S. Lengvinaite et al. / Reactive & Functional Polymers 71 (2011) 574–578
575
Thin films of the materials were prepared by spin-coating from
their chloroform solutions. Solutions for preparation of cross-
linked films contained 7 wt% of {4-[(2-hydroxytetradecyl)-oxyl]-
phenyl}-phenyliodonium hexafluorantimonate as initiator for the
cationic polymerization of oxetane units of 3 or 4. The cross-link-
able films were irradiated (standard handheld UV lamp) for
2 min at room temperature. Afterwards, to further advance the
cross-linking process in the growing network, the films were an-
nealed at 180 °C for 7 min. The resulting polymer networks were
found to be insoluble in organic solvents.
m
, cmꢂ1): 3048 (aromatic CAH), 2963, 2858 (aliphatic CAH), 976
(CAOAC in oxetane ring), 741; 694 (CH@CH).
2.2.3. N,N-Di[9,9-di(3-methyloxetan-3-ylmethyl)fluoren-2-yl]-N-
phenylamine (3).
A 23.5 mg (0.025 mmol) of Pd2(dba)3, 10.5 mg, (0.05 mmol) of t-
Bu3P and toluene (7 ml) were charged under nitrogen in a two neck
flask equipped with a reflux condenser. The mixture was stirred at
room temperature for 10 min. Then 1.06 g (2.6 mmol) of 2-bromo-
9,9-di(3-methyloxetan-3-ylmethyl)fluorene (2), 0.1 g (1.1 mmol)
of aniline and 1.47 g (15.6 mmol) of t-BuONa were added into
the reaction mixture, and it was stirred under nitrogen for 24 h
at 80 °C. The mixture was cooled and quenched by an addition of
ice water. The product was extracted with ethyl acetate. The com-
bined extract was dried over anhydrous MgSO4. The crude product
was purified by silica gel column chromatography using ethyl ace-
tate and hexane mixture (vol. ratio 1:3) as an eluent. Yield: 0.23 g
(31%) of yellowish crystals. M.p.: 253–254 °C.
The multilayer electroluminescent devices were fabricated on
glass substrates and had the typical structure with the organic layers
sandwiched between a bottom ITO anode and a top metal cathode.
Before use in device fabrication, the ITO-coated glass substrates
were carefullycleaned andtreated with UV/ozone rightbefore depo-
sition of the organic layers. PEDOT layers were deposited by spin-
coating and heated at 120 °C for 30 min. The hole transporting layers
(HTL)weremadebyspin-coatinga25–30 nmlayerofthederivatives
3 or 4. Cross-linkable HTL contained the mentioned initiator and
were converted to insoluble networks as described above. Tris(quin-
olin-8-olato)aluminum (Alq3) or poly(9,9-dioctylfluorene-2,7-diyl-
co-2,5-di(phenyl-4-yl)-2,1,3-benzothiadiazole) (PFBT)were used
as green light emitters. The polymer was spin-coated from its tolu-
ene solution onto the cross-linked hole transporting network. Evap-
oration of Alq3 as well as of Al cathode was done at a pressure of
3 ꢁ 10ꢂ6 mbar in vacuum evaporation equipment.
1H NMR spectrum (300 MHz, CDCl3, d, ppm): 7.66–7.05 (m, 19H,
Ar), 4.28 (d, 4H, CH2 of oxetane ring, J = 6 Hz), 4.23 (d, 4H, CH2 of oxe-
tane ring, J = 6 Hz), 3.7 (d, 4H, CH2 of oxetane ring, J = 6 Hz), 3.55 (d,
2H, CH2 of oxetane ring, J = 6 Hz), 2.48 (d, 4H, 2 ꢁ CCH2C, J = 14 Hz),
2.33 (d, 4H, 2 ꢁ CCH2C, J = 14 Hz), 0.57 (s, 12H, 4 ꢁ CH3). 13C NMR
spectrum (75.4 MHz, CDCl3, d, ppm): 24.41, 39.97, 49.75, 53.01,
77.31, 83.92, 84.57, 120.04, 121.40, 123.31, 124.22, 124.53, 125.11,
126.22, 128.09, 129.62, 134.99, 136.45, 147.99, 149.97.
MS (APCI+, 20 V), m/z (%): 759.2 ([M + H]+, 100). IR (KBr, , cmꢂ1):
3035 (aromatic CAH), 2959; 2864 (aliphatic CAH), 1487; 1450
(CAN), 976 (CAOAC in oxetane ring), 741; 694 (CH@CH of mono
substituted benzene). Elemental analysis for C52H55N4O4,% Calc.:
C 82.40, H 7.31, N 1.85, O 8.44;% Found: C 82.31, H 7.43, N 1.85.
The current–voltage and luminance-voltage characteristics
were recorded under forward bias using a computer controlled
Keithley 2400 source meter and a PR650 Spectrometer [14]. All
measurements were performed at ambient conditions in air.
