Synthesis And Characterization Of Polyaniline By Doping Of Lignosulfonate And Lignosulfonate Modified Carbon Nanotube

In conductive polymer family,polyaniline,PANI,has excellent physics and chemistry properties,special dope mechanism and well environmental stability.Besides,it is cheap,easily obtained due to the synthesize technique conveniently and it seems as the most probable conductive macromolecule to realize the industrial application.However, it is exactly that this material has many defects,such as poor crystal property,hard to dissolve in water and organic solvent,low conductive property,hard to melt,badly flexible,etc.Therefore,it has much more disfigurement in machining capability.In order to enhance its application capability,this paper introduced to adopt lignosulfonate,LGS,as emulsifier and polymerization template or to adopt LGS modified carbon nanotube,CNT,for synthesizing dissolvable and higher conductive PANI.LGS is a polyanion with the sulfonated groups and usually prepared with different cations,e.g.the sodium(LGS-Na),calcium(LGS-Ca) and magnesium(LGS-Mg) and they are very easy to dissolve in the water.In terms of its molecular structure we can see that LGS contains both hydrophilic groups,e.g.sulfonic groups,and hydrophobic groups,e.g. carbon chain and phenolic hydroxyl.Since these LGSs have different surface properties,we can use them as emulsifier and dopant to synthesize conductive PANI(PANI-LGSs) by emulsion polymerization. In the emulsion polymerization process,we put forward the mechanism which LGS as emulsifier to synthesize conductive PANI,when the LGS is believable not only played as the emulsifier,but also to guide the aggregation as template.This was proven by recorded FT-IR,UV-vis spectra,EA analysis.WAXD analysis showed that LGS doped in PANI is part of the crystal,and doped structure variable closely.TGA show that the thermal stability of PANI/LGS-Ca to be better as compared with other LGSs and all LGS-doped PANIs showed high conductivities especially the values increased seeming to be two orders of magnitude compared to the pure PANI.The conductivity of the PANI/LGS-Ca is 430 times higher than that of the pure PANI.The results show that the yields of PANI/LGSs increased with the increasing of LGSs amount added in the emulsion polymerizations.Conductivity measurement suggested that LGSs is capable as emulsifier to dope PANI to improve the solubility in organic solvents.In this case the LGS doped PANI,PANI/LGS-Ca,was dissolved in NMP,DMSO,DMF,MEK and other organic solvents.SEM analysis further found that all these PANI-LGSs are in nano-particlesBecause LGS-Ca has the higher surface energy than other two LGSs, we use LGS-Ca as surfactant to modify multiwall CNT,MWNTs,via self assembly.EA,FT-IR and SEM results confirm that MCNT was successfully modified by LGS-Ca.The obtained MWNTs-LsCa was dispersed in solution as a template to synthesis PANI.We found that this noncovalent modification effectively avoids the agglomeration for MWNTs to lead PANI with more high solubility and condutivity.A related polymerization mechanism for understanding above process was deduced as that the MWNTs-LsCa was a dopant which doped in PANI to yield PANI/MWNTs-LsCa.This novel PANI has been found with better crystallinity than that of the pure PANI and SEM showed its morphology to be a nanofiber with a diameter less than 250 nm.This indicated that the MWNTs-LsCa is well dispersed in the PANI and which to be wrapped by PANI chains.The solubility of PANI/MWNTs-LsCa is better than that of the pure PANI,especially it can reach more than 8g/100mL concentration in NMP and DMSO.The electrical conductivity of PANI/MWNTs-LsCa at 55.427 S/cm is observed which seems to be of interest because this value is 279 times higher than that of the neat PANI prepared with the same method in this case.A schematic for this process is outlined.We also measured the dynamic surface adsorption of PANI, PANI/LGS-Ca and PANI/MWNTs-LsCa via capillary rise method. According to recorded adsorption curves,the kinetic equation and related parameters were obtained.And this furthermore lead to calculate the dynamic surface tension for PANI,PANI/LGS-Ca and PANI/MWNTs-LsCa by the van Oss-Good-Chaudhury combinatorial theory.Results showed that the PANI/MWNTs-LsCa has the highest surface free energy than others.