THE ROLE OF ORGANOSILICATES ON THE DIELECTRIC RELAXATIONS OF BIOMEDICAL THERMOPLASTIC POLYURETHANE NANOCOMPOSITES

The molecular dynamics of a series of biomedical poly(dimethylsiloxane)(PDMS)-based thermoplastic polyurethane nanocomposites (TPU) containing low and high aspect ratio organosilicates was investigated using broadband dielectric spectroscopy (DRS). The microphase separated morphology and degrees of separation, extensively characterized in a previous publication, were used to aid the interpretation of the molecular dynamics. Three relaxations were identified in dielectric spectra of the neat host TPU and nanocomposites over the measured temperature and frequency range: the low temperature process associated with local motion of the PDMS phase (α1), the higher temperature process which is associated with the mixed phase segmental motion (α2), and Maxwell –Wagner – Sillars (MWS) interfacial polarization (α3) process. The incorporation of organoclays has previously been shown to influence the morphology of these TPU systems, consequently affecting their dielectric behaviour. In this work the segmental relaxation time and temperature of 1 , 2 , and 3 process of the TPU are significantly altered by the presence of the low aspect ratio organo -hectorite. These significant changes in the TPU dynamics were due to very strong interactions between the exfoliated organo-hectorite and the TPU matrix, with the low aspect ratio nanofiller effectively acting as an interfacial compatibilizer. The dielectric spectroscopy data confirmed the existence of phase mixing in the E5-325 TPU containing organo-hectorite