Macromolecules, Vol. 36, No. 4, 2003
Linear-Dendritic Block Copolymers 1069
were recorded on a Nicolet IR 400 spectrophotometer with
sample films deposited on ZnSe plates (Infracal).
LDBC Syn th esis. ter t-Bu tyld im eth ylsilyl 3,5-Bis(ter t-
bu tyld im eth ylsiloxy)ben zoa te (1). 3,5-Dihydroxybenzoic
acid (10 g, 64 mmol) and tert-butyldimethylsilyl chloride (31.35
g, 208 mmol) were combined with 100 mL of dry toluene in a
64.10, 69.13, 70.53, 70.91 (228 C, CH
2
O), 110.34 (4 C, Ar C-2),
112.60 (2 C, Ar C-4), 131.55 (2 C, Ar C-1), 156.64 (4 C, Ar C-3),
-
1
2
166.44 (2 C, CO). FT-IR: ν (cm ) (PEG CH ) 2885, (G1 CdO)
1716.
(
HO)
flask was added zinc tetrafluoroborate hydrate (0.120 g, 0.564
mmol) with 5 mL of deionized (DI) water. P [G1]-PEG5K-[G1]-
(3) (0.520 g, 0.091 mmol) was then added together with an
2 2
[G1]-P EG5K-[G1](OH) (4). To a 25 mL pear-shaped
2
50 mL two-neck round-bottom flask. The reagents were
2
stirred vigorously, triethylamine (29.83 mL, 214 mmol) was
added dropwise, and the mixture was refluxed under nitrogen
for 24 h. The mixture was then placed into a 1000 mL
separatory funnel and was washed with 350 mL of water and
P
2
additional 5 mL of water. The mixture was stirred at 70 °C
for 24 h, the clear solution was extracted three times with 15
mL of chloroform, and all collected organic fractions were
combined and dried with magnesium sulfate. The drying agent
was filtered off, and the solvent was removed by rotary
evaporator under reduced pressure at 60 °C. The viscous
product was then placed in a vacuum oven for 8 h at 60 °C.
When cooled to room temperature, the product appeared as a
clear glassy solid; yield 97.0%.
2
5 mL of brine. The toluene layer was collected and washed
twice more with 100 mL of water. The organic fraction was
then dried with magnesium sulfate and filtered, and the
solvent was removed by rotary evaporator under reduced
pressure and heating. The product was then allowed to dry
under reduced pressure in a vacuum oven overnight at 90 °C.
The triprotected ester appeared as a light-brown solid and was
1H NMR (CDCl
3
): δ 3.34-3.91 (m, 452 H, PEG CH
2
O),
stored in a desiccator prior to use; yield 91%.
4
.39-4.46 (t, 4 H, PEG(CH
G1ArH), 7.01-7.09 (d, 4 H, G1ArH). H NMR (CD
.36-3.91 (m, 452 H, PEG CH O), 4.37-4.44 (t, 4 H, PEG-
CH OCOPh) ), 6.45-6.49 (t, 2 H, G1ArH), 6.91-6.97 (d, 4 H,
G1ArH). C NMR (CDCl ): δ 64.07, 69.14, 70.52, 70.68, 70.91
O), 107.96 (4 C, Ar C-2), 108.53 (2 C, ArC-4), 131.85
2 C, Ar C-1), 157.87 (4 C, Ar C-3), 166.48 (2 C, CO). FT-IR:
2
OCOPh) ) 6.61-6.67 (t, 2 H,
2
1
H NMR (CDCl
Si(CH ), 0.98 (s, 18 H, PhOSiC(CH
SiC(CH ), 6.47-6.55 (t, 1 H ArH), 7.13-7.14 (d, 2 H,
ArH). C NMR (CDCl ): δ -4.86 (2 C, COOSi(CH ), -4.47
4 C, PhOSi(CH ), 17.73 (1 C, COOSiC), 18.20 (2 C, PhOSiC),
5.55 (3 C, COOSiC(CH ) d, 26.62 (6 C, PhOSiC(CH ),
14.87 (2 C, ArCH), 117.02 (1 C, ArCH), 133.15 (1 C, ArC-
3
): δ 0.21 (s, 12 H, PhOSi(CH
3
)
2
), 0.37 (s, 6
1
3
OD): δ
H, CO
CO
2
3
)
2
3 3
)
, 1.02 (s, 9 H,
3
(
2
2
3 3
)
2
2
1
3
3
3
)
2
13
3
(
2
1
3 2
)
(
(
228 C, CH
2
3
)
3
3 3
)
-1
ν (cm ) (ArOH) 3313, (PEG CH
[G2]-P EG5K-[G2]P (5). (HO)
4) (0.500 g 0.095 mmol), 3,5-bis(tert-butyldimethylsiloxy)-
benzoyl chloride (2) (0.275 g, 0.686 mmol), and 18-crown-6
0.012 g, 0.046 mmol) were combined in a 50 mL two-neck
2
) 2883, (G1 CdO) 1721.
