Research On Preparation And Properties Of Polyaniline Materials Doped With Functional Acid

Polyaniline (PANI) has been a research hotspot as its excellent properties and its good anticorrosionperformance. In this paper, PANI nanomaterials were prepared by directly mix oxidation in different acidsystems. The morphology and structure of PANI were characterized by SEM, IR and UV-Visspectrometers, the solubility and conductivity of PANI also were measured. The impact of the molecularstructure and functional groups of doped acid on the morphology, structure and properties of PANInanomaterials was researched. With the ammonia solution as dedoing agent, dedoing condition wasresearched. Dedoped PANI was redoped with functional acid to improve its anticorrosion performance.Based on the PANI nanomaterials doped with functional acid, PANI/epoxy composite coatings wereprepared. The anticorrosion performance of the coatings on the mild steel were tested by electrochemicalmeasurement technology in3.5%NaCl solution, the anticorrosion mechanism also was investigated. Themain results are as follows.(1) PANI materials were prepared by directly mix oxidation in H2SO4, HCl, H3PO4and p-toluenesulfonic acid (TSA), sulfosalicylic acid (SSA), camphor sulfonic acid (CSA), dodecyl benzene sulfonicacid (DBSA) systems respectively. SEM results showed that PANI nanomaterials with various morphologycan be prepared in different acid systems. PANI nanofibers doped with H2SO4and HCl showed the longerfiber and the smoother surface. PANI doped with SSA showed the higher conductivity, which was0.5S/cm,PANI doped with H3PO4showed the smaller conductivity, which was only5.6×10-3S/cm.(2) PANI nanofibers were synthesized in propandioic acid (PA), succinic acid (SA), malic acid (MA)and tartaric acid (TA) systems respectively. Morphology and property analysis results showed that themolecular structure and the polar groups of polycarboxylic acid exsited certain influence on themorphology, structure and properties of PANI. The diameter and the length of PANI nanofibers wereimproved with the increase of the length of molecule chain of polycarboxylic acid, the solubility also wasenhanced, but the conductivity and the yield were reduced. The length of PANI nanofibers displayed asubstantial improvement owing to the conjugative effect of hydroxyl groups in the molecular structure ofpolycarboxylic acid, the conductivity also was increased, whereas the solubility declined. PANI doped with TA showed the better morphology, with that the fiber diameter was about100nm and the fiber length wasseveral microns. The yield and the conductivity of PANI doped with TA were higher, which were102%and2.13×10-2S/cm respectively. The solubility of PANI doped with SA in1-Methyl-2-pyrrolidone (NMP)was higher, which was0.57g at room temperature.(3) Dedoing condition that ammonia concentration was0.0025mol/L and dedoing time was30minwas obtained. The morphology of PANI showed that dedoping process had no significant effect on itsnanostructure. Based on the dedoped PANI, redoped PANI was prepared with H3PO4, CSA, TA, SSA andTSA respectively. IR and UV-Vis results showed that PANI redoped with TSA, SSA and TA possessedthe obvious doping effect.(4) Doped and redoped PANI were prepared in H3PO4, TSA and TA systems respectively, andPANI/epoxy composite coatings were prepared. The open circuit potential (OCP) and electrochemicalimpedance spectroscopy (EIS) results showed that every coating gave the certain anticorrosion ability.PANI redoped with TA showed the higher OCP, which was0.012V in the initial stage and was fallingslowly with the immersing. And it was-0.326V after immersed120days. The impedance value of PANIhad suffered a significant decrease at the beginning of the soaking because the coating was permeated bycorrosive medium. The impedance value of redoped PANI and doped PANI tended to stabilization afterimmersed22days and60days respectively, particularly redoped PANI revealed the higher impedance.PANI redoped with TA showed a higher impedance, and the impedance value was3.48×107·cm2afterimmersed120days, which was an order of magnitude higher than its doped state. The anticorrosionperformance of redoped PANI was more superior than doped PANI, the reasons of which were thatredoped PANI can retain the better nanofiber morphology which can improve the anticorrosionperformance. And redoped PANI showed higher dopant anionic release capacity, and the interactionbetween the released dopant anion and metal can strengthen the protective action of PANI materials.