Syntheses and Characterization of Four Phosphaphenanthrene and Phosphazene-based Flame Retardants

Article abstract of DOI:10.1080/10426507.2014.902828

Four novel intumescent flame retardants containing phosphaphenanthrene and phosphazene groups were synthesized by using the classic Atherton-Todd reaction and Kabachnik-Fields reactions. 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was first

Full text of DOI:10.1080/10426507.2014.902828

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Phosphorus, Sulfur, and Silicon and the
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Syntheses and Characterization of Four
Phosphaphenanthrene and Phosphazene-
based Flame Retardants
a
a
ab
b
a
Peng Jiang , Xiaoyu Gu , Sheng Zhang , Jun Sun , Shende Wu &
a
Qian Zhao
a
Key Laboratory of Carbon Fiber and Functional Polymers (Beijing
University of Chemical Technology), Ministry of Education, Beijing,
1
00029, China
b
Fire Safety Material Laboratory, College of Materials Science &
Engineering, Beijing University of Chemical Technology, Beijing,
00029, China
1
Accepted author version posted online: 11 Jun 2014.Published
online: 16 Oct 2014.
To cite this article: Peng Jiang, Xiaoyu Gu, Sheng Zhang, Jun Sun, Shende Wu & Qian Zhao
(
2014): Syntheses and Characterization of Four Phosphaphenanthrene and Phosphazene-
based Flame Retardants, Phosphorus, Sulfur, and Silicon and the Related Elements, DOI:
0.1080/10426507.2014.902828
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Phosphorus, Sulfur, and Silicon, 189:1–12, 2014
Copyright ꢀ
Taylor & Francis Group, LLC
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ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2014.902828
SYNTHESES AND CHARACTERIZATION OF FOUR
PHOSPHAPHENANTHRENE AND PHOSPHAZENE-
BASED FLAME RETARDANTS
1
1
1,2
2
Peng Jiang, Xiaoyu Gu, Sheng Zhang, Jun Sun, Shende
1
1
Wu, and Qian Zhao
Key Laboratory of Carbon Fiber and Functional Polymers (Beijing University of
Chemical Technology), Ministry of Education, Beijing 100029, China
1
2
Fire Safety Material Laboratory, College of Materials Science & Engineering,
Beijing University of Chemical Technology, Beijing 100029, China
GRAPHICAL ABSTRACT
Abstract Four novel intumescent flame retardants containing phosphaphenanthrene
and phosphazene groups were synthesized by using the classic Atherton–Todd reaction
and Kabachnik–Fields reactions. 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide
(DOPO) was firstly reacted with hexa-aminophenoxy-cyclotriphosphazene (compound 2)
in the presence of carbon tetrachloride and triethylamine (Atherton-Todd reaction) to
obtain hexa-(phosphaphenanthrene-anmino-phenoxyl)-cyclotriphosphazene (compound 3).
Moreover, the condensation of hexa-aminophenoxy-cyclotriphosphazene with formaldehyde,
salicylaldehyde, 4-hydroxybenzaldehyde respectively, followed by the addition of DOPO
Received 5 November 2013; accepted 6 March 2014.
Address correspondence to Sheng Zhang, College of Materials Science and Engineering, Beijing Uni-
versity of Chemical Technology, 15 Beisanhuan East Road, Chaoyang District, Beijing, China. E-mail: zhang-
sheng@mail.buct.edu.cn
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gpss.
1

