Waterborne Poly(urethane-urea)s Nanocomposites Reinforced with Clay, Reduced Graphene Oxide and Respective Hybrids: Synthesis, Stability and Structural Characterization

Nanocomposites based on waterborne poly(urethane-urea)s (NWPUU) containing hydrophilic montmorillonite (MMT) clay, reduced graphene oxide (rGO) or MMT/rGO hybrids were produced by a green synthesis method. Polymer matrices were based on poly(ethylene glycol-block-propylene glycol) (PEG-b-PPG) (with different contents of PEG-based segments), poly(propylene glycol) (PPG), isophorone diisocyanate (IPDI), dimethylolpropionic acid (DMPA) and hydrazine. Aqueous dispersions were characterized in terms of particle hydrodynamic diameter (DH) and rheological parameters and respective cast films were investigated by X-ray diffraction (XRD), low-field nuclear magnetic resonance (NMR) relaxometry and Fourier-transform infrared spectrometry (FTIR). Pseudoplastic dispersions with DH < 200 nm were stable for more than 12 months. The formation of exfoliated structures suggested the homogeneous nanodispersion of MMT silicate layers and rGO nanosheets. MMT/rGO synergism and layer-to-layer interactions suggested segregation of phases. Hydrogen bonds between polar groups of nanoloads and rigid segments of WPUU influenced the structure and molecular dynamics of the chains.