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Synthesis and properties of poly(phthalazinone ether ketone ketone)s containing pendent methyl groups
Materials Science and Engineering B 132 (2006) 20–23
Synthesis and properties of poly(phthalazinone ether ketone ketone)s containing pendent methyl groups Lei Ying, Xiao-Ling Yang, Juan Feng, Chen-Yi Wang, Lin Cheng ∗ Department of Materials Science and Engineering, Huaqiao University, Quanzhou, Fujian 362021, China
Abstract A new class of poly(phthalazinone ether ketone ketone)s has been prepared by aromatic nucleophilic displacement polycondensation from an activated dichloride monomer 1 and several phthalazinone containing bisphenol-like monomers 2a–c. The formation of the polymers was confirmed by FT-IR and 1 H NMR spectra, and the synthesized polymers 3a–c have good solubility in common organic solvents, high glass transition temperatures (Tg s) in range of 239–255 ◦ C and excellent thermal stability. Moreover, tough, flexible and transparent thin films can be readily prepared by both spin coating and solution casting approach. Good solubility in common organic solvents coupled with salient thermal stability demonstrates this class of polymers could be excellent candidate for high performance polymers. © 2006 Elsevier B.V. All rights reserved. Keywords: Soluble; Poly(arylene ether)s; Phthalazinone; 1,4-Bis(chlorobenzoyl)benzene
1. Introduction The pursuance of high performance polymers as matrix resins in advanced composites for application in aerospace and military industries has attracted much attention. Thermoplastic high performance polymers have unique combination of chemical, physical and mechanical properties as well as the potential for low-cost composite fabrication. Being an important class of thermoplastic polymers, poly(arylene ether)s were used extensively because of their excellent comprehensive properties. Generally, poly(arylene ether)s are prepared by the aromatic nucleophilic displacement reaction of an activated aromatic dihalide compound with an alkali metal bis-phenolate in polar aprotic medium. Since dichloro monomers are much cheaper than the corresponding difluorides, many efforts were paid to prepare cost-effective poly(arylene ether)s via dichloro monomers. It is well known that aromatic polymers containing heterocyclic rings would have much higher glass transition temperatures and better mechanical properties after the introduction of heterocyclic rings into polymer backbone. Representative heterocyclic groups that have been incorporated in poly(arylene ether)s include imide, phenylquinoxaline, imidazole, 1,3,4-oxadiazole, benzoxazole, benzimidazole, benzothiazole, pyrazine, etc. Among them, phthalazinone-based poly-
mer families have received much interests recently, because the asymmetric, kink and non-coplanar phthalazinone moiety could impart polymers good solubility without scarifying their good thermal stability and mechanical properties [1–4]. In continuation of our efforts [2–4] to improve upon the properties of phthalazinone-based polymers by rational molecular design of monomers, we have prepared a series of soluble poly(phthalazinone ether ketone ketone)s (PPEKKs) from 1,4-bis(chlorobenzoyl)benzene 1 and some derivatives of 4(4-hydroxyphenyl)-2,3-phthalazin-1-one 2a–c via a novel N–C coupling reaction. Evidently, it is a versatile and cost-effective approach of preparing phthalazinone containing high performance polymers [5–7]. Our synthetic procedure allows the incorporation of a variety of substituted methyl groups into the backbone of this class of polymers via several different kinds of phthalazinone containing bisphenol-like monomers as shown in Scheme 1. The resultant polymers have interesting variations of properties that may arise out of pendent methyl groups. In this article, synthesis and properties of a series of poly(phthalazinone ether ketone ketone)s containing pendent methyl groups will be discussed in detail. 2. Experimental 2.1. Materials
∗
Corresponding author. Fax: +86 595 22686969. E-mail address: [email protected] (L. Cheng).
