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Radiation preparation and application of the linear thermosensitive binary copolymers
Radiat. Phys. Chem. Vol. 52. Nos I
6, pp. 261 264, 1998 IS" 1998ElsevierScienceLtd. All rightsreserved Printed in Great Britain PII: S0969-806X(98)00152-2 o969-8o6x/98s19.oo+ 0.00
Pergamon
RADIATION
PREPARATION
LINEAR
THERMOSENSITIVE
AND APPLICATION BINARY
OF THE
COPOLYMERS
YI MIN, LI JUN, ZHANG JIANBO, JIANG GUILIN, QIN JIANHUA, AND HA HONGFEI Department of Technical Physics, Peking University, Beijing 100871, China ABSTRACT Linear poly(NIPAAm-co-X), with X being AAc or 4-VP, was synthesized by means of y radiation induced polymerization in tetrahydrofuran (THF). The binary copolymers obtained are possessed of water-soluble, temperature sensitivity. It was also found that raising pH leads to a higher LCST when X is AAc. Prepared copolymers were used to concentrate metal ions, such a s UO22*iCRE3+and Cr(VI) in dilute aqueous solution, which showd obvious concentration effect. The conditions of ion concentration were given and the mechanism was discussed preliminary. KEYWARDS Radiation polymerization, Temperature sensitivity, Poly(NIPAAm-co-X), Concentration of metal ions INTRODUCTION Linear polymers, with N-isopropylacrylamide (NIPAAm) as main monomer, demonstrate good solubility in aqueous solutions at low temperatures but separate from solution when the temperature is raised above the lower critical solution temperature(LCST). Because this kind of polymer has temperature sensitivity and is easily intellectualized (Ngugenand,1989; Ta1,1972), it has received increasing attention in recent years for applications such as chemical separation, biomolecule coupling, and drug purification. Authors ever used white powder product of polyNIPAAm synthesized by means of'/radiation induced polymerization to concentrate and separate metal ions from dilute aqueous solution, which showed high concentration effect for Au 3÷ but no tangible proofs for UO22+ etc.(Yi,1993). In this paper, the Linear thermosensitive binary copolymers , poly(NIPAAm-co-X), X being AAc or 4-VP, were prepared and used to study the concentration effect for matel ions UO22+, RE 3+, and Cr(VI) etc.. Results showed a good prospect in chemical seperation. EXPERIMENTAL Materials
N-isopropylacrylamide (NIPAAm), from Kodak Chem. Co., was recrystallized by using solvent of benzene and n-hexene (1:1). Acrylic acid (AAc), from Beijing Chem. Co., and 4-VP, 96%, from Zur Synthese Merck-Schuchardt, Germany, were purified by decompress distillation. Other organic solvents, including tetrahydrofuran (THF) and diethyl ether etc., domestic products, were used without further purification. Infrared spectrometer, 683 model, Pekin Elmer, USA; all other apparatus used including 6°Co radiation equipment, spectrophotometry etc. are domestic. Method
Copolymer synthesis. Synthesis of linear poly (NIPAAm-co-X), with X=AAc, 4VP, was carried out by means of y radiation induced polymerization in THF in ~b-14mm radiation glass tube sealed. Dried nitrogen was bubbled through the transparent solution for 20min prior to polymerization. After polymerization at room 261
Yi Minet al.
262
temperature, the copolymer was precipitated by adding 5 volumes of diethyl ether and then product was obtained after washing and drying. Metal Ion Concentration Determination Ion Cr(VI) was determined by sys-Diphenyl Carbaxide regent, R E 3~ and UO22" by uranium reagent (III) colorimetric analysis, detailed method showed reference (Chen, 1983). RESULTS AND DISCUSSION
Effect of the polymerization condition on the property of the product Effect of the dose and the dose rate on the property of the copolymer According to the previous work (Yi, 1993), radiation dose D = 1--7 kGy, dose rate 40Gy/min are suitable for polymerization of linear thermosensitive polymer. Dose of 3.0 kGy and dose rate 40 Gy/min were chosen for copolymerization of NIPAAm--AAc, with amounts of AAc <20%, white powder of copolymer exhibiting LCST 30.3 iaewas obtaind. For copolymer of NIPAAm-4VP, however, until 8.3 kGy, white powder of copolymer with LCST (27--29i~e) was obtained, as a result of 4VP is more stable than AAc under radiation and hence higher dose is needed for copolymerization of NIPAAm--4VP. No effect of dose rate on both copolymerization was observed. Infrared spectrum ofpoly(NIPAAm--co--AAc) and poly(NIPAAc--co--4VP) IR spectrum of copolymers synthesized above was showed in Fig. 1.