2.2. Materials
2.2.4. N,N0-Di[9,9-di(3-methyloxetan-3-ylmethyl)fluoren-9-yl]-N,N0-
diphenylbenzidine (4)
2-Bromofluorene (1), benzyl triethyl ammonium chloride
(BEAC), NaOH, aniline, N,N-diphenylbenzidine, sodium tert-butox-
ide (t-BuONa), tri(tert-butyl)phosphine {(t-Bu)3P)} solution (1.0 M
in toluene), tris(dibenzylideneacetone)dipalladium(0) {Pd2(dba)3}
and Alq3 were received from Sigma–Aldrich.
A 10 mg (0.01 mmol) of Pd2(dba)3, 4.4 mg (0.02 mmol) of t-Bu3P
and toluene (4 ml) were charged under nitrogen in a two neck flask
equipped with a reflux condenser. The mixture was stirred at room
temperature for 10 min. Then 0.49 g (1.1 mmol) of 2-bromo-9,9-
di(3-methyloxetan-3-ylmethyl)fluorene (2), 0.1 g (0.3 mmol) of
N,N0-diphenylbenzidine and 0.69 g (6.6 mmol) of t-BuONa were
added into the reaction mixture, and it was stirred under nitrogen
for 18 h at 80 °C. The mixture was cooled and quenched by an addi-
tion of ice water. The product was extracted into ethyl acetate. The
combined extract was dried over anhydrous MgSO4. The crude
product was purified by silica gel column chromatography using
ethyl acetate and hexane (vol. ratio 1:3) as an eluent. Yield:
0.25 g (21%) of yellow amorphous powder.
2.2.1. 3-Bromomethyl-3-methyloxetane was obtained from Chemada
Fine Chemicals
Poly(9,9-dioctylfluorene-2,7-diyl-co-2,5-di(phenyl-4_-yl)-2,1,3-
benzothiadiazole) (PFBT) was prepared by the procedure as
described earlier [15]. The polymer was used as an green light
emitter in OLEDs.
2.2.2. 2-Bromo-9,9-di(3-methyloxetan-3-ylmethyl)fluorene (2)
A 5 g (20 mmol) of 2-bromofluorene (1) and 0.2 g (0.92 mmol)
of BEAC were dissolved in 20 ml of DMSO and 20 ml of aqueous so-
dium hydroxide solution (50%) were added. After 5 min 8.42 g
(50 mmol) of 3-bromomethyl-3-methyloxetane were added drop
wise into the reaction mixture. The two-phase system was stirred
at 80 °C for 6 h under argon atmosphere. After TLC control the reac-
tion mixture was treated with 2 N HCl and extracted with chloro-
form. After extraction the organic layer was dried over MgSO4.
After filtration and evaporation of the solvent, the crude product
was purified by silica gel column chromatography using ethyl ace-
tate and hexane (vol. ratio 1:3) as eluent. Yield: 5.6 g (68%) of
orange crystals. M.p.: 128–129 °C.
1H NMR spectrum (300 MHz, CDCl3, d, ppm): 7.73–7.05 (m, 32H,
Ar), 4.3–4.22 (m, 8H, CH2 of oxetane ring), 3.71 (d, 2H, CH2 of oxe-
tane ring, J = 5.5 Hz), 3.56 (d, 6H, CH2 of oxetane ring, J = 5.6 Hz),
2.55–2.36 (m, 8H, 4 ꢁ CCH2C), 0.56 (s, 12H, 4 ꢁ CH3). 13C NMR
spectrum (75.4 MHz, CDCl3, d, ppm): 24.41, 39.97, 49.75, 53.01,
77.31, 83.92, 84.57, 120.04, 121.40, 123.31, 124.22, 124.53,
125.11, 126.22, 127.62, 128.09, 129.62, 134.99, 136,45, 140.95,
147.12, 147.99, 148.01, 149.97.
MS (APCI+, 20 V), m/z (%): 1002.5 ([M + H]+, 100). IR (KBr, , cmꢂ1):
3035 (aromatic CAH), 2956; 2864 (aliphatic CAH), 1489; 1451
(CAN), 969 (CAOAC in oxetane ring), 744; 696 (CH@CH of mono
substituted benzene). Elemental analysis for C70H68N2O4% Calc.: C
83.97, H 6.85, N 2.80, O 6.39;% Found: C 83.91, H 6.80, N 2.84.
1H NMR spectrum (300 MHz, CDCl3, d, ppm): 7.62–7.22 (m, 7H,
Ar), 4.47 (d, 2H, CH2 of oxetane ring, J = 5.7 Hz), 4.32 (d, 2H, CH2 of
oxetane ring, J = 5.7 Hz), 3.59 (d, 2H, CH2 of oxetane ring,
J = 5.6 Hz), 3.50 (d, 2H, CH2 of oxetane ring, J = 5.6 Hz), 2.54 (d,
2H, CCH2C, J = 14 Hz), 2.45 (d, 2H, CCH2C, J = 14 Hz), 0.40 (s, 6H,
2 ꢁ CH3). MS (APCI+, 20 V), m/z (%): 414.4 ([M + H]+, 100). IR (KBr,
3. Results and discussion
The synthetic route of cross-linkable aromatic amines (3–4)
containing fluorenyl fragments is shown in Scheme 1. 2-Bromo-