Improvement in structural, thermal, charge transport and mechanical properties of poly (methyl methacrylate)/polyindole composites for optoelectronic devices

This study encompasses the synthesis, characterization, optical properties, thermal, mechanical, and electrical characteristics of a series of in situ polymerized poly (methyl methacrylate) (PMMA) with different contents of polyindole (PIN) composites. The formation of composites was characterized by FTIR, UV-visible, XRD, FE-SEM, AFM, DSC and TGA. Tensile testing techniques was used to determine mechanical properties such as tensile strength, modulus, hardness and impact strength of PMMA/PIN. Impedance spectroscopy was used to study the electrical properties of the prepared composites. The interaction between the NH moiety of indole and ester groups of PMMA was established through FTIR. The optical bandgap energy determined from UV spectroscopy shows a declining trend, whereas the refractive index grows significantly with the loading of indole up to 5 wt%. The decrease in broadness and intensity of the XRD peak confirmed the presence of an indole component in the PMMA matrix. The holes in the surface morphology of PMMA was changed into uniformly dispersed particles, confirming the dispersion of PIN in the PMMA matrix. The surface roughness obtained from AFM increases with the addition of PIN to PMMA. DSC measurements show that the glass transition temperature of the polymer increases with the inclusion of the indole moiety. TGA indicates that the addition of PIN has a positive effect on the thermal stability of PMMA/PIN composites. The results of mechanical testing showed an increase in Youngs modulus, tensile strength, and impact strength with the addition of PIN. The AC impedance results show an increase in the dielectric constant and conductivity of PMMA with the PIN addition. PMMA/PIN composites with high tensile strength, conductivity and dielectric constant can be used in the fabrication of optoelectronic devices and EMI shielding.