0921-5107/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.mseb.2006.02.005
All materials were commercially available and used as received unless otherwise noted. 1,4-Bis(chlorobenzoyl) ben-
L. Ying et al. / Materials Science and Engineering B 132 (2006) 20–23
21
Scheme 1. Synthesis of poly(phthalazinone ether ketone ketone)s.
zene (1) was synthesized according to the literature procedure [8], recrystallized from N,N-dimethylacetamide (DMAc) and dried under vacuum for 10 h prior to use. 4-(2-Methyl-4-hydroxyphenyl)-2,3-phthalazin-1-one (2a), 4-(3-methyl-4-hydroxy phenyl)-2,3-phthalazin-1-one (2b) and 4-(2,3-dimethyl-4hydroxyphenyl)-2,3-phthalazin-1-one (2c) were synthesized according to the literature procedure [7,9] and recrystallized from N,N-dimethylformamide (DMF) and dried under vacuum for 10 h prior to use.
was observed, respectively. Inherent viscosities (ηinh = ln ηr /c) were measured at a concentration of 0.5 g dL−1 in chloroform at 30 ◦ C with Ubbelohde viscometer. Solubility of polymers was determined using 2 mg of polymer in 3 ml of solvent. WAXD patterns were obtained at room temperature on a Rigaku D/MAX 2500 powder diffractometer with scanning speed of 4◦ min−1 and recorded the patterns in 2θ range of 10–40◦ .
2.2. Synthesis of polymer
As depicted in Scheme 1, a new class of poly(phthalazinone ether ketone ketone)s 3a–c was synthesized by the reaction of an activated dichloride monomer 1 and several phthalazinone containing bisphenol-like monomers 2a–c in a dipolar aprotic medium of DMAc. During the polymerization, the phthalazinone NH group behaves like phenolic OH groups, thereby the polymers could be formed from a novel N C coupling reaction through step growth polycondensation. In all cases, the polymers were obtained with quantitative yields and the inherent viscosities (ηinh ) ranged from 0.39 to 0.56 as shown in Table 1. The formation of poly(phthalazinone ether ketone ketone)s was confirmed by FT-IR and 1 H NMR spectroscopic data. The FT-IR spectrum of polymer 3a clearly exhibits the characteristic absorption at about 1668 (C O), 1597 and 1496 (aromatic rings), and 1245 cm−1 (C O C), respectively. There was no absorption in the range of 3100–3400 cm−1 of the characteristic absorption for NH and −OH. Moreover, the comparison of 1 H NMR spectra of monomer 2a and polymer 3a is shown in Fig. 1. Two sharp peaks of 12.8 and 9.6 ppm corresponding to phthalazinone N H and phenolic O H protons were absent in polymer spectrum, and all other peaks shift to lower fields comparing to the monomer. The spectroscopic data of other polymers
The synthesis of this class of poly(arylene ether)s was conducted in a similar method, and typical procedure was described as follows. A 100 ml three-necked flask equipped with a nitrogen inlet, mechanical stirrer, and Dean-Stark trap fitted with a condenser was charged with 1.7761 g (5 mmol) of 1 and 1.2614 g (5 mmol) of 2a. The monomers were carefully washed into flask with 15 ml of DMAc. An excess of K2 CO3 (1.04 g, 7.5 mmol) and approximate 10 ml toluene were added. The mixture was heated to 140 ◦ C for more than 5 h to ensure complete dehydration. After toluene was removed by Dean-Stark trap, the temperature was increased to 165 ◦ C and maintained at this temperature for more than 10 h until it became very viscous. The mixture was precipitated into 400 ml of methanol–water (1:1) solution containing 4 ml acetic acid with vigorous stirring followed by filtration. The resultant polymer 3a was washed thoroughly with hot water and then dissolved with chloroform and precipitated in methanol. After filtered, it was dried at 150 ◦ C under vacuum overnight. The yields were essentially quantitative for all the polymerization (>95% yield).
