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Toward Homogeneous Nanostructured Polyaniline/Resin Blends
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
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2011 (English)In: ACS APPLIED MATERIALS & INTERFACES, ISSN 1944-8244, Vol. 3, no 5, 1681-1691 p.Article in journal (Refereed) Published
Abstract [en]

The high interest in applications of conducting polymers, especially polyaniline (PANI), makes it important to overcome limitations for effective usage due to poor processability and solubility. One promising approach is to make blends of PANT in polymeric resins. However, in this approach other problems related to the difficulty of achieving a homogeneous PANI dispersion arise. The present article is focused on this general problem, and we discuss how the synthesis method, choice of dopant and solvent as well as interfacial energies influence the dispersibility. For this purpose, different synthesis methods and dopants have been employed to prepare nanostructures of polyaniline. Dynamic light scattering analysis of dispersions of the synthesized particles in several solvents was employed in order to understand how the choice of solvent affects PANT aggregation. Further information on this subject was achieved by scanning electron microscopy studies of PANT powders dried from various solutions. On the basis of these results, acetone was found to be a suitable dispersion medium for PANI. The polymer matrix used to make the blends in this work is a UV-curing solvent-free resin. Therefore, there is no low molecular weight liquid in the system to facilitate the mixing process and promote formation of homogeneous dispersions. Thus, a good compatibility of the components becomes crucial. For this reason, surface tension and contact angle measurements were utilized for characterizing the surface energy of the PANI particles and the polyester acrylate (PEA) resin, and also for calculating the interfacial energy between these two components that revealed good compatibility within the PANI/PEA blend. A novel technique, based on centrifugal sedimentation analysis, was employed in order to determine the PANT particle size in PEA resin, and high dispersion stability of the PANI/PEA blends was suggested by evaluation of the sedimentation data.

Place, publisher, year, edition, pages
2011. Vol. 3, no 5, 1681-1691 p.
Keyword [en]
conducting polymer, polyaniline, synthesis methods, particle size, interfacial energy, dispersion stability, LUMiSizer dispersion analyzer
National Category
Materials Engineering
URN: urn:nbn:se:kth:diva-34404DOI: 10.1021/am2002179ISI: 000290843800042ScopusID: 2-s2.0-80053645678OAI: diva2:420895
QC 20110607Available from: 2011-06-07 Created: 2011-06-07 Last updated: 2014-11-03Bibliographically approved
In thesis
1. Functional composite coatings containing conducting polymers
Open this publication in new window or tab >>Functional composite coatings containing conducting polymers
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Organic coatings are widely used to lower the corrosion rate of metallic structures. However, penetration of water, oxygen and corrosive ions through pores present in the coating results in corrosion initiation and propagation once these species reach the metal substrate. Considering the need for systems that offer active protection with self-healing functionality, composite coatings containing polyaniline (PANI) conducting polymer are proposed in this study. In the first phase of my work, PANI was synthesized by various methods and characterized. The rapid mixing synthesis method was chosen for the rest of this study, providing PANI with high electrical conductivity, molecular structure of emeraldine salt, and morphology of spherical nanoparticles. PANIs doped with phosphoric and methane sulfonic acid revealed hydrophilic nature, and I showed that by incorporating a long-chain alkylphosphonic acid a hydrophobic PANI could be prepared. The second phase of my project was dedicated to making homogenous dispersions of PANI in a UV-curable resin based on polyester acrylate (PEA). Interfacial energy studies revealed the highest affinity of PEA to PANI doped with phosphoric acid (PANI-PA), and no attractive or long-range repulsive forces were measured between the PANI-PA surfaces in PEA.This is ideal for making conductive composites as, along withno aggregation tendency, the PANI-PA particles might come close enough to form an electrically connected network. Highly stable PEA/PANI-PA dispersions were prepared by pretreatment of PANI-PA in acetone followed by mixing in PEA in small portions under pearl-milling. The third phase of my project dealt with kinetics of the free radical polymerization that was utilized to cure the PEA/PANI-PA mixture. UV-vis absorption studies suggested a maximum allowed PANI-PA content of around 4 wt.% in order not to affect the UV curing behavior in the UV-C region. Real-time FTIR spectroscopy studies, using a laboratory UV source, revealed longer initial retardation of the photocuring and lower rates of crosslinking reactions for dispersions containing PANI-PA of higher than 3 wt.%. The presence of PANI-PA also made the formulations more sensitive to changes in UV light intensity and oxygen inhibition during UV curing. Nevertheless, curing of the dispersions with high PANI-PA content, of up to 10 wt.%, was demonstrated to be possible at either low UV light intensities provided the oxygen replenishment into the system was prevented, or by increasing the UV light intensity to very high levels. In the last phase of my project, the PEA and PEA/PANI-PA coatings, cured under high intensity UV lamps, were characterized. SEM analysis showed small PANI-PA particles to be closely packed within the matrix, and the electrical conductivity of the composite films was measured to be in the range of semiconductors. This suggested the presence of a connected network of PANI-PA, as confirmed by investigations of mechanical and electrical variations at the nanoscale by PeakForce TUNA AFM. The data revealed the presence of a PEA-rich layer at the composite-air interface, and a much higher population of the conductive network within the polymer matrix. High current signal was correlated with a high elastic modulus, consistent with the level measured for PANI-PA, and current-voltage studies on the conductive network showed non-Ohmic characteristics. Finally, the long-term protective property of the coatings was characterized by OCP and impedance measurements. Short-term barrier-type corrosion protection provided by the insulating PEA coating was turned into a long-term and active protection by addition of as little as 1 wt.% PANI-PA. A large and stable ennoblement was induced by the coatings containing PANI-PA of up to 3 wt.%. Higher content of PANI-PA led to poorer protection, probably due to the hydrophilicity of PANI-PA facilitating water transport in the coating and the presence of potentially weaker spots in the film. An iron oxide layer was found to fully cover the metal surface beneath the coatings containing PANI-PA after final failure observed by electrochemical testing.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xviii, 85 p.
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:42
Conducting polymer, Polyaniline, Conductive network, Nanocomposite, Active corrosion protection, Interfacial energy, UV curing
National Category
Polymer Technologies
Research subject
urn:nbn:se:kth:diva-155132 (URN)978-91-7595-301-4 (ISBN)
Public defence
2014-11-20, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20141103

Available from: 2014-11-03 Created: 2014-10-30 Last updated: 2016-02-02Bibliographically approved

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