Macromolecules, Vol.41, No.4, 1323-1327, 2008
A methodology for the indirect determination and spatial resolution of shear modulus of PDMS - Silica Elastomers
A methodology is described that allows for the spatial resolution of shear modulus in silica-filled PDMS elastomers via H-1 relaxation measurements and stray-field imaging (STRAFI) techniques. Traditional Hahn echoes provide a simple, robust route to the extraction of a proton residual dipolar coupling constant (RDC), a direct measure of chain mobility and a parameter that can be corollated to numerous mechanical properties. Defining a dimensionless RDC eliminates any artifacts associated with low-field measurement and allows the RDC to become independent of field strength. A direct correlation between the NMR determined dimensionless RDC and results from dynamic mechanical analysis are presented, then employed via STRAFI to determine spatial variations in moduli associated with irradiated elastomeric materials. Reliable performance, despite poorly optimized STRAFI conditions, is demonstrated with an error of no more than 22% between the calculated shear modulus and the measured value via DMA.