دانلود رایگان مقاله کنترل مورفولوژی در لایه های نازک فیلم پلیمری

Abstract

In this work, smooth polymer films of PS, PLA and their blends, with thicknesses ranging from 20 nm up to 400 nm and very few defects on the surface were obtained by dip-coating. In contrast to the process of spin-coating which is conventionally used to prepare thin films of polymer blends, we showed that depending on the deposition parameters (withdrawal speed and geometry of the reservoir), various morphologies such as layered films and laterally phase-separated domains could be formed for a given blend/solvent pair, offering much more opportunities compared to the spin-coating process. This diversity of morphologies was explained by considering the superposition of different phenomena such as phase separation process, dewetting and vitrification in which parameters such as the drying time, the compatibility of the polymer/solvent pairs and the affinity of the polymer towards the interfaces were suspected to play a significant role. For that purpose, the process of dip-coating was examined within the capillary and the draining regimes (for low and high withdrawal speed respectively) in order to get a full description of the thickness variation and evaporation rate as a function of the deposition parameters.

4. Conclusion

We demonstrated that the morphology of the dried films, for a givenpolymer/solventpair canbedrivenby thedepositionparameters (withdrawal speed and geometry of the reservoir) which allow much more opportunities compared to the spin-coating process where the morphology in the latter case is mostly driven by the composition of the solution to be deposited. We have interpreted the various morphologies obtained (layers and laterally phaseseparated domains) by considering the superposition of different phenomena such as phase separation process, dewetting and vitrification. Parameters such as the drying time, the compatibility of the polymer/solvent pairs and the affinity of the polymer towards the interfaces were suspected to play a great role in the control of the morphologies. In this context, the process of dip-coating was carefully examined within the capillary and the draining regimes (for low and high withdrawal speed respectively) in order to get a full description of the thickness variation and evaporation rate as a function of the deposition parameters. This study is of high interest for the control of the morphology in thin films of polymer blends which are considered as serious candidates for advanced functional systems such as sensors, photovoltaic devices or smart templates for lithographic applications.