title: Molecular model for light-driven spiral mass transport in azopolymer films.
abstract: Azopolymer films exposed to nonuniform illumination exhibit a phenomenon of light-induced mass transport, leading to the formation of permanent relief patterns on the film surface. Its underlying microscopic mechanism remains unclear, despite many years of research effort. Here we introduce a model of the mass migration process based on anisotropic light-driven molecular diffusion. A key ingredient of our model is an enhanced molecular diffusion in proximity of the free polymer surface, which is essential for explaining, in particular, the recently observed spiral-shaped reliefs resulting from vortex-beam illumination.
authors.affiliation: CNR-SPIN, Complesso Universitario di Monte Sant'Angelo, 80126 Napoli, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Ambrosio
authors.affiliation: CNR-SPIN, Complesso Universitario di Monte Sant'Angelo, 80126 Napoli, Italy and Dipartimento di Fisica, Università di Napoli "Federico II," Complesso Universitario di Monte Sant'Angelo, 80126 Napoli, Italy.
authors.forename: Pasqualino
authors.initials: P
authors.lastname: Maddalena
authors.affiliation: CNR-SPIN, Complesso Universitario di Monte Sant'Angelo, 80126 Napoli, Italy and Dipartimento di Fisica, Università di Napoli "Federico II," Complesso Universitario di Monte Sant'Angelo, 80126 Napoli, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Marrucci