Direct Evidence of Graphene‐Induced Molecular Reorientation in Polymer Films

Abstract

For the first time, direct evidence of graphene-induced molecular reorientation in polymer films using polarization modulated infrared reflection absorption spectroscopy (PM-IRRAS) are presented. By creating favorable electrostatic interactions, graphene-polymer interfaces can be controlled by varying polymer and solvent composition. After trans of unmodified graphene from copper onto a polymer substrate, polymer chain rearrangement relative to the orientation at the polymer-copper interface is observed using PM-IRRAS. Transfer success is characterized using both optical transmission measurements and Raman spectroscopy to quantify the transfer fidelity, i.e. graphene coverage fraction. Taken together, oxygen-containing poly(ethylene-co-vinyl acetate)shows more polymer chain rearrangement and better graphene coverage compared to oxygen-free polyethylene. Polymer composition seems to dominate graphene-polymer interactions while solvent choice has a smaller effect on transfer quality. These results are the first direct measurement of this effect and point towards the possibility of engineering graphene-polymer interactions for specific applications.

Mapping graphene layer number at few-micron-scale spatial resolution over large areas using laser scanning

“…Because this method relies on optical transmission, graphene layer numbers up to the asymptotic limit of transmission through graphene, stated in equation ( 4), can be considered. We demonstrate excellent graphene coverage agreement with traditional image-based analyses and have previously shown agreement with Raman-based analysis [11]. In this work, we utilize a rastered laser beam across sample area to provide high-precision data.…”

“…Barren areas where graphene transfer was unsuccessful are easily identifiable in both the transmission data and final layer map. In a previous work [11], we compared this coverage analysis to Raman measurements and found exceptional agreement, implying that our optical transmission method can reliably detect the graphene coverage fraction. Thus, transfer success can be considered by measuring both graphene coverage and layer consistency in a non-destructive manner.…”

“…CVD is a tunable process that can produce the uniform, largearea graphene sheets needed for device fabrication [10]. Maximizing the fidelity of transfer to the target substrate and minimizing damage during the transfer process are critical to scaling this technology up to large areas and commercial volumes [11]. Useful efforts have made graphene detection on these native metal foils possible via thermal annealing [12] and plasma etching [13].…”