J. Xu et al.
ThermochimicaActa671(2019)119–126
2.2. Synthesis of siloxane-containing benzoxazines
water, saturated salt solution. Then, the solution was dried with an-
hydrous sodium sulfate, and the solvent was removed using a rotary
evaporator. A viscous crude product was obtained. After purifying by
column chromatography with pertroleum ether/ethyl acetate (8:1) as
eluent solvent, the pure product was obtained with a yield of 34.5%.
FTIR (KBr, cm−1): 2962 (eCH3 stretching), 1379 (CH2 wagging), 1257
(CeOeC asymmetric stretching), 1025 (CeOeC symmetric stretching),
1147 (CeNeC asymmetric stretching), 932 (out-of-plane bending of
CeH on benzene ring connected to oxazine ring, Ph–O–Si stretching).
1H-NMR (400 MHz, CDCl3, ppm): 7.27–7.28 (1 H, AreH), 7.13–7.17 (2
H, AreH), 6.99–7.03 (6 H, AreH), 6.90–6.93 (2 H, AreH), 6.84–6.86 (4
H, AreH), 6.77–6.80 (1 H, AreH), 5.31 (4 H, O−CH2eN), 4.58 (4 H,
Ar−CH2eN), 0.21 (6 H, SieCH3). 13C NMR (100 MHz, CDCl3, ppm):
116.92, 120.25, 120.44, 120.77, 120.96, 126.75, 127.84, 143.12,
143.33, 149.08, 149.28, 154.41(the carbons of benzene ring), 80.44
(2C, OeCH2eN), 50.97 (2C, AreCH2eN), 0.86 (2C, SieCH3).
2.2.1. Synthesis of bis(p-aminophenoxy)siloxanes
The bis(p-aminophenoxy)dimethylsiloxane (ADMS) was synthesized
according to the procedure reported by F. Rafiemanzelat et al. [21] In a
500-mL three neck flask equipped with a magnetic stirrer, condenser,
and constant-pressure funnel under nitrogen, THF(203 mL), toluene
(40 mL), TEA (12 mL), and p-aminophenol (17.9 g, 164.22 mmol) were
added. The mixture was heated to reflux, and dimethyldichlorosilane
(10.3 mL, 85.59 mmol) in 80 mL THF was gradually added to the well-
stirred slurry mixture. After the addition was completed, the mixture
was refluxed and stirred for 30 h. The color of the slushy mixture was
light yellow at first and then gradually turned milky. After the reaction
was completed, the mixture was cooled to room temperature. The white
byproduct triethylamine hydrochloride was filtered off using a sand
funnel and silica gel powder (200 mesh). The filtrate was rotary eva-
porated to remove the solvent. The residue was then redissolved in
chloroform and filtered. The filtrate was rotary evaporated, and the
residue was dried in a vacuum at 60℃. The product was obtained with a
yield of 73%. FTIR (KBr, cm−1): 3376 (eNH2, stretching), 2958 (eCH3
stretching), 1211 (C–Si symmetric stretching), 1077 (Si–O asymmetric
stretching), 910 (Ph–O–Si stretching), 839 (CeSi asymmetric
stretching). 1H-NMR (400 MHz, CDCl3, ppm): 6.74–7.26 (4 H, AreH),
6.57–6.60 (4 H, AreH), 3.14 (4 H, AreNH2), 0.30, (6 H, SieCH3).
bis(p-aminophenoxy)methylphenylsiloxane (AMPS) was synthe-
sized following a similar procedure, and their yields was 77%. FTIR
(KBr, cm−1): 3352 (–NH2 stretching), 2996, (eCH3 stretching), 1228
(C–Si symmetric stretching), 1082 (Si–O asymmetric stretching), 938
(PheOeSi stretching), 830 (CeSi asymmetric stretching). 1H-NMR
(400 MHz, CDCl3, ppm): 7.69–7.71 (2 H, Ar–H), 7.35–7.39(3 H, AreH),
6.73–6.77(4 H, AreH), 6.49-6.52(4 H, AreH), 3.34 (4 H, AreNH2),
0.49 (3 H, SieCH3).
