Morphological and Elastic Transition of Polystyrene Adsorbed Layers on Silicon Oxide
Year: 2020
Authors: Dinelli F., Pingue P., Signore G., Napolitano S.
Autors Affiliation: CNR, Ist Nazl Ottica INO, Pisa, Italy; Scuola Normale Super Pisa, Lab NEST, Pisa, Italy; CNR, Ist Nanosci, Pisa, Italy; Fdn Pisana Sci Onlus, Pisa, Italy; Univ Libre Bruxelles ULB, Fac Sci, Lab Polymer & Soft Matter Dynam Expt Soft Matter, Brussels, Belgium.
Abstract: Herein we present a study on the formation of irreversibly adsorbed layer of polystyrene molecules on silicon oxide surfaces. Various scanning probe microscopy techniques have been employed to study both the morphology and the mechanical properties of these self-assembled thin polymeric layers. More in detail, standard contact mode, force versus distance spectroscopy and ultrasonic force microscopy have been employed to obtain spatially-resolved maps and, thus, observe the physisorption of polystyrene on native silicon oxide substrate in function of time. Thick films, spin coated from a toluene solution, have been annealed at a temperature above the glass transition for increasing time intervals, and finally thoroughly rinsed in toluene. We have found that isolated islands of adsorbed chains are already present after an annealing time of half an hour. Prolonged annealing determines a progressive increase of the covered areas, whereas the formation of a complete flat layer requires 24 h. The pattern observed is in line with expected evolution of an unstable system, corresponding to the phenomenon of spinodal dewetting. Adhesion measurements show that the films present a reduced snap-off and the formation of a meniscus between tip and surface for annealing time up to 8 h. On the other hand, elastic measurements allow us to observe a progressive increase of the elastic modulus, with a complete transition for annealing time above 20 h. This is indication that a dense packing of the polystyrene molecules occurs, in line with the predictions of current models on the kinetics of irreversible adsorption. Lay Description Herein we present a study on the formation of irreversibly adsorbed layer of polystyrene molecules on silicon oxide surfaces. Various scanning probe microscopy techniques have been employed to study both the morphology and the mechanical properties of these self-assembled thin polymeric layers. Thick polystyrene films, spin coated from a toluene solution, have been thermally annealed at a temperature above the glass transition for increasing time intervals, and finally thoroughly rinsed in toluene. We have found that isolated islands of adsorbed chains are already present after an annealing time of half an hour. Prolonged annealing determines a progressive increase of the covered areas, whereas the formation of a complete flat layer requires twenty-four hours. The adsorption pattern observed is in line with expected evolution of an unstable system, corresponding to the phenomenon of spinodal dewetting. Adhesion and elastic measurements have allowed us to observe a progressive increase of the packing density of the polystyrene molecules, in agreement with the predictions of current models on the kinetics of irreversible adsorption.
Journal/Review: JOURNAL OF MICROSCOPY
Volume: 280 (3) Pages from: 280 to: 286
More Information: SN acknowledges financial support from the Action Concerte Recherche – ULB under project ´SADI´ and Fonds de la Recherche Scientifique – FNRS under Grant ´EXOTICAGE´.KeyWords: Adhesion; elasticity; physisorption; polymers; polystyrene; silicon oxide; SPM; UFM
DOI: 10.1111/jmi.12954Citations: 1data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2024-10-27References taken from IsiWeb of Knowledge: (subscribers only)Connecting to view paper tab on IsiWeb: Click hereConnecting to view citations from IsiWeb: Click here