3. Results and discussion
2.3. Characterizations 1H
NMR spectra were measured on a Bruker AM-300 MHz instrument with dimethylsulfoxide (DMSO-d6 ) or chloroform (CDCl3 ) as solvent and tetramethylsilane (TMS) as internal standard. IR spectra (films for polymers) were recorded on a Nicolet Magna 470 spectrometer. Glass transition temperatures (Tg s), taken as the midpoint of the change in the slope of the baseline, were measured on a TA 5200-M DSC instrument at a heating rate of 10 ◦ C min−1 in N2 . Thermal gravimetric analysis (TGA) of the polymer samples was measured on a DuPont2000 SDT-2960 instrument at a heating rate of 20 ◦ C min−1 in N2 , and Td5 and Td10 reported as the temperature at which 5 and 10% weight loss
Table 1 Properties of poly(phthalazinone ether ketone ketone)s Polymer
ηinh a (g dL−1 )
Tg (◦ C)
Td5 b (◦ C)
Td10 c (◦ C)
800 ◦ C residued (%)
1a 1b 1c
0.56 0.42 0.39
242 239 255
447 460 431
520 530 446
70 70 66
Measured at a concentration of 0.5 g dL−1 in CHCl3 at 30 ◦ C. Temperature of 5% weight loss determined in nitrogen. c Temperature of 10% weight loss determined in nitrogen. d Char yield calculated as the percentage of solid residue after heating from room temperature to 800 ◦ C in nitrogen. a
b
22
L. Ying et al. / Materials Science and Engineering B 132 (2006) 20–23
Table 2 Solubility of poly(phthalazinone ether ketone ketone)s Polymer
CHCl3
DMAc
DMF
NMP
THF
Pyridine
m-Cresol
Concentrated H2 SO4
3a 3b 3c
++ ++ ++
+ + +
+− − −
++ ++ ++
+− +− +−
++ ++ ++
++ + ++
++ ++ ++
+ +: fully soluble at room temperature; +: soluble; + −: partially soluble; −: insoluble.
gave the similar results as polymer 3a, which demonstrated the structures were well matched with assigned. The thermal behavior of the polymers was investigated by DSC and TGA as reported in Table 1. As expected, the polymers 3a–c exhibit comparatively high Tg s ranged from 239 to 255 ◦ C, which may primarily attribute the incorporation of kink, bulky phthalazinone architecture into polymer backbone could not singly restrict segmental mobility and hinder the chain rotation but also significantly enhance the entanglement of polymer backbone. All the polymers were stable up to 430 ◦ C in nitrogen, and their thermal degradation occurs in two-stage process because the scission of the pendent methyl groups may occur before the cleavage of the bonds of polymer backbone. Furthermore, the excellent thermal stability of these polymers, taking polymer 3a, for example, was confirmed by the high percentage of solid residue after heating from room temperature to 800 ◦ C in nitrogen as shown in Fig. 2. As can be seen in Table 2, all synthesized polymers exhibit excellent solubility in common organic solvents such as chloroform, pyridine and N-methylpyrrolidinone (NMP). Probably, this can be ascribed that the polymer main chain was twisted by the kink, non-coplanar phthalazinone architecture. And as a result, tough, flexible and transparent thin films could be easily prepared by spin coating or casting processes, which make them potentially useful as high temperature membrane. According to wide-angle X-ray diffraction and thermal analysis, all of the polymers are amorphous because the kink phthalazinone architecture inhibits molecular packing into regular structures. Indeed, only a very broad diffraction trace was observed by wide-angle X-ray scatter. Moreover, there is no
Fig. 2. DSC and TGA curves of poly(phthalazinone ether ketone ketone) 3a.