pNIPA,~n
1 PNIPA.&m-c,o-AAc
PNIPAAm-.co-4VP
t
Fig. 1 IR spectrum of polymers Comparing IR spectrum of poly(NIPAAm-co-X) with that of polyNIPAAm, -COOH peaks of 1088 and 1049 were found when X was AAc and pyridine peaks of 1600,1548, 1090, and 823 were found when X was 4VP. These results showed AAc and pyridine was existed in the copolymer respectively. Effect ofpH on LCST of copolymer At various pH systems, LCSTs of poly(NIPAAm--co--AAc) were measured separately, it was found that the linear copolymer had the pH sensitivity as well (shown in Fig.2).
10th International Meeting on Radiation Processing
o0
263
45
_J
25
. ,., ,, ,~., 1.5 2.0 2.5 3 . ~ ) d . 5
4.0
.,. 4.5
, 5.0
Fig.2 Effect ofpH on LCST From Fig.2, it can be seen that increasing the pH from 1.83 to 4.95 led to an increased LCST for poly(NIPAAm--AAc), while data of LCST were 32.6i2e at various pH, with pH=3.60, 4.00 and 5.60 for polyNIPAAm. The results suggest that the copolymer containing COOH group is charged by ionizing at high pH, and charge density plays a critical role in determining the LCST of the polymers. Increasing charge leads to a large increase in LCST.
Application of linear binary copolymer in concentration of metal ions in aqueous solution Concentration of UO22+ ions UO22~ ions were concentrated from the dilute aqueous solution in which [UO22~] was 3.18i,~10 -4 mol/L by using the solution of 1 g/L poly(NIPAAm-co-AAc), with AAc amount 10.9%. Concentration yields at various pH were given in table 1 Table 1. Effect ofpH on concentration of UO22~ions pH
2.28
3.18
3.48
3.78
CY*
0
10.7
38.8
56.6
cY: concentrationyiled From table 1, it can be seen that concentration effect of copolymer for UO22" was found at pH 3, the concentration yield increased rapidly with a little increase in pH, because six-element-ring compound of COOH with UO22÷ was formed. No concentration effect was observed when using polyNIPAAm at various pH though amount of polymer used was increased. Continuous increasing pH value of the systems will be meaningless because of the lacking stability of UO22+ in the systems where the pH is higher than 4. Concentration of RE 3+ions Ion R E 3~- w a s separated from aqueons solution by using 1.0g/L ofpoly(NIPAAm-co-AAc) and 2.0g/1 of polyNIPAAm respectively, with various RE 3÷ ion concentrations at constant pH and various pH at constant ion concentration. Results were given in Fig.3. From Fig.3, it can be seen that the concentration effect of poly(NIPAAm-co-AAc) is higher than that of polyNIPAAm, which was found not only for Er 3~ but for Nd3-,Ga 3+ and Tm 3~ etc.. Because polyNIPAAm is nonionizing polymer that wasn't influenced by pH, on the contrary, poly(NIPAAm-co-AAc) takes place ionization at high pH which does good to ion concentration, pH 2 to 4 was suggested when hydrolysis of these metal ions was considered.
264
Yi M i n e t al.
100-
NIPA,,a,r~AAc) 1.0g/I
1130NIP~AAc) 1.0g/I
80-
80-
•
-"--602.
