Cross-link density, viscoelasticity and swelling of hydrogels as affected by dispersion of multi-walled carbon nanotubes

We investigate the development of the cross-link density, viscoelasticity and swelling behavior of polyethylene glycol monoacrylate (PEGMA) as affected by the dispersion of multi-walled carbon nanotubes, CNTs, in the volume fraction, φ, range of 10^-4 to 5 × 10^-3. Linear viscoelastic material functions of the PEGMA-CNT suspensions depend on the state of the dispersion of the nanotubes. The dynamic properties, especially the storage moduli, increase with the better dispersion of the CNTs into an interconnected network. Upon UV-curing of PEGMA-CNT the dynamic properties decrease significantly with the increasing concentration of CNTs suggesting that the formation of the CNT network prior to curing decreases the mobility of PEGMA to give rise to a reduction in the cross-link density of the PEGMA-CNT. The decrease of the cross-link density becomes more significant with better dispersion of the nanotubes. The decrease of the cross-link density of the PEGMA-CNT hydrogels increases their rates of swelling in water and phosphate buffered saline, PBS.