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nitrogen atmosphere. The proton transfer reaction was car-
ried out for 30 min and the obtained 2-(dimethylammoniu-
m)ethyl methacrylate-butyrate (HDMAEMA-butyrate) PIL
was characterized. 1H NMR (500 MHz, CDCl3, d ppm) 6.14
(s, 1H, ¼¼CH), 5.59(s, 1H, CH), 4.34(t, 2H, ACOOCH2, 2.82 (s,
2H, CH2AN), 2.41 (s, 6H, CH3N), 2.27 (t, 2H, CH2ACOO),
1.96 (s, 3H, CH3AC¼¼), 1.65 (m, 2H, ACH2A), 0.97 (t, 3H,
CH2ACH3). 13C NMR (500 MHz, CDCl3, d ppm) 177.16,
166.37, 135.48, 125.29, 60.58, 56.30, 43.63, 36.83, 18.19,
17.66, and 13.30.
SCHEME 1 Proposed reaction for the synthesis of monomeric
PILs.
The reactor was purged with N2 for 30 min and then
immersed in an oil bath at 70 ꢀC for 3 h. After polymeriza-
tion, the water was eliminated by evaporation in the rotavap
and the polymer conversion was analyzed by 1H NMR
(>95% in all the cases). 1H NMR (500 MHz, CDCl3, d ppm)
4.11 (s, 2H, ACOOCH2, 2.69 (s, 2H, CH2AN), 2.4–2.3 (m, 8H,
CH3N), 2.25–1.7(m, 2H, ACH2ACOO), 1.65 (m, 2H,
COACH2ACH2A), 1.35–125 (m, 4H, ACH2ACH2A), and
1.25–0.75 (m, 6H, ACH3). GPC–SEC in water equipped with
light-scattering detector gave a Mw ¼ 1.287 ꢂ 105 g/mol;
Mw/Mn ¼ 1.53.
Same procedure was used for the other monomers.
HDMAEMA-acetate: 1H NMR (500 MHz, CDCl3, d ppm) 6.12
(s, 1H, ¼¼CH), 5.58(s, 1H, CH), 4.34(t, 2H, ACOOCH2, 2.86 (s,
2H, CH2AN), 2.44 (s, 6H, CH3N), 1.99 (s, 3H, CH3AC¼¼), and
1.94 (s, 3H, ACH3ACOO).13C NMR (500 MHz, CDCl3, d ppm)
174.82, 166.07, 135.48, 125.22, 60.21, 55.63, 21.03, and
17.39. HDMAEMA-hexanoate: 1H NMR (500 MHz, CDCl3, d
ppm) 6.15 (s, 1H, ¼¼CH), 5.60 (s, 1H, CH), 4.34 (t, 2H,
ACOOCH2, 2.81 (s, 2H, CH2AN), 2.41 (s, 6H, CH3N), 2.27 (t,
2H, CH2ACOO), 1.96 (s, 3H, CH3AC¼¼), 1.65 (m, 2H,
COACH2ACH2A), 1.34 (t, 4H, ACH2ACH3), and 0.90 (t,
ACH3). 13C NMR (500 MHz, CDCl3, d ppm) 177.16, 166.37,
135.48, 125.29, 60.58, 56.30, 43.63, 36.83, 18.19, 17.66, and
13.30.
General Procedure for Emulsion Polymerization of
HDMAEMA-Oleate
In a typical experiment, a poly(HDAMAEMA-oleate) latex was
synthesized by charging 3 g of HDMAEMA-oleate monomer,
0.006 g of surfactant Disponil A (nonionic), 0.003 g of AIBN
initiator to a 100-mL glass reactor filled with 60 mL of water.
The reactor was purged with N2 for 30 min and then
immersed in an oil bath at 70 ꢀC for 4 h. Reaction was carried
out under N2 at a stirring rate of 150 rpm. After the reaction,
the monomer conversion was measured by 1H NMR (88%).