2
P. JIANG ET AL.
(
Kabachnik-Fields reaction) to the imine linkage to obtain hexa-(phosphaphenanthrene-
methyl-amino-phenoxyl)-cyclotriphosphazene (compound 4), hexa-(phosphaphenanthrene-
methyl-(o-hydroxybenzal)-amino-phenoxyl)-cyclotriphosphazene (compound 5), and hexa-
(phosphaphenanthrene-methyl-(p-hydrobenzal)-amino-phenoxyl)-cyclotriphosphazene (com-
pound 6). The structures of compounds 3–6 were determined by FTIR, NMR, and elemental
analysis. A preliminary investigation on compound 5 as a flame retardant for PLA has been
carried out, and the result shows that the limiting oxygen index (LOI) of the PLA sample can
reach up to 30% at the presence of only 5% compound 5.
Keywords Flame retardants; synthesis; phosphaphenanthrene; phosphazene
INTRODUCTION
Organophosphorus compounds have attracted much attention because of their wide
range of applications in coordination chemistry, material science, homogeneous catalysis,
pharmaceutical, and auxiliaries for polymers such as antioxidants and flame retardants
1
–5
and so on. Recently, several new phosphorus heterocycles, especially the nitrogen-
phosphorus containing flame retardants with high nitrogen and phosphorus content have
been reported to exhibit good flame retardancy, with reduced toxic effects and have at-
tracted much attention.6 There has also been great interest from the flame retardant
community regarding phosphorus containing molecules (e.g., 9, 10-dihydro-9-oxa-10-
phosphaphenanthrene-10-oxide (DOPO) for epoxy) and nitrogen-phosphorus containing
molecules (e.g., Hexa-chloro-cyclotriphosphazene (HCCP) for epoxy, PLA, polybenzox-
azines) as environmentally friendly alternatives to the existing, and often used, harmful
halogenated flame retardants.8 However, the above-mentioned reactive DOPO, phosp-
hazene compounds and their derivatives could only be introduced to thermosets mainly
,7
–12
15–17
through chemical reaction, which has restricted their application in many cases.
In this paper, the versatile Atherton–Todd reaction and the Kabachnik–Fields reaction
were used to obtain novel derivatives containing phosphaphenanthrene and cyclotriphosp-
hazene double functional groups which can be used as intumescent flame retardant additives.
Poly (lactic acid) (PLA) is an aliphatic polyester produced via the polymerization of the
renewable fermentation product lactic acid. The often used approaches for flame retarding
18
PLA include: (a) blending with char forming polymer, (b) using of conventional flame
retardants (such as ATH, MTH, phosphorus-containing compounds, and halogenated com-
1
9–22
pounds),
nanotubes (MWNT)),2
reported that the LOI value of the sample with 5 wt% monomeric IFR triazinephosphamide
(c) using of nanoparticles (such as organomodified clay, multi-walled carbon
3–30
31,32
(d) using of intumescence flame retardants (IFR).
It was
32
could only reach 28% with V-2 grade in UL-94 test. P/N containing flame retardants
have been recently regarded as the most promising alternatives to halogen-containing flame
retardants. However, the high loading is usually required to meet the flame retardant stan-
dards, which can cause significant reduction to the strength and other properties. Thereby
it is essential to obtain flame retardants with high-efficiency to reduce the negative effects
on mechanical properties. Figures 1 and 2 show the synthetic routes of this work.
RESULTS AND DISCUSSION
Synthesis and Characterization of Compound 3
The Atherton-Todd reaction was used as a very effective single-step route to yield
phosphoramidates from diphenyl and dialkyl phosphorus, which was reported by Atherton

NOVEL PHOSPHORUS-CONTAINED FLAME RETARDANTS
3
Figure 1 Schematic diagram for the synthesis of compound 1 and compound 2.
13
and Todd originally (Figure 3). H-phosphinates or secondary phosphine oxides react with
amines or alcohols to obtain corresponding coupling and high stereospecifical products with
16
inversion of configuration at the phosphorus center. Meanwhile, the reaction mechanism
has been further investigated, and mild conditions can be applied to organophosphorus
17
chemistry. An organophosphorus compound which containing a P H bond can result
in the in situ formation of a P (O)-Cloxychloride species under the action of carbon
tetrachloride and triethylamine.
Compound 3 was synthesized by reacting compound 2 with P(O)-Cloxychlo-
ridespecies which formed by P H bond in DOPO under the action of carbon tetrachloride
using the triethylamine as acid-binding agent to absorb HCl. The reaction of the intermedi-
ate DOP-Cl with the nucleophile amine is the rate limited step. So the formed intermediate
DOP-Cl reacted with the nucleophilic amine at higher temperatures and required longer
Figure 2 Schematic diagram for the synthesis of compound 3–6 using Atherton–Todd and Kabachnik–Fields
reactions.

