titanium dioxide
10.1002/spepro.002675
Alginate enhances formation of polyaniline alginate/titanium dioxide nanocomposites Chitragara Basavaraja, Do Sung Huh, and Eun Ae Jo
Conductivity measurements show that alginate successfully acts as template to form a composite with improved morphological, thermal, and electrical properties. Polyaniline (PANI) is a conducting polymer that is well known for its mechanical flexibility, environmental stability, and conductivity that can be tailored to various levels. The latter is controlled by doping, which changes the oxidation state by adding various levels of acids or bases. An increasing demand for conductive polymeric materials (such as PANI) is driven by their potential application in lightweight battery electrodes, electromagnetic-shielding devices, anticorrosion coatings, sensors, and other conductive applications.1–6 PANI can be combined with metal oxides (MOs) such as titanium dioxide (TiO2 ) to further improve its processability, mechanical properties, and conductivity. TiO2 has been examined in recent years because it is also known as a photocatalyst7 that accelerates the formation of hydroxyl radicals in the presence of light. Hydroxyl radicals are powerful oxidizing agents that can disinfect and deodorize air, water, and surfaces in environmental-decontamination applications.8–12 PANI-MO composites are challenging to create because it is difficult to achieve chemical interactions between PANI and MOs. Surfactants, such as camphor, dodecyl benzene, and naphthalene sulphonic acid, have been used as both dopants and templates that enhance interactions by creating a structure on which PANI-MO composites can form. However, this synthetic method requires a relatively large dopant that reduces the interaction between PANI chains. This problem has motivated many researchers to investigate water-soluble biopolymers (such as polyvinyl alcohol and carboxy methyl cellulose8, 9 ) as templates for PANI-composite formation. Alginate, a water-soluble biopolymer that is used in, e.g., medical products and food thickeners, is attractive because of its compatibility with environmental and biological systems. The goal of our research was to synthesize PANI-TiO2 composites in the presence of an alginate biological template to improve morphological, thermal, and electrical properties of PANI and PANI-MO
Figure 1. Formation of polyaniline alginate (PA)/titanium dioxide (PAT) nanocomposite thin films. (a) Formation of aniline alginate network. (b) Polymerization of aniline alginate in the presence of titanium dioxide (TiO2 ) to obtain PAT composite. (c) Formation of PAT thin films. APS: Ammonium persulfate. NMP: N-methyl-2-pyrrolidinone. CH3 ONa: Sodium methoxide.
composites. We synthesized polyaniline alginate (PA)/TiO2 (PAT) nanocomposite powders by in situ deposition from the oxidative polymerization of aniline in the presence of alginate. In this self-assembly process the alginate acts simultaneously as dopant and template. Figure 1 depicts a schematic model for the synthesis of PAT thin films. In Figure 1(a), the aniline alginate network is formed by untrasonication for 2h. In Figure 1(b), the PAT nanocomposite is synthesized by in situ doping polymerization in the presence of TiO2 nanoparticles and alginate, using ultrasonication at 10ı C in ammonium persulfate. In Figure 1(c), a PAT thin film is formed.
Continued on next page
10.1002/spepro.002675 Page 2/2
and functional coatings. We plan to investigate methods of fabricating the polymer composite film for surface-functionality modification. In particular, we will study how self-organization controls surface morphology.
Author Information Chitragara Basavaraja, Do Sung Huh, and Eun Ae Jo Inje University Gimhae, South Korea References
Figure 2. DC electrical conductivity () versus temperature of the PA and PAT composites. PAT-02 and PAT-04 contain 0.02 and 0.04 molar concentration TiO2 , respectively. S: Siemens.
