abstract

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CHEMICAL MODIFICATION OF PVC INTO POLYMER-SUPPORTED
OXAZOLINONES AND TRIAZOLES
Magdy Y. Abdelaal* and Tariq R. Sobahi
Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203,
Jeddah 21589, Saudi Arabia
ABSTRACT
PVC (P1) was converted into polymer-supported oxazolinone and triazole
derivatives after sequential chemical assembly of the reactive groups onto PVC.
Firstly, poly(vinyl chloride-co-vinylaminoaniline) (P2) was prepared by reacting
of PVC with p-phenylenediamine. The primary aromatic amino group in P2 was
diazotized and reacted with hippuric acid to form the supported oxazolinone
derivative (P3) which could be converted into supported triazole derivatives (P4)
- (P6) on further interaction with substituted anilines. The involved ring opening
and preferred cyclization reactions have been clearly addressed based on
spectroscopic and elemental analyses of the products. Also the ability for metal
chelation has been roughly tested through the interaction with Cu(II) ions.
Keywords: Functional polymers, PVC, oxazolinone, chemical modification, triazole
1. INTRODUCTION
Functionalization of polymers has widespread applications as the obtained
functionalized polymers acquire the reactivity of the introduced functionality while keeping
the main features of the base polymeric matrix [1 - 5]. Hence, many functionalized polymers
have been prepared through the reaction of a base polymer with different chemically reactive
species such as aldehydes [6, 7], phenols [8] and ketones [9]. Functionalization can also be
achieved through physical blending of some organic compounds such as phenolic compounds
[10]. Some heterocyclic compounds showed stabilizing efficiency for rubber mixes [11] and
their ability for metal chelation is expected as well. Considering the problems in case of
physical blending which leading the additives to bloom to the surface of the blend, the
chemical blending or functionalization would be beneficial in comparison. Oxazolinones and
triazoles are known as common classes of organic compounds and a lot of work have been
performed to synthesize different 1,2,4-triazoles either through solution- or solid- phase
synthesis strategy. However, a little work has been established in the light of supporting them
onto polymer matrices [12 - 17]. The supported organic compounds in the current work have
* Permanent Address of Correspondence: Chemistry Department, Faculty of Science,
Mansoura University, ET-35516 Mansoura, Egypt; e-mail: [email protected]
been firstly synthesized in the last decade by our group and since that time there is no bulk
work has been devoted [11].
The present work deals with chemical modification of (P1) into polymer-supported
oxazolinone and triazole derivatives through sequential chemical assembly of the reactive
species onto (P1) matrix. Characterization of the obtained modified polymers as well as
estimation of the reaction efficiency has been achieved and the possible ability for metal
chelation has been also roughly tested through the interaction with Cu(II) ions.
2. EXPERIMENTAL
All chemicals were purchased from Aldrich Co., USA unless otherwise mentioned and
used without further purification. The modification reactions are represented in Scheme 1.
2.1. Conversion of (P1) into poly(vinyl chloride-co-vinylaminoaniline) (P2):
(P1) has been converted into poly(vinyl chloride-co-vinylaminoaniline) (P2) through
chemical modification of (P1) with p-phenylenediamine (1). This could be achieved parallel
to the method reported before [11]. Elemental and FT-IR spectroscopic analyses have
concluded the formation of the above mentioned copolymer (P2) with 70% conversion. The
reaction conversion has been calculated from the elemental analysis on the basis of mole
fraction concept [18].
2.2. Conversion of PVC copolymer P2 into oxazolinone-supported polymer (P3):
A cold suspension of finely powdered P2 (16.1g, 0.1 mole Ar-NH2 group) in 100 ml
of 0.5 M HCl was diazotized with sodium nitrite (35g, 0.5 mole). The reaction mixture was
coupled with hippuric acid (2) (22g, 0.12 mole) in 70 ml acetic anhydride containing 3g of
freshly fused sodium acetate. After stirring the suspension for 1h while the temperature was
kept at 0-5C, the reaction mixture was then filtered off and washed successively with water,
ethanol, acetone and finally with ether. The yellowish green product (P3) was dried under
vacuum at 40C to constant weight and then subjected for elemental and FT-IR spectroscopic
analyses.
