The synthesis and properties of conducting polyaniline for the production of novel elastomer blends

Conductive elastomers, used in applications like antistatic coatings, artificial muscles, and sensors, are typically made from metal filler, carbon black, or conducting polymer powders blended with synthetic or natural elastomers. This project focused on synthesizing conductive polyanilines and blending them with rubbers to enhance thermal stability, compatibility, and mechanical and electrical properties through various mixing techniques.

Novel polyaniline nanotubes were synthesized using an in-situ-soft templating chemical method with vitamin C and nicotinic acid (NA) as dopants and structure-guiding agents. By optimizing the molar ratio of vitamin C to aniline (0.3), polyaniline nanotubes with diameters of 80-120 nm and a conductivity of 2x 10-4 Siem were produced. Adjusting the NA/aniline ratio (0.5) resulted in nanotubes with diameters of 80-150 nm and conductivity of 3.8x 10-6 Siem. Different ratios led to various polyaniline structures, such as nanosheets and nanofibers.

Blends of polyepichlorohydrin (PECH) terpolymer rubber and polyaniline doped with dodecylbenzenesulfonic acid (PANI-DBSA) were examined. Both materials had compatible solubility parameters. Blends with different PANI-DBSA proportions were cast from solution onto PTFE substrates. Differential scannmg calorimetry (DSC) and thermogravimetric acid (TGA) were used to assess thermal stability of the blends, revealing that PANI-DBSA proportion influenced stability. Thermomechanical analysis (TMA) studied the glass transition in the blends, and electrical conductivities for unvulcanised blends were found to be around 10-9 Siem for 1 wt% PANI-DBSA, with the highest conductivity 4.81 x 10-4 Siem at 40 wt% PANI-DBSA, and percolation threshold l.lwt¾ (1.3 vol%). The electrical conductivity of all the sulfur-vulcanised blends with a conductivity threshold 1.1 wt% (1.03 vol%) and 6 wt% (5.5 vol%) of PANI-DBSA were achieved.

FTIR spectra of vulcanized PECH/PANI-DBSA blends showed shifts indicating changes in intermolecular interactions. X-ray diffraction and optical microscopy examined the effects of PANI-DBSA on blend morphology. Stretching vulcanized blends in the direction of flow improved electrical conductivities. Tensile testing according to British Standards Institution (BSI) requirements evaluated properties like tensile strength and Young's modulus. Strain-stress data and crosslink density calculations suggested that these vulcanized blends, with reversible electrical properties and compatible mechanical properties, could be developed into flexible smart materials.