Next, we investigated the conduction mechanism of PAT-composite films for different weight percentages of TiO2 by measuring the DC conductivity versus temperature in the range of 300–500K. Figure 2 shows that conductivity increases with a rise in temperature for all compositions. Conductivity also increases with an increase in the volume fraction of TiO2 in PA, from pure PA to molar concentrations of 0.02 and 0.04M TiO2 powder used in the polymerization reaction. This increase in conductivity with rising temperature indicates that the composites behave as semiconductors. Thus, our conductivity data may be analyzed using Mott’s variable-range-hopping (VRH) model,12, 13 which is widely used to explain the DC conductivity of disordered and amorphous materials.12–15 In polymers with nondegenerate ground states, charge transport is caused by polarons and bipolarons.14 This is consistent with the existence of high-density states in the band gap. Charge-carrier localization may give rise to polaron formation, and charge transport may be considered due to VRH. In addition to studying conductivity, we conducted UV-visible and Fouriertransform IR spectral studies that reveal successful chemical interaction between PA and TiO2 . Electron microscopy demonstrated that TiO2 nanoparticles have a significant effect on composite morphology. In summary, these results show that alginate acts as a good template to increase the chemical interaction between PANI and TiO2 and enhance the nanocomposite’s properties. Our simple, inexpensive method can be easily tapped for industrial applications. These nanocomposites can be exploited in various fields such as in electric devices, sensors,
1. J. Bhadra and D. Sarkar, Self-assembled polyaniline nanorods synthesized by facile route of dispersion polymerization, Mater. Lett. 63, p. 69, 2009. 2. A. Rahy and D. Y. Yang, Highly conductive polyaniline nanofibers, Mater. Lett. 62 (28), p. 4311, 2008. 3. T. M. Wu, Y. W. Lin, and C. S. Liao, Preparation and characterization of polyaniline/multi-walled carbon nanotube composites, Carbon 43 (4), p. 734, 2005. 4. R. Sainz, A. M. Benito, M. T. Martinez, J. F. Galindo, J. Sotres, A. M. Bari, B. Coraze, O. Chauvet, and W. K. Maser, Soluble self-aligned carbon nanotube/polyaniline composites, Adv. Mater. 17 (3), p. 278, 2005. 5. Z. X. Wei, M. X. Wan, T. Lin, and L. M. Dai, Polyaniline nanotubes doped with sulfonated carbon nanotubes made via a self-asembly process, Adv. Mater. 15 (2), p. 136, 2003. 6. M. Baibarac, I. Baltog, S. Lefrant, J. Y. Mevellec, and O. Chauvet, Polyaniline and carbon nanotubes based composites containing whole units and fragments of nanotubes, Chem. Mater. 15 (1), p. 4149, 2003. 7. S.J. Su and N. Kuramoto, Processable polyaniline-titanium dioxide nanocomposites: effect of titanium dioxide on the conductivity, Synth. Met. 114 (2), p. 147, 2000. 8. H. Zhang, R. L. Zong, J. C. Zhao, and Y. F. Zhu, Dramatic visible photocatalytic degradation performances due to synergetic effect of TiO2 with PANI, Environ. Sci. Technol. 42, p. 3803, 2008. 9. R. K. Mohammad, H. Y. Jeong, S. L. Mu, and T. L. Kwon, Preparation of conducting polyaniline/TiO2 composite submicron-rods by the gamma-radiolysis oxidative polymerization method, React. Funct. Polym. 68, p. 1371, 2008. 10. L. Zhang, P. Liu, and Z. Su, Preparation of PANI-TiO2 nanocomposites and their solid-phase photocatalytic degradation, Polym. Degrad. Stabil. 91, p. 2213, 2006. 11. L. Zhang, M. Wan, and Y. Wei, Polyaniline/TiO2 microspheres prepared by a templatefree method, Synth. Met. 151 (1), p. 1, 2005. 12. P. Gacesa, Bacterial alginate biosynthesis: recent progress and future prospects, Microbiol. 144, p. 1133, 1998. 13. J. C. Chiang and A. G. Macdiarmid, Polyaniline: protonic acid doping of the emeraldine form to the metallic regime, Synth. Met. 13 (1–3), p. 193, 1986. 14. C. Basavaraja, Y. Veeranagouda, K. Lee K, R. Pierson, and D. S. Huh, Surface characterization and electrical behavior of polyaniline-polymannuronate nanocomposites, J. Polym. Sci. B: Polym. Phys. 47, p. 36, 2009. 15. E. M. Genies, A. Boyle, M. Lapkowski, and C. Tsintavis, Polyaniline: a historical survey, Synth. Met. 36 (2), p. 139, 1990.
