Synthesis, characterization, physicochemical and dielectric properties of siloxane, polyimide and their blends

Abstract

Very low molecular weight polydimethylsiloxane (PDMS) has been synthesized and characterized by using Infrared spectroscopy (IR), nuclear magnetic resonance, thermogravimetric analysis (TGA) and differential scanning calorimetry. Molecular weight distribution of PDMS has been determined by using multiple angle light scattering and size exclusion chromatography while hydrodynamic radii have been determined by quasi elastic light scattering. Electrical properties fo PDMS were determined using broadband dielectric analyzer with variable temperature and frequency. Polyamic acid has been synthesized and characterized. Two polymers were blended at precursor stage and cured following unique time-temperature profile. Both the component in blends are characterized by using IR and TGA. Dielectric properties of both neat polyimide and its blend have been evaluated using broad band dielectric analyzer in variable temperature and frequency range. PDMS was found to dominate the surface characteristics of the blends as determined by scanning electron microscopy and optical microscopy. Possible mechanism of blend formation has been proposed wherein concurrent amicacid catalyzed equilbration and immobilization of siloxane moiety due to charge transfer complexation existing between the two componenets visualized to occur.

Keywords:

• Polyimide
• Polydimethylsiloxane
• Multiple angle light scattering
• Dielectric spectroscopy