HDMAEMA-octanoate: 1H NMR (500 MHz, CDCl3, d ppm)
6.15 (s, 1H, ¼¼CH), 5.60(s, 1H, CH), 4.34 (t, 2H, ACOOCH2,
2.81 (s, 2H, CH2AN), 2.41 (s, 6H, CH3N), 2.27 (t, 2H,
CH2ACOO), 1.96 (s, 3H, CH3AC¼¼), 1.65 (m, 2H,
COACH2ACH2A), 1.34 (t, 4H, ACH2A CH3), and 0.90 (t,
ACH3). 13C NMR (500 MHz, CDCl3, d ppm) 177.05, 166.11,
135.36, 125.04, 60.43, 56.82, 43.45, 34.49, 30.74, 24.37,
21.75, 18.01, and 13.23. HDMAEMA-oleate: 1H NMR (500
MHz, CDCl3, d ppm) 6.15 (s, 1H, ¼¼CH), 5.60(s, 1H, CH), 5.40
(s, 2HA CH¼¼), 4.34 (t, 2H, ACOOCH2, 2.81 (s, 2H, CH2AN),
2.41 (s, 6H, CH3N), 2.30 (t, 2H, CH2ACOO), 2.08 (m, 4H,
CH2ACH¼¼), 1.96 (s, 3H, CH3AC¼¼), 1.65 (m, 2H,
COACH2ACH2A), 1.29 (t, 16H, ACH2A), and 0.90 (t, 3
ACH3). 13C NMR (500 MHz, CDCl3, d ppm) 176.79, 165.93,
135.40, 129.64,124.92, 127.32, 60.42, 56.23, 43.47,34.48,
30.74, 29.13, 28.72, 28.57, 26.55, 24.96, 22.04, 17.51and
13.41.
RESULTS AND DISCUSSION
At first, a series of PIL monomers were synthesized by react-
ing a methacrylic Brønsted base such as the tertiary amine,
N-(2-(dimethylamino)ethyl) methacrylate (DMAEMA) with
different carboxylic acids such as acetic acid, butyric acid,
hexanoic or caproic acid, octanoic or caprylic acid, benzoic
acid, and oleic acid (Scheme 1). The reactants were mixed at
room temperature by simultaneous addition in an equimolar
amount as neat liquids to eliminate the effects of the exo-
thermic neutralization reactions. By this method, a series of
protic ionic monomers were readily synthesized without
need of purification steps. As the PILs are formed by neutral-
ization reaction, a possible equilibrium may exist and usually
the proton transfer is incomplete, resulting in the formation
of neutral ion-pairs. The difference in pKaaq values between
the acid and the base and their chemical nature is still a
matter of discussion in the ionic liquid community although
a value of DpKaaq > 6 seem to be enough for full ionization.
In our case, all the monomer characterizations were in good
1
HDMAEMA-benzoate: H NMR (500 MHz, CDCl3, d ppm) 8.07
(s, 2H, arom), 7.50 (s, 1H, arom), 7.41 (s, 2H, arom), 6.15 (s,
1H, ¼¼CH), 5.56 (s, 1H, CH), 4.44 (t, 2H, ACOOCH2, 3.02 (s,
2H, CH2AN), 2.58 (s, 6H, CH3N), and 1.94 (s, 3H, ACH3). 13C
NMR (500 MHz, CDCl3, d ppm) 170.81, 166.05, 135.05,
133.28, 131.01, 130.79, 127.44, 122.51, 59.80, 55.90, 42.96,
and 17.44.
General Procedure for Free Radical Polymerization of
Protic Ionic Liquid Monomers
Methacrylic PIL monomers (HDMAEMA-acetate, HDMAEMA-
1
accordance to PILs formation due to the shift in the H NMR
butyrate,
HDMAEMA-hexanoate,
HDMAEMA-octanoate,
signals associated to the methylene group near to the nitro-
gen atom and the methylene group near to the carboxylate
together with the appearance of a new band in the carboxy-
late region of the FTIR (1550–1600 cmꢁ1) (Supporting infor-
mation, Fig. S1).
HDMAEMA-benzoate, and HDMAEMA-oleate) were polymer-
ized using conventional free radical polymerization. Typically,
to a 50-mL glass reactor, monomer (HDMAEMA-hexanoate, 2
g), AIBA (0.01 g), and distilled water (40 g) were charged.
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JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY 2012, 50, 1049–1053