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Influence of solvent and molecular weight on thickness and surface topography of spin‐coated polymer films
Author(s) -
Spangler Lora L.,
Torkelson John M.,
Royal J. Scot
Publication year - 1990
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760301104
Subject(s) - polymer , solvent , materials science , polystyrene , dichloromethane , toluene , viscosity , polymer chemistry , molar mass distribution , solvent effects , chemical engineering , analytical chemistry (journal) , composite material , organic chemistry , chemistry , engineering
The influence of polymer molecular weight, molecular weight distribution, and polymer‐solvent interactions on the thickness and topography of spin‐coated polymer films was examined. For films prepared from dilute solutions, highly volatile solvents or fair or “poor” solvents for the polymer adversely affect film surfaces causing nonuniformities (waves) to appear. However, if the concentration of these solutions is increased to approximately the concentration at which entanglements are formed, nearly uniform films are produced even if the solvent employed is highly volatile, such as dichloromethane. When toluene is employed as the solvent, which has a relatively low volatility and therefore forms nearly flat film surfaces, films prepared from dilute solution were found to have thicknesses, h , proportional to η o 0.34Ω −0.49 for polystyrene and η o −0.39Ω −0.49 for poly(methylmethacrylate) where η o is the zero‐shear rate solution viscosity and Ω is the rotational speed at which the films were prepared. These results suggest that the exponents associated with η o and Ω may be nearly independent of the type of polymer used as long as flat films are produced. Finally, the molecular weight parameter most important in controlling final film thickness for films made from dilute solutions is M v , the viscosity‐average molecular weight.