c 2010 Society of Plastics Engineers (SPE)
Alginate enhances formation of polyaniline alginate/titanium dioxide nanocomposites Chitragara Basavaraja, Do Sung Huh, and Eun Ae Jo
Conductivity measurements show that alginate successfully acts as template to form a composite with improved morphological, thermal, and electrical properties. Polyaniline (PANI) is a conducting polymer that is well known for its mechanical flexibility, environmental stability, and conductivity that can be tailored to various levels. The latter is controlled by doping, which changes the oxidation state by adding various levels of acids or bases. An increasing demand for conductive polymeric materials (such as PANI) is driven by their potential application in lightweight battery electrodes, electromagnetic-shielding devices, anticorrosion coatings, sensors, and other conductive applications.1–6 PANI can be combined with metal oxides (MOs) such as titanium dioxide (TiO2 ) to further improve its processability, mechanical properties, and conductivity. TiO2 has been examined in recent years because it is also known as a photocatalyst7 that accelerates the formation of hydroxyl radicals in the presence of light. Hydroxyl radicals are powerful oxidizing agents that can disinfect and deodorize air, water, and surfaces in environmental-decontamination applications.8–12 PANI-MO composites are challenging to create because it is difficult to achieve chemical interactions between PANI and MOs. Surfactants, such as camphor, dodecyl benzene, and naphthalene sulphonic acid, have been used as both dopants and templates that enhance interactions by creating a structure on which PANI-MO composites can form. However, this synthetic method requires a relatively large dopant that reduces the interaction between PANI chains. This problem has motivated many researchers to investigate water-soluble biopolymers (such as polyvinyl alcohol and carboxy methyl cellulose8, 9 ) as templates for PANI-composite formation. Alginate, a water-soluble biopolymer that is used in, e.g., medical products and food thickeners, is attractive because of its compatibility with environmental and biological systems. The goal of our research was to synthesize PANI-TiO2 composites in the presence of an alginate biological template to improve morphological, thermal, and electrical properties of PANI and PANI-MO
Figure 1. Formation of polyaniline alginate (PA)/titanium dioxide (PAT) nanocomposite thin films. (a) Formation of aniline alginate network. (b) Polymerization of aniline alginate in the presence of titanium dioxide (TiO2 ) to obtain PAT composite. (c) Formation of PAT thin films. APS: Ammonium persulfate. NMP: N-methyl-2-pyrrolidinone. CH3 ONa: Sodium methoxide.
composites. We synthesized polyaniline alginate (PA)/TiO2 (PAT) nanocomposite powders by in situ deposition from the oxidative polymerization of aniline in the presence of alginate. In this self-assembly process the alginate acts simultaneously as dopant and template. Figure 1 depicts a schematic model for the synthesis of PAT thin films. In Figure 1(a), the aniline alginate network is formed by untrasonication for 2h. In Figure 1(b), the PAT nanocomposite is synthesized by in situ doping polymerization in the presence of TiO2 nanoparticles and alginate, using ultrasonication at 10ı C in ammonium persulfate. In Figure 1(c), a PAT thin film is formed.
Continued on next page
10.1002/spepro.002675 Page 2/2
and functional coatings. We plan to investigate methods of fabricating the polymer composite film for surface-functionality modification. In particular, we will study how self-organization controls surface morphology.
Author Information Chitragara Basavaraja, Do Sung Huh, and Eun Ae Jo Inje University Gimhae, South Korea References
Figure 2. DC electrical conductivity () versus temperature of the PA and PAT composites. PAT-02 and PAT-04 contain 0.02 and 0.04 molar concentration TiO2 , respectively. S: Siemens.