endothermic melting peak shown until 300 ◦ C in DSC curves demonstrating this class of polymers is amorphous. 4. Conclusion A new class of soluble poly(phthalazinone ether ketone ketone)s with pendent methyl groups was synthesized from an activated dichloride monomer 1 and several phthalazinone containing bisphenol-like monomers 2a–c via a novel N–C coupling reaction. The resultant polymers 3a–c exhibit high Tg s over 239 ◦ C and excellent thermal stability. They have good solubility in common organic solvents and could be casted transparent, tough films and all the polymers are amorphous. Good solubility coupled with salient excellent thermal stability suggests this class of poly(arylene ether)s could be excellent candidates for high performance polymers. Acknowledgements This project was supported by the Key Natural Science Foundation of Fujian Province (E0320003) and the authors would like to extend their thanks to Prof. Z.H. Liu at Shannxi Normal University for recording the NMR spectra. References
Fig. 1. Comparison of 1 H NMR spectra of monomer 2a and polymer 3a.
[1] A.S. Hay, U.S. Patent 5,237,062 (1993). [2] X.G. Jian, L. Cheng, J. Polym. Sci. Part A: Polym. Chem. 37 (1999) 1565.
L. Ying et al. / Materials Science and Engineering B 132 (2006) 20–23 [3] L. Cheng, X.G. Jian, S.Z. Mao, J. Polym. Sci. Part A: Polym. Chem. 40 (2002) 3489. [4] L. Cheng, X.G. Jian, J. Appl. Polym. Sci. 92 (2004) 1516. [5] Y.Z. Meng, X.G. Jian, H.B. Zheng, H. Song, H.J. Zhang, A.S. Hay, Polym. Mater. Sci. Eng. (Chinese) 10 (2) (1994) 22.
23
[6] Y.J. Liu, X.G. Jian, S.J. Liu, J. Appl. Polym. Sci. 82 (2001) 823. [7] Z.Q. Lu, L. Cheng, J. Li, K. Zhang, S. Yi, J.G. Qin, J. Polym. Sci. Part A: Polym. Chem. 42 (2004) 925. [8] P.M. Hergenrother, B.J. Jensen, S.J. Havens, Polymer 29 (1988) 358. [9] L. Cheng, L. Ying, et al., Manuscript in preparation.
Synthesis and properties of poly(phthalazinone ether ketone ketone)s containing pendent methyl groups Lei Ying, Xiao-Ling Yang, Juan Feng, Chen-Yi Wang, Lin Cheng ∗ Department of Materials Science and Engineering, Huaqiao University, Quanzhou, Fujian 362021, China
Abstract A new class of poly(phthalazinone ether ketone ketone)s has been prepared by aromatic nucleophilic displacement polycondensation from an activated dichloride monomer 1 and several phthalazinone containing bisphenol-like monomers 2a–c. The formation of the polymers was confirmed by FT-IR and 1 H NMR spectra, and the synthesized polymers 3a–c have good solubility in common organic solvents, high glass transition temperatures (Tg s) in range of 239–255 ◦ C and excellent thermal stability. Moreover, tough, flexible and transparent thin films can be readily prepared by both spin coating and solution casting approach. Good solubility in common organic solvents coupled with salient thermal stability demonstrates this class of polymers could be excellent candidate for high performance polymers. © 2006 Elsevier B.V. All rights reserved. Keywords: Soluble; Poly(arylene ether)s; Phthalazinone; 1,4-Bis(chlorobenzoyl)benzene