Phenol/bis(p-aminophenoxy)methylphenylsiloxane-based benzox-
azine (P-amps) was synthesized following a similar procedure, and the
yield was 41.7%. FTIR (KBr, cm−1): 2961 (eCH3 stretching), 1380
(CH2 wagging), 1259 (CeOeC asymmetric stretching), 1024 (CeOeC
symmetric stretching), 1121 (CeNeC asymmetric stretching), 940 (out-
of-plane bending of C–H on benzene ring connected to oxazine ring, Ph-
O-Si stretching). 1H-NMR (400 MHz, CDCl3, ppm): 7.91–7.92 (1 H,
AreH), 7.78–7.80 (1 H, AreH), 7.51–7.58 (3 H, AreH), 7.45–7.49 (1 H,
AreH), 7.25–7.29 (2 H, AreH), 7.11–7.15 (5 H, AreH), 6.99–7.08 (7 H,
AreH), 6.92–6.94 (1 H, AreH), 5.39 (4 H, O−CH2–N), 4.65 (4 H,
AreCH2eN), 0.72 (3 H, SieCH3). 13C NMR (100 MHz, CDCl3, ppm):
117.34, 120.73, 121.19, 121.38, 127.19, 128.26, 128.38, 128.53,
131.12, 134.12, 134.53, 143.80, 149.38 (the carbons of benzene ring),
80.70 (OeCH2eN), 51.23 (AreCH2eN), -3.00 (SieCH3).
Phenol/bis(p-aminophenoxy)diphenylsiloxane-based benzoxazine
(P-adps) was synthesized following a similar procedure, and the yield
was 57.3%. FTIR (KBr, cm−1): 1338 (CH2 wagging), 1233 (CeOeC
asymmetric stretching), 1037 (CeOeC symmetric stretching), 1121
(CeNeC asymmetric stretching), 942 (out-of-plane bending of CeH on
benzene ring connected to oxazine ring, Ph–O–Si stretching). 1H-NMR
(400 MHz, (CD3)2SO, ppm): 7.68–7.70 (4 H, AreH), 7.45–7.47(2 H,
AreH), 7.38–7.42(4 H, AreH), 7.04–7.08(4 H, AreH), 6.95–6.97(4 H,
AreH), 6.68–6.70(2 H, AreH), 6.83–6.87(6 H, AreH), 5.31 (4H,
OeCH2eN), 4.52 (4H, AreCH2eN). 13C NMR (100 MHz, (CD3)2SO,
ppm): 116.65, 119.54, 120.07, 120.88, 121.66, 127.61, 128.06, 128.76,
131.36, 131.57, 135.01, 143.29, 147.93, 154.41 (the carbons of ben-
zene ring), 79.21 (OeCH2eN), 49.66 (AreCH2eN).
bis(p-aminophenoxy)diphenylsiloxane (ADPS) was synthesized fol-
lowing a similar procedure, and their yields were 81%. FTIR (KBr,
cm−1): 3449 (eNH2 stretching), 1215 (C-Si symmetric stretching),
1097 (SieO asymmetric stretching), 940 (PheOeSi stretching), 835
(CeSi asymmetric stretching). 1H-NMR (400 MHz, CDCl3, ppm): 7.73 (4
H, AreH), 7.71 (2 H, AreH), 7.32–7.41 (4 H, AreH), 6.75–6.77 (4 H,
AreH), 6.47–6.49 (4 H, AreH), 3.36 (4 H, AreNH2).
2.2.2. Synthesis
benzoxazines
of
phenol/bis(p-aminophenoxy)
siloxane-based
Phenol/bis(p-aminophenoxy)dimethylsiloxane-based benzoxazine
(P-adms) was synthesized as the following procedure. In a 250-mL
round-bottom flask, paraformaldehyde (9.45 g, 316.58 mmol), phenol
(14.17 g, 150.75 mmol), and BADMS (20.65 g, 75.37 mmol) were dis-
solved in 90 mL of trichloromethane and refluxed for 12 h. After cooling
to room temperature, the solution was removed by rotary evaporation.
The crude product was extracted with methylene chloride and succes-
sively washed with 10% sodium hydroxide aqueous solution, deionized
2.2.3. Preparation of siloxane-containing polybenzoxazines
The benzoxazine monomers P-adms, P-amps and P-adps were cured
following a similar procedure and the polybenzoxazines were abbre-
viated as PP-adms, PP-amps, PP-adps, respectively. The obtained ben-
zoxazine monomers was placed in an oven and then heated to cure at
220 °C for 2 h and 240 °C for 2 h. Scheme 1 shows the synthetic route of
Scheme 1. Synthetic route of siloxane-containing benzoxazine monomers.
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