Macromolecules, Vol. 36, No. 5, 2003
Controlled Monomer Insertion of Styrene 1495
tetramethylsilane (TMS) as an internal standard in chloro-
form-d (CDCl3). IR spectra were obtained with a Perkin-Elmer
Spectrum One infrared spectrometer as thin films on NaCl or
23.11, 33.88, 42.55, 42.58, 44.99, 45.08, 60.20, 60.55, 66.15,
66.60, 84.29, 127.61, 127.70, 127.94, 140.43, 156.16 (CdO). FT-
IR (neat, cm-1): 3336, 3100-2850, 1702 (CdO), 1533, 1461,
1377, 1364, 1264, 1142, 1049, 757, 700. Anal. Calcd for
1
neat. Monomer conversion was determined by H NMR of the
crude reaction mixtures (calculated from integral ratio between
vinyl protons 5.74 ppm and aliphatic protons 0.8-2.2 ppm of
polystyrenes). Number- and weight-average molecular weights
(Mn and Mw, respectively) and polydispersity (Mw/Mn) were
estimated by gel permeation chromatography (GPC) in THF
at 40 °C on a polystyrene gel column [Shodex GPC KF-804L
column (300 × 8.0 mm)] that was connected to a TOSOH
system equipped with a refractive index (RI) detector at a flow
rate of 0.8 mL min-1. The columns were calibrated against
six standard polystyrene samples (Mn ) 800-152 000; Mw/Mn
) 1.03-1.10). Analytical thin-layer chromatography (TLC) was
performed on commercial Merck plates coated with silica gel
(0.25 mm thick).
C25H41N3O5: C, 64.77; H, 8.91; N, 9.06. Found: C, 64.66; H,
8.88; N, 8.98. HRMS exact mass calculated for [M + 1]+
C
25H41N3O5 464.3124; found 464.3123.
Mod el P olym er iza tion . In a typical run, a mixture of
TEMPO-based initiator 2 (23.2 mg, 0.05 mmol) and styrene
(1.15 mL, 10.0 mmol) was charged in a polymerization tube,
degassed, and sealed off under vacuum. The mixture was
incubated at 125 °C for 2 h, and after dilution with chloroform
the solution was poured into methanol. The precipitate was
purified by reprecipitation with a chloroform/methanol system
and dried in vacuo to give the polymer 3 as a white powder
(236 mg, 22% yield). Mn ) 5700, Mw/Mn ) 1.22. 1H NMR:
δ/ppm 0.22 (br), 0.80-2.40 (br, aliphatic H), 3.07 (br, CH2),
3.80-5.00 (br, CH, CH2), 6.20-7.40 (br, aromatic H). 13C
NMR: δ/ppm 11.18, 20.96, 23.13, 40.31, 41.0-47.0 (br), 59.22,
94.07, 125.0-130.0 (br), 144.5-146.0 (br), 156.20 (CdO),
156.35 (CdO). FT-IR (NaCl, cm-1): 3100-2850, 1724 (CdO),
1601 (CdC), 1493, 1453, 1219, 1028, 907, 757, 698. 539. Anal.
Calcd for C427H443N3O5: C, 90.07; H, 7.78; N, 0.74. Found: C,
90.28; H, 7.89; N, 0.67.
TEMP O-Ba sed P olyu r eth a n e (4). HMDI (485 µL, 3.00
mmol) and 1 drop of DBTDL were added to the solution of
TEMPO-based diol 1 (880 mg, 3.00 mmol) in dry DMF (3 mL).