~60.
v
n,4o~
0
,
2
~CIPAAM 2.0g/I
40
z~ 3
,
4
,
5
20
6
'
0
pH
I
5
'
I
'
I
'
I
'
I
'
I
'
I
'
10 15 20 25 30 35 q r 3 . X l 0 -6 (g/ITIJ)
Fig.3 Effect ofpH and ion concentration on concentration yield
Concentration of Cr(VI) using polymers that have different molecular weight Cr(VI), 1 g/L , at pH 2.5--3.0, was concentrated by using products synthesized above. Molecular weight of polymers was calculated by using equation of [rl] = KMv ~, where ct=0.5, K=14.5iAI0 2 . Measurement of polymer intrinsic viscosity was carried out at 20.0_+0.1i~e. The effect of raising molecular weight of copolymer on concentration yeild is not obvious. The good concentration effect was obtained by using polyNIPAAm whose Mv is 2.2i,h,105--4.2iA105, which suggests a good prospect in controlling of water pollution. Concerned research is in progress. CONCLUSIONS 1. The linear thermosensitive binary copolymers, poly(NIPAAm-co-X), with X being AAc or 4-VP, were synthesized by means of 7 radiation induced polymerization in tetmhydrofuran (THF). 2.Poly(NIPAAm-co-AAc) was also possessed ofpH sensitivity. 3.Metal ions UO22+, RE 3+ and Cr(VI) were concentrated by using copolymers or polyNIPAAm synthsized above, which suggest a good prospect in chemical concentration. REFERENCES
Chen G. Z. and Huanj X. Z. (1983) UV-visible Spectrophotometer, Atomic Energy Press Beijing,China). Nguyenand A. L. and Luong J. H. T. (1989) Synthesis and Application of Water-soluble, Reactive Polymers for Purification and Immobilization of Biomolecules. Biotech. and Bioeng. 34, 1186. Tae Gwan Park and Hoffman Allan S. (1972) Synthesis and Characterization of pH and /or Temperature Sensitive Hydrogels. J. Applied Polymer Science 46, 659. Yi M., Li J., and Ha H. F. (1993) Radiation Preparation of the Water-soluble Temperature Sensitive Polymers in Organic Solvents. Radiat. Phys. Chem. 46 (4-6), 855.
6, pp. 261 264, 1998 IS" 1998ElsevierScienceLtd. All rightsreserved Printed in Great Britain PII: S0969-806X(98)00152-2 o969-8o6x/98s19.oo+ 0.00
Pergamon
RADIATION
PREPARATION
LINEAR
THERMOSENSITIVE
AND APPLICATION BINARY
OF THE
COPOLYMERS
YI MIN, LI JUN, ZHANG JIANBO, JIANG GUILIN, QIN JIANHUA, AND HA HONGFEI Department of Technical Physics, Peking University, Beijing 100871, China ABSTRACT Linear poly(NIPAAm-co-X), with X being AAc or 4-VP, was synthesized by means of y radiation induced polymerization in tetrahydrofuran (THF). The binary copolymers obtained are possessed of water-soluble, temperature sensitivity. It was also found that raising pH leads to a higher LCST when X is AAc. Prepared copolymers were used to concentrate metal ions, such a s UO22*iCRE3+and Cr(VI) in dilute aqueous solution, which showd obvious concentration effect. The conditions of ion concentration were given and the mechanism was discussed preliminary. KEYWARDS Radiation polymerization, Temperature sensitivity, Poly(NIPAAm-co-X), Concentration of metal ions INTRODUCTION Linear polymers, with N-isopropylacrylamide (NIPAAm) as main monomer, demonstrate good solubility in aqueous solutions at low temperatures but separate from solution when the temperature is raised above the lower critical solution temperature(LCST). Because this kind of polymer has temperature sensitivity and is easily intellectualized (Ngugenand,1989; Ta1,1972), it has received increasing attention in recent years for applications such as chemical separation, biomolecule coupling, and drug purification. Authors ever used white powder product of polyNIPAAm synthesized by means of'/radiation induced polymerization to concentrate and separate metal ions from dilute aqueous solution, which showed high concentration effect for Au 3÷ but no tangible proofs for UO22+ etc.(Yi,1993). In this paper, the Linear thermosensitive binary copolymers , poly(NIPAAm-co-X), X being AAc or 4-VP, were prepared and used to study the concentration effect for matel ions UO22+, RE 3+, and Cr(VI) etc.. Results showed a good prospect in chemical seperation. EXPERIMENTAL Materials
N-isopropylacrylamide (NIPAAm), from Kodak Chem. Co., was recrystallized by using solvent of benzene and n-hexene (1:1). Acrylic acid (AAc), from Beijing Chem. Co., and 4-VP, 96%, from Zur Synthese Merck-Schuchardt, Germany, were purified by decompress distillation. Other organic solvents, including tetrahydrofuran (THF) and diethyl ether etc., domestic products, were used without further purification. Infrared spectrometer, 683 model, Pekin Elmer, USA; all other apparatus used including 6°Co radiation equipment, spectrophotometry etc. are domestic. Method
Copolymer synthesis. Synthesis of linear poly (NIPAAm-co-X), with X=AAc, 4VP, was carried out by means of y radiation induced polymerization in THF in ~b-14mm radiation glass tube sealed. Dried nitrogen was bubbled through the transparent solution for 20min prior to polymerization. After polymerization at room 261
Yi Minet al.
