Nonideality in Silicone Network Formation via Solvent Swelling and 1 H Double-Quantum NMR
The versatile crosslinking chemistry of poly(dimethylsiloxane) (PDMS) based materials affords a large research space in which polymers with widely varying elastomeric properties may be synthesized. Parameters such as chain length, crosslink density, crosslink functionality, filler content, and chain chemistry can all be modified to produce materials with specific physical and mechanical properties. Commercial polysiloxane based, ‘silicone’ elastomers are generally intractable, which makes the precise characterization of their networks problematic. We report here the application of equilibrium solvent uptake analysis and 1 H double-quantum nuclear magnetic resonance ( 1 H DQ NMR) spectroscopy to determine the network topology of end-linked PDMS networks with non-ideal network topology. Despite their structural complexity, we can quantify both the classical and non-classical contributions to network structure using 1 H DQ NMR which are in reasonable agreement with solvent uptake data. These findings serve as the foundation for future investigations of even more complex commercial silicones using 1 H DQ NMR.