Eliciting impact of nano-clay reinforcement and processing schemes on polyurethane chain dynamics by gold sputtering patterns (GSPs)

This article narrates how processing “bias” affects polymer chain dynamics due to variable 2D-nanofiller interfaces. Importance of this biasing can be assessed by the significant improvement in thermal and mechanical properties we have recently published for polyurethane-2D clay nanocomposite coatings. We intricately look at the nanoscale structure and subsequent interface formation between 2D clay and PU chains to understand the changes in morphology. Polyurethane (PU) chain dynamics was observed through the gold (Au) sputtered patterns in field emission electron microscopy (FESEM) images. These were fitted with circles and our findings confirm the presence of an attractive interface between PU and 2D nanoclay. Circle fitting elicits important data like the critical area ( $A_c$ ) and critical relative frequency ( $f_c$ ) which are used to evaluate the polymer chain dynamics and morphology. We find that $f_c$ is related to circularity, and reinforcing nanoclay to the PU matrix enhances $f_c$ by 4.6% and 6.9% with simultaneous use of ultrasonic bath and high shear homogenizer. This is further correlated with the already established methods of small angle X-Ray scattering (SAXS) and Fourier transform infrared (FTIR) spectroscopy to generate a fresh perspective on interfacial interactions in PU-2D clay nanocomposites.