4
P. JIANG ET AL.
Figure 3 General scheme for the Atherton–Todd reaction.
reaction time. Further investigation relating to the replacement of the carbon tetrachloride
by bromotrichloromethane is being undertaken in our lab in order to increase the reaction
speed.
Synthesis and Characterization of Compound 4–6
The procedure of Kabachnik–Fields reaction includes three components: (a) carbonyl
compound, (b) diakylphosphite, and (c) amine. The general formula is shown in Figure 4.
It shows that this is a one-pot, three-component procedure by using carbonyl
compound, amine, and dialkylphosphite; however, this is a multi-step procedure
which has a complex mechanism.1 It is the most remarkable pathway to synthesize
α-aminophosphonates. Figure 5 shows the multi-step procedure of the Kabachnik–Fields
reaction in detail. Indeed, it was reasonable supposed that one possibility of the formation
of a Schiff base is the reaction between carbonyl compound and the primary amine.
The Schiff base (C N) is so active that it reacts immediately with P H bonds in
dialkylphosphite, followed by the Pudovik-type addition reaction. The other possible route
4
(route 2 in Scheme 5) assumes that α-hydroxyphosphonate is formed by the Abramov
addition of the diakylphosphite to the carbonyl group of oxo component (C O bond), and
then the amino component furnishes the direct nucleophilic amination by substituting the
hydroxyl in α-hydroxyphosphonates.33
The Kabachnik–Fields reaction can be catalyzed by Lewis acid or magnesium per-
chlorate.34 Also the reaction can be promoted by the microwave pathway which is a sol-
vent free synthesis of phosphono- and phosphinoylmethylated N-heterocycles undergo the
35
Kabachnik-Fields reaction. Compounds 4–6 were synthesized by nucleophilic addition of
DOPO on the imine linkage which was generated by the reaction between compound 2 and
a solution of carboxide (formaldehyde, salicyladldehyde, and 4-hydroxybenzaldehyde).
Figure 4 General scheme for the Kabachnik–Fields reaction.

NOVEL PHOSPHORUS-CONTAINED FLAME RETARDANTS
5
Figure 5 The mechanism of the Kabachnik–Fields reaction.
The Thermal Stability of Compounds 3–6
Figure 6 shows the thermal degradation behavior of compound 3–6 in N2.
The onset degradation temperature, the mass loss temperature at various degradation
stages and the residue mass were compared in order to evaluate the thermal stability of
compound 3–6. It is observed that the thermal stability of compound 3 is different from
the other three compounds. The temperature at 3.6 wt% mass loss for compound 3, T-3.6
◦
◦
wt%, is about 210 C. The minor mass loss before 300 C assigns to the scission of trace
◦
water and intermolecular cross-linking, while the major weight-loss stage between 330 C
and 610 C is due to the degradation of the phenoxyl groups and the phosphaphenanthrene
◦
groups. Compounds 4–6 show similar thermal behavior despite different structures of R
groups (shown in Figure 2). The whole degradation process can be divided into three
◦
◦
stages. The first stage is from 230 C to 300 C, and 4% mass loss can be observed during
this stage, which may be attributed to the dehydration of the hydroxide or intermolecular
cross-linking.10 The second degradation stage is between 290 to 440 C, and it has 11%
◦
mass loss which is attributed to the elimination reaction of the instable methyl group. The
◦
◦
maximal degradation rate can be seen between 450 C and 550 C, which is attributed to
36
the breakage of P-C bonds between phosphaphenanthrene and phosphazene groups. The
last degradation stage is from 550 C to 900 C, during which ammonia is released. Phos-
◦
◦
phazene bonds and O P O bonds in DOPO part may decompose to produce phosphoric
acid or metaphosphoric acid.3
6,37
It is suggested the presence of these P-contained acids
can promote the char formation and the release of ammonia may be helpful to form an
intumescent char structure. One can also see that compound 3, 4, 5, and 6 has char residue
◦
of 28%, 18%, 28%, and 30% at 900 C, respectively.