The reaction mixture was stirred at room temperature under
nitrogen for 30 min. After the addition of methanol (1 mL),
the reaction mixture was poured into water. The precipitate
was purified by reprecipitation with a chloroform/hexane
system and dried in vacuo to give the polymer 4 as a white
powder (1.28 g, 98% yield). Mn ) 2700, Mw/Mn ) 1.58. 1H
NMR: δ/ppm 0.66 (br, CH3), 1.0-2.0 (br, CH2, CH3), 3.11 (br,
CH2), 3.65 (s, terminal group (CH3)), 4.19 (br, CH), 4.62 (br,
CH, NH), 4.88 (br, CH2), 7.30 (s, aromatic H). 13C NMR: δ/ppm
21.10, 26.20, 29.87, 33.96, 40.73, 45.03, 48.81, 51.99, 60.28,
60.60, 63.10, 66.24, 66.74, 84.33, 127.68, 127.75, 128.00,
140.45, 156.19 (CdO), 157.07 (CdO). FT-IR (NaCl, cm-1):
3333, 3100-2850, 1700 (CdO), 1533, 1456, 1377, 1363, 1258,
1143, 1048, 757, 700.
2-Ben zoyl-1-p h en yleth yl-TEMP O. Briefly, distilled sty-
rene (300 mL, 2.62 mol), benzoyl peroxide (BPO, 4.70 g, 19.4
mmol), and 4-hydroxy-TEMPO (3.00 g, 17.4 mmol) were
charged into a round-bottom flask. The mixture was incubated
at 90 °C under nitrogen for 30 min. The crude product was
purified by flash chromatography eluting with 2:1 hexane/
chloroform (v/v) increased to chloroform. The isolated oil was
purified by reprecipitation with a chloroform/hexane system
and dried in vacuo to give the 2-benzoyl-1-phenylethyl-TEMPO
1
as a white powder (1.31 g, 19% yield). H NMR: δ/ppm 0.74
(s, 3H, CH3), 1.11 (s, 3H, CH3), 1.25 (s, 3H, CH3), 1.41 (s, 3H,
CH3), 1.40-2.00 (m, 4H, CH2), 3.95 (m, 1H, CH), 4.65 (dd, J
) 11 Hz, 6 Hz, 2H, CH2), 5.06 (t, J ) 5 Hz, 1H, CH), 7.26-
7.93 (m, aromatic 10H). 13C NMR: δ/ppm 21.24, 33.95, 34.06,
34.17, 48.75, 48.80, 60.38, 60.56, 62.99, 66.59, 84.08, 127.60,
127.88, 128.06, 128.24, 129.51, 130.04, 132.83, 140.26, 166.28.
FT-IR (neat, cm-1): 3510, 3100-2800, 1694 (CdO), 1450, 1363,
1267, 1138, 1042, 766, 716, 699.
TEMP O-Ba sed Diol (1). Aqueous 2 N sodium hydroxide
(3.5 mL of a 2 N solution) was added to the solution of the
2-benzoyl-1-phenylethyl-TEMPO (994 mg, 2.50 mmol) in etha-
nol (15 mL), and the solution was heated at reflux under
nitrogen for 5 h. After cooling, the solution was evaporated to
dryness and partitioned between water and dichloromethane.
Then the aqueous layer was extracted with dichloromethane,
and the combined organic layers were dried with magnesium
sulfate and evaporated to dryness. The crude product was
purified by flash chromatography eluting with 1:3 ethyl
acetate/ hexane (v/v). The isolated oil was purified by repre-
cipitation with a chloroform/hexane system and dried in vacuo
to give the TEMPO-based diol 1 as a white powder (623 mg,
85% yield); mp 121-122 °C. 1H NMR: δ/ppm 1.20 (s, 3H, CH3),
1.27 (s, 3H, CH3), 1.31 (s, 3H, CH3), 1.53 (s, 3H, CH3), 1.40-
2.00 (m, 4H, CH2), 2.08 (br, 1H, OH), 3.72 (m, 1H, CH2), 3.97-
(br, 1H, CH), 4.21 (m, 1H, CH2), 5.25 (dd, J ) 9 Hz, 7 Hz, 1H,
CH), 5.43 (br, 1H, OH), 7.26-7.35 (m, aromatic 5H). 13C
NMR: δ/ppm 21.17, 21.46, 32.94, 34.65, 48.67, 48.86, 60.74,