2.3. Conversion of (P3) into supported-polymers triazole (P4) - (P6):
A mixture of (P3) (19g, 0.1 mole of the oxazolinone residue) and the investigated
substituted aromatic amines (1), (3) and (4) (0.12 mole) was soaked for 12h in 70 ml glacial
acetic acid and refluxed with stirring for further 8h. The reaction mixture was left overnight to
stand at room temperature. The modified polymeric product was filtered off and washed
thoroughly with water, acetone and finally with ether. The reaction products (P4) - (P6) were
dried under vacuum at 40C to constant weight and then subjected for elemental and FT-IR
spectroscopic analyses.
2.4. Loading of the dentate polymer (P2) - (P6) with Cu(II) ions:
To about 0.5g of finely powdered modified PVC samples (P2) - (P6), solution of
copper acetate (50ml, 0.1M) was added and stirred for 12h at room temperature. The mixture
was filtered off and washed thoroughly with distilled water and the metal-loaded modified
(P1) samples were separated off. The metal uptake by the modified PVC samples was
determined through back determination of the excess Cu(II) in the filtrate and the raw data are
listed in Table 1. The metal-loaded samples (P2M) - (P6M) were subjected to FT-IR
spectroscopic analysis.
Characterization results for all the modified (P1) samples are summarized in Table 1
for the elemental analysis, reaction conversion % and the overall reaction yield % and in
Table 2 for FT-IR spectroscopic analysis.
3. RESULTS AND DISCUSSION
The chemical modification of polyvinyl chloride (P1) is of great importance as it can
be utilized in many application directions. In the present work, (P1) has been modified into
polymer-supported oxazolinone and triazole derivatives through sequential chemical
assembly of the reactive species onto (P1) matrix.
3.1. Characterization of poly(vinyl chloride-co-vinylaminoaniline) (P2)
Scheme 1 represents the overall reaction sequence. Accordingly, (P1) was converted
into poly(vinyl chloride-co-vinylaminoaniline) (P2) through the reaction with pphenylenediamine (1) parallel to the previously reported method [11] and the formation of the
copolymer (P2) with 70% conversion have been concluded from elemental and FT-IR
spectroscopic analyses. (P2) showed absorption at 2850 cm-1 corresponding to CH-N bonding
formed by alkylation of (1) with (P1). The unreacted NH2 groups and the obtained NH bonds
in (P2) are responsible for the absorption shown at 3480 cm-1 and 3350 cm-1, respectively.
Also, insertion of the aniline residues was confirmed by the absorption at 1590 cm-1
corresponding to C=C aromatic in (P2). Comparison of FT-IR spectrum of (P2) with that of
(P1) clearly proves such modification of (P1) as it showed absorption bands only at 705 cm-1
corresponding to C-Cl bond in addition to the absorption at 1675 cm-1 for C=C bonds that are
mostly occurred in (P10) or arise during the chemical reactions and thermal treatment as well
(see Table 2).
On the other hand, elemental analysis was used also to prove the achievement of the
reaction as well as to estimate the reaction yield based on the mole fraction concept where the
carbon content increased from 38.38% to 69.32% and decreased from 56.8% to 9.39% for
chlorine while nitrogen was appeared in 17.44% content. These data are corresponding to
70% for both the conversion % and the overall reaction yield (see Table 1).
Scheme 1
3.2. Characterization of oxazolinone-supported polymer (P3)
The primary aromatic amino groups in (P2) were diazotized and reacted with hippuric
acid (2) to form the supported oxazolinone derivative (P3) as a yellowish green product.
During the reaction of diazotized (P2) with hippuric acid (2) the obtained product undergoes
azo - hydrazo tautomerism resulting in formation of (P7a&b) or reorientation in such a way
that hydroxyimino group faces hydrazo NH group (P7c).
The intramolecular OH/NH interaction in the reoriented hydroxyiminohydrazo form
(P7c) may result in formation of 3-carboxy-1,2,4-triazolyl derivative (P8) which has been
excluded hence there is no C=O absorption of free carboxylic group in the FT-IR spectrum.
On the other hand, absorption at 3320 cm-1 and at 1050 cm-1 for NH and C-O-C, respectively,
were observed confirming the formation of 5-oxazolinone derivative (P3a) or its conformer
(P3c). Moreover, absorption at 3500 cm-1 and 1565 cm-1 related to OH and N=N groups
justifies the formation of the tautomer 5-oxazolol derivative (P3b). Scheme 2 represents the
possible mechanism for the reaction of the diazotized (P2) with (2) to form the polymersupported oxazolinone functionality.
