Li AX, et al. Sci China Chem October (2011) Vol.54 No.10
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lithium (PSLi) with polystyrene (PS) backbone bearing
1,1-diphenylethene (DPE) pendant groups, sequential
polymerization of tBMA, and hydrolysis reaction of ob-
tained PS-PS-PtBMA. The self-assembly behavior of
PS-PS-PMAA in THF-water mixture was also preliminary
investigated.
cipitated into methanol. The polymer 2 was dissolved/ pre-
cipitated with dichloromethane/methanol three times and
dried in vacuo at 50 ºC for 12 h. The conversion of C=O to
1
C==C is nearly quantitative indicated by H NMR spectrum
and IR spectrum of 2 as reported in ref. [9].
1H NMR (CDCl3, δ, ppm): 1.15–2.40 (–CH2–CH–Ph),
4.75–4.95 (–CH2–O–), 5.20–5.40 (CH2== CPh2), 6.2–7.3
(phenyl ring). IR (KBr, cm–1): 1604, and 1508 (aryl), 1242
(–CH2O–).
2 Experimental
2.1 Materials
2.3
Synthesis of centipede-like copolymer PS-PS-
Styrene was purified by distillation over calcium hydride.
tBMA was purified by distillation over calcium hydride and
dibutyl magnesium. Tetrahydrofuran (THF) was refluxed
with a Na-K alloy and benzophenone until a characteristic
blue color was evident. Lithium chloride (LiCl, 99.7%) was
dried in a vacuum oven at 120 ºC for 1 d. n-Butyllithium
(n-BuLi, Aldrich, 1.6 M in hexane) and other reagents were
used as received.
PtBMA (4)
The anionic polymerization of styrene was performed at –78
ºC using n-BuLi as an initiator and THF as a solvent. After
0.5 h, an aliquot of polymer solution was taken out for gel
permeation chromatography (GPC) measurement. Subse-
quently the living PSLi was introduced quickly into the so-
lution of PS backbone bearing DPE pendant groups 2. The
reaction was carried out for 1 h and the cooled tBMA was
injected into the reactor rapidly. The polymerization of
tBMA was terminated by addition of degassed methanol
after 40 min. The polymer 4 was isolated by precipitation
into methanol and dried in vacuum at 50 ºC for 12 h.
2.2 Synthesis of PS backbone bearing DPE pendant
groups (2)
PS backbone bearing DPE pendant groups (2) was synthe-
sized according to the method reported in our earlier work [9].
To a three-necked flask, 4-hydroxybenzophenone, 4-
vinylbenzyl chloride, sodium bicarbonate, and N,N-dime-
thylformamide were added. The reaction was carried out at
105 °C for 3 h with stirring under nitrogen flow. Upon
cooling, the red-brown reaction mixture was poured into
water, and this was followed by extraction with dichloro-
methane. After recrystallization from petroleum ether, white
4-vinylbenzyloxy benzophenone was obtained in 80% yield.
1H NMR (CDCl3, δ, ppm): 5.13 (s, 2H, –CH2O–), 5.25,
5.28 (d, 1H, CH2== CH–), 5.74, 5.79 (d, 1H, CH2== CH–),
6.69–6.71 (q, 1H, CH2==CH–). IR (KBr, cm–1): 1640 (C==O),
1604, 1503 (aryl), 1250, 1173 (–CH2O–), 1604, 1015 (vinyl).
To an ampole charged with nitrogen, 4-vinylbenzyloxy
benzophenone, PhCH2Cl, CuCl, 2,2'-bipyridine, and diphe-
nyl ether were added. After three freeze-vacuum-thaw cy-
cles, the ample was sealed in vacuo. The reaction was per-
formed at 130 °C for 24 h and terminated by quenching in
liquid nitrogen. The polymer was isolated by precipitation
into methanol and was dissolved/precipitated with di-
chloromethane /methanol three times. The final product (1)
was dried in vacuo at 50 °C for 12 h.
2.4 Synthesis of amphiphilic centipede-like copolymer
PS-PS-PMAA (5)
1.0 g centipede-like copolymer PS-PS-PtBMA was dis-
solved in 40 mL dioxane. The excess trifluoracetic acid
(TFA) was added dropwise to the reaction solution (based
on the ester groups presented). The hydrolysis reaction was
carried out at 65 °C for 24 h. The product was precipitated
in hexane and then dried under vacuum.
2.5 Preparation of PS-PS-PMAA micellar solution
THF solution of PS-PS-PMAA (5) graft copolymer (3
mg/mL) was added dropwise to water or water-THF solu-
tion with vigorous stirring to obtain micellar solution.
2.6 Characterization
1
All H NMR spectra were recorded on a Bruker AV400
spectrometer using CDCl3 as a solvent and tetramethylsilane
(TMS) as the internal reference. FTIR spectra were record-
ed on a 20SX IR spectrometer using KBr pellets. GPC
measurements were carried out in THF (1 mL/min) at 35 °C
using a Waters 515 liquid chromatography equipped with
three linear Styragel columns (HR3, HR4, and HR6) and a
2414 refractive index detector. Monodisperse PS samples
were used as standards for calibration. Static Light Scatter-
ing (SLS) measurements were performed in THF at 25 °C
with a DAWN HELEOS 18-angle light scattering detector
1H NMR (CDCl3, δ, ppm): 0.80–2.40 (–CH2–CH–Ph),
4.75–5.10 (–CH2–O–), 6.2–7.3 (phenyl ring). IR (KBr,
cm–1): 1650 (C=O), 1600, and 1506 (aryl), 1250 (–CH2O–).
Methyltriphenylphosphonium iodide and equal molar so-
dium hydride were suspended in anhydrous THF, and the
mixture was refluxed for 12 h under argon. Thereafter, the
solution of polymer 1 in THF was added dropwise at 0 °C.
After 12 h of refluxing, the reaction was terminated by ace-
tone. After filtration, the liquid was concentrated and pre-