title: Quantitative evaluation of evaporation rate during spin-coating of polymer blend films: Control of film structure through defined-atmosphere solvent-casting.
abstract: Thin films of polymer mixtures made by spin-coating can phase separate in two ways: by forming lateral domains, or by separating into distinct layers. The latter situation (self-stratification or vertical phase separation) could be advantageous in a number of practical applications, such as polymer optoelectronics. We demonstrate that, by controlling the evaporation rate during the spin-coating process, we can obtain either self-stratification or lateral phase separation in the same system, and we relate this to a previously hypothesised mechanism for phase separation during spin-coating in thin films, according to which a transient wetting layer breaks up due to a Marangoni-type instability driven by a concentration gradient of solvent within the drying film. Our results show that rapid evaporation leads to a laterally phase-separated structure, while reducing the evaporation rate suppresses the interfacial instability and leads to a self-stratified final film.
authors.affiliation: Department of Physics and Astronomy, University of Sheffield, S3 7RH, Sheffield, UK. p.mokarian@ucc.ie
authors.forename: P
authors.initials: P
authors.lastname: Mokarian-Tabari
authors.forename: M
authors.initials: M
authors.lastname: Geoghegan
authors.forename: J R
authors.initials: JR
authors.lastname: Howse
authors.forename: S Y
authors.initials: SY
authors.lastname: Heriot
authors.forename: R L
authors.initials: RL
authors.lastname: Thompson
authors.forename: R A L
authors.initials: RA
authors.lastname: Jones
mesh_terms: D020099:Coated Materials, Biocompatible / Q000032:analysis* / Q000737:chemistry; D004581:Electronics; D044367:Phase Transition; D011108:Polymers / Q000032:analysis* / Q000737:chemistry; D012997:Solvents / Q000737:chemistry*; D013499:Surface Properties; D013816:Thermodynamics; D014050:Toluene / Q000737:chemistry; D055548:Vapor Pressure; D014835:Volatilization
chemical_list: D020099:Coated Materials, Biocompatible; D011108:Polymers; D012997:Solvents; D014050:Toluene