1. Introduction The pursuance of high performance polymers as matrix resins in advanced composites for application in aerospace and military industries has attracted much attention. Thermoplastic high performance polymers have unique combination of chemical, physical and mechanical properties as well as the potential for low-cost composite fabrication. Being an important class of thermoplastic polymers, poly(arylene ether)s were used extensively because of their excellent comprehensive properties. Generally, poly(arylene ether)s are prepared by the aromatic nucleophilic displacement reaction of an activated aromatic dihalide compound with an alkali metal bis-phenolate in polar aprotic medium. Since dichloro monomers are much cheaper than the corresponding difluorides, many efforts were paid to prepare cost-effective poly(arylene ether)s via dichloro monomers. It is well known that aromatic polymers containing heterocyclic rings would have much higher glass transition temperatures and better mechanical properties after the introduction of heterocyclic rings into polymer backbone. Representative heterocyclic groups that have been incorporated in poly(arylene ether)s include imide, phenylquinoxaline, imidazole, 1,3,4-oxadiazole, benzoxazole, benzimidazole, benzothiazole, pyrazine, etc. Among them, phthalazinone-based poly-
mer families have received much interests recently, because the asymmetric, kink and non-coplanar phthalazinone moiety could impart polymers good solubility without scarifying their good thermal stability and mechanical properties [1–4]. In continuation of our efforts [2–4] to improve upon the properties of phthalazinone-based polymers by rational molecular design of monomers, we have prepared a series of soluble poly(phthalazinone ether ketone ketone)s (PPEKKs) from 1,4-bis(chlorobenzoyl)benzene 1 and some derivatives of 4(4-hydroxyphenyl)-2,3-phthalazin-1-one 2a–c via a novel N–C coupling reaction. Evidently, it is a versatile and cost-effective approach of preparing phthalazinone containing high performance polymers [5–7]. Our synthetic procedure allows the incorporation of a variety of substituted methyl groups into the backbone of this class of polymers via several different kinds of phthalazinone containing bisphenol-like monomers as shown in Scheme 1. The resultant polymers have interesting variations of properties that may arise out of pendent methyl groups. In this article, synthesis and properties of a series of poly(phthalazinone ether ketone ketone)s containing pendent methyl groups will be discussed in detail. 2. Experimental 2.1. Materials
∗
Corresponding author. Fax: +86 595 22686969. E-mail address: [email protected] (L. Cheng).
0921-5107/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.mseb.2006.02.005
All materials were commercially available and used as received unless otherwise noted. 1,4-Bis(chlorobenzoyl) ben-
L. Ying et al. / Materials Science and Engineering B 132 (2006) 20–23
21
Scheme 1. Synthesis of poly(phthalazinone ether ketone ketone)s.
zene (1) was synthesized according to the literature procedure [8], recrystallized from N,N-dimethylacetamide (DMAc) and dried under vacuum for 10 h prior to use. 4-(2-Methyl-4-hydroxyphenyl)-2,3-phthalazin-1-one (2a), 4-(3-methyl-4-hydroxy phenyl)-2,3-phthalazin-1-one (2b) and 4-(2,3-dimethyl-4hydroxyphenyl)-2,3-phthalazin-1-one (2c) were synthesized according to the literature procedure [7,9] and recrystallized from N,N-dimethylformamide (DMF) and dried under vacuum for 10 h prior to use.
was observed, respectively. Inherent viscosities (ηinh = ln ηr /c) were measured at a concentration of 0.5 g dL−1 in chloroform at 30 ◦ C with Ubbelohde viscometer. Solubility of polymers was determined using 2 mg of polymer in 3 ml of solvent. WAXD patterns were obtained at room temperature on a Rigaku D/MAX 2500 powder diffractometer with scanning speed of 4◦ min−1 and recorded the patterns in 2θ range of 10–40◦ .
