Emersion or Drying of a Wet Surface

When a polymer surface that has been kept in liquid water is emerged from liquid water and kept in dry condition, the reverse process to what is described in the water immersion occurs. This phenomenon is identical to what is described in the dry air situation above (Sec. 3) except that the starting point or the reference state is different. However, when this process is viewed as the recovery process of the decay of hydrophobicity, which took place when the sample was immersed in water the first time, there are significant differences in both the rate of change and the extent of recovery. This discrepancy is due to the fact that these processes are different processes, i.e., the driving force for the surface configuration change in the immersion and that in the emersion are completely different, and these processes are not a part of a reversible process. 

The influence of water immersion has little effect on very hydrophobic polymers consequently, the effect of emersion is nearly identical to the case without water immersion. The influence of water immersion becomes progressively greater with the increase of hydrophilicity. With highly hydrophilic polymers, the surface of water-immersed polymer is completely different from that of dry polymer, and consequently the emersion becomes drying process of wet polymers. 

Surface Modification is Appiied to Make the Surface Hydrophiiic 

The surface modification is applied on hydrophobic polymers in this case, and the complication due to change of bulk phase due to water immersion is small. The decay of hydrophilic characteristics or hydrophobic recovery is similar to that occurring in air. 

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