COOSi), 156.47 (2 C, ArCO), 166.18 (1 C, PhCOOSi).
,5-Bis(ter t-bu tyld im eth ylsiloxy)ben zoyl Ch lor id e (2).
P
4
4
2
[G1]-PEG5K-[G1](OH)
2
3
(
To a 250 mL two-neck pear-shaped flask were added 10 mL
of dry dichloromethane, the triprotected ester 1 (10 g, 20.1
mmol), and benzyltrimethylammonium chloride (0.0689 g,
(
pear-shaped flask with dry nitrogen feed. 10 mL of dry THF
was added together with 0.10 mL of dry toluene as a SEC
marker. The reactants were gently heated and allowed to mix
well. Potassium carbonate (0.252 g, 1.82 mmol) was added,
and the reaction proceeded for 2.5 h at room temperature. The
potassium carbonate was then filtered off, and the solution of
crude product was added dropwise to 200 mL of hexane under
stirring. The product formed a white precipitate. The mixture
was allowed to stir for 15 min, and the precipitate was collected
0
.371 mmol). The mixture was set to a medium stir and flushed
with dry nitrogen while fresh oxalyl chloride (3.5 mL, 40.4
mmol) was slowly added dropwise. The reaction mixture was
then heated at reflux for 18 h. The solvent and excess oxalyl
chloride were removed via rotary evaporator under reduced
pressure and heating to 70 °C, and the residue was subse-
quently placed in a vacuum oven for 8 h at 70 °C. The crude
product was then purified by short-column flash chromatog-
raphy, eluting with hexane/methylene chloride (4:1, v/v). The
solvent was removed by rotary evaporator under reduced
pressure. The solid residue was dried in a vacuum oven for 8
h under reduced pressure at 60 °C. When cooled to room
temperature, the product appeared as a white crystalline solid;
in a 30 mL, 6-10 µm, Buchner glass frit-filter; yield 96%.
1
H NMR (CD
3
OD): δ 0.24 (s, 24 H, PhOSi(CH
), 3.34-3.91 (m, 452 H, PEG CH
.53 (t, 4 H, PEG(CH OCOPh) ), 6.60-6.67 (t, 4 H, G2ArH),
.23-7.31 (d, 8 H, G2ArH), 7.49-7.54 (t, 2 H, G1ArH), 7.82-
3
)
2
), 1.01 (s,
3
4
7
6 H, PhOSiC(CH
3
)
3
2
O), 4.46-
2
2
yield 90%.
1
3
1
7.88 (d, 4 H, G1ArH). C NMR (CDCl
CH ), 18.20 (8 C, PhOSiC), 25.64 (24 C, PhOSiC(CH
64.55, 69.04, 70.54, 72.32 (228 C, CH O), 113.37 (8 C, G2 Ar
C-2), 115.60 (4 C, G2 ArC-4), 117.82 (4 C, G1 Ar C-2), 120.63
2 C, G1 ArC-4),130.45 (4 C, G2 Ar C-1), 132.27 (2 C, G1 Ar
C-1), 151.26 (4 C, G1 Ar C-3),156.78 (8 C, G2 Ar C-3), 164.29
3
): δ -4.41 (16 C, PhOSi-
H NMR (CDCl
3
): δ 0.23 (s, 12 H, PhOSi(CH
), 6.62-6.64 (t, 1 H, ArH), 7.19-7.20 (d, 2
H, ArH). C NMR (CDCl ): δ -4.48 (4 C, PhOSiCH ), 18.18
2 C, PhOSiC), 25.56 (6 C, PhOSiC(CH ), 116.13 (2 C, ArCH),
19.01 (1 C, ArCH), 134.73 (1 C, ArCCOCl), 156.86 (2 C,
3 2
) ), 0.99 (s, 18
(
3
)
2
3 3
)
),
3 3
H, PhOSiC(CH )
1
3
2
3
3
(
1
3 3
)
(
ArCO), 167.94 (1 C, PhCOCl).