6
P. JIANG ET AL.
◦
Figure 6 TGA curves for compound 3–6 at a heating rate of 10 C/min in N2.
The Preliminary Mechanical Properties and Fire Performance
of Compound 5 in PLA
A preliminary investigation on compound 5 as flame retardant for PLA has been
carried out. The PLA composites were obtained by mixing PLA pellets with compound 5
in a micro twin-screw extruder (Wuhan Rayzong Ming Plastics Machinery Co., Ltd, China)
◦
with a screw speed of 50 rpm at 160 C. Specimens for burning tests were obtained from
compression moulded plates. The formula and the composition ratio were shown in Table 1.
All the samples have same phosphorus content 0.52% except sample S1. Table 2 shows
that the PLA samples can reach V-0 at the presence of 5% compound 5, and has a limiting
Figure 7 The side chain structure of compound 3.

NOVEL PHOSPHORUS-CONTAINED FLAME RETARDANTS
7
Table 1 Formulations for PLA composites
Sample
PLA/g
Compound 5/g
HCCP/g
DOPO/g
P (wt.%)
S1
S2
S3
S4
S5
100
95
96.4
95.6
96.3
0
5
0
0
0
0
0
0
4.4
0.5
0
0
3.6
0
0
0.52
0.52
0.52
0.52
3.2
oxygen index (LOI) value of 30% which is increased from 21.5% of pure PLA. However,
the sample S3, S4, and S5 have poor effect in terms of LOI and UL-94 test results. It can be
concluded that DOPO or HCCP alone or both of them cannot improve the flame retardancy
of PLA significantly, whereas compound 5 can. The mechanical tests were carried out
on a CMT4104 pulling machine (made in SANS Company, China), according to D-1708
◦
criterion. The specimens were tested with a speed of 500 mm/min at 25 C. Table 2 presents
the mechanical properties of neat PLA and PLA composites. It shows that the addition of
compound 5, like most organic fillers, can decrease the mechanical properties. The tensile
strength and the impact strength are reduced by about 12.5% and 20%, respectively, after
the addition amount of 5% compound 5. It is proposed that the unevenly dispersion, air
bubbles or cavities existed inside the composites are responsible for the decrease.
EXPERIMENTAL
Materials and Instrumentation
9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was provided by
Guangzhou Shengshida Chemical Co. Ltd., China. Hexa-chloro-cyclotriphosphazene
(
(
HCCP) was purchased from Zibo Lanyin Chemical Co.Ltd., China. 4-acetamidophenol
98%), K2CO3, Salicylaldehyde, 4-hydroxybenzaldehyde were provided by Beijing
Chemical reagent Co. Ltd., China. PLA was supplied by Cargill Dow. All the solvents
were dried before used.
1
13
NMR spectra were recorded in DMSO-d6 for proton ( H), carbon ( C), and phos-
31
phorus ( P) using a Bruker AV400 NMR spectrometer. Fourier transform infrared (FTIR)
spectra were recorded using Thermo Nicolet Nexus 670, USA by KBr disc method. Dif-
ferential scanning calorimetry (DSC) were carried out using a NETZSCH DSC204F1
instrument under nitrogen atmosphere with a flow rate of 20 mL/min and a scan rate of
Table 2 LOI, UL-94 and mechanical test results for PLA composites
UL94
Sample
LOI (%)
Classification
Drip
Tensile strength (MPa)
Impact strength (KJ/m2)
S1
S2
S3
S4
S5
21.5
30
22.1
24
NCa
V-0
NC
V-2
NC
Y
Y
Y
Y
Y
56( ± 2)
49( ± 1)
56( ± 1)
51( ± 1)
46( ± 2)
2.5( ± 0.1)
2.0( ± 0.1)
2.4( ± 0.1)
2.1( ± 0.1)
1.9( ± 0.1)
22.5
aNC: no classification.

