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changed from dark brown to yellow with a large number of
bubbles. The polymerization reaction was terminated when
bubbles were no longer observed in the reaction vessel. Aer
distilling the solvent, the product was dissolved in 5.0 mL of
toluene and precipitated with 25.0 mL of methanol. The step
was repeated ve times to remove the low molecular weight
polymer and unreacted BD1. Subsequently, MTP was obtained
as a clear, pale brown gum (3.2 g, 22% yield) aer evaporating
the solvent under vacuum. The TMP synthesis route was similar
to that of the MTP (4.5 g, 26% yield). The MTP and TMP
2.2.1 Synthesis of 1,2-di(4-methoxyphenyl)-2-hydroxy-
ethanone (BHE1) and 1,2-di(3,4,5-trimethoxyphenyl)-2-
hydroxy-ethanone (BHE2). BHE1 was synthesized by
condensing 4-methoxybenzaldehyde (11.0 g, 80.0 mmol) in the
presence of thiamine hydrochloride (VB1) (1.2 g, 4.0 mmol) in
25.0 mL of KOH ethanol solution (1.0 mol Lꢂ1). The reaction
ꢀ
was run at 60 C for 2 h. Following cooling with ice, the crude
product was ltered and washed with distilled water. The
product was then re-crystallized from ethanol to provide pure
BHE1 (8.0 g, 74% yield) as light yellow crystals, mp 108.9–110.2
ꢀC (lit:18 108.0–111.0 ꢀC). The BH2 synthesis route was siꢀmilar to
that of the BH1 (13.2 g, 84.1% yield), mp 165.2–165.6 C (lit:19
165–166 ꢀC).
1
structures were analyzed by H NMR and FT-IR.
MTP. 1H NMR (CDCl3, 400 MHz, dppm): 3.63–3.66 (d, 6H,
OCH3); 5.78–5.98 (d, 3H, CH]CH2); 6.40–6.48 (d, 4H, Ar-H);
6.62–6.71 (d, 4H, Ar-H); 7.11–7.28 (d, 11H, Ar-H); peaks at 0.09
ppm were attributed to C–H on Si atoms in the skeleton of
polysiloxane. FT-IR (KBr, n/cmꢂ1): 3057.7 [n(Ar-H)]; 2962.9,
1515.6 [n(C–H)]; 1410.8 [n(CH]CH2)]; 1134.6 [n(C–O)]; 1096.4,
1016.6 [n(Si–O–Si)].
2.2.2 Synthesis of 1,2-di(4-methoxyphenyl)ethane-1,2-
dione (BED1) and 1,2-di(3, 4,5-trimethoxyphenyl)ethane-1,2-
dione (BED2). BED1 was synthesized by oxidizing BHE1 (6.3 g,
23.0 mmol) using anhydrous cupric sulphate (0.6 g, 3.0 mmol)
and ammonium nitrate (2.0 g, 24.0 mmol) in 35.0 mL of 80%
acetic acid. The reaction was reuxed at 110 ꢀC for 90 min. The
product appeared as a solid yellow mass aer cooling. Aer
extensively washing with distilled water, the product was re-
crystallized from ethanol to provide pure BED1 (4.8 g, 76%
TMP. 1H NMR (CDCl3, 400 MHz, d ppm): 3.38–3.41 (d, 6H,
2OCH3); 3.65–3.72 (d, 12H, 4OCH3); 5.95–6.07 (d, 3H, CH]CH2);
7.30–7.39 (d, 4H, Ar-H); 7.41–7.49 (m, 11H, Ar-H). Peaks at 0.15
ppm were attributed to C–H on Si atoms in the polysiloxane skel-
eton. FT-IR (KBr, n/cmꢂ1): 3109.6 [n(Ar-H)]; 2989.5, 1515.6 [n(C–H)];
1400.2 [n(CH]CH2); 1184.3 [n(C–O)]; 1069.0, 1021.2 [n(Si–O–Si)].
The 3,4-di(4-methoxy phenyl)-2,5-diphenyl phenyl content in
MTP was 17.0% calculated from the ratio of the integral at d 6.40–
7.28 ppm (attributed to Ar-H in the multiphenyl moiety) to that at
about d 0.09 ppm (attributed to Si–CH3). The contents of the
remaining vinyl groups were determined to be 2.9% calculated
from the ratio of the integral at d 5.78–5.98 ppm (attributed to
Si–vinyl) to that at about d 0.09 ppm (attributed to Si–CH3) based
on the 1H NMR spectra.21 Using the similar calculation method,
the 3,4-di(3,4,5-trimethoxy phenyl)-2,5-diphenyl phenyl content
in TMP was 16.9%. The remaining vinyl groups were 3.1%.
yield) as yellow crystals, mp 132.0–133.0 C (lit:18 130–133 C).
