H. Liu et al. / Polymer 52 (2011) 1908e1916
1909
is isolated from the guaiac resin. It is the main constituent of
creosote obtained from wood tar (beech). Guaiacol and derivatives
have been known and used for more than a century. Their main
uses are antiseptics, gastric sedatives, flavorings, deodorants,
fungicides and parasiticides [15,16].
To prepare this polymer, a new monomer was synthesized, its
radical polymerization was studied, and preliminary antibacterial
tests of polymers were carried out using Bacillus subtilis as Gram-
positive bacteria.
was added. The reaction mixture was kept under stirring at room
temperature for 5 h. The mixture was extracted by diethyl ether and
washed with water, the organic phase was washed by NaHCO3
(10 wt.-% in water), then washed with saturated NaCl solution.
The organic phase was dried over MgSO4 and evaporated. The
4-hydroxy-3-methoxy-benzaldehyde oxime (white crystalline
solid) was obtained with a yield of 67%.
0.62 g (3.71 mmol) of 4-hydroxy-3-methoxy-benzaldehyde
oxime, 120 mg of 10% Pd/C, 2.4 ml of HCl (37%), 60 ml of absolute
ethanol were added in a flask, the flask was firstly kept under
vacuum and then under H2 flow. The mixture was stirred at room
temperature for 3 h. The obtained mixture was filtered through
celite, the filtrate was evapored and a light yellow powder of
4-hydroxy-3-methoxy-benzylamine hydrochloride was obtained
with a quantitative yield.
2. Experimental part
2.1. Chemical materials
Guaiacol (99 þ %), DowexÒ 50WX8, 200e400 mesh and
H2SO4 (P.A.) were obtained from Acros, acryloyl chloride was
obtained from Fluka, vanillin (99%) was obtained from Alfa Aesar,
Pd/C palladium (10 wt.-% on activated carbon) was obtained
from Aldrich, hydroxylamine hydrochloride 97% was obtained
from Janssen Chimica, absolute ethanol, min 99.5%, dime-
thylformamide (DMF), toluene and HCl 37% were obtained from
VWR, all these products were used without purification.
N-hydroxymethylacrylamide (48 wt.-% solution in water) was
obtained from Aldrich and dried by freeze-drying. Dime-
thylsulfoxyde (DMSO) was dried on molecular sieve. Tetrahy-
drofuran (THF) was distilled from sodium and benzophenone.
Triethylamine and diethyl ether were distilled on calcium
hydride. 2,20-Azobis(2-methylpropionitrile) (AIBN) was recrys-
tallized from ethanol.
Before the synthesis of NA, 200 mg (1.06 mmol) of 4-hydroxy-
3-methoxy-benzylamine hydrochloride was dissolved in 2 ml of
water. 2 ml of NaOH solution (0.5 N in water, 1 mmol) was added
under stirring, a white precipitate formed. The product was filtered
and dried at room temperature. 4-hydroxy-3-methoxy-benzyl-
amine was obtained.
100 mg (0.65 mmol) of 4-hydroxy-3-methoxy-benzylamine,
0.18 ml (1.29 mmol) of triethylamine, 10 ml of anhydrous THF and
47
ml (0.59 mmol) of acryloyl chloride were added into a flask
cooled with an ice-bath under argon. The mixture was kept stirring
at room temperature for 3 h. Then, the product was extracted by
CH2Cl2, the organic phase was washed by a HCl solution (0.01 N),
then washed with a saturated NaCl solution, dried over MgSO4 and
then evaporated. A yield of 41% was obtained.
1H NMR (MeOD)
d
(ppm) ¼ 3.70 (s, 3H, O-CH3), 4.21 (d, 2H,
2.2. Monomers synthesis
CH2eNH), 5.55 (t, 1H, CH]), 6.12 (d, 2H, CH2]), 6.60 (d, 2H, eCH]
CHe aromatic), 6.74 (d, 1H, eCHe aromatic).
2.2.1. Synthesis of N-(4-hydroxy-3-methoxy-benzyl)-acrylamide
(NA) by FriedeleCraft reaction (catalyzed by cationic exchange
resin)
13C NMR (MeOD)
d
(ppm) ¼ 44.8 (eCH2-), 57.2 (eCH3), 112.9,
116.9, 122.2 and 131.1 (aromatic), 127.1 (CH2]), 132.2 (CH]), 147.2
and 149.2 (]CeO), 168.0 (C]O).
4.05 g (40 mmol) of N-hydroxymethylacrylamide, 4.5 ml
(40.4 mmol) of guaiacol were dissolved in 40 ml of absolute
ethanol in a 100 ml flask, and 28 g of cationic exchange resin was
added. The reaction mixture was kept stirring for 6 days at 35 ꢁC.
Then 20 ml of absolute ethanol was added to the mixture under
stirring. The cationic exchange resin was filtered off and the
filtrate was concentrated to give a yellow liquid. The yellow liquid
was poured into 20 ml of diethyl ether. The obtained solution was
kept in refrigerator and white crystal of NA formed. The crystals
were filtered and washed with diethyl ether. A yield of 25% was
obtained.
Elemental analyses:
C11H13NO3 207 : Calcd. C 63.76, H 6.32, N 6.76, O 23.16; Found C
63.55, H 6.47, N 6.63, O 23.29.
Melting point: 145e147 ꢁC.
IR (KBr): 3325 (OH), 3097 (NH), 1655 (C]O), 1596 cmꢀ1 (C]C).
2.3. Radical polymerization
2.2.2. Synthesis of N-(4-hydroxy-3-methoxy-benzyl)-acrylamide
(NA) by FriedeleCraft reaction (catalyzed by H2SO4)
2.3.1. Synthesis of poly [N-(4-hydroxy-3-methoxy-benzyl)-
acrylamide] (PNA)
2.24 g (22 mmol) of N-hydroxymethylacrylamide and 2.7 ml
(24 mmol) of guaiacol (2-methoxyphenol) were dissolved in 12 ml
of absolute ethanol. The mixture was cooled with an ice-bath, and
1.8 ml of H2SO4 was added under stirring. The reaction mixture was
kept stirring for 4 days at 35 ꢁC. Then the product was extracted by
CH2Cl2 and washed by H2O. The organic phase was evaporated
under reduced pressure to give a yellow liquid. The yellow liquid
was poured into diethyl ether and white precipitate of NA formed.
The crude product was recrystallized from ethanol, a yield of 31%
was obtained.
400 mg (1.93 mmol) of NA, 4 mg (0.024 mmol) of AIBN, 2 ml of
toluene and 2 ml of DMF were added into a flask under an argon
flow for 10 min. Then the mixture was kept under stirring at 70 ꢁC
for 1, 2, 4, 6, 18 or 24 h. After the polymerization, the polymer was
precipitated in 40 ml of cold Et2O. The polymer (white solid) was
filtered and dried in a desiccator.
2.4. Protection of eOH groups
50 mg (0.242 mmol of eOH) of PNA, 1 ml of acetic anhydride,
1 ml of pyridine were added in a flask. The mixture was stirred at
100 ꢁC for 5 h. The product was extracted with dichloromethane
and washed with water. The organic phase was washed with
NaHCO3, dried over anhydrous MgSO4 and concentrated under
reduced pressure to obtain the product.
2.2.3. Synthesis of N-(4-hydroxy-3-methoxy-benzyl)-acrylamide
(NA) in three steps
2.0 g (13.2 mmol) of vanillin and 15 ml of acetic acid were added
into a flask. 0.86 ml of a solution of NaOH (50 wt.-% in water) was
added. Then 1.08 g (15.5 mmol) of hydroxylamine hydrochloride