8
P. JIANG ET AL.
Figure 8 The side chain structure of compound 4.
◦
◦
1
0 C/min over a temperature range of 30–300 C. The limiting oxygen index (LOI) values
and UL-94 vertical burning test were carried out on a JF-3 type instrument (Jiangning,
China) and a CZF-3 instrument (Jiangning, China) according to national standard of China
GB/T2406-93 and GB4609-84 respectively. The dimension of the sample for LOI and UL-
1
13
9
4 test is 100 × 6.5 × 3 mm and 125 × 13 × 3 mm, respectively. Sample FT-IR, H, C,
31
and P NMR for compounds 3–6 are presented in the Supplemental Materials (Figures
S3–S18)
Preparation of Compound 1 and 2
Compound 1. Compound 1 was synthesized by reacting hexa-chloro-cyclotriph-
osphazene (HCCP) with excess 4-acetamidophenol in the presence of K2CO3 in acetone
15
to yield compound 1. The detailed procedures were reported by Joaquin. White crystals.
◦
◦
Yield: 95%, m.p.:260 C–263 C.
1
H NMR (DMSO-d6, TMS, ppm): δ = 9.9 (s, 1H, NH), δ = 6.7–7.5 (dd, J = 8.0 Hz,
31
J = 8.0 Hz, 4H, Ar H), δ = 2.1 (s, 3H, CH3). P NMR (DMSO-d6, ppm): δ = 9.2 (s,
−1
3
P). FTIR (KBr, cm ): 1668 (vs) (C O); 3300 (s, br), 3140 (m), 3074 (m) (N H); 1198
(vs, br), 1177 (vs, br) (P N); 955 (P O).
Figure 9 The side chain structure of compound 5.

NOVEL PHOSPHORUS-CONTAINED FLAME RETARDANTS
9
Figure 10 The side chain structure of compound 6.
Compound 2. Compound 1 was hydrolyzed by sodium hydroxide in methanol to
yield compound 2 as reported.15 White power. Yield: 90%. MP: 256 C–260 C. H NMR
◦
◦
1
(
DMSO d6, TMS, ppm): δ = 6.5–6.6 (dd, J = 8.0 Hz, J = 8.0 Hz, 4H; OC6H4N), δ = 4.5
31
−1
(s, 2H; NH2). P NMR (DMSO-d6, ppm): δ = 10.9 (s, 3P). FTIR (KBr, cm ): 3460 (w),
3
440 (m), 3412 (w), 3340 (s, br) ( NH); 1199 (vs,br), 1177 (vs,br) (P N); 965 (s) (P O).
Preparation of hexa-(phosphaphenanthrene-anmino-phenoxyl)-cyclotriphosphaz-
ene, compound 3
DOPO (0.09 mol, 20 g), carbon tetrachloride (0.12 mol, 20 g) and acetone (200 mL)
were added to a three-neck flask equipped with a mechanical stirring, a thermometer, and an
addition funnel which was charged with compound 2 (0.016 mol, 12 g) and triethylamine
(
0.12 mol, 13 g). The compound 2 and triethylamine mixture were added dropwise in 30 min
◦
under vigorous stirring at 40 C. The yellow sediment was separated out after 3 h under
N2 atmosphere. Then the mixture was washed by excess water to remove the triethylamine
hydrochloride, followed by washing with excess acetone to remove the unreacted DOPO or
compound 2. The spectroscopically pure product was obtained as a faint yellow power after
◦
◦
◦
keeping 48 h in vacuum at 70 C to remove the solvent. Yield: 85%. MP: 175 C–180 C.
1
H NMR(DMSO-d6,TMS,ppm): δ = 3.0 (s, 1H, NH), δ = 6.5–8.6 (m, 12H, Ar H),
1
3
C NMR (DMSO-d6, TMS, ppm), δ = 150.9 (C1), 115.8 (C2), 130.7 (C3), 125.3 (C4),
1
1
23.7 (C5), 124.4 (C6), 133.3 (C7), 128.5 (C8), 132.1 (C9), 123.3 (C10), 135.9 (C11),
31
25.6 (C12), 125.3 (C13), 130.7 (C14), 120.2 (C15), 149.1 (C16). P NMR (DMSO-d6,
−1
ppm): δ = 8.1 (s, 1P); 9.0 (s, 3P). FTIR (KBr, cm ): 3189 (vs), 3401 (s) ( NH); 1199
(vs, br), 1177 (vs, br) (P N); 965 (s) (P O); 1200 (P O Ph); 1275 (s) (P O); 1429 (s),
1
6
478 (s) (P C). Elemental analysis Calcd. (%) for C108H78N9O18P9: C, 62.70; H, 3.77; N,
.10; P, 13.5. Found: C, 63.10; H, 3.50; N, 6.30.
3
.4. Preparation of Compounds 4–6
A solution of carboxide (formaldehyde (36 mmol, 1.1 g), or salicylaldehyde
25 mmol, 3.1 g), or 4-hydroxybenzaldehyde (25 mmol, 3.1 g) in acetone (200 mL) was
(