2.2. Synthesis of polymer
As depicted in Scheme 1, a new class of poly(phthalazinone ether ketone ketone)s 3a–c was synthesized by the reaction of an activated dichloride monomer 1 and several phthalazinone containing bisphenol-like monomers 2a–c in a dipolar aprotic medium of DMAc. During the polymerization, the phthalazinone NH group behaves like phenolic OH groups, thereby the polymers could be formed from a novel N C coupling reaction through step growth polycondensation. In all cases, the polymers were obtained with quantitative yields and the inherent viscosities (ηinh ) ranged from 0.39 to 0.56 as shown in Table 1. The formation of poly(phthalazinone ether ketone ketone)s was confirmed by FT-IR and 1 H NMR spectroscopic data. The FT-IR spectrum of polymer 3a clearly exhibits the characteristic absorption at about 1668 (C O), 1597 and 1496 (aromatic rings), and 1245 cm−1 (C O C), respectively. There was no absorption in the range of 3100–3400 cm−1 of the characteristic absorption for NH and −OH. Moreover, the comparison of 1 H NMR spectra of monomer 2a and polymer 3a is shown in Fig. 1. Two sharp peaks of 12.8 and 9.6 ppm corresponding to phthalazinone N H and phenolic O H protons were absent in polymer spectrum, and all other peaks shift to lower fields comparing to the monomer. The spectroscopic data of other polymers
The synthesis of this class of poly(arylene ether)s was conducted in a similar method, and typical procedure was described as follows. A 100 ml three-necked flask equipped with a nitrogen inlet, mechanical stirrer, and Dean-Stark trap fitted with a condenser was charged with 1.7761 g (5 mmol) of 1 and 1.2614 g (5 mmol) of 2a. The monomers were carefully washed into flask with 15 ml of DMAc. An excess of K2 CO3 (1.04 g, 7.5 mmol) and approximate 10 ml toluene were added. The mixture was heated to 140 ◦ C for more than 5 h to ensure complete dehydration. After toluene was removed by Dean-Stark trap, the temperature was increased to 165 ◦ C and maintained at this temperature for more than 10 h until it became very viscous. The mixture was precipitated into 400 ml of methanol–water (1:1) solution containing 4 ml acetic acid with vigorous stirring followed by filtration. The resultant polymer 3a was washed thoroughly with hot water and then dissolved with chloroform and precipitated in methanol. After filtered, it was dried at 150 ◦ C under vacuum overnight. The yields were essentially quantitative for all the polymerization (>95% yield).
3. Results and discussion
2.3. Characterizations 1H
NMR spectra were measured on a Bruker AM-300 MHz instrument with dimethylsulfoxide (DMSO-d6 ) or chloroform (CDCl3 ) as solvent and tetramethylsilane (TMS) as internal standard. IR spectra (films for polymers) were recorded on a Nicolet Magna 470 spectrometer. Glass transition temperatures (Tg s), taken as the midpoint of the change in the slope of the baseline, were measured on a TA 5200-M DSC instrument at a heating rate of 10 ◦ C min−1 in N2 . Thermal gravimetric analysis (TGA) of the polymer samples was measured on a DuPont2000 SDT-2960 instrument at a heating rate of 20 ◦ C min−1 in N2 , and Td5 and Td10 reported as the temperature at which 5 and 10% weight loss
Table 1 Properties of poly(phthalazinone ether ketone ketone)s Polymer
ηinh a (g dL−1 )
Tg (◦ C)
Td5 b (◦ C)
Td10 c (◦ C)
800 ◦ C residued (%)
1a 1b 1c
0.56 0.42 0.39
242 239 255
447 460 431
520 530 446
70 70 66
Measured at a concentration of 0.5 g dL−1 in CHCl3 at 30 ◦ C. Temperature of 5% weight loss determined in nitrogen. c Temperature of 10% weight loss determined in nitrogen. d Char yield calculated as the percentage of solid residue after heating from room temperature to 800 ◦ C in nitrogen. a
b
22
L. Ying et al. / Materials Science and Engineering B 132 (2006) 20–23
Table 2 Solubility of poly(phthalazinone ether ketone ketone)s Polymer
CHCl3
DMAc
DMF
NMP
THF
Pyridine
m-Cresol
Concentrated H2 SO4
3a 3b 3c
++ ++ ++
+ + +
+− − −
++ ++ ++
+− +− +−
++ ++ ++
++ + ++
++ ++ ++
+ +: fully soluble at room temperature; +: soluble; + −: partially soluble; −: insoluble.
