Synthesis and characterization of cyclohexene oxide functional ...

cationic species are quite reactive towards these groups. In this
article, we present the results of a study of the preparation of
CHO end-functional macromonomers via ATRP of styrene monomer
using a new CHO-functional initiator and a Cu(I)Br/bipyridine
catalyst system.
2. Experimental
2.1. Materials
Styrene (St) (Fluka) and cyclohexene oxide (CHO) (Aldrich)
were distilled over calcium hydride (CaH 2) and stored in a refrigerator
under nitrogen before use. The compounds 3-cyclohexene-1methanol
(Aldrich), 2-bromopropanoyl bromide (Aldrich),
3-chloroperoxybenzoic acid (Aldrich), and sodium bicarbonate
(NaHCO 3) (Merck) were used as received. The compound 2,2-dimethoxy-2-phenyl
acetophenone (DMPA) (Irgacure 651), the photoinitiator,
was purchased from Ciba Specialty Chemicals and used
as received without further purification. Dichloromethane (CH2Cl2)
(Lab-scan) pyridine (Lab-scan), diphenyliodonium hexafluorophosphate
(Ph2I + PF 6 ) (Fluka), CuBr (Aldrich), 2,2 0 -bipyridine (Merck)
and all other solvents and chemicals were used as received.
2.2. Synthesis of 3-cyclohexenylmethyl-2-bromopropanoate (CH–Br)
For this synthesis, 3-cyclohexene-1-methanol (5.02 mL,
44.6 mmol), pyridine (5.40 mL, 66.9 mmol), and 30 mL dry CH2Cl2
were added to a two-necked round-bottom flask fitted with a magnetic
stirrer, nitrogen inlet–outlet and an addition funnel containing
2-bromopropanoyl bromide (7.07 mL, 66.90 mmol) and 5 mL
dry CH2Cl2. The flask was placed in an ice-water bath. The solution
of 2-bromopropanoyl bromide was added dropwise over a period
of 1 h under nitrogen. The mixture was stirred at 0 °C for 30 min.
The mixture was then allowed to reach room temperature and stirred
at that temperature overnight. The solution was washed with
0.2 N HCl and several times with water. Finally, the solution was
dried with MgSO4, and the solvent was removed by vacuum distillation.
A yellowish liquid product was obtained. Yield: 9.97 g, 91%.
C10H15O2Br: (247,131): Calcd. C, 48.60%; H, 6.07%, Found: C,
48.12%; H, 6.01%. 1 H NMR (acetone-d 6, d/ppm): 5.92–5.52 (m, 2H,
HC@CH), 4.75–4.41 (q, 1H, CH–Br), 4.28–3.82 (m, 2H, OCH2),
2.16–1.96 (m, 1H, OCH 2CH), 1.84–1.65 (d, 3H, CH 3CH), 1.51–1.16
(m, 6H, methylene protons of cyclohexene oxide group). FT-IR
Table 1
Synthesis of CHO end-functional macromonomers of PSt by ATRP a using CHO–Br as initiator.
(cm 1 ): 3024 (C@C–H stretch), 1739 (C@O ester band), 1651 (C@C
stretch).
2.3. Synthesis of cyclohexene oxide (CHO) functional ATRP initiator
(CHO–Br)
Epoxidation of the 3-cyclohexenylmethyl-2-bromopropanoate
was performed under inert atmosphere at 0 °C. The obtained 3cyclohexenylmethyl-2-bromopropanoate
(4 g, 16.18 mmol), sodiumbicarbonate
(5.437 g, 64.72 mmol), 3-chloroperoxybenzoic acid
(5.58 g, 32.37 mmol) and 20 mL of dry CH 2Cl 2 were added into a
100-mL three-necked round-bottom flask fitted with a condenser,
a magnetic stirrer, and a nitrogen inlet–outlet. The flask was placed
in an ice-water bath and stirred for 30 min. Then, the mixture was
allowed to reach room temperature and stirred at that temperature
for 2 h. After the reaction, the reaction mixture was added into
100 mL of water, and then extracted several times with CH 2Cl 2. Finally,
the solution was dried with MgSO4, and the solvent was removed
by vacuum distillation. A yellowish oily product was
obtained. Yield: 2.25 g, 53%.
C 10H 15O 3Br: (263,130): Calcd. C, 45.64%; H, 5.70%, Found: C,
45.12%; H, 5.54%. 1 H NMR (acetone-d6, d/ppm): 4.73–4.42 (q, 1H,
CH–Br), 4.41–3.86 (m, 2H, OCH 2), 3.23–3.00 (m, 2H, CH–O–CH,
epoxide protons), 2.24–1.94 (m, 1H, OCH2CH), 1.82–1.62 (d, 3H,
CH 3CH), 1.60–1.00 (m, 6H, methylene protons of cyclohexene oxide
group). FT-IR (cm 1 ): 1739 (C@O ester band), 920 (epoxide band),
2.4. Synthesis of cyclohexene oxide end-functional macromonomer of
polystyrene by atom transfer radical polymerization (CHO-PSt)
A Schlenk tube equipped with a magnetic stirrer was used. The
system was vacuumed and back-filled with nitrogen several times.
The catalyst (CuBr), ligand bipyridine (bpy), initiator (CHO–Br), and
monomer (St) were introduced under inert atmosphere. The tube
was placed in an oil bath warmed at 110 °C and stirred at that temperature.
After a given time (see Table 1), the mixture was diluted
with THF and poured into ten-fold methanol. The macromonomer
(CHO-PSt) was collected after filtration and dried at 40 °C in vacuum
overnight. In order to remove the complex salt from the polymer,
it was redissolved in THF and passed through an alumina
column, followed by precipitation in methanol.
1 H NMR (acetone-d6, d/ppm): 7.52–6.39 (m, 5H, Ar–H), 4.60 (q,
1H, CH–Br), 3.84–3.63 (m, 2H, OCH2), 3.23–3.00 (m, 2H, CH–O–CH,
Run [I] 10 2 (mol L 1 ) Time (min) Conversion (%) Mn theo
b
Mn GPC Mw/Mn 1 9.7 180 45 4500 3650 1.21 4200
2 28.9 90 39 1490 1590 1.27 1920
3 57.9 60 59 1160 970 1.24 1025
a
Temperature 110 °C, [St]0 = 8.75 mol L 1 (in bulk), [I]:[CuBr]:[Bpy] = 1:1:3.
b
Determined by GPC according to PSt standards.
Table 2
Photoinitiated cationic polymerization of CHO-PSt macromonomer a .
M n H NMR
Run Photoinitiaton type Activator (mol L 1 ) Wavelength (k, nm) Mn Mw/Mn 1 Direct – 300 3940 1.60
2 Promoted DMPA (5810 –3 ) 350 4110 1.44
3 Sensitized Anthracene (5 10 3 ) 350 6200 1.75
Conversions were calculated using the following formula: Conv.% = (W – W 0)/W 100 ; where W and W 0 are the total polymer obtained and unreacted macromonomer.
a Macromonomer: 200 g L 1 with Mn = 1590; onium salt, Ph 2I + PF 6 :5 10 3 mol L 1 ; temperature: room temperature; solvent: CH 2Cl 2; irradiation time: 5 h; conversions:
>99%.
M. Degirmenci et al. / Reactive & Functional Polymers 70 (2010) 28–34 29