ꢀ
ꢀ
The BED2 synthesis route was similar to that of the BED1 (7.8 g,
87.1% yield), mp 192.2–192.9 C (lit:19 192–193 ꢀC).
ꢀ
2.2.3 Synthesis of 3,4-di(4-methoxyphenyl)-2,5-diphenyl-
cyclopentadienone (BD1) and 3,4-di(3,4,5-trimethoxy phenyl)-
2,5-diphenylcyclopentadienone (BD2). BD1 was synthesized by
the reaction of BED1 (5.4 g, 20.0 mmol) and 1,3-diphenylacetone
(4.6 g, 22.0 mmol) in 20.0 mL of dry ethanol. When the mixture
was heated near its boiling point, 5.0 mL of KOH ethanol solution
(3.0 mol Lꢂ1) was added dropwise. The reaction was heated to
reux at 75 ꢀC for a further 30 min. The abovementioned solution
was cooled to room temperature and ltered to obtain the crude
product. The product was then re-crystallized with ethanol to
obtain the desired BD1 (5.4 g, 64.3% yield) as a red-brown solid
powder, mp 238.0–239.5 ꢀC. The BD2 synthesis route was similar
2.3 Preparation of capillary column
Prior to coating, the capillary tubes were rinsed with 5 mL of
dichloromethane and purged with a continuous stream of N2 at
260 ꢀC for 1 h. The columns were then statically coated with 0.80%
(w/v) MTP and TMP solution containing 4% (w/w) dicumylperoxide
of MTP or TMP as a radical initiator. Both of the coated capillary
columns had a lm thickness of 0.50 mm. The capillary columns
were then conditioned under a constant ow of nitrogen from
40 ꢀC (maintained for 0.5 h) to 160 ꢀC at 1 ꢀC minꢂ1 (maintained
for 2 h) and followed to 360 ꢀC at 1 ꢀC minꢂ1 (maintained for 24 h).
The 15 m TMP columns were treated at 370 ꢀC for 24 h. The
prepared MTP and TMP columns (30 m ꢁ 0.25 mm) were called
columns I and II, respectively. The prepared MTP and TMP
columns (15 m ꢁ 0.25 mm) were called columns A and B,
respectively.
ꢀ
to that of BD1 (7.4 g, 61.7% yield), mp 165.2–165.9 C. The BD1
and BD2 structures were analyzed by 1H NMR and FT-IR.
1
BD1. H NMR (CDCl3, 400 MHz, dppm): 3.81 (d, 6H, OCH3);
6.72–6.76 (d, 4H, Ar-H); 6.85–6.89 (m, 6H, Ar-H); 7.23–7.28 (d,
8H, Ar-H). FT-IR (KBr, n/cmꢂ1): 3105.8 [n(C–H)]; 1879.6 [n(C]
O)]; 1247.9 [n(C–O)]; 815.2, 764.5 [n(Ar-H)].
1
BD2. H NMR (CDCl3, 400 MHz, dppm): 3.47 (s, 12H, 4OCH3);
3.86 (s, 6H, 2OCH3); 6.63–6.65 (d, 4H, Ar-H); 7.19–7.25 (m, 4H, Ar-
H); 7.28–7.32 (d, 6H, Ar-H). FT-IR (KBr, n/cmꢂ1): 3009.6 [n(C–H)];
1708.9 [n(C]O)]; 1240.2, 1126.4 [n(C–O)]; 846.7, 734.8 [n(Ar-H)].
2.2.4 Synthesis of MTP and TMP. The MTP and TMP were
prepared through
a Diels–Alder reaction between cyclo-
pentadienone and methyl vinyl polysiloxanes (MVP). Accord-
ingly, 20% vinyl content of the MVP side chain was obtained
according to a literature method.20 MVP (7.0 g, containing 18.3
mmol vinyl of the side chain) and BD1 (8.8 g, 20.0 mmol) were
added to a dry four-necked round bottom ask containing 50.0
mL of dry diphenyl ether. The mixture was heated at 240 ꢀC for
72 h under nitrogen atmosphere. The color of the solution
3. Results and discussion
3.1 Column efficiency
Table 1 shows the chromatographic properties of the two
columns. The column efficiencies determined at liner velocity
76516 | RSC Adv., 2016, 6, 76514–76523
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