Macromolecules Article Synthesis ofTetrat-phemylenbs( Scheme 2.Synthetic Routes of EP-1 and EP-2 synt (2486g 018 5c霸NOH into the s h 40to89 onixog cldo pr 24 h in a vacuum R={入O》 m EP2 ,128.23 FTR(KBr,cm:3383(N-H1264(P=O方：1033(P-O910 13951(d 4C). 147 xy]p ate (EP1).sg of DI 1(0.005 .53.7 50.1 6.1 d to 13 24d27 5 (Soth EP d ep H Th. with d ed with DDMn a:l e M. then oduct EP1(.3 nfor hea 9 sion of 80 mm mm x3 mm for flam reta FTR(KB,cm:3300N-H01265(P=01027(P-0)910 (2 (dd 200 (m MR (CDO 46 NM Cl ppm): 9 and C NMR h DMS CDC ing at 400 ar 14702c21 s.4C).131.72(s,2C).144.48( (Ds e) DSC8000 de (10 wt of DP2)as the ed in a thre con nd 2 2 h. then a light yellow whn the rsported as the average of five Synthesis of Tetraethyl(1,4-phenylenebis(azanediyl))bis((4- hydroxy-3-methoxyphenyl)methylene)diphosphonate (DP2). DP2 was also synthesized by a quintessential condensation reaction between vanillin and p-phenylenediamine followed by an addition reaction with diethyl phosphite. 20 g (0.13 mol) of vanillin was dissolved in 150 mL of ethanol in a 500 mL three-neck flask equipped with a magnetic stirrer and a reflux condenser. 6.4884 g (0.06 mol) of p-phenylenediamine dissolved in 50 mL of ethanol was added dropwise into the flask over a period of 0.5 h at 25 °C, and they were reacted at 40 °C for 1 h. Then diethyl phosphite (24.86 g, 0.18 mol) and zinc chloride (0.5 g) as the catalyst for the addition reaction were added into the system, and the mixture was heated from 40 to 80 °C under a nitrogen atmosphere and kept at 80 °C for 8 h. Finally, the mixture was poured into 1000 mL of H2O and stirred for 0.5 h after being cooled to room temperature. A light yellow solid was collected by filtration; then the light yellow crystalline product DP2 (23.4 g) with the yield of around 88.3% was obtained after being washed with acetone twice followed by drying at 70 °C for 24 h in a vacuum oven. The synthetic route is illustrated in Scheme 1. FTIR (KBr), cm−1 : 3390 (O−H, N−H); 1285 (PO); 1040 (P− O).1 H NMR (DMSO-d6, ppm): δ = 1.02 (t, 6H), 1.16 (t, 6H), 3.62 (m, 2H), 3.71 (s, 6H), 3.82 (m, 2H), 4.00 (p, 4H), 4.65 (dd, 2H), 5.39 (dd, 2H), 6.51 (d, 4H), 6.64 (d, 2H), 6.81 (d, 2H), 7.05 (s, 2H), 8.84 (s, 2H). 13C NMR (DMSO-d6, ppm): δ = 16.68 (dd, 4C), 54.54 (s, 2C), 56.08 (s, 4C), 62.5 (m, 2C), 112.99 (s, 2C), 115.37 (s, 4C), 121.32 (s, 2C), 128.23 (s, 2C), 139.51 (d, 4C), 146.2 (s, 2C), 147.66 (s, 2C). Synthesis of Tetraethyl(4,4′-methylenebis(4,1-phenylene)- bis(azanediyl))bis((3-methoxy-4-(oxiran-2-ylmethoxy)phenyl)- methylene)diphosphonate (EP1). 5 g of DP1 (0.0058 mol), 53.7 g of epichlorohydrin (0.58 mol), and 0.5 g of tetrabutylammonium bromide (10 wt % of DP1) as the catalyst were placed in a three￾necked flask equipped with a magnetic stirrer and a reflux condenser, and the mixture was reacted at 80 °C for 3 h. After being cooled to 5 °C, 2.32 g of 40 wt % aqueous sodium hydroxide solution (0.058 mol NaOH) was added dropwise into the flask and reacted for 5 h. The solution was washed with distilled water three times after diluted with dichloromethane; then a light yellow solid was collected after removing dichloromethane and epichlorohydrin. Finally, the light yellow solid product EP1 (5.3 g) with the yield of around 93.5% was obtained after being washed with petroleum ether twice followed by drying at 50 °C for 24 h in a vacuum oven. The synthetic route is illustrated in Scheme 2. FTIR (KBr), cm−1 : 3300(N−H); 1265 (PO); 1027 (P−O); 910 (epoxy). 1 H NMR (CDCl3, ppm): δ = 1.07 (t, 6H), 1.27 (t, 6H), 2.72 (dd, 2H), 2.88 (t, 2H), 3.37 (s, 2H), 3.70 (m, 4H), 3.84 (s, 6H), 4.01 (m, 8H), 4.19 (dt, 2H), 4.62 (d, 2H), 6.47 (t, 4H), 6.91 (dd, 10H). 13C NMR (CDCl3, ppm): δ = 16.38 (dd, 4C), 40.06 (s, 1C), 44.92 (s, 2C), 50.13 (s, 2C), 55.17 (s, 1C), 55.96 (s, 4C), 56.68 (s, 1C), 63.23 (d, 2C), 70.12 (s, 2C), 111.37 (s, 2C), 113.71 (s, 2C), 113.93 (s, 4C), 120.19 (d, 4C), 129.41 (s, 4C), 131.72 (s, 2C), 144.48 (s, 2C), 147.60 (s, 2C), 149.59 (s, 2C). Synthesis of Tetraethyl(1,4-phenylenebis(azanediyl))bis((3- methoxy-4-(oxiran-2-ylmethoxy)phenyl)methylene)- diphosphonate (EP2). 