Next, we investigated the conduction mechanism of PAT-composite films for different weight percentages of TiO2 by measuring the DC conductivity versus temperature in the range of 300–500K. Figure 2 shows that conductivity increases with a rise in temperature for all compositions. Conductivity also increases with an increase in the volume fraction of TiO2 in PA, from pure PA to molar concentrations of 0.02 and 0.04M TiO2 powder used in the polymerization reaction. This increase in conductivity with rising temperature indicates that the composites behave as semiconductors. Thus, our conductivity data may be analyzed using Mott’s variable-range-hopping (VRH) model,12, 13 which is widely used to explain the DC conductivity of disordered and amorphous materials.12–15 In polymers with nondegenerate ground states, charge transport is caused by polarons and bipolarons.14 This is consistent with the existence of high-density states in the band gap. Charge-carrier localization may give rise to polaron formation, and charge transport may be considered due to VRH. In addition to studying conductivity, we conducted UV-visible and Fouriertransform IR spectral studies that reveal successful chemical interaction between PA and TiO2 . Electron microscopy demonstrated that TiO2 nanoparticles have a significant effect on composite morphology. In summary, these results show that alginate acts as a good template to increase the chemical interaction between PANI and TiO2 and enhance the nanocomposite’s properties. Our simple, inexpensive method can be easily tapped for industrial applications. These nanocomposites can be exploited in various fields such as in electric devices, sensors,
1. J. Bhadra and D. Sarkar, Self-assembled polyaniline nanorods synthesized by facile route of dispersion polymerization, Mater. Lett. 63, p. 69, 2009. 2. A. Rahy and D. Y. Yang, Highly conductive polyaniline nanofibers, Mater. Lett. 62 (28), p. 4311, 2008. 3. T. M. Wu, Y. W. Lin, and C. S. Liao, Preparation and characterization of polyaniline/multi-walled carbon nanotube composites, Carbon 43 (4), p. 734, 2005. 4. R. Sainz, A. M. Benito, M. T. Martinez, J. F. Galindo, J. Sotres, A. M. Bari, B. Coraze, O. Chauvet, and W. K. Maser, Soluble self-aligned carbon nanotube/polyaniline composites, Adv. Mater. 17 (3), p. 278, 2005. 5. Z. X. Wei, M. X. Wan, T. Lin, and L. M. Dai, Polyaniline nanotubes doped with sulfonated carbon nanotubes made via a self-asembly process, Adv. Mater. 15 (2), p. 136, 2003. 6. M. Baibarac, I. Baltog, S. Lefrant, J. Y. Mevellec, and O. Chauvet, Polyaniline and carbon nanotubes based composites containing whole units and fragments of nanotubes, Chem. Mater. 15 (1), p. 4149, 2003. 7. S.J. Su and N. Kuramoto, Processable polyaniline-titanium dioxide nanocomposites: effect of titanium dioxide on the conductivity, Synth. Met. 114 (2), p. 147, 2000. 8. H. Zhang, R. L. Zong, J. C. Zhao, and Y. F. Zhu, Dramatic visible photocatalytic degradation performances due to synergetic effect of TiO2 with PANI, Environ. Sci. Technol. 42, p. 3803, 2008. 9. R. K. Mohammad, H. Y. Jeong, S. L. Mu, and T. L. Kwon, Preparation of conducting polyaniline/TiO2 composite submicron-rods by the gamma-radiolysis oxidative polymerization method, React. Funct. Polym. 68, p. 1371, 2008. 10. L. Zhang, P. Liu, and Z. Su, Preparation of PANI-TiO2 nanocomposites and their solid-phase photocatalytic degradation, Polym. Degrad. Stabil. 91, p. 2213, 2006. 11. L. Zhang, M. Wan, and Y. Wei, Polyaniline/TiO2 microspheres prepared by a templatefree method, Synth. Met. 151 (1), p. 1, 2005. 12. P. Gacesa, Bacterial alginate biosynthesis: recent progress and future prospects, Microbiol. 144, p. 1133, 1998. 13. J. C. Chiang and A. G. Macdiarmid, Polyaniline: protonic acid doping of the emeraldine form to the metallic regime, Synth. Met. 13 (1–3), p. 193, 1986. 14. C. Basavaraja, Y. Veeranagouda, K. Lee K, R. Pierson, and D. S. Huh, Surface characterization and electrical behavior of polyaniline-polymannuronate nanocomposites, J. Polym. Sci. B: Polym. Phys. 47, p. 36, 2009. 15. E. M. Genies, A. Boyle, M. Lapkowski, and C. Tsintavis, Polyaniline: a historical survey, Synth. Met. 36 (2), p. 139, 1990.
c 2010 Society of Plastics Engineers (SPE)