262
temperature, the copolymer was precipitated by adding 5 volumes of diethyl ether and then product was obtained after washing and drying. Metal Ion Concentration Determination Ion Cr(VI) was determined by sys-Diphenyl Carbaxide regent, R E 3~ and UO22" by uranium reagent (III) colorimetric analysis, detailed method showed reference (Chen, 1983). RESULTS AND DISCUSSION
Effect of the polymerization condition on the property of the product Effect of the dose and the dose rate on the property of the copolymer According to the previous work (Yi, 1993), radiation dose D = 1--7 kGy, dose rate 40Gy/min are suitable for polymerization of linear thermosensitive polymer. Dose of 3.0 kGy and dose rate 40 Gy/min were chosen for copolymerization of NIPAAm--AAc, with amounts of AAc <20%, white powder of copolymer exhibiting LCST 30.3 iaewas obtaind. For copolymer of NIPAAm-4VP, however, until 8.3 kGy, white powder of copolymer with LCST (27--29i~e) was obtained, as a result of 4VP is more stable than AAc under radiation and hence higher dose is needed for copolymerization of NIPAAm--4VP. No effect of dose rate on both copolymerization was observed. Infrared spectrum ofpoly(NIPAAm--co--AAc) and poly(NIPAAc--co--4VP) IR spectrum of copolymers synthesized above was showed in Fig. 1.
pNIPA,~n
1 PNIPA.&m-c,o-AAc
PNIPAAm-.co-4VP
t
Fig. 1 IR spectrum of polymers Comparing IR spectrum of poly(NIPAAm-co-X) with that of polyNIPAAm, -COOH peaks of 1088 and 1049 were found when X was AAc and pyridine peaks of 1600,1548, 1090, and 823 were found when X was 4VP. These results showed AAc and pyridine was existed in the copolymer respectively. Effect ofpH on LCST of copolymer At various pH systems, LCSTs of poly(NIPAAm--co--AAc) were measured separately, it was found that the linear copolymer had the pH sensitivity as well (shown in Fig.2).
10th International Meeting on Radiation Processing
o0
263
45
_J
25
. ,., ,, ,~., 1.5 2.0 2.5 3 . ~ ) d . 5
4.0
.,. 4.5
, 5.0
Fig.2 Effect ofpH on LCST From Fig.2, it can be seen that increasing the pH from 1.83 to 4.95 led to an increased LCST for poly(NIPAAm--AAc), while data of LCST were 32.6i2e at various pH, with pH=3.60, 4.00 and 5.60 for polyNIPAAm. The results suggest that the copolymer containing COOH group is charged by ionizing at high pH, and charge density plays a critical role in determining the LCST of the polymers. Increasing charge leads to a large increase in LCST.
