Spin coating from a molecular point of view: its concentration regimes, influence of molar mass and distribution

Abstract

Spin coating has been investigated utilizing many different polymer solutions. The residual film thickness depends not only on the spinning velocity ω and concentration c₀, but also on molar mass M and molar mass distribution – simple models are presented. The concentration dependence is discussed with respect to different effects in low and high concentration regimes. Semi-empirical equations are given for practical use and are compared with experiments. In particular, a model is developed to correlate the Mark-Houwink-Staudinger equation with the residual film thickness which also describes the dependence of film thickness on spinning time consistently with observations by a simple equation. A novel description defining a molecular elementary process during spin coating allows one to describe the influence of molar mass distribution and results in a general definition of a novel spin coat molar mass average, M_sp. Spin coating is suggested as a full method for molar mass determination of polymers. Experimental studies are also shown which demonstrate the successful application of the concepts.