Adsorption of Polymer Chains onto a Solid Surface during Spin Coating Process

The contact of macromolecules with solid surfaces, a ubiquitous process in both nature and various industries, results in the formation of a polymer interfacial layer on these surfaces. Given that the structure and properties of the polymer interfacial layer are challenging to relax and play a crucial role in the molecular dynamics of the upper layer, it is essential to understand the chain adsorption process onto solid surfaces. In this study, we extended our investigation beyond the previously explored adsorption process that occurs without the application of external forces. Our focus was on visualizing the impact of the spin coating process on the adsorption of double-stranded deoxyribonucleic acid (dsDNA), employed as a model for string-like molecules, onto a solid surface. Molecular-level real-space observations revealed that chains adsorbed with an anisotropically elongated state under a higher centrifugal force, whereas many chains adsorbed in the form of a random coil when the centrifugal force was small. In addition, it was found that the morphology of resulting adsorbed chains were markedly influenced by the adsorption state during the spin application, rather than being solely determined by the centrifugal force. Our macromolecular pictures aid in comprehending and manipulating buried morphology near solid surfaces and in the fabrication of promising materials, including polymer composites and layered organic devices.