10
P. JIANG ET AL.
added to a solution of compound 2 (2.5 mmol, 2 g) in acetone under N2 atmosphere in
a flame-dried three-neck flask11 and an addition funnel which was charged with DOPO
(
25 mmol, 5.45 g) and acetone (100 mL). The mixture was added dropwise in 30 min
◦
under vigorous stirring and the temperature of the reaction was fixed at around 45 C for
3
h. The resulting yellow compound was filtered off and washed with a large excess of
◦
water, acetone, hexane, diethyl ether, respectively, and finally dried in vacuum at 70 C for
48 h.
Hexa-(phosphaphenanthrene-methyl-amino-phenoxyl)-cyclotriphosphazene, com-
pound 4
Yield: 85%. MP: 180 C. H NMR (DMSO-d6, TMS, ppm): δ = 5.7 (s, 1H, NH), δ =
◦
1
13
4
.0 (d, J = 21 Hz, 2H, CH2 ), δ = 6.6–8.2 (m, 12H, Ar H). C NMR (DMSO-d6, TMS,
ppm): δ = 139.2 (C1), 113.1 (C2), 115.4 (C3), 148.6 (C4), 50.1 (C5), 123.9 (C6), 124.5
(
(
1
C7), 133.8 (C8), 128.52 (C9), 132.1 (C10), 120.7 (C11), 135.0 (C12), 125.4 (C13), 124.5
31
C14), 130.6 (C15), 120.7 (C16), 148.4 (C17). P NMR (DMSO-d6, ppm): δ = 32.1 (s,
−1
P); 9.8 (s, 3P). FTIR (KBr, cm ):3424 (vs), 3314 (s) ( NH ); 2852 (w), 2908 (w), 2801
(
(
w) ( CH); 1199 (vs, br),1166 (vs, br) (P N); 955 (s) (P O); 1203 (P O Ph); 1263 (s)
P O); 1433 (s), 1480 (s) (P C). Elemental analysis Calcd. (%) for C114H90N9O18P9: C,
63.59; H, 4.18; N, 5.86; P, 13.0. Found: C, 61.89; H, 4.60; N, 5.31.
Hexa-(phosphaphenanthrene-methyl-(o-hydroxybenzal)-amino-phenoxyl)-
cyclotriphosphazene, compound 5
◦
1
Yield: 88%. MP: 185 C. H NMR (DMSO-d6, TMS, ppm): δ = 9.6 (s, 1H, OH),
δ = 5.3 (d, J = 12 Hz, 1H, NH), 4.9(s, 1H, NH), δ = 3.4(s, 1H, N CH P ).
1
3
C NMR (DMSO-d6, TMS, ppm): δ = 129.1 (C1), 118.9 (C2), 155.1 (C3), 131.6 (C4),
1
28.6 (C5), 122.6 (C6), 50.5 (C7), 123.7 (C8), 124.4 (C9), 133.6 (C10), 128.4 (C11), 132.1