Application of linear binary copolymer in concentration of metal ions in aqueous solution Concentration of UO22+ ions UO22~ ions were concentrated from the dilute aqueous solution in which [UO22~] was 3.18i,~10 -4 mol/L by using the solution of 1 g/L poly(NIPAAm-co-AAc), with AAc amount 10.9%. Concentration yields at various pH were given in table 1 Table 1. Effect ofpH on concentration of UO22~ions pH
2.28
3.18
3.48
3.78
CY*
0
10.7
38.8
56.6
cY: concentrationyiled From table 1, it can be seen that concentration effect of copolymer for UO22" was found at pH 3, the concentration yield increased rapidly with a little increase in pH, because six-element-ring compound of COOH with UO22÷ was formed. No concentration effect was observed when using polyNIPAAm at various pH though amount of polymer used was increased. Continuous increasing pH value of the systems will be meaningless because of the lacking stability of UO22+ in the systems where the pH is higher than 4. Concentration of RE 3+ions Ion R E 3~- w a s separated from aqueons solution by using 1.0g/L ofpoly(NIPAAm-co-AAc) and 2.0g/1 of polyNIPAAm respectively, with various RE 3÷ ion concentrations at constant pH and various pH at constant ion concentration. Results were given in Fig.3. From Fig.3, it can be seen that the concentration effect of poly(NIPAAm-co-AAc) is higher than that of polyNIPAAm, which was found not only for Er 3~ but for Nd3-,Ga 3+ and Tm 3~ etc.. Because polyNIPAAm is nonionizing polymer that wasn't influenced by pH, on the contrary, poly(NIPAAm-co-AAc) takes place ionization at high pH which does good to ion concentration, pH 2 to 4 was suggested when hydrolysis of these metal ions was considered.
264
Yi M i n e t al.
100-
NIPA,,a,r~AAc) 1.0g/I
1130NIP~AAc) 1.0g/I
80-
80-
•
-"--602.
~60.
v
n,4o~
0
,
2
~CIPAAM 2.0g/I
40
z~ 3
,
4
,
5
20
6
'
0
pH
I
5
'
I
'
I
'
I
'
I
'
I
'
I
'
10 15 20 25 30 35 q r 3 . X l 0 -6 (g/ITIJ)
Fig.3 Effect ofpH and ion concentration on concentration yield
Concentration of Cr(VI) using polymers that have different molecular weight Cr(VI), 1 g/L , at pH 2.5--3.0, was concentrated by using products synthesized above. Molecular weight of polymers was calculated by using equation of [rl] = KMv ~, where ct=0.5, K=14.5iAI0 2 . Measurement of polymer intrinsic viscosity was carried out at 20.0_+0.1i~e. The effect of raising molecular weight of copolymer on concentration yeild is not obvious. The good concentration effect was obtained by using polyNIPAAm whose Mv is 2.2i,h,105--4.2iA105, which suggests a good prospect in controlling of water pollution. Concerned research is in progress. CONCLUSIONS 1. The linear thermosensitive binary copolymers, poly(NIPAAm-co-X), with X being AAc or 4-VP, were synthesized by means of 7 radiation induced polymerization in tetmhydrofuran (THF). 2.Poly(NIPAAm-co-AAc) was also possessed ofpH sensitivity. 3.Metal ions UO22+, RE 3+ and Cr(VI) were concentrated by using copolymers or polyNIPAAm synthsized above, which suggest a good prospect in chemical concentration. REFERENCES
Chen G. Z. and Huanj X. Z. (1983) UV-visible Spectrophotometer, Atomic Energy Press Beijing,China). Nguyenand A. L. and Luong J. H. T. (1989) Synthesis and Application of Water-soluble, Reactive Polymers for Purification and Immobilization of Biomolecules. Biotech. and Bioeng. 34, 1186. Tae Gwan Park and Hoffman Allan S. (1972) Synthesis and Characterization of pH and /or Temperature Sensitive Hydrogels. J. Applied Polymer Science 46, 659. Yi M., Li J., and Ha H. F. (1993) Radiation Preparation of the Water-soluble Temperature Sensitive Polymers in Organic Solvents. Radiat. Phys. Chem. 46 (4-6), 855.