Synthesis of poly(dimethylsiloxane)/polyindole composites and investigation of their properties

In this study, polyindole (PIN) and poly(dimethylsiloxane)/polyindole (PDMS/PIN) conducting composites were synthesized by chemical polymerization and their structures were characterized by various methods and techniques. In the experiments, iron (III) chloride (FeCl3) was used as an oxidizing agent and the ratio of oxidant/monomer was 5/2. Firstly, PIN was synthesized and obtained with 85% yield. Then, PDMS/PIN composites containing various amounts of PIN were synthesized. The conductivities of PIN and PDMS/PIN composites at various temperatures were measured by using four-probe technique. It was observed that the conductivities of PIN and PDMS/PIN composites increased with increasing temperature. The conductivity of PIN was determined with a value of 2,16x10?3 S cm-1 at the room temperature. Among the PDMS/PIN composites, 91% PIN containinig composite had the highest conductivity with a value of 9,61x10?4 S cm-1. From Gouy scale magnetic susceptibility measurements, it was revealed that PIN, having PDMS(9%)/PIN(91%) and PDMS(%26)/PIN(74%) of composites were found to have polaron nature whereas including PDMS(51%)/PIN(49%), PDMS(65%)/PIN(35%), and PDMS(92%)/PIN( 8%) composites were found to have bipolaron nature. Formation of the polymer and composites were supported by FTIR and UV analyses. From FTIR analyses, it was suggested that the polymerization reaction occurred via 2,3-propagation mechanism. The solubility tests showed that PIN and PDMS/PIN composites were relatively more soluble in polar organic solvents. The results of density measurements were demonstrated that the density increased with increasing amount of PDMS in the composites. The thermal properties of PIN and PDMS/PIN composites were investigated by using thermogravimetric (TGA) and differential scanning calorimetry (DSC) analyses, and adequate thermal stabilities. Morphological structures of the PDMS/PIN composites were clarified by using scanning electron microscopy (SEM). The results of X-ray diffraction (XRD) showed the amorphous structure of the PIN and PDMS/PIN composites. C, H and N contents of PIN, PDMS and PDMS/PIN composites were determined by elemental analysis. It was found out that calculated and experimental values of the polymer and composites were compatible with each other. Amount of Fe (mg/g) in the PIN and PDMS/PIN composites structures were determined by Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES). The highest mechanical strength was obtained for PDMS(92%)/PIN(8%) composite from the stress-strain experiments.