(
C12), 120.6 (C13), 135.5 (C14), 125.3 (C15), 124.8 (C16), 130.5 (C17), 120.1 (C18), 149.3
31
(C19), 139.2 (C20), 114.5 (C21), 141.6(C22), 143.9 (C23). P NMR (DMSO-d6, ppm): δ =
−1
2
3
9
8.7, 32.3, 36.0 (s, 1P); 9.20 (s, 3P). FTIR (KBr, cm ): 3392 (s, br) ( OH); 3190 (vs),
070 (s) ( NH ); 2964 (w), 2850 (w), 2737 (w) ( CH); 1195 (vs, br),1172 (vs, br) (P N);
47 (s) (P O); 1203 (P O Ph); 1275 (s) (P O); 1459 (s), 1477 (s) (P C). Elemental
analysis Calcd. (%) for C150H114N9O24P9: C, 66.59; H, 4.21; N, 4.7. P, 10.4. Found: C,
66.10; H, 4.30; N, 4.90.
Hexa-(phosphaphenanthrene-methyl-(p-hydrobenzal)-amino-phenoxyl)-
cyclotriphosphazene, compound 6
◦
1
Yield: 90%. MP: 180 C. H NMR (DMSO-d6, TMS, ppm): δ = 9.4 (s, 1H, OH), δ
13
=
5.1 (d,J = 20 Hz, 1H, NH ),4.66(s, 1H, NH ), 3.36 (1H, N CH P-). C NMR
(
DMSO-d6, TMS, ppm): δ = 156.9 (C1), 115.3 (C2), 130.4 (C3), 125.4 (C4), 56.7 (C5),
1
1
1
3
23.4 (C6), 124.5 (C7), 133.6 (C8), 128.2 (C9), 132.1 (C10), 123.8 (C11), 135.3 (C12),
26.2 (C13), 125.1 (C14), 131.4 (C15), 120.6 (C16), 149.0 (C17), 139.3 (C18), 118.9 (C19),
3
1
43.7 (C20), 148.7 (C21). P NMR (DMSO-d6, ppm): δ = 28.7, 31.3, 35.9 (s, 1P); 9.30(s,
−1
P). FTIR (KBr, cm ): 3323 (s, br) ( OH); 3196 (vs), 3064 (s) ( NH ); 2963 (w), 2810
(
(
w) ( CH); 1196 (vs, br),1173 (vs, br) (P N); 951 (s) (P O); 1203 (P O Ph); 1270 (s)
P O); 1448 (s), 1478 (s) (P C). Elemental analysis Calcd. (%) for C150H114N9O24P9: C,
66.59; H, 4.21; N, 4.7. P, 10.4. Found: C, 66.55; H, 4.40; N, 5.10.
CONCLUSION
Four novel compounds 3–6 containing phosphaphenanthrene and phosphazene
groups were synthesized respectively, and their structures were confirmed and charac-
terized by FTIR, NMR, and elemental analysis. The LOI value of PLA sample containing