5 g of DP2 (0.0065 mol), 60.1 g of epichlorohydrin (0.65 mol), and 0.5 g of tetrabutylammonium bromide (10 wt % of DP2) as the catalyst were placed in a three￾necked flask equipped with a magnetic stirrer and a reflux condenser, and the mixture was reacted at 80 °C for 3 h. After being cooled to 5 °C, 2.6 g of 40 wt % aqueous sodium hydroxide solution (0.065 mol of NaOH) was added dropwise into the flask and reacted for 5 h. The solution was washed with distilled water three times after diluted with dichloromethane; then a light yellow solid was collected after removing dichloromethane and epichlorohydrin. Finally, the white solid product EP2 (4.3 g) with the yield of around 75.2% was obtained after being washed with petroleum ether twice followed by drying at 50 °C for 24 h in a vacuum oven. The synthetic route is illustrated in Scheme 2. FTIR (KBr), cm−1 : 3383 (N−H); 1264 (PO); 1033 (P−O); 910 (epoxy). 1 H NMR (CDCl3, ppm): δ = 1.14 (t, 6H), 1.27 (t, 6H), 2.74 (dd, 2H), 2.90 (t, 2H), 3.39 (s, 2H), 3.71 (m, 2H), 3.85 (s, 6H), 4.03 (m, 8H), 4.19 (dt, 2H), 4.55 (d, 2H), 6.43 (s, 4H), 6.92 (m, 6H). 13C NMR (CDCl3, ppm): δ = 16.37 (dd, 4C), 44.95 (s, 2C), 50.11 (s, 2C), 55.98 (d, 4C), 57.52 (s, 2C), 63.16 (m, 2C), 70.10 (s, 2C), 111.30 (s, 2C), 113.61 (s, 2C), 115.45 (s, 4C), 120.18 (d, 2C), 129.62 (s, 2C), 139.24 (d, 2C), 147.55 (s, 2C), 149.54 (s, 2C). Preparation of the Cured Epoxy Resins. Both EP1 and EP2 were cured with a commonly used curing agent DDM. Epoxy monomers were mixed with DDM in a 1:1 equiv ratio. The mixtures were cured by a plate vulcanizer at 200 °C for 3 min (1 min for removing bubbles, 2 min for heat pressing) to get films with thickness of approximately 100 μm for thermal and mechanical properties examination. The mixtures were also melted and poured into stainless steel molds and cured at 160 °C for 2 h to obtain samples with dimensions of 80 mm × 6.5 mm × 3 mm for flame retardancy investigation. Both films and rectangular samples were postcured at 200 °C for 2 h and 230 °C for 2 h in a vacuum oven. For comparison, commonly used bisphenol A epoxy resin (DGEBA) was also cured with the same curing agent. Characterization. 1 H NMR and 13C NMR spectra were recorded by an AVANCE III Bruker NMR spectrometer (Bruker, Switzerland) with DMSO-d6 and CDCl3 as solvents, operating at 400 and 75.5 MHz, respectively. The infrared spectra (FTIR) were measured with a NICOLET 6700 FTIR (NICOLET, America) using the KBr pellet method. Differential scanning calorimetry (DSC) measurements were performed under a nitrogen atmosphere on a Mettler Toledo Star 1 apparatus and a PerkinElmer DSC8000 apparatus for nonisothermal curing kinetics and glass transition temperature (Tg), respectively. The mixtures (around 3−5 mg) of epoxy monomers and DDM were taken for the study of nonisothermal curing kinetics. A heat scan ranging from 50 to 250 °C was performed at varying heating rates of 5, 10, 15, and 20 °C min−1 , respectively. Cured samples (around 8−10 mg) were heated from 50 to 250 °C at a heating rate of 20 °C min−1 and held at 250 °C for 3 min to eliminate thermal history, and then they were cooled to 50 °C at a cooling rate of 20 °C min−1 followed by being heated again to 250 °C at a rate of 20 °C min−1 . The Tg was obtained from the second heating curve of the cured epoxy resins. Cured samples with dimensions of 30 mm × 0.5 mm × 100 μm were used to examine tensile properties by a Universal Mechanical Testing Machine (Instron 5569A) with a cross-head speed of 0.5 mm min−1 . The tensile properties of each sample were reported as the average of five Scheme 2. Synthetic Routes of EP-1 and EP-2 Macromolecules Article DOI: 10.1021/acs.macromol.7b00097 Macromolecules 2017, 50, 1892−1901 1894