Macromolecules, Vol. 37, No. 5, 2004
Functional Polymers for Construction of Multilayers 1851
Mon om er E. In a two-neck round-bottom flask equipped
with condenser, 150 mg of NaH (60% dispersed in mineral oil)
(3.75 mmol) was suspended in 5 mL of anhydrous THF. 1.071
g (1.5 mmol) of compound 5 dissolved in 5 mL of anhydrous
THF was added to the suspension very slowly under N2 flow
while magnetically stirring at room temperature. Upon addi-
tion, bubbling was observed and the suspension became a clean
solution. Within a few minutes, a highly viscous brown liquid,
immiscible with THF, was formed. The reaction mixture was
refluxed before 0.887 g (4.5 mmol) of bromoacetaldehyde
diethylacetal was added. The reaction mixture was refluxed
overnight. The viscous brown liquid disappeared, and a solid
precipitate formed. The solid was filtered out, and water was
added to the residue. The organic was extracted with ethyl
acetate, and the combined organic layer was dried over Na2-
SO4. Na2SO4 was filtered out, and the filtrate was concen-
trated. The pure product was obtained by column chromatog-
raphy (7:3 ethyl acetate:hexane) (1 g, 70%). 1H NMR (400 MHz,
CDCl3): δ 1.17 (t, 12H, J ) 7.1 Hz), 3.49 (d, 4H, J ) 5.3 Hz),
3.51-3.67 (m, 28H), 3.72-3.75 (m, 4H), 3.83 (t, 4H, J ) 4.8
Hz), 5.06 (t, 4H, J ) 4.8 Hz), 4.59 (t, 2H, J ) 5.2 Hz), 7.19 (s,
2H). [M + Cl]-: Calcd 981.64; Found 981.2.
Mon om er F . To a solution of 1,4-diiodo-2,5-dihydroxyben-
zene (347 mg, 0.96 mmol) and 398 mg (2.88 mmol) of potas-
sium carbonate in 15 mL of acetone and 0.45 mL of DMF was
added 818 mg (2.02 mmol) of compound 9. The reaction
mixture was refluxed overnight. Potassium carbonate was
filtered out, and water was added to the filtrate. The organic
was extracted with ethyl acetate and CH2Cl2. The combined
organic layer was dried over Na2SO4. Na2SO4 was filtered out,
and the filtrate was concentrated. The pure product was
obtained by column chromatography (9:1 ethyl acetate:metha-
nol) (385 mg, 49%). 1H NMR (400 MHz, CDCl3): δ 2.13 (s, 6H),
3.63-3.67 (m, 20H), 3.74-3.77 (m, 4H), 3.85 (t, 4H, J ) 4.8
Hz), 4.08 (t, 4H, J ) 4.8 Hz), 4.10 (s, 4H), 7.21 (s, 2H). [M +
H]+: Calcd 827.26; Found 826.7.
Gen er a l P r oced u r e of Heck P olym er iza tion . Monomer
(492 mg, 0.65 mmol for monomer A) was weighted into a 10
mL round-bottom flask. 1,2-Bis(4-vinylphenyl)ethane (152 mg,
065 mmol), palladium(II) acetate (0.03 equiv, 4.5 mg, 0.02
mmol), tri-o-tolylphosphine (0.12 equiv, 24 mg, 0.08 mmol),
tributylamine (3 equiv, 361 mg, 1.95 mmol), and dry DMF (3
mL) were added. The flask was fitted with condenser and
heated in an oil bath at 60-70 °C for 24 h under static
nitrogen. The solution mixture turned dark yellow as the
reaction progressed and became very viscous with formation
of some black precipitate. The reaction mixture was then
poured into methanol (150 mL) with stirring. Upon addition,
an orange-brown precipitate formed. Stirring continued in the
absence of light for 12 h. The precipitate was collected by
filtration, redissolved in CH2Cl2, and filtered through Celite
to remove residual catalyst. The solution was concentrated and
precipitated by excess methanol. To obtain pure polymer, the
precipitation was carried out twice. A similar procedure was
used to obtain polymers B, C, D, and E. Polymer A: 1H NMR
(500 MHz, CDCl3): δ 1.34-1.40 (br, 20H), 1.54 (br, 4H), 1.64
(br, m, 4H), 1,87 (br, 4H), 2.94 (br, 4H), 3.83 (br, 4H), 3.95
(br, 4H), 4.05 (br, 4H), 4.83 (t, 2H, J ) 4.8 Hz) 7.11-7.46 (br,
m, 14H). Polymer B: 1H NMR (400 MHz, CDCl3): δ 1.26-
1.87 (br, m, 32H), 2.93 (br, 4H), 4.05 (br, m, 4H), 4.19 (t, 4H,
J ) 6.6 Hz), 7.10-7.47 (br, m, 14H), 7.72 (br, 2H), 7.81 (br,
2H). Polymer C: 1H NMR (500 MHz, CDCl3): δ 2.92 (br, 4H),
3.57-3.66 (br, m, 16H), 3.72 (t, 4H, J ) 4.8 Hz), 3.82 (t, 4H,
J ) 4.5 Hz), 3.90 (t, 4H, J ) 4.5 Hz), 4.33 (t, 4H, J ) 4.5 Hz),
7.04-7.44 (br, m, 14H), 7.68 (m, 2H), 7.77 (m, 2H). Polymer
D: 1H NMR (500 MHz, CDCl3): δ 2.14 (s, 6H), 2.56 (t, 4H, J
) 6.8 Hz), 2.69 (t, 4H, J ) 6.5 Hz), 2.92 (br, 4H), 3.59-3.70
(br, m, 16H), 3.77 (br, m, 4H), 3.91 (t, 4H, J ) 4.8 Hz), 4.18 (t,
4H, J ) 4.8 Hz), 4.22 (t, 4H, J ) 4.8 H),7.03-7.24 (br, m, 14
H). Polymer F : 1H NMR (400 MHz, CDCl3): δ 2.10 (s, 6H),
2.92 (br, m, 4H), 3.63-3.69 (20 H), 3.76 (br, m, 4H), 3.91 (t,
4H, J ) 4.8 Hz), 4.06 (s, 4H), 4.21 (t, 4H, J ) 4.8 Hz) 7.06-
7.45 (br, m, 14H).
