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

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, Msp. 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.