Direct bonding techniques of polymer to metals are important for lightweight structural applications. However, the molecular mechanisms that control bonding strength remain unrevealed. We investigate the polyamides(PAs)－Al2O3 interface under tensile strain using all-atom molecular dynamics simulations. We elucidate three distinct conformational modes—tail elongation, loop-to-tail transition, and chain desorption. Conformational changes in adsorbed chains are investigated by introducing a segmental-scale structural descriptor, the local radius of gyration. In the elastic regime, the tensile stress is governed by PA bulk chemistry: aromatic PAMXD6 resists deformation better than aliphatic PA6. After yielding, the Al2O3 surface termination is crucial. PAMXD6 chains desorb from OH-terminated surfaces. However, PA6 chains adsorb to OH-terminated surfaces and indicate local conformational changes through loop-to-tail transitions. In contrast, both PA6 and PAMXD6 chains adsorb non-terminated surfaces that remain bonding owing to rigid trains and loops. These findings unveil how chemical functional groups control the conformational dynamics and bonding strength and provide design guidelines for polymer－metal hybrid materials with high bonding strength.
YOSHIDA et al. (Wed,) studied this question.