Spontaneous planarization of nanoscale phase separated thin film

Abstract

Structure of complex fluid at mesoscales is influenced by interfacial effects. We describe the dynamic response in such films to sudden change in interfacial tension. In a self-assembled block copolymer film, the monolayer of 15 nm diam cylindrical discrete phases close to the surface commence to sink at an average rate of 0.16 nm/day in response to the interfacial tension change. Surprisingly, this spontaneous planarization occurs, even though the cylinders are covalently stitched to the matrix. A simple model explains the observed behavior. The observation may lead to approaches to tailor the structure of mesoscale thin films of complex fluids for long-range order that are desirable for nanoscale device fabrication.

Study of the time evolution of the surface morphology of thin asymmetric diblock copolymer films under solvent vapor

“…When the film is brought out of the chamber to solvent-free air, the film/air interfacial tension abruptly increases, and the surface undulation is produced. The undulations can be dampened by increasing the thickness of the surface layer and diffusing more PS from the 'interior' area to the surface [32].…”

Influence of the linkage type between the polymer backbone and side groups on the surface segregation of methyl groups during film formation

“…Similar results were reported by treating triblock copolymer SBS and SIS films under toluene vapor. 36,37 However, opposite results have also been observed. Turturro 38 showed that for a given evaporation rate range, microdomains of 1,4-PB and PS blocks were present together on the free surface, independent of copolymer composition and molecular weight.…”

“…21,[26][27][28][29][30][31] It was reported 5,21,28,29 that the segregation of the fluorinated moieties was affected greatly by micelle stability in the corresponding casting solution and by the evaporation rate of the solvent, when a methyl methacrylate (MMA) and 2-perfluorooctylethyl methacrylate (FMA) block copolymer (PMMA-b-PFMA) film was prepared from its micelle solution using a PMMA block as the micelle corona and PFMA block as the micelle core. 36,37 However, opposite results have also been observed. E-mail: wxinping@yahoo.com, wxinping@zstu.edu.cn; Fax: +86-571-8684-3600; Tel: +86-571-8684-3600 of a micelle-like aggregate structure at the film surface, on which the PMMA coronas were partly exposed to the surface.…”

“…13,[32][33][34][35][36]38,39 Such equilibrium surfaces, however, are not often achieved during the casting process, clearly indicating the presence of kinetic and thermodynamic effects related to the specific characteristics and evaporation conditions of the casting solvent. 13,[32][33][34][35][36]38,39 Such equilibrium surfaces, however, are not often achieved during the casting process, clearly indicating the presence of kinetic and thermodynamic effects related to the specific characteristics and evaporation conditions of the casting solvent.…”

“…To date, considerable research has focused on the surface structure of polymers at equilibrium free surfaces. 13,[32][33][34][35][36]38,39 Such equilibrium surfaces, however, are not often achieved during the casting process, clearly indicating the presence of kinetic and thermodynamic effects related to the specific characteristics and evaporation conditions of the casting solvent. Solution casting is a preparation method of practical importance, and is used in many industrial applications.…”