Synthesis and characterizations of high permittivity ultraviolet cured soft elastomeric networks and composites applicable as dielectric electroactive polymer

The objective of this thesis was preparation and characterizations of high permittivity ultraviolet (UV) cured elastomeric networks and composites applicable as dielectric electroactive polymers (DEAPs). At present, none of the commercially available elastomers such as acrylics, poly (dimethyl siloxane) (PDMS) and polyurethanes are designed with the requirements specific for DEAPs. Thus there is a need to develop elastomers with low elastic modulus, low viscous and dielectric losses and high relative permittivity. Interpenetrating networks and fumed silica reinforced composites of poly (propylene oxide) (PPO) were prepared which showed marked improvements in properties compared to the acrylic elastomers. But difficulties in curing by industrial processes and handling of these elastomers posed as limitations. So the focus was on optimizing UV induced thiol-ene reactions for curing commercially available PDMS. UV curing of PDMS was successfully established which eliminated the major drawbacks of widely used platinum catalyzed addition curing of PDMS. An advanced sequential curing used to form the PDMS networks showed low elastic modulus and low viscous losses than the former-developed processes due to better control over the heterogeneity of the networks. The sequential curing approach was successfully used to incorporate conductive multiwalled carbon nanotubes (MWCNTs) in higher concentrations than usual without making the elastomers conductive. The PDMS-MWCNT composites also showed high relative permittivity, low elastic modulus and low viscous and dielectric losses. Thus the elastomers developed in this project show promising properties to be considered as potential DEAPs.