NOVEL PHOSPHORUS-CONTAINED FLAME RETARDANTS
11
only 5% compound 5 can reach up to 30%. It is suggested that the high efficiency of
compound 5 in improving the flame retardancy of PLA is because of the high content
of both phosphorus and nitrogen. Further investigation on thermal degradation behavior,
fire performance and the flame retardant mechanism of these compounds in polymers are
undertaking in our laboratory and will be discussed in our future publications.
FUNDING
The authors would like to thank the financial support of National Natural Science
Foundation of China (No. 21374004 and No. 51373018).
SUPPLEMENTAL MATERIAL
Supplemental data for this article can be accessed on the publisher’s website, www.
tandfonline.com/gpss
REFERENCES
1
2
3
4
5
6
7
8
9
. Koll a´ r, L.; Keglevich, G. Chem.Rev. 2010, 110, 4257-4302.
. Levchik, S. V.; Weil, E. D. J. Fire Sci. 2006, 24, 345-364.
. Levchik, S. V.; Weil, E. D. Polym. Int. 2005, 54, 11-35.
. Li, Z.; Han, J. Bioorg. Med. Chem. 2003, 11, 4171-4178.
. M e´ vel, M.; Montier, T. Bioconjugate Chem. 2007, 18, 1604-1611.
. Laoutid, F.; Bonnaud, L. Mater. Sci. Eng., R. 2009, 63, 100-125.
. Lu, S. Y.; Hamerton, I. Prog. Polym. Sci. 2002, 27, 1661-1712.
. Rakotomalala, M.; Wagner, S. Materials. 2010, 3, 4300-4327.
. Zang, L.; Wagner, S. Polym. Adv. Technol. 2011, 22, 1182-1191.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
0. Tao, K.; Li, J. Polym. Degrad. Stab. 2011, 96, 1248-1254.
1. Wu, X.; Zhou, Y. Polymer. 2011, 52, 1004-1012.
2. Zhang, T.; Cai, Q. J. Appl. Polym. Sci. 2005, 95, 880-889.
3. Atherton, F.; Openshaw, H. J. Chem. Soc. 1945, 660-663.
4. Zefirov, N. S.; Matveeva, E. D. Arkivoc. 2008, 1, 1-17.
5. Barber a´ , J.; Jim e´ nez, J. J. Mater. Chem. 2006, 18, 5437-5445.
6. Wang, G.; Shen, R. J. Org. Chem. 2010, 75, 3890-2.
7. Wagner, S.; Rakotomalala, M. Heteroat. Chem. 2012, 23, 216-222.
8. Kimura, K.; Horikoshi, Y. Fujitsu Sci. Tech. J. 2005, 41, 173-180.
9. Bourbigot, S.; Duquesne, S. J. Mater. Chem. 2007, 17, 2283-2300.
0. Nishida, H.; Fan, Y. Ind. Eng. Chem. Res. 2005, 44, 1433-1437.
1. Kubokawa, H.; Hatakeyama, T. Fiber. 1999, 55, 349-355.
2. Bourbigot, S.; Duquesne, S. Mol. Cryst. Liq. Cryst. 2008, 486, 1367-1381.
3. Gilman, J. W.; Jackson, C.L. Chem. Mater. 2000, 12, 1866-1873.
4. Bourbigot, S.; Vanderhart, D. L. Polymer. 2004, 45, 7627-7638.
5. Zheng, X.; Wilkie, C. A. Polym. Degrad. Stab. 2003, 81, 539-550.
6. Bourbigot, S.; Fontaine, G. Polym. Adv. Technol. 2011, 22, 30-37.
7. Wang, S.; Tambraparni, M. Macromolecules. 2009, 42, 5251-5255.
8. Allen, M. J.; Tung, V. C. Chem. Rev. 2009, 110, 132-145.
9. Fukushima, K.; Murariu, M. Polym. Degrad. Stab. 2010, 95, 1063-1076.
0. Murariu, M.; Dechief, A. L. Polym. Degrad. Stab. 2010, 95, 889-900.
1. Reti, C.; Casetta, M. Polym. Adv. Technol. 2008, 19, 628-635.
2. Zhan, J.; Song, L. Polym. Degrad. Stab. 2009, 94, 291-296.

12
P. JIANG ET AL.
33. Keglevich, G.; Balint, E. Molecules. 2012, 17, 12821-12835.
34. Bhagat, S.; Chakraborti, A. K. J. Org. Chem. 2007, 72, 1263-1270.
3
5. Keglevich, G.; Szekr e´ nyi, A. Heteroat. Chem. 2008, 19, 207-210.
36. Lin, C. H.; Wang, C. S. Polymer. 2001, 42, 1869-1878.
37. Mathew, D.; Nair, C. P. R. Polym. Int. 2000, 49, 48-56.
38. Ye, J.; Liang, G. Polym. Degrad. Stab. 2013, 98, 597-608.