mL), acetone (10 mL), and water (2 mL). To the solution, 1
mL of concentrated HCl was added. The reaction mixture was
heated and stirred magnetically at 45-50 °C for 24 h.
Saturated NaHCO3 was added to the reaction mixture until
the reaction mixture became neutral. The organic layer was
extracted with CH2Cl2 (3 × 30 mL). Combined organic layers
were dried over Na2SO4. Solvent was removed under reduced
pressure, and the product was dried under vacuum for 24 h
to afford polymer G (76 mg). 1H NMR (400 MHz, CDCl3): δ
1.23-1.54 (br, m, 24H), 1.84 (br, 4H), 2.36 (br, m, 4H), 2.92
(br, 4H), 4.03 (br, 4H), 7.08-7.45 (br, m, 14H), 9.72 (s, 2H).
Am in ooxy-Su bstitu ted P olym er (P olym er s H a n d I).
Polymer C (86 mg) was dissolved in THF (3 mL). Hydrazine
(excess) was diluted with 2 mL of THF and added dropwise
into the solution mixture. The reaction mixture was heated
to 45 °C and stirring continued for 12 h, and some white
precipitate was formed over time. The white precipitate was
removed by filtration. 5 mL of water was added, and the
organic layer was extracted with CH2Cl2 (3 × 30 mL).
Combined organic layers were dried over Na2SO4. Solvent was
removed under reduced pressure, and the product was dried
under vacuum for 24 h to afford polymer I (65 mg). Polymer
H was prepared with using polymer B instead of polymer C
in a similar way. Polymer H: 1H NMR (500 MHz, CDCl3): δ
1.22-1.88 (br, m, 32H), 2.93 (br, m, 4H), 3.66 (t, 4H, J ) 6.5
Hz), 4.05 (br, m, 4H), 7.14-7.45 (br, m, 24H). Polymer I: 1H
NMR (500 MHz, CDCl3): δ 2.86 (m, 4H), 3.62-4.2 (br, m, 32H),
7.01-7.44 (br, m, 14H).
Mu ltila yer Assem bly. To afford multilayer assembly,
substrates were functionalized with oxyamine surface groups.
First, glass substrates were sonicated in 5 wt % KOH for 3 h
while silicone wafers were dipped in NH4OH/H2O2/H2O (1/1/
5) for 6 h at 80 °C. These substrates were immersed in a
toluene solution of N-[11-(chlorodimethylsilanyl)undecyloxy]-
acetimidic acid ethyl ester12 for 12 h. Protected oxyamine
surface groups were further treated with concentrated HCl/
ethanol (1/25) for 12 h followed by sequential washing with
0.1 N Na2CO3, water, and ethanol. The substrates derivatized
with oxyamine groups were immersed in a chloroform solution
of the aldehyde-substituted polymer (G) (2 mg/mL) for 30 min
at room temperature. The film was then put in a chloroform
bath and rigorously shaken for 5 min before drying with
nitrogen. The film was subsequently immersed into a solution
of oxyamine-substituted polymer (I) (2 mg/mL) for 30 min at
room temperature to form the second polymer layer. Repetition
of alternative dipping in aldehyde- and aminooxy-derivatized
polymer gave the corresponding multilayer films. In the case
of gold/silicon wafer substrate for GARA FT-IR spectroscopy,
surface functionalization was carried out in the same way
described in the ref 7.
In str u m en ta tion . 1H NMR spectra were recorded on a
Bruker AM 400 or AM 500 spectrometer. Molecular weights
and distributions of polymers were determined by using gel
permeation chromatography (GPC) with a Waters Associates
liquid chromatograph equipped with a Waters 510 HPLC
pump, a Waters 410 differential refractometer, and a Waters
486 tunable absorbance detector. THF was used as the eluent
and polystyrene as the standard. UV/vis spectra were collected
by using a Shimadzu UV-2401PC recording spectrophotometer.
The GARA FT-IR spectroscopy experiments were performed
with a Nicolet Magna-IR 560 Fourier transform infrared
spectrometer fitted with an 85° grazing angle reflectance
accessory (SpectraTech) and an internal mercury cadmium
tellurite (MCT) detector. The reflectance signal was averaged
for 10 000 scans at 4 cm-1 resolution. Ellipsometric film
thickness measurements were made on a Gaertner model
L116C single-color optical ellipsometer equipped with a helium-
neon laser operating at 632.8 nm and interfaced to a personal
computer. Measurements were made at an incident angle of
70°. The real and imaginary indices of refraction were mea-
sured at 10 or more locations on each substrate before
monolayer formation. An average of these numbers were then
input to the software to determine the thickness of resulting
film, which was also measured at least 10 or more points. The
tapping mode AFM imaging of the sample was performed
Ald eh yd e-Su bstitu ted P olym er (P olym er G). Polymer
A (81 mg) was dissolved in a solution of methylene chloride (8