Scheme 2
3.3. Characterization of polymers -supported triazole (P4) and (P5):
After preparation and characterization of the polymer-supported oxazolinone (P3), the
obtained product has been further reacted with different aniline derivatives (1) and (3). Under
the reaction conditions, the primary aromatic amino group of (1) and (3) may attack the intramolecular ester functionality in the polymer-supported oxazolinone (P3) resulting in the
formation of the corresponding polymer-supported 1,2,4-triazolyl-3-carboxanilides (P4) and
(P5) as represented in Scheme 3.
Scheme 3
This reaction may undergo simultaneous ring opening amidation of the oxazolinone
ring accompanied by regeneration of two conformers of hydroxyimine functionality
(P9a&P10a) and (P9b&P10b). Both conformers may undergo condensation cyclization
resulting in formation of polymer-supported triazolyl tautomers (P4a&P5a) and (P4b&P5b).
Characterization of the obtained products (P4) and (P5) proved their chemical structure either
with the aid of FT-IR spectroscopic analysis or with elemental analysis. Both (P4) and (P5)
showed approximately similar absorption at 3350 cm-1 (NH), 1670 cm-1 (CONH), 1620 cm-1
(C=N) and 3500 cm-1 (OH) in addition to the absorption at 1590 cm-1 for C=C aromatic. (P4)
showed further absorption at 3480 cm-1 corresponding to p-NH2 functionality. Occurrence of
hydroxyl group absorption in (P4) in addition to the amide functionality concludes the
presence of such amide functionality in the two tautomeric forms (P4a) and (P4b) as
represented in Scheme 4. This holds also true for the obtained product (P5). Elemental
analysis data of (P4) (C; 66.11%, H; 5.12%, N; 16.66 & Cl; 4.78) and (P5) (C; 66.94%, H;
4.88%, N; 19.06 & Cl; 4.88) concluded that (P4) was obtained in 78% conversion and 35%
overall reaction yield while (P5) was obtained in 71% conversion and 32% overall reaction
yield (see Table 1). There is another possible way for (P3) to react either with (1) or with (3)
through the intramolecular dehydration of the conformer (P9a) and (P10a). This would lead
to form the corresponding tautomers (P11a-d) and (P12a-d). Such tautomers are containing in case of their formation - imidazolone hydrazo- (P11a,d) and (P12a,d) or imidazololazo(P11b,c) and (P12b,c) functionalities. Also, they would be free from acyclic amide groups.
The obtained products showed absorption at 1670 cm-1 and 3500 cm-1 corresponding to
CONH and OH groups, respectively while the absorption in the range of 1560 - 1570 cm-1
was absent. This confirms the formation of the above described (P4a&b) and (P5a&b) and
excludes the formation of (P11a-d) and (P12a-d) tautomers.
Scheme 4
3.4. Characterization of polymers-supported 2-benzimidazolyl-1,2,4-triazole (P6):
On the other hand, by using (4) instead of (1) or (3) the ortho amino group in the
corresponding polymer-supported 1,2,4-triazolylcarboxanilide derivative (P14a,b) can
undergo further dehydration to produce the corresponding polymer-supported 2benzimidazolyl-1,2,4-triazolyl derivative (P6) as suggested in Scheme 5. The suggested
mechanism for the concerned reaction is parallel to that mentioned above for the reaction of
(P3) with (1) and (3). The possibility of (P14) to be occur in two tautomers (P14a) and
(P14b) facilitates the dehydration reaction of the tautomer (P14b) resulting in the formation
of the obtained polymer-supported 2-benzimidazolyltriazolyl derivative (P6). FT-IR analysis
of P6 showed absorption at 3300 cm-1 and 1624 cm-1 corresponding to NH and C=N
functionalities whereas absorption of either carbonyl or NH2 group is absent (see Table 2).
This confirms the intramolecular amidation of the ortho amino group in the corresponding
triazole derivative (P14) during the reaction of (P3) with (4) resulting in formation of the
corresponding polymer-supported 2-benzimidazolyltriazolyl derivative (P6) as suggested
before. Scheme 5 shows two possible inter-convertible forms for (P6) through either
tautomerization or free rotation around the bond linking the 2-benzimidazolyl and the 1,2,4triazolyl moieties in (P6). Also, elemental analysis (C; 68.68, H; 4.92, N; 19.48 & Cl; 5.08)
confirmed the formation of (P6) in 67% conversion and 30% overall reaction yield as shown
in Table 1.
