
to form the protected diol bithiophene 9 [Scheme 3(a)]. This
coupling reaction was performed in DMF with mild heating
and a palladium (0) catalyst. The TBDMS protecting groups
were then removed with TBAF in THF to provide the bithio-
Bifunctionalized quaterthiophenes were synthesized in a
similar manner as was employed for the terthiophene syn-
0
theses, as shown in Scheme 5. Using 5,5 -bis(tributyl-
0
28
stannyl)-2,2 -bithiophene 20
in twofold Stille couplings
with brominated compounds 3 and 7 allowed for the prepa-
ration of the protected quaterthiophenes, 22 and 25, respec-
tively. As with the previous oligomers, the protecting groups
were removed to provide the free diol or free diamine. The
silyl protecting groups of 21 were removed by TBAF to give
3
2
phene diol 10. Similarly, the bromide 7 and the stannane 8
derived from the Boc-protected amine 6 were coupled under
Stille conditions to form the Boc-protected diamine bithio-
phene 11 [Scheme 3(b)]. The Boc protecting groups were
removed by treatment with HCl forming the hydrochloride
salt 12, which was then treated with KOH to form the free-
3
2
the diol 22. Boc-protecting groups of 23 were removed
with HCl, and the resulting hydrochloride salt 24 was
3
3
treated with KOH to give the free-base diamine 25. The
protected quaterthiophenes have been synthesized on 100
mg scales. The oligothiophene diamines prepared in this
work (13, 19, 25) were previously reported by Muguruma
3
3
base diamine bithiophene 13. Both protected bithiophenes
have been synthesized on gram scales.
SCHEME 3 Syntheses of (a) bithiophene diol 10 and (b) bithiophene diamine 13.
4
868
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ARTICLE
SCHEME 4 Syntheses of (a) terthiophene diol 16 and (b) terthiophene diamine 19.
3
3
et al. Attempts to reproduce the preparative chemistry
described in this work either failed completely or led to
impure product mixtures which could not be purified due to
the instability of the silane derived ‘‘STABASE’’ protecting
group used. After attempts to follow these reported synthetic
pathways failed, Stille-based cross-coupling approaches were
developed as described here.
form polymers in the same way as the oligothiophenes. This
synthesis is shown in Scheme 6.
Oligothiophenes and naphthalene diimides have interesting
optoelectronic properties. The protected alcohol and amine
precursors described above may be easily incorporated into
other systems. These molecules may be of interest for the
construction of field-effect transistor sensors that rely on
3
6
In addition to oligothiophenes, a diimide derivative of
active semiconductor layers with polar functional groups.
1
,4,5,8-naphthalenetetracarboxylic dianhydride 26 was stud-
However, the final deprotected diol and diamine monomers
can be challenging to work with due to poor solubility
resulting from a lack of solubilizing side chains. The chain
ied. 26 was treated with ethanolamine to produce the
desired naphthalene diimide 27,
3
5
which was used to
SCHEME 5 Syntheses of (a) quaterthiophene diol 22 and (b) quaterthiophene diamine 25.
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solubility extended to dichloromethane and THF, which are
commonly used as mobile phases for GPC. To obtain GPC
data, polymer samples were refluxed in THF but did not dis-
solve completely. The filtered solutions containing soluble
materials were then evaluated by GPC—these data are pre-
sented in Table 1. The measured degree of polymerization is
low, but these data only represent the soluble fraction of the
polymer. In some cases, elastomeric free-standing films were
SCHEME 6 Synthesis of naphthalene diimide 27.
extenders are sparingly soluble in common chlorinated sol-
vents, ethereal solvents, methanol, ethanol, and toluene. Bet-
ter but still poor solubility was observed in dimethylsulfox-
ide (DMSO) and DMF.
32
isolated after filtration (e.g., ref. ) suggesting an entangled
material with a higher actual molecular weight. Such insolu-
24,37
bilities have been reported
for these types of systems,
and we expect to solve this problem in the future through
2
6
the use of a more solubilizing soft segment.