gave the similar results as polymer 3a, which demonstrated the structures were well matched with assigned. The thermal behavior of the polymers was investigated by DSC and TGA as reported in Table 1. As expected, the polymers 3a–c exhibit comparatively high Tg s ranged from 239 to 255 ◦ C, which may primarily attribute the incorporation of kink, bulky phthalazinone architecture into polymer backbone could not singly restrict segmental mobility and hinder the chain rotation but also significantly enhance the entanglement of polymer backbone. All the polymers were stable up to 430 ◦ C in nitrogen, and their thermal degradation occurs in two-stage process because the scission of the pendent methyl groups may occur before the cleavage of the bonds of polymer backbone. Furthermore, the excellent thermal stability of these polymers, taking polymer 3a, for example, was confirmed by the high percentage of solid residue after heating from room temperature to 800 ◦ C in nitrogen as shown in Fig. 2. As can be seen in Table 2, all synthesized polymers exhibit excellent solubility in common organic solvents such as chloroform, pyridine and N-methylpyrrolidinone (NMP). Probably, this can be ascribed that the polymer main chain was twisted by the kink, non-coplanar phthalazinone architecture. And as a result, tough, flexible and transparent thin films could be easily prepared by spin coating or casting processes, which make them potentially useful as high temperature membrane. According to wide-angle X-ray diffraction and thermal analysis, all of the polymers are amorphous because the kink phthalazinone architecture inhibits molecular packing into regular structures. Indeed, only a very broad diffraction trace was observed by wide-angle X-ray scatter. Moreover, there is no
Fig. 2. DSC and TGA curves of poly(phthalazinone ether ketone ketone) 3a.
endothermic melting peak shown until 300 ◦ C in DSC curves demonstrating this class of polymers is amorphous. 4. Conclusion A new class of soluble poly(phthalazinone ether ketone ketone)s with pendent methyl groups was synthesized from an activated dichloride monomer 1 and several phthalazinone containing bisphenol-like monomers 2a–c via a novel N–C coupling reaction. The resultant polymers 3a–c exhibit high Tg s over 239 ◦ C and excellent thermal stability. They have good solubility in common organic solvents and could be casted transparent, tough films and all the polymers are amorphous. Good solubility coupled with salient excellent thermal stability suggests this class of poly(arylene ether)s could be excellent candidates for high performance polymers. Acknowledgements This project was supported by the Key Natural Science Foundation of Fujian Province (E0320003) and the authors would like to extend their thanks to Prof. Z.H. Liu at Shannxi Normal University for recording the NMR spectra. References
Fig. 1. Comparison of 1 H NMR spectra of monomer 2a and polymer 3a.
[1] A.S. Hay, U.S. Patent 5,237,062 (1993). [2] X.G. Jian, L. Cheng, J. Polym. Sci. Part A: Polym. Chem. 37 (1999) 1565.
L. Ying et al. / Materials Science and Engineering B 132 (2006) 20–23 [3] L. Cheng, X.G. Jian, S.Z. Mao, J. Polym. Sci. Part A: Polym. Chem. 40 (2002) 3489. [4] L. Cheng, X.G. Jian, J. Appl. Polym. Sci. 92 (2004) 1516. [5] Y.Z. Meng, X.G. Jian, H.B. Zheng, H. Song, H.J. Zhang, A.S. Hay, Polym. Mater. Sci. Eng. (Chinese) 10 (2) (1994) 22.
23
[6] Y.J. Liu, X.G. Jian, S.J. Liu, J. Appl. Polym. Sci. 82 (2001) 823. [7] Z.Q. Lu, L. Cheng, J. Li, K. Zhang, S. Yi, J.G. Qin, J. Polym. Sci. Part A: Polym. Chem. 42 (2004) 925. [8] P.M. Hergenrother, B.J. Jensen, S.J. Havens, Polymer 29 (1988) 358. [9] L. Cheng, L. Ying, et al., Manuscript in preparation.