Scheme 5
3.5. Application of (P2) - (P6) as metal chelating matrix for Cu(II) ions:
The obtained modified PVC samples (P2) - (P6) were treated with an aqueous
solution of copper acetate to check roughly their ability to form chelates with Cu(II) ions. The
metal uptake by the modified PVC samples was determined through back determination of
the excess Cu(II) ions in the filtrate while the metal-loaded samples (P2M) - (P6M) were
subjected to FT-IR spectroscopic analysis (see Table 2). The raw data for metal uptake by
these polymers are listed in Table 1. FT-IR characterization of the metal-loaded samples (P2)
- (P6) proved the metal chelation of the above mentioned polymeric samples with Cu(II) ions.
The concerned absorption peaks are shifted after treatment with the metal ion solution as
shown in Table 1. Scheme 6 represents the different structural forms of the investigated
samples (P3) - (P6) and the more favorable forms for chelation have been framed. (P2) is not
included in Scheme 6 because it has only one possibility for chelation as it is a monodentate
matrix.
Scheme 6
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Lassalle, V.L.; Failla, M.D.; Valles, E.M. and Martin-Martinez, J.M., J. Adhes. Sci.
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[4]
Izaoumen, N.; Bouchta, D.; Zejli, H.; El Kaoutit, M.; Stalcup, A.M. and Temsamani,
K.R., Talanta, 66(1), 111 (2005).
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Mathiyarasu, J.; Senthilkumar, S.; Phani, K.L.N. and Yegnaraman, V., J. Appl.
Electrochem., 35(5), 513 (2005).
[6]
Sarhan, A.A.; Abdelaal, M.Y.; Ali, M.M. and Abdel-Latiff, E.H., Polymer 40, 233
(1998).
[7]
Sarhan, A.A.; El-Shehawy, A.A. and Abdelaal, M.Y., React. Funct. Polym. 50(2), 139
(2002).
[8]
Abdelaal, M.Y.; Kenawy, I.M.M. and Hafez, M.A.H., J. Appl. Polym. Sci. 77(14), 3044
(2000).
[9]
Sarhan, A.A.; Afsah, E.M.; Abdelaal, M.Y. and Ibrahim, M.R., React. Funct. Polym. 32,
231 (1997).
[10] Sobahi, T.R., Mans. J. Chem. 32(2), 73 (2005).
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Polym. Degrad. Stab. 57, 283 (1997).
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CAPTIONS
Scheme 1: Modification of (P1) into polymer-supported oxazolinone and triazole (P2) - (P6)
Scheme 2: Formation of the polymer-supported oxazolinone derivative (P3)
Scheme 3: Reaction of (P3) with (1) and (3)
Scheme 4: Outlines for the possible mechanism of the reaction of (P3) with (1) and (3)
Scheme 5: Suggested mechanism for the reaction of (P3) with (4)
Scheme 6: Metal chelates of the obtained polymeric samples (P3) - (P6)
Table 1: Elemental analysis data and metal uptake for the chemically modified (P1)
Table 2: FT-IR spectroscopic data for the chemically modified (P1)
NH2
H2N
CH2
CH
Cl
(1)
i. NaNO 2 /HCl
ii. Hippuric acid (2)
P
n
P
NH
NH2
