Dynamics of polymer film formation during spin coating

Abstract

Standard models explaining the spin coating of polymer solutions generally fail to describe the early stages of film formation, when hydrodynamic forces control the solution behavior. Using in situ light scattering alongside theoretical and semi-empirical models, it is shown that inertial forces (which initially cause a vertical gradient in the radial solvent velocity within the film) play a significant role in the rate of thinning of the solution. The development of thickness as a function of time of a solute-free liquid (toluene) and a blend of polystyrene and poly(methyl methacrylate) cast from toluene were fitted to different models as a function of toluene partial pressure. In the case of the formation of the polymer blend film, a concentration-dependent (Huggins) viscosity formula was used to account for changes in viscosity during spin coating. A semi-empirical model is introduced, which permits calculation of the solvent evaporation rate and the temporal evolution of the solute volume fraction and solution viscosity.

Thermocapillary flow of thin Cu-water nanoliquid film during spin coating process

“…The value of Prandtl number Pr % 6:8 for the base liquid water is obtained using the definition of Prandtl number and thermophysical properties of water (see , Table 1) along with l f ¼ 1 Â 10 À3 Pa s at 20 C. The results presented in Figs. 4,5,6,7,8,9,10,11,12 are based on the thermal conductivity model predicted by the Maxwell [46] and in rest of the figures we have considered the effective thermal conductivity model given by Yu and Choi [47]. Figure 4 shows variation of the film thickness H with time t for different values of the nanoparticle volume fraction /.…”

“…The effect of solvent evaporation in spin coating process was first included by Myerhofer [5]. Y. Mouhamad et al [6] studied the effects of concentration dependent viscosity and solvent evaporation on the development of thin polymer film during spin coating process. Middleman [7] studied the effect of induced air-flow on the thinning of a liquid film over the rotating disk.…”

Effect of surface preparation of copper on spin-coating driven self- assembly of fullerene molecules

“…In particular, the spin-coating process can be approximated to consist of two distinct phases namely the filmthinning phase due to radial outflow of the solution and the solvent evaporation phase. Based on 2 Mouhamad et al [19], the film-thinning phase lasts up to a few seconds, during which the predominant growth of rods takes place. With increasing RPM the thinning phase duration becomes shorter leading to a consequently shorter time for growth of the self-assemblies.…”

“…This leads to smaller-sized self-assemblies at higher RPM. Using an exponential fit for the data published in Mouhamad et al [19], at 4000 and 200 RPM the thinning phase is estimated to last for about 0.05 and 1.26 seconds respectively. In addition, during the evaporation phase, further growth can occur, due to short-range diffusion of fullerene molecules in the vicinity of the selfassemblies.…”

Overview of printing and coating techniques in the production of organic photovoltaic cells

“…As the centrifugation occurs, the solvent, which is normally volatile, evaporates and dilutes the film until the final thickness (from 100 to 200 nm) is obtained. 7,44,45 The film thickness is controlled empirically, "As there is no linear relationship between film thickness and coating parameters (such as spin speed, acceleration, coating time, and solution concentration)." 45(p033302-1) Spin coating, due to its simplicity of use, is the most widely used laboratory technique to manufacture small and uniform thin film OPVs.…”