61.78, 62.66, 69.06, 83.86, 126.80, 127.97, 128.23, 128.32,
138.58. FT-IR (neat, cm-1): 3350, 3100-2850, 1635, 1452,
1376, 1248, 1183, 1042, 907, 761, 699, 544. Anal. Calcd for
Con tr olled Mon om er In ser tion of Styr en e. In a typical
run, a mixture of the prepared polyurethane 4 (Mn ) 2700,
Mw/Mn ) 1.58, 20 mg, 0.04 mmol initiating sites) and styrene
(1.15 mL, 10.0 mmol) was charged in a polymerization tube,
degassed, and sealed off under vacuum. The mixture was
incubated at 125 °C for 2 h, and after dilution with chloroform
the solution was poured into methanol. The precipitate was
purified by reprecipitation with a chloroform/methanol system
and dried in vacuo to give the polymer 5 as a white powder
1
(253 mg, 23.8% yield). Mn ) 28 900, Mw/Mn ) 1.84. H NMR:
δ/ppm 0.21 (br, CH3), 0.38 (br, CH3), 0.66 (br, CH3), 0.90-2.40
(br, aliphatic H), 3.08 (br, CH2), 3.64 (s, terminal group (CH3)),
3.80-5.00 (br, CH, CH2), 6.20-7.40 (br, aromatic H). 13C
NMR: δ/ppm 20.97, 26.18, 29.82, 33.91, 40.31, 41.0-47.0 (br),
59.22, 60.32, 125.0-130.0 (br), 144.5-146.0 (br), 156.17 (Cd
O), 156.36 (CdO). FT-IR (NaCl, cm-1): 3100-2850, 1724 (Cd
O), 1601 (CdC), 1493, 1453, 1219, 1028, 907, 757, 698, 540.
Anal. Calcd for C2158H2239N17O29: C, 89.80; H, 7.76; N, 0.83.
Found: C, 90.61; H, 7.84; N, 0.51.
C
17H27NO3: C, 69.59; H, 9.28; N, 4.77. Found: C, 69.68; H,
9.21; N, 4.67. HRMS exact mass calculated for [M + 1]+ C17H27
-
NO3 294.2069; found 294.2064.
TEMP O-Ba sed Mod el Com p ou n d (2). n-Propyl isocyan-
ate (187 µL, 2.00 mmol) and 1 drop of DBTDL were added to
the solution of the TEMPO-based diol 1 (293 mg, 1.00 mmol)
in dry N,N-dimethylformamide (DMF) (1 mL). The reaction
mixture was stirred at room temperature under nitrogen for
15 h. The crude product was purified by flash chromatography,
eluting with 3:1 hexane/ethyl acetate (v/v). The crude product
was purified by reprecipitation with a chloroform/hexane
system and dried in vacuo to give the TEMPO-based model
compound 2 as a white powder (460 mg, 99% yield); mp 117-
119 °C. 1H NMR: δ/ppm 0.66 (s, 3H, CH3), 0.89 (m, 6H, CH3),
1.12 (s, 3H, CH3), 1.28 (s, 3H, CH3), 1.37 (s, 3H, CH3), 1.46
(m, 4H, CH2), 1.40-2.00 (m, 4H, CH2), 3.08 (m, 4H, CH2), 4.19
(br, 1H, CH), 4.60-5.0 (br, 5H, CH, CH2, NH), 7.25-7.32 (m,
aromatic 5H). 13C NMR: δ/ppm 11.06, 11.15, 21.01, 23.05,
Resu lts a n d Discu ssion
The model reaction of controlled monomer insertion
into polyurethane was carried out according to Scheme
1. Diol 1 was treated with n-propyl isocyanate catalyzed
by DBTDL to afford the model compound 2 quantita-
tively. Styrene was polymerized in bulk with 2 as an
initiator. The number-average molecular weight (Mn)
and polydispersity (Mw/ Mn) of the resulting polymers
were determined by GPC with polystyrene standards.
Mn and Mw/ Mn are plotted as a function of conversion
in Figure 2. The dashed line in Figure 2 reveals the
theoretical Mn. The Mn increases with conversion, and