[G1]-P EG5K-[G1]P (3). To a 50 mL two-neck pear-
-1
(
2
4 C, G2 CO). 164.29 (2 C, G1 CO). FT-IR: ν (cm ) (PEG CH
883, (G2 CdO) 1740, (G1 CdO) 1727.
HO) [G2]-P EG5K-[G2](OH) (6). To a 25 mL pear-shaped
2
)
P
2
2
shaped flask with a dry nitrogen feed were added PEG (0.500
g, 0.100 mmol), 3,5-bis(tert-butyldimethylsiloxy)benzoyl chlo-
ride (2) (0.143 g, 0.357 mmol), and 10 mL of THF, freshly
distilled from sodium benzophenone. Dry toluene (0.010 mL)
was also added as a SEC marker. The reaction mixture was
gently heated to promote dissolution and then allowed to mix
well for 15 min. Sodium hydroxide (0.100 g, 2.5 mmol) was
added, and the reaction mixture was stirred at room temper-
ature for 1.5 h. SEC was used to monitor the reaction progress.
Upon the reaction’s completion, the mixture was filtered
through a 30 mL, 10-20 µm, Buchner glass-frit filter. The
collected clear solution was added dropwise to 200 mL of
hexane under stirring. The desired product formed a white
precipitate. The mixture was allowed to stir for no less than
(
4
4
flask were added zinc tetrafluoroborate hydrate (0.360 g, 1.510
mmol) and 5 mL of DI water, and the solution was allowed to
stir. P [G2]-PEG5K-[G2]P (5) (0.550 g, 0.0818 mmol) was
4 4
added with an additional 3 mL of water and 2 mL of methanol.
After stirring at 70 °C for 24 h, the reaction mixture was
extracted three times with 15 mL of chloroform, and all
collected organic fractions were combined and dried with
magnesium sulfate. The mixture was then filtered into a 100
mL round-bottom flask, and the solvent removed by rotary
evaporator under reduced pressure and heating at 60 °C. The
viscous product was placed in a vacuum oven for 8 h at 60 °C.
After cooling to room temperature the product appeared as a
clear glassy solid; yield 94%.
1
5 min to remove the unreacted monomer; then the precipitate
was collected on a 30 mL, 6-10 µm, Buchner glass-frit filter.
After drying the product appeared as a white powder; yield
1H NMR (CD
4.46-4.53 (t, 4 H, PEG(CH
G2ArH), 7.08-7.11 (d, 8 H, G2ArH), 7.42-7.47 (t, 2 H,
3
OD): δ 3.34-3.90 (m, 452 H, PEG CH
2
O),
2
OCOPh) ), 6.54-6.57 (t, 4 H,
2
9
8%.
1H NMR (CDCl
H, PhOSiC(CH ), 3.35-3.90 (m, 452 H, PEG CH
.45 (t, 4 H, PEG(CH OCOPh) ), 6.49-6.52 (t, 2 H, G1ArH),
.10-7.13 (d, 4 H, G1 ArH). C NMR (CDCl
), 18.15 (2 C, PhOSiC), 25.66 (6 C, PhOSiC(CH
13
3
): δ 0.19 (s, 12 H, PhOSi(CH
3
)
2
), 0.97 (s, 18
O), 4.40-
G1ArH), 7.79-7.82 (d, 4 H, G1ArH). C NMR (CDCl
64.60, 69.01, 70.51, 70.73, 72.51 (228 C, CH O), 108.97 (8 C,
G2 Ar C-2), 109.04 (4 C, G2 ArC-4), 120.48 (4 C, G1 Ar C-2),
120.61 (2 C, G1 ArC-4), 130.40 (4 C, G2 Ar C-1), 132.27 (2 C,
G1 Ar C-1), 151.26 (4 C, G1 Ar C-3), 158.13 (8 C, G2 Ar C-3),
3
): δ
3
)
3
2
2
4
7
2
2
1
3
3
): δ -4.44 (4 C,
),
PhOSi(CH
3
)
2
3 3
)