(P1)
N
(P2)
O
NH 2
N
O
Ph
R
P
P
P
N
Ph
N
N
N
O
HN
N H
N
=
CH 2 CH
NH
Ph
N
N
(P6)
(P3)
R = p-NH 2 (1)
= p-OH (3)
R = o-NH 2 (4)
R
(P4) & (P5)
Scheme 1
x = 0.30
= 0.45
= 0.35
= 0.32
= 0.30
( P2)
( P3)
( P4)
( P5)
( P6)
R = p-NH 2 ( 1, P4)
= p-OH ( 3, P5)
= o-NH 2 ( 4)
x
i. NaNO 2 /HCl
ii. Hippuric acid (2)
P
P
P
N
NH2
NH
N
(P2)
N
H
O
O
N
HO
P
O
O
N
(P7a)
N
Ph
(P7c)
(P7b)
OH/CO 2 H
inte raction
P
NH
O
NH
N
O
O
O
N
Ph
(P3a)
Scheme 2
N
O
OH
O
(P3b)
Ph
N
Ph
(P3c)
P
N
H
N
O
Ph
P
N
N
N
OH/NH
interaction
P
N
Ph
HO
HO HO
Ph
NH
OH
N
(P8)
P
P
P
NH2
NH
N
O
N
R
(1), (3)
N
Ph
N
N
H
O
N
N
O
N H
O
Ph
N
N
Ph
(P3)
R = NH 2 (1), (P4)
R = OH (3), (P5)
R
R
(P4a) & (P5a)
(P4b) & (P5b)
Scheme 3
P
P
NH2
NH
NH
N
N
NH
HO
R
O
(1)&(3)
(P3)
O
N
N
Ph
N
O
+
O
P
NH
OH
N
NH
Ph
R
R
(P9a) & (P10a)
(P9b) & (P10b)
- H2O
- H2O
P
P
N
P
N
NH
N
HO
N
N
N
N
Ph
O
N H
N
O
Ph
N
N
Ph
R
R
(P4a) & (P5a)
(P11b) & (P12b)
R
(P11a) & (P12a)
P
P
N
NH
N
N
Ph
P
N
N
OH
N
N
Ph
O
N
R
(P11d) & (P12d)
R = NH2 (1), (P4), (P9), (P11)
N
HO
N
R
(P11c) & (P12c)
Ph
N
R
(P4b) & (P5b)
R = OH (3), (P5), (P10), (P12)
Scheme 4
Ph
P
P
NH2
NH
N
NH
N
NH2
+
O
H2N
N
O
O
H2N
NH
HO
(P3)
O
Ph
N
NH
Ph
(P13a)
(P13b)
- H2O
P
NH
OH
N
N
(4)
Ph
P
- H2O
P
N
N
N
HO
Ph
N
N
NH
O
N
N
H2N
N
P
H2N
Ph
N H
N
O
N
H2N
P
N
Ph
(P15b)
(P14a)
P
- H2O
N
HO
H2N
(P15a)
N
Ph
N
N
N
H
- H2O
N
N
P
N
(P14b)
Ph
N
Ph
N
(P16a)
H
N
N
P
N
P
N
P
Ph
N
N
N
N
H
N
H
N
N
Ph
(P6a)
N H
N
N
N
N
N
N
Ph
(P6b)
(P16b)
(P16c)
Scheme 5
P
N
N
P
P
N
+
N
O
N
O
Ph
N
+
Cu N
Ph
N
+
N
(P3Mc)
P
N
N
O
Ph
(P3Mb)
P
Ph
R
(P4Ma)&(P5Ma)
+ N
Cu
P
N
N
Ph
N
N
R
(P4Mb)&(P5Mb)
Scheme 6
Ph
N
N
O
Cu
O
O
Ph
P
Cu
N
O
(P3Ma)
N
N
Cu
Cu
O
+
N
+
N
N
N
N
N
(P6Ma)
(P6Mb)
+
Cu
Table 1: Elemental analysis data and metal uptake for the chemically modified (P1)
Sample
P1
P2
P3
P4
P5
P6
C (%)
H (%)
38.38
69.32
65.18
66.11
66.94
68.68
4.78
7.08
4.45
5.12
4.88
4.92
Elemental Analysis Data
Conversion
N (%) Cl (%)
(%)
56.80
17.44
9.39
70
17.07
5.69
64
19.06
4.78
78
16.66
4.88
71
19.48
5.08
67
Overall
Yield (%)
70
45
35
32
30
Metal Uptake
(mg/g)
285
150
200
205
105
Table 2: FT-IR spectroscopic data for the chemically modified (P1)
Sample
P1
P2
P3
P4
P5
P6

705
1675
2850
3480
3350
1590
3320
1621
1050
3500
1590
3350
1670
1620
3480
3500
1590
3350
1670
1622
3500
1590
3300
1624
Metal-Unloaded Polymer
Description
-C-Cl
-C=C-CH-N-NH2
-NH
C=C aromatic
-NH
-C=N-C-O-C-OH
C=C aromatic
-NH
-CONH-C=N-NH2
-OH
C=C aromatic
-NH-CONH-C=N-OH
C=C aromatic
-NH-C=Nabsence of C=O, NH2
(cm-1)

705
1673
3460
Metal-Loaded Polymer
Description
-C-Cl
-C=CShift of NH2 absorption peak
due to possible chelating
(cm-1)
1572
1675
1658
-N=N-C=C-C=C-O-.+Metal
1612
3460
-N=C-O-.+Metal
Shift for NH2 absorption peak
1613
3482
-N=C-O-.+Metal
Ph-O-.+Metal
3289
Shift of NH- absorption peak
due to possible chelating
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