Polymer Dynamics and Nanoscale Structure in Nanocomposites for Cement Application

Calcium silicate hydrate (C-S-H) - based polymer composites are of growing interest for their application in cement-based materials, as they demonstrate a brick-and-mortar architecture that significantly improves mechanical properties, but aggregation of C-S-H within the polymer matrix still poses significant challenges. The addition of cellulose nanocrystals (CNC) to these composites has been found to improve dispersion of the C-S-H as well as mechanical properties, as a result of the hydrogen bonding and calcium coordination between CNC and C-S-H. While macroscale mechanical properties have been the primary focus of previous work, there exists a gap in understanding of the local dynamics and interactions that take place in these composite systems. This study explores fundamental structure-property relationships of CNC/C-S-H/polyvinyl alcohol (PVA) nanocomposites of varying composition. In particular, broadband dielectric spectroscopy will be utilized to highlight the slowed polymer dynamics as a result of interaction with the CNC/C-S-H particles, compared to the faster bulk polymer dynamics of non-interacting PVA. X-ray scattering measurements will be used to elucidate the anisotropic nature of these composites, with a preferred orientation apparent between the CNC and C-S-H particles. Lastly, this fundamental dynamic and structural information will be connected to macroscale mechanical properties, to shed insight on new design rules for this class of nanocomposites for cement application.