Polymer Syntheses
The diol and diamine chain extenders were used as compo-
nents in the synthesis of segmented polyurethanes or poly-
ureas, respectively. Polymerization reactions were carried
Thermal Data
The thermal properties of these polymers were fairly compa-
rable, and representative DSC and TGA data are shown in
Figure 1. DSC measurements indicate the phase change
behavior of the polymer. In this case, the two signals
recorded are likely melting and solidification of the polymer
at slightly above room temperature. For all polymers, these
thermal properties of the material are dominated by the
PTMO segments rather than by differences in hard domain
interactions. TGA provides data on the decomposition of the
polymer. This experiment measured the decrease in mass, as
temperature is increased. As shown, polymer 29 was stable
8
out in the same manner as those in the Rubner work, as
shown in Scheme 7. The first step in this sequence, forming
the macromonomer 28, had to be performed under pseudo
high dilution conditions via slow addition (utilizing a syringe
pump) of a PTMO solution into the MDI solution with vigor-
ous stirring. MDI and PTMO were mixed in a 2:1 ratio, so
that the PTMO was end-capped with MDI. Once the macro-
monomer was generated, a diol or diamine chain extender
was added quickly to allow for reaction with the isocyanate
groups at the termini of the macromonomer to form the seg-
mented polymer. After 2–6 days, the polymerization reaction
was cooled to room temperature then poured into methanol
and filtered to collect the product. This method was used to
form a variety of segmented polyurea (R ¼ NH) and poly-
urethane (R ¼ O) materials (Scheme 8).
ꢁ
up to ꢄ300 C and then began to decompose.
NMR Spectra
The bithiophene diol containing polymer 29 was soluble
enough to allow acquisition of NMR data in deuterated DMF.
Figure 2 shows the NMR spectra of bithiophene containing
polymer 29 (top), bithiophene diol monomer 10 (middle),
and MDI (bottom). The aromatic region peaks of 10 and MDI
shift and coalesce into the aromatic peaks of the polymer.
The spectrum of 29 shows two distinct urethane NAH peaks
Molecular Weights
The polymers synthesized through this method are very
poorly soluble in a variety of common solvents. This poor
SCHEME 7 Representative chain-extension polymerization of diisocyanate macromonomers.
4
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SCHEME 8 Structures of synthesized segmented polyurethanes.
TABLE 1 GPC Data for Synthesized Polymers
Repeat Unit
Number of
Repeats (y)
Polydispersity
Index
Polymer
Mass (g/mol)
M
w
M
n
2
3
3
3
3
3
3
9
0
1
2
3
4
5
3628.8
3626.9
58,800
77,400
23,700
43,600
6.5
2.48
1.78
12.0
Polymer too insoluble for analysis
3709.0 41,500 22,600
Polymer too insoluble for analysis
6.1
1.84
3791.1
3756.8
37,600
70,700
14,300
34,100
3.8
9.1
2.63
2.07
at above 9 ppm, indicating that the alcohol/isocyanate poly-
condensation was successful. The dominant signals in the
polymer NMR are from the PTMO chains (marked with
asterisks). The other polymers were too insoluble to obtain
NMR data in common solvents such as CDCl , CD Cl , DMSO,
and DMF. These materials did dissolve in a mixture of tri-
fluoroacetic acid-d and CDCl3 but decomposition also
occurred.
them (30, 32, and 34) are presented in Figure 3. The gen-
eral trend with relation to oligomer length is maintained for
both the monomers and the polymers. Longer oligothio-
phenes absorb longer wavelength, lower energy light as
expected due to the longer conjugation pathway. The absorp-
tion maxima (kmax) for the monomers and respective poly-
mers occur at nearly the same wavelength: the bithiophene
diamine 13 kmax is at 315 nm, while the polymer 30 kmax is
3
2
2
318 nm. Terthiophene diamine 19 has a kmax at 363 nm, and
UV–Vis
polymer 32 has a kmax at 370 nm. The kmax of 25, the qua-
terthiophene diamine, is at 398 nm, and in the correspond-
ing polymer 34, the kmax is at 400 nm. This indicates that
UV–vis absorption spectra of the protected diamine oligothio-
phenes (11, 17, and 23) and the polymers formed from
FIGURE 1 (a) DSC and (b) TGA data for bithiophene derived polymer 29.
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lene diimide containing polymer 35 show similar vibronic
fine structure in both the solution and the film. The major
vibronic peaks in solution were observed at 357 and 378
nm. This fine structure is less distinct in the film spectrum,
and the peaks were observed at 363 and 380 nm.
Cyclic Voltammetry
Figure 5 shows solution cyclic voltammetry (CV) data which
were collected for the naphthalene diimide monomer 27 and
the corresponding polymer 35 incorporating this unit. The
samples analyzed were filtered solutions in THF containing
0.1M TBAP as an electrolyte. These measurements were
taken using a platinum button working electrode versus a
þ
Ag/Ag reference. The peak reduction current of the poly-
mer was observed at a slightly less negative potential
(ꢂ0.93 V) than that for the monomer (ꢂ0.98 V). We could
not observe the second reduction for the diimide core under
ambient conditions. Anodic CV experiments were also
attempted on solutions the oligothiophene containing poly-
mers but no oxidation was observed due to the poor solubil-
ity of these materials in the electrolyte solutions. A solution
of polymer and electrolyte was drop-cast onto electrodes but
dissolved in solution when the CV experiment was
attempted, resulting in no signal being observed.
7
FIGURE 2 NMR spectra (400 MHz, DMF-d ) of bithiophene con-
taining polymer 29 (top), bithiophene diol monomer 10 (mid-
dle), and MDI (bottom). * denotes peaks from PTMO chains, x
denotes protio DMF peaks, and o denotes the residual water
peak.
the optoelectronic properties of the chromophores are not
being perturbed once incorporated into the polyureas and
that the polymers are well-solvated in acetic acid solution
rather than involved in any hard-segment segregation that
should also perturb the observed electronic properties.
CONCLUSIONS
A series of oligothiophene and naphthalene diimide chain
extenders have been synthesized and utilized in the synthe-
sis of segmented polyurethanes and polyureas. These materi-
als have been evaluated through a variety of characterization
techniques. The polymers are thermally robust and maintain
the optoelectronic properties of the chromophore incorpo-
rated into the system. Although the solubilities were poor
and the thermal properties were dominated by the soft
PTMO segment, we expect this approach to be generally ap-
plicable to the incorporation of other soft segments with
greater solubilities. Future studies will examine the effect of
using shorter PTMO chains to form polymers, because
smaller PTMO segments may allow greater interaction
In addition to the solution phase UV–vis spectra, data
have been obtained for polymer films drop-cast from solu-
tion onto glass slides. Representative spectra are shown in
Figure 4. Drop-cast films of the oligothiophene containing
polymers, such as terthiophene diamine containing polymer
32, show a broad, featureless absorption centered around
376 nm with the low-energy band edge red shifted from the
solution values. This is not uncommon for conjugated poly-
mer thin films and reflects chromophore aggregation in the
solid state, enhanced solid state planarity, excitonic coupling,
and other such factors. The UV–vis spectra of the naphtha-
FIGURE 3 UV–vis spectra (in acetic acid) of (a) protected oligothiophene diamines and (b) polymers synthesized utilizing them.
Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
[
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FIGURE 4 UV–vis spectra of (a) polymer 32 in acetic acid solution, (b) drop-cast film of polymer 32, (c) polymer 35 in acetic acid
solution, and (d) drop-cast film of polymer 35. [Color figure can be viewed in the online issue, which is available at
wileyonlinelibrary.com.]
þ
FIGURE 5 Cyclic voltammetry (vs. Ag/Ag reference) of (a) the naphthalene diimide 27 and (b) polymer 35 in THF containing 0.1M
TBAP. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
between hard domains in the resulting material. The pres-
ence of these interactions may perturb the optoelectronic
properties of the systems in a way not observed in this
study.
5 Hoeben, F. J. M.; Jonkheijm, P.; Meijer, E. W.; Schenning, A.
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