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

Abstract

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.

GRAPHICAL ABSTRACT

Circle fitting treatment FESEM images of polyurethane (PU) nanocomposites. Difference in the gold sputtering patterns (GSPs) of PU on the surface of nanoclay (below) can be clearly observed as compared to the GSPs of bare PU (above).

Highlights

1. 1 wt% C30B-PU nanocomposite coatings were prepared using 3 processing schemes.

2. FESEM images revealed gold sputtered patterns from the differently processed samples.

3. Circle fitting analysis on GSPs helped in understanding the polymer nanofiller interface.

4. Growth conformation of polymer chains in and around the 2D nanofiller provides fresh perspective into polymer chain dynamics.

Keywords:

• Chain mobility
• polymer conformation
• attractive interface
• reorganization
• FESEM
• degree of phase separation (DPS)
• gold sputtering patterns (GSPs)
• circularity

Acknowledgments

The authors thank Covestro (India) Private Limited for providing us with the necessary materials on- gratis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Additional information

Funding

We acknowledge the contribution of SAP (UGC, New Delhi), PURSE (DST, New Delhi) and TEQIP-III grants accorded to Dr. SSBUICET. We acknowledge the financial assistance given by DST-UT (S&T&RE/RP/147/Sanc/09/2017/1123-1129) and DRDO (DMSDE Kanpur) (TR/0569/CARS-130 dated 16/12/2021). We acknowledge the receiving of collaborative grant from Nottingham Trent University